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1
Lewis, DC, e LA Sparrow. "Implications of soil type, pasture composition and mineral content of pasture components for the incidence of grass tetany in the South East of South Australia". Australian Journal of Experimental Agriculture 31, n. 5 (1991): 609. http://dx.doi.org/10.1071/ea9910609.
Testo completoAbstract (sommario):
The occurrence of grass tetany related deaths in cattle grazing pasture in the South East of South Australia is related to soil type. The greatest losses occur on the solodised solonetz soils, with few, if any, on the rendzina or siliceous sand soils in the region. Pastures from 3 soil types were sampled on 2 occasions during the growing period, and soils were sampled once. Comparisons were made for the pasture components of potassium (K), calcium (Ca) and magnesium (Mg) concentrations in soils, and K, Ca, Mg, nitrogen (N) and sulfur (S) concentrations in plants. In the July sampling, the mean herbage K/(Ca + Mg) ratio for both annual and perennial grass species grown on the solodised solonetz soils exceeded 2.2 but was below 2 for the other 2 soil types. At the same time the mean K/(Ca + Mg) ratio for soil-extractable cations was 0.10 for the solodised solonetz soils but only 0.058 and 0.025 for the rendzina and siliceous sand soils. A critical value for the K/(Ca + Mg) ratio for the soil extractable cations of 0.07-0.08 is suggested. Of the 22 sites in the investigation, grass tetany deaths had occurred on 9 within the previous 5 years; all of these were classified as solodised solonetz soils. Deaths were reported in late autumn and winter, and in all cases the dominant pasture species growing at these sites in July were grasses. It is suggested that deaths ceased in spring because there was either a change to legume dominance or an increase in air temperature.
2
O'Sullivan, Cathryn A., Steven A. Wakelin, Ian R. P. Fillery e Margaret M. Roper. "Factors affecting ammonia-oxidising microorganisms and potential nitrification rates in southern Australian agricultural soils". Soil Research 51, n. 3 (2013): 240. http://dx.doi.org/10.1071/sr13039.
Testo completoAbstract (sommario):
Ammonia-oxidising archaea (AOA) have recently been described as having an important role in soil nitrification. However, published data on factors which influence their distribution and their impact on a soil’s potential nitrification rates (PNR) are sparse, particularly compared with the amount of information available regarding ammonia-oxidising bacteria (AOB). This study had two aims. First, to investigate which environmental factors affect the AOA : AOB ratio in soils from two agricultural regions, and second, to explore whether the abundance of either AOA or AOB correlated with PNR. Samples were collected from 45 sites within the cropping regions of Western Australia and South Australia. Soils were tested for pH, NH4+/NO3–, organic carbon (C), total nitrogen (N), C : N ratio, PNR, and electrical conductivity. Climate data were obtained from the Queensland Climate Change Centre for Excellence SILO website. Abundances of AOA and AOB were measured using real-time PCR quantification of the gene encoding the ammonia monooxygenase enzyme (amoA). Multivariate statistical analysis was applied to assess correlations between PNR, soil properties, and abundance of AOA or AOB. In the majority samples AOA were present, but their abundance, and the AOA : AOB ratio, varied considerably between sites. Multivariate analysis showed that the distribution of AOA and AOB and the AOA : AOB ratio were strongly correlated with climatic and seasonal factors. Sites where samples were collected during dry, hot periods tended to be AOA-dominated, whereas samples collected during cool, wet periods tended to be AOB-dominated or have equal abundances of AOA and AOB. The PNRs were correlated with total N content, organic C content, and soil pH. There was no clear correlation between AOA or AOB and PNR. This study shows that both AOA and AOB are widespread in Western Australian and South Australian soils and their abundance and ratio are affected by climate and season. It also shows that PNR is more strongly influenced by soil fertility factors than by the AOA : AOB ratio.
3
Latta, R. A., e A. Lyons. "The performance of lucerne - wheat rotations on Western Australian duplex soils". Australian Journal of Agricultural Research 57, n. 3 (2006): 335. http://dx.doi.org/10.1071/ar04016.
Testo completoAbstract (sommario):
In field experiments on duplex soils in the south-eastern and central Western Australian wheatbelt, lucerne (Medicago sativa L.) was compared with subterranean clover (Trifolium subterraneum L.) in pasture–crop rotations. Comparative pasture plant densities and biomass, soil water content, available soil nitrogen, wheat grain yield, and protein content were measured during 2 and 3 years of pasture followed by 2 and 1 year of wheat, respectively. Lucerne densities declined by 60–90% over the 3-year pasture phase but produced up to 3 times more total annual biomass than weed-dominant annual pastures and similar total annual biomass when annual pastures were legume dominant. Lower soil water contents were measured under lucerne than under annual pastures from 6 months after establishment, with deficits up to 60 mm in the 0–1.6 m soil profile. However, significant rain events and volunteer perennial weeds periodically negated comparative deficits. Wheat yields were lower following lucerne (1.3 t/ha) than following an annual pasture (1.8 t/ha) in a low-rainfall season, higher (3.7 v. 2.9 t/ha) in a high-rainfall season, and much higher when the previous annual pastures were grass dominant (3.4 v. 1.5 t/ha). Grain protein contents were 1–2% higher in response to the lucerne pasture phase. Overcropping wheat into a lucerne pasture of 19 plants/m2 reduced wheat grain yields, but a lucerne density of 4 plants/m2 reduced yields only where rainfall was low. The study has shown that lucerne–wheat rotations provide a productive farming system option on duplex, sodic soils in both the south-eastern and central cropping regions of Western Australia. This was most evident in seasons of above-average summer and growing-season rainfall and when compared with grass-dominant annual pastures.
4
Angus, J. F., A. F. van Herwaarden, D. P. Heenan, R. A. Fischer e G. N. Howe. "The source of mineral nitrogen for cereals in south-eastern Australia". Australian Journal of Agricultural Research 49, n. 3 (1998): 511. http://dx.doi.org/10.1071/a97125.
Testo completoAbstract (sommario):
The relative importance of soil mineral nitrogen (N) available at the time of sowing ormineralised during the growing season was investigated for 6 crops of dryland wheat. The soil mineral N in the root-zone was sampled at sowing and maturity and the rate of net mineralisation in the top 10 cm was estimated by sequential sampling throughout the growing season, using an in situ method. Mineralisation during crop growth was modelled in relation to total soil N, ambient temperature, andsoil water content. Mineral N accumulated before sowing varied by a factor of 3 between the sites (from 67 to 195 kgN/ha), while the net mineralisation during crop growth varied by a factor of 2 (from 43 to 99 kgN/ha). The model indicated that 0·092% of total N was mineralised per day when temperature and water were not limiting, with rates decreasing for lower temperatures and soil water contents. When tested with independent data, the model predicted the mineralisation rate of soil growing continuous wheat crops but underestimated mineralisation of soil in a clover-wheat rotation. For crops yielding <3 t/ha, the supply of N was mostly from mineralisation during crop growth and the contribution from mineral N accumulated before sowing was relatively small. For crops yielding >4 t/ha, thesupply of N was mostly from N present in the soil at the time of sowing. The implication is that for crops to achieve their water-limited yield, they must be supplied with an amount of N greater than can be expected from mineralisation during the growing season, either from fertiliser or from mineral N accumulated earlier.
5
Lewis, DC, TD Potter, SE Weckert e IL Grant. "Effect of nitrogen and phosphorus fertilizers on the seed yield and oil concentration of oilseed rape (Brassica napus L.) and the prediction of responses by soil tests and past paddock use". Australian Journal of Experimental Agriculture 27, n. 5 (1987): 713. http://dx.doi.org/10.1071/ea9870713.
Testo completoAbstract (sommario):
The response of oilseed rape to applied nitrogen and phosphorus was investigated in 2 areas of the South East of South Australia. The nitrogen rates applied varied from 0 to 50 kg/ha, while phosphorus rates applied in the Mundulla area ranged from 0 to 20 kg/ha and 0 to 34 kg/ha in the Millicent area. At 9 sites in the Mundulla area, where soils were primarily sandy loam over clay, oilseed rape yields were increased significantly by applied nitrogen at 7 sites and by applied phosphorus at 2 sites. On heavy black clay and peat soils in the Millicent area, oilseed rape yields were increased significantly by applied nitrogen at 5 of the 12 sites and by applied phosphorus at 6 sites. Of the measured soil variables, anaerobic ammonium nitrogen measured in the top 10 cm best predicted responses in seed yield to applied nitrogen. The critical nutrient range was 45-65 mg/kg. The response of oilseed rape to applied nitrogen was highly correlated with past paddock use but varied between the 2 areas. From the prediction equations developed, it was concluded that, in the Mundulla area, a significant (P< 0.05) nitrogen response was likely if the oilseed rape followed 2 or more crops, the last a non-legume, but was unlikely if the oilseed rape followed 1 or more years of pasture. At Millicent, a nitrogen response was likely if the oilseed rape was grown as the sixth crop in a continuous cropping program, and was unlikely if it was the first or second crop in the rotation, provided the preceding crop was a non-legume. The response of oilseed rape to applied phosphorus was highly correlated to extractable soil phosphorus measured in the top 10 cm (Colwell). The critical nutrient range was 20-25 mg/kg for the sandy loam soils at Mundulla and 40-50 mg/kg for the black clay and peat soils at Millicent. Nitrogen applications significantly increased seed oil content at 6 sites, significantly decreased it at 2 sites and had no effect at 13 sites. Phosphorus significantly increased seed oil content at only 1 site, significantly decreased it at 3 sites, and had no effect at the other 17 sites.
6
Smiles, D. E., e C. J. Smith. "A survey of the cation content of piggery effluents and some consequences of their use to irrigate soils". Soil Research 42, n. 2 (2004): 231. http://dx.doi.org/10.1071/sr03059.
Testo completoAbstract (sommario):
Piggery effluent contains high concentrations of potassium, and its repeated irrigation raises soil exchangeable potassium to levels, relative to divalent cations, that may degrade soil structure. We surveyed 6 big piggeries extending from south-eastern Queensland on a self-mulching Vertosol, to an Arenic Rudosol in south-eastern South Australia. We sampled effluent used for irrigation and also soil profiles to permit 'fenceline' comparisons between soils that had and had not been irrigated. The major water-soluble cations sodium (Na+), potassium (K+), calcium (Ca2+), and magnesium (Mg2+) were measured in the effluent and the soil saturation extracts, and also their exchangeable forms on air-dried soil samples. Ammonium-nitrogen (NH4+-N) was also assayed. The effluents were similar, with pH values between 7.5 and 8 together with very high water-soluble NH4-N, lower values for K+ and Na+, and quite low concentrations of Ca2+ and Mg2+. Cation concentrations varied across effluents; sodium and potassium adsorption ratios (SAR and KAR) were relatively constant but smaller than an ammonium adsorption ratio (Am-AR), which we conceive to estimate the influence of NH4+-N relative to the divalent cations in the effluent. Exchangeable K+ ratios in all profiles that had been irrigated were greater than their non-irrigated partners, as were the KAR values in their saturation extracts. Despite high concentrations of NH4+-N and high values of Am-AR in the effluents, there was no evidence of exchangeable NH4+ in the soils when sampled, which, we presume, is rapidly taken up by plants or oxidised. We present data that support a useful relationship between total cation content and effluent and the soil saturation extract electrical conductivity (EC), We also observed a modest increase in the EC of the saturation extract of irrigated soils. Farm records were insufficient to permit material balance calculations.
7
Bauhus, J., PK Khanna e RJ Raison. "The effect of fire on carbon and nitrogen mineralization and nitrification in an Australian forest soil". Soil Research 31, n. 5 (1993): 621. http://dx.doi.org/10.1071/sr9930621.
Testo completoAbstract (sommario):
The causes of onset of nitrification in a soil collected under an ashbed which was produced when heaped slash was burned, and for its absence in an unburnt soil, were investigated for an acid forest soil from south-eastern Australia. The occurrence of nitrification in ashbed soils was assessed in laboratory incubations extendig to 151 days to determine if it could be attributed to (a) an increase in pH, (b) an additional supply of P, (c) the removal of chemical inhibitors, and (d) the lack of competition with heterotrophs killed during soil heating. The treatments were: percolated and unpercolated ashbed soil from 0-5 and 5-10 cm depth; unburnt soil from 0-5 cm untreated and with added lime or added P; and burnt and unburnt soil from 5-10 cm depth. In addition, each treatment had an identical where the soil was inoculated with nitrifying garden soil. Compared with the unburnt surface soil (0-5 cm), ashbed soil had higher pH (3.6 units), higher mineral N (3 times) and slightly elevated NaHCO3-extractable P. During 151 days of incubation, microbial respiration in surface ashbed soil, measured as CO2 evolution, initially exceeded the values obtained in unburnt soil but then decreased to only 72% of unburnt soil at the end of the incubation period. In ashbed soil, the microbial biomass N content was low but its C/N ratio was high. Net N mineralization (Nmin) in ashbed soil was not significantly different from unburnt or phosphate fertilized soils (13.1, 14.7 and 17.8 mg N,in kg-' respectively) but was lower than in limed soil (59.3 mg Nmin kg-1). Percolation of surface ashbed soil with distilled water removed high amounts of salts and increased microbial respiration and N mineralization. Inoculation of soils with a slurry from a nitrifying garden soil induced nitrification in every treatment, regardless of their ammonium content, pH or other limiting component. Nitrification was also stimulated in unburnt surface soil on the addition of lime and P. Autotrophic nitriflers were active only in surface ashbed soils and probably in limed soils. P addition promoted heterotrophic nitrification. It was concluded that soil heating reduced competition between autotrophs and heterotrophs for ammonium and that ash supplies nutrients, such as K and Ca which stimulate nitrification. Low pH was not a limiting factor for nitrification but a high pH may promote the establishment of autotrophic nitrifiers.
8
Cooke, JW, GW Ford, RG Dumsday e ST Willatt. "Effect of fallowing practices on the growth and yield of wheat in south-eastern Australia". Australian Journal of Experimental Agriculture 25, n. 3 (1985): 614. http://dx.doi.org/10.1071/ea9850614.
Testo completoAbstract (sommario):
The effects on crop establishment, crop development and the yield of wheat of two methods of fallow preparation, at each of three lengths of fallow were investigated over 5 years on red duplex and associated soils in north-central Victoria. The two methods of preparation were: scarifying, which involved the repeated use of a tined tillage implement; and herbicide application, which involved the repeated use of non-residual herbicides to control weeds during the fallow phase. The three lengths of fallow were winter, spring and autumn, which were approximately 10, 8 and 2 months respectively. Grain yield on the scarifier treatments was 0.26 t/ha greater (P<0.10) than on the herbicide treatments. Grain yield on winter fallow was 0.46 and 0.56 t/ha greater (Pt0.01) than on spring and autumn fallows, respectively. Crop yield was positively correlated (R2= 0.49) with soil nitrate determined at the time the crop was sown, but was independent of available soil water content determined at that time. Winter fallowing conserved 15 and 29 mm more water than did spring and autumn fallowing respectively, and mineralized 26 and 28 kg/ha more nitrogen than did spring and autumn fallows respectively. Crop establishment (No. of plants/m of row) on the herbicide treatment was 89% (P< 0.05) of that on the scarifier treatment, but this was not the reason for the reduced grain yield on the herbicide treatment. The lower yields were caused by depressed crop vigour (number of spikes/m of row) which in turn was largely a consequence of the inefficient uptake of nitrogen. The yield benefits of scarifying appear to reflect the importance of the initial two or three cultivations.
9
Pérez-Fernández, María A., e Byron B. Lamont. "Nodulation and performance of exotic and native legumes in Australian soils". Australian Journal of Botany 51, n. 5 (2003): 543. http://dx.doi.org/10.1071/bt03053.
Testo completoAbstract (sommario):
Six Spanish legumes, Cytisus balansae, C. multiflorus, C. scoparius, C. striatus, Genista hystrix and Retama sphaerocarpa, were able to form effective nodules when grown in six south-western Australian soils. Soils and nodules were collected from beneath natural stands of six native Australian legumes, Jacksonia floribunda, Gompholobium tomentosum, Bossiaea aquifolium, Daviesia horrida, Gastrolobium spinosum and Templetonia retusa. Four combinations of soils and bacterial treatments were used as the soil treatments: sterile soil (S), sterile inoculated soils (SI), non-treated soil (N) and non-treated inoculated soils (NI). Seedlings of the Australian species were inoculated with rhizobia cultured from nodules of the same species, while seedlings of the Spanish species were inoculated with cultures from each of the Australian species. All Australian rhizobia infected all the Spanish species, suggesting a high degree of 'promiscuity' among the bacteria and plant species. The results from comparing six Spanish and six Australian species according to their biomass and total nitrogen in the presence (NI) or absence (S) of rhizobia showed that all species benefitted from nodulation (1.02–12.94 times), with R.�sphaerocarpa and C. striatus benefiting more than the native species. Inoculation (SI and NI) was just as effective as, or more effective than the non-treated soil (i.e. non-sterile) in inducing nodules. Nodules formed on the Spanish legumes were just as efficient at fixing N2 as were those formed on the Australian legumes. Inoculation was less effective than non-treated soil at increasing biomass but just as effective as the soil at increasing nitrogen content. Promiscuity in the legume–bacteria symbiosis should increase the ability of legumes to spread into new habitats throughout the world.
10
Chen, Wen, Graeme Blair, Jim Scott e Rod Lefroy. "Nitrogen and sulfur dynamics of contrasting grazed pastures". Australian Journal of Agricultural Research 50, n. 8 (1999): 1381. http://dx.doi.org/10.1071/ar98104.
Testo completoAbstract (sommario):
The experimental area was located at the Big Ridge 2 site, CSIRO, Chiswick (30°31′S, 151°39′E), 20 km south of Armidale, New South Wales, Australia. The site was established in 1955. In March 1966, phalaris and white clover were sown and pastures were fertilised annually with superphosphate until 1993. There were 3 pasture treatments, each with 2 replicates: degraded pasture (low phalaris content), phalaris dominant, and phalaris–white clover. Each of 6 experimental plots was divided into 3 strata. Two representative areas 1 m by 0.5 m were selected in each stratum of each treatment. The selected areas were labelled with 34S-enriched (90%) elemental sulfur and 15N-enriched (99%) NH4Cl solution. All plots were grazed continuously by sheep. No effect of pasture type on N leaching was apparent in this experiment. Seasonal variation of total soil mineral N in different soil layers, low 15N recovery down to 60 cm soil depth, and low nitrate-N concentrations in drainage water obtained in this experiment suggest that synchronisation of pasture growth with mineralisation and nitrification, together with ammonium domination of the soil N system, is the key ecological feature in preventing N leaching in this environment. Unlike N, potential S leaching was found with evidence of a large amount of sulfate stored deeper in the soil profile and high S concentrations in drainage water. High KCl-40 extractable S concentration in the top 20 cm soil layers was associated with the long history of superphosphate application. Long-term applications of superphosphate (1967–93), together with an increase in sulfate sorption capacity at lower soil depths, resulted in a large amount of sulfate stored at greater depth. However, retention of the 34S applied in 1995 in the top 10 cm soils suggests that sulfate-S movement down the soil profile is slow.
11
Groves, RH, PJ Hocking e A. Mcmahon. "Distribution of Biomass, Nitrogen, Phosphorus and Other Nutrients in Banksia marginata and B. ornata Shoots of Different Ages After Fire." Australian Journal of Botany 34, n. 6 (1986): 709. http://dx.doi.org/10.1071/bt9860709.
Testo completoAbstract (sommario):
The heathland form of Banksia marginata Cav. regenerates rarely from seed but commonly by resprout- ing from buds on lateral roots, whereas Banksia ornata F. Muell. regenerates only from seed, usually released after fire. The two species co-occur in heath vegetation on nutrient-poor soils in south-eastern South Australia and western Victoria. Shoots were sampled from stands of B. marginata aged from 1 to 25 years and of B. ornata aged from 1 to 50+ years after fire in the Little Desert National Park, western Victoria. B. marginata, the resprouter, distributed a greater proportion of the total shoot dry matter and content of all nutrients to vegetative growth over its shorter life span than B. ornata, the non-sprouter. About 50% of the total phosphorus in B. ornata shoots at 50+ years was present in cones (including seeds) compared with only about 20% in B. marginata shoots at a comparable stage of senescence (25 years). This difference between the species was also true to a lesser degree for nitrogen. There were considerable differences between other nutrients in their distribution patterns in shoots. Nutrients could be grouped together on the basis of distribution in shoots more satisfactorily than on presumed physio- logical roles. Stems were major sites of nutrient accumulation in both species. The content of a particular nutrient in seeds as a proportion of the content in the living parts of the shoot ranged from 0.03% (Na, Mn) to 2.0% (P) in B. marginata, and from 0.3% (Na) to as high as 31% (P) in B. ornata. Concen- trations of all nutrients except sodium were much higher in seeds than in the woody cones or vegetative organs of both species; seeds of B. ornata were particularly rich in calcium and manganese. We conclude that the different patterns of distribution of biomass and nutrients, especially nitrogen and phosphorus, within shoots of the two species reflect their different regenerative modes after fire. Introduction Phosphorus and, to a lesser extent, nitrogen limit the growth of sclerophyllous shrubs on nutrient-poor soils in southern Australia
12
Perrett, Christine, Olusegun O. Osunkoya e Cameron Clark. "Cat's claw creeper vine, Macfadyena unguis-cati (Bignoniaceae), invasion impacts: comparative leaf nutrient content and effects on soil physicochemical properties". Australian Journal of Botany 60, n. 6 (2012): 539. http://dx.doi.org/10.1071/bt12055.
Testo completoAbstract (sommario):
Macfadyena unguis-cati (L.) Gentry (Bignoniaceae) is a major environmental weed in coastal Queensland, Australia. There is a lack of quantitative data on its leaf chemistry and its impact on soil properties. Soils from infested vs uninfested areas, and leaves of M. unguis-cati and three co-occurring vine species (one exotic, two native) were collected at six sites (riparian and non-riparian) in south-eastern Queensland. Effects of invasion status, species, site and habitat type were examined using univariate and multivariate analyses. Habitat type had a greater effect on soil nutrients than on leaf chemistry. Invasion effect of M. unguis-cati on soil chemistry was more pronounced in non-riparian than in riparian habitat. Significantly higher values were obtained in M. unguis-cati infested (vs. uninfested) soils for ~50% of traits. Leaf ion concentrations differed significantly between exotic and native vines. Observed higher leaf-nutrient load (especially nitrogen, phosphorus and potassium) in exotic plants aligns with the preference of invasive plant species for disturbed habitats with higher nutrient input. Higher load of trace elements (aluminium, boron, cadmium and iron) in its leaves suggests that cycling of heavy-metal ions, many of which are potentially toxic at excess level, could be accelerated in soils of M. unguis-cati-invaded landscape. Although inferences from the present study are based on correlative data, the consistency of the patterns across many sites suggests that M. unguis-cati may improve soil fertility and influence nutrient cycling, perhaps through legacy effects of its own litter input.
13
Wilson, Brian R., Phoebe Barnes, Terry B. Koen, Subhadip Ghosh e Dacre King. "Measurement and estimation of land-use effects on soil carbon and related properties for soil monitoring: a study on a basalt landscape of northern New South Wales, Australia". Soil Research 48, n. 5 (2010): 421. http://dx.doi.org/10.1071/sr09146.
Testo completoAbstract (sommario):
There is a growing need for information relating to soil condition, its current status, and the nature and direction of change in response to management pressures. Monitoring is therefore being promoted regionally, nationally, and internationally to assess and evaluate soil condition for the purposes of reporting and prioritisation of funding for natural resource management. Several technical and methodological obstacles remain that impede the broad-scale implementation of measurement and monitoring schemes, and we present a dataset designed to (i) assess the optimum size of sample site for soil monitoring, (ii) determine optimum sample numbers required across a site to estimate soil properties to known levels of precision and confidence, and (iii) assess differences in the selected soil properties between a range of land-use types across a basalt landscape of northern NSW. Sample site size was found to be arbitrary and a sample area 25 by 25 m provided a suitable estimate of soil properties at each site. Calculated optimum sample numbers differed between soil property, depth, and land use. Soil pH had a relatively low variability across the sites studied, whereas carbon, nitrogen, and bulk density had large variability. Variability was particularly high for woodland soils and in the deeper soil layers. A sampling intensity of 10 samples across a sampling area 25 by 25 m was found to yield adequate precision and confidence in the soil data generated. Clear and significant differences were detected between land-use types for the various soil properties determined but these effects were restricted to the near-surface soil layers (0–50 and 50–100 mm). Land use has a profound impact on soil properties near to the soil surface, and woodland soils at these depths had significantly higher carbon, nitrogen, and pH and lower bulk density than the other land uses. Soil properties between the other non-woodland land-use types were largely similar, apart from a modestly higher carbon content and higher soil acidity under improved pasture. Data for soil carbon assessment should account for equivalent mass, since this significantly modified carbon densities, particularly for the lighter woodland soils. Woodland soils had larger quantities of carbon (T/ha corrected for equivalent mass) than any other land-use type, and in order to maintain the largest quantity of carbon in this landscape, retaining trees and woodland is the most effective option. Results from this work are being used to inform further development the NSW Statewide Soil Monitoring Program.
14
Bolland, M. D. A., J. S. Yeates e M. F. Clarke. "Single and coastal superphosphates are equally effective as sulfur fertilisers for subterranean clover on very sandy soils in high rainfall areas of south-western Australia". Australian Journal of Experimental Agriculture 43, n. 9 (2003): 1117. http://dx.doi.org/10.1071/ea02168.
Testo completoAbstract (sommario):
To reduce leaching of phosphorus (P) from fertilised pastures to shallow estuaries in the high rainfall (>800 mm annual average) areas of south-western Australia, and to supply extra sulfur (S) for subterranean clover (Trifolium subterraneum L.) in pasture, 'coastal superphosphate' was developed as a possible alternative P and S fertiliser to single superphosphate. Coastal superphosphate is made by adding phosphate rock and elemental S to single superphosphate as it comes out of the den before granulation. It has about 3 times more sulfur (S) and one-third the water-soluble P content than single superphosphate. Four long-term (5-year) field experiments were conducted in south-western Australia to compare the effectiveness of single and coastal superphosphate as S fertilisers for subterranean clover pasture grown on very sandy soils that are frequently S deficient after July each year due to leaching of S from soil. Seven different amounts of S were applied as fertiliser annually. Fertiliser effectiveness was assessed from clover herbage yield and S concentration in dried herbage. Fertiliser nitrogen was not applied in these experiments as this was the normal practice for pastures in the region when the research was conducted.Both coastal and single superphosphates were equally effective per unit of applied S for producing dried clover herbage and increasing S concentration in herbage. Previous research on very sandy soils in the region had shown that coastal superphosphate was equally or more effective per unit of applied P for production of subterranean clover herbage. It is, therefore, concluded that coastal superphosphate is a suitable alternative S and P fertiliser for clover pastures on very sandy soils in the region. The concentration of S in dried clover herbage that was related to 90% of the maximum yield (critical S) was about 0.20–0.35% S during August (before flowering) and 0.15–0.20% S during October (after flowering).
15
Evans, J., NA Fettell, DR Coventry, GE O'Connor, DN Walsgott, J. Mahoney e EL Armstrong. "Wheat response after temperate crop legumes in south-eastern Australia". Australian Journal of Agricultural Research 42, n. 1 (1991): 31. http://dx.doi.org/10.1071/ar9910031.
Testo completoAbstract (sommario):
At 15 sites in the cereal belt of New South Wales and Victoria, wheat after lupin or pea produced more biomass and had a greater nitrogen (N) content than wheat after wheat or barley; on average these crops assimilated 36 kg N/ha more. The improved wheat yield after lupin averaged 0 . 9 t/ha and after pea 0.7 t/ha, increases of 44 and 32% respectively. The responses were variable with site, year and legume. Soil available N was increased by both lupin and pea and the levels of surface inorganic N measured at the maturity of first year crops was often related to N in wheat grown in the following year. Of two possible sources of additional N for wheat after legumes, namely mineral N conserved in soil by lupin or pea (up to 60 kg N/ha) and the total N added in the residues of these legumes (up to 152 kg N/ha), both were considered significant to the growth of a following wheat crop. Their relative contribution to explaining variance in wheat N is analysed, and it is suggested wheat may acquire up to 40 kg N/ha from legume stubbles. Non-legume break crops also increased subsequent wheat yield but this effect was not as great as the combined effect of added N and disease break attained with crop legumes.
16
Bolland, M. D. A., e I. F. Guthridge. "Responses of intensively grazed dairy pastures to applications of fertiliser nitrogen in south-western Australia". Australian Journal of Experimental Agriculture 47, n. 8 (2007): 927. http://dx.doi.org/10.1071/ea06014.
Testo completoAbstract (sommario):
For the first time, we quantified pasture dry matter (DM) responses to applied fertiliser nitrogen (N) for intensively grazed, rain-fed, dairy pastures on sandy soils common in the Mediterranean-type climate of south-western Australia. The pastures are composed of subterranean clover (Trifolium subterraneum L.) and annual and Italian ryegrass (Lolium rigidum Gaud. and L. multiflorum Lam.). Six rates of N, as urea (46% N), were applied to 15 m by 15 m plots four times during 2002 and after each of the first 5–7 grazings in 2003 and 2004, throughout the typical April–October growing season. Total rates of N applied in the first year of the experiments were 0, 60, 120, 160, 200 and 320 kg N/ha, which were adjusted in subsequent years as detailed in the ‘Materials and methods’ section of this paper. The pastures in the experiments were rotationally grazed, by starting grazing when ryegrass plants had 2–3 leaves per tiller. The amount of pasture DM on each plot was measured before and after each grazing and was then used to estimate the amount of pasture DM consumed by the cows at each grazing for different times during the growing season. Linear increases (responses) of pasture DM to applied N occurred throughout the whole growing season when a total of up to 320 kg N/ha was applied in each year. No maximum yield plateaus were defined. Across all three experiments and years, on average in each year, a total of ~5 t/ha consumed DM was produced when no N was applied and ~7.5 t/ha was produced when a total of 200 kg N/ha was applied, giving ~2.5 t/ha increase in DM consumed and an N response efficiency of ~12.5 kg DM N/kg applied. As more fertiliser N was applied, the proportion of ryegrass in the pasture consistently increased, whereas clover content decreased. Concentrations of nitrate-N in the DM consistently increased as more N was applied, whereas concentrations of total N, and, therefore, concentration of crude protein in the DM, either increased or were unaffected by applied N. Application of N had no effect on concentrations of other mineral elements in DM and on dry matter digestibility and metabolisable energy of the DM. The results were generally consistent with findings of previous pasture N studies for perennial and annual temperate and subtropical pastures. We have shown that when pasture use for milk production has been maximised in the region, it is profitable to apply fertiliser N to grow extra DM consumed by dairy cows; conversely, it is a waste of money to apply N to undergrazed pastures to produce more unused DM.
17
Waymouth, Vicky, Rebecca E. Miller, Sabine Kasel, Fiona Ede, Andrew Bissett e Cristina Aponte. "Soil Bacterial Community Responds to Land-Use Change in Riparian Ecosystems". Forests 12, n. 2 (28 gennaio 2021): 157. http://dx.doi.org/10.3390/f12020157.
Testo completoAbstract (sommario):
Riparian forests were frequently cleared and converted to agricultural pastures, but in recent times these pastures are often revegetated in an effort to return riparian forest structure and function. We tested if there is a change in the soil bacterial taxonomy and function in areas of riparian forest cleared for agricultural pasture then revegetated, and if soil bacterial taxonomy and function is related to vegetation and soil physicochemical properties. The study was conducted in six riparian areas in south-eastern Australia, each comprising of three land-use types: remnant riparian forest, cleared forest converted to pasture, and revegetated pastures. We surveyed three strata of vegetation and sampled surface soil and subsoil to characterize physicochemical properties. Taxonomic and functional composition of soil bacterial communities were assessed using 16S rRNA gene sequences and community level physiological profiles, respectively. Few soil physiochemical properties differed with land use despite distinct vegetation in pasture relative to remnant and revegetated areas. Overall bacterial taxonomic and functional composition of remnant forest and revegetated soils were distinct from pasture soil. Land-use differences were not consistent for all bacterial phyla, as Acidobacteria were more abundant in remnant soils; conversely, Actinobacteria were more abundant in pasture soils. Overall, bacterial metabolic activity and soil carbon and nitrogen content decreased with soil depth, while bacterial metabolic diversity and evenness increased with soil depth. Soil bacterial taxonomic composition was related to soil texture and soil fertility, but functional composition was only related to soil texture. Our results suggest that the conversion of riparian forests to pasture is associated with significant changes in the soil bacterial community, and that revegetation contributes to reversing such changes. Nevertheless, the observed changes in bacterial community composition (taxonomic and functional) were not directly related to changes in vegetation but were more closely related to soil attributes.
18
Sadras, Víctor, David Roget e Garry O'Leary. "On-farm assessment of environmental and management constraints to wheat yield and efficiency in the use of rainfall in the Mallee". Australian Journal of Agricultural Research 53, n. 5 (2002): 587. http://dx.doi.org/10.1071/ar01150.
Testo completoAbstract (sommario):
The responses of wheat grain yield to soil properties, weather, root diseases, and management practices were investigated in 75 grower-managed crops in the Mallee region of South Australia, Victoria, and New South Wales during 3 growing seasons. Fourteen cultivars were represented in the sampled crops, with Frame being the most common (56%). The most widespread crop sequence was wheat after pasture (43% of wheat crops), followed by wheat after fallow or cereal (both about 20%); 12% of the wheat was sown after legumes. Wheat after cereal was more common in drier sites, and wheat after fallow in wetter sites. Wheat yield was proportional to Fischer’s photothermal coefficient around flowering, and ranged from nil to 4.7 t/ha. On average, wheat crops sown after cereals yielded 0.4 t/ha less than their counterparts sown after fallow, and 0.7 t/ha less than those after legumes. Sowing date ranged from 24 April to 21 July; yield declined with delayed sowing at an average rate of 17 kg/ha.day. Growing season rainfall (April–October) ranged from 111 to 266 mm, and accounted for 27% of the variation in grain yield. Soil water content at sowing (0–1 m) ranged from 32 to 330 mm; yield increased with initial soil water at an average rate of 6 kg/ha.mm. Grain yield per unit growing season rainfall was generally low, with 75% of crops producing <12 kg grain/ha.mm; the maximum ratio was 21 kg/ha.mm. Soil constraints, including sodicity, alkalinity, salinity, and boron toxicity, reduced yield in part by reducing availability of stored soil water. Owing to severity of chemical constraints increasing with soil depth, grain yield and yield per unit growing season rainfall were both inversely related to the proportion of water stored deeper in the soil (0.5–1 m). Yield was unrelated to nitrogen, both initial and applied. Larger amounts of nitrogen accumulated in soils with more severe constraints partially accounted for the lack of association between yield and nitrogen.
19
Hackney, B. F., J. Jenkins, J. Powells, C. E. Edwards, S. De Meyer, J. G. Howieson, R. J. Yates e S. E. Orgill. "Soil acidity and nutrient deficiency cause poor legume nodulation in the permanent pasture and mixed farming zones of south-eastern Australia". Crop and Pasture Science 70, n. 12 (2019): 1128. http://dx.doi.org/10.1071/cp19039.
Testo completoAbstract (sommario):
Pasture legumes must be adequately and effectively nodulated in order to reach nitrogen-fixation targets. Of 225 pasture paddocks sampled across the Central Tablelands, Central West, Monaro and Riverina regions of New South Wales, 93% had inadequate legume nodulation. Legume content was significantly higher in the mixed faming zone (>50%, Central West and Riverina) than the permanent pasture zone (26%, Central Tablelands; 28% Monaro). Available phosphorus (P) was below critical levels in 40% of paddocks sampled and sulfur (S) in 73% of paddocks; >35% of all paddocks had soil pHCa <5.0. Deficiency of P was more prevalent in the Central Tablelands (63% of paddocks), whereas S deficiency occurred more frequently in the Central West (95% of paddocks). Legume nodule scores were associated with host legume species, soil pH, available P and/or S, and cation exchange capacity, which collectively accounted for 73% of variation. For Trifolium spp., at soil pHCa >5.55, nodulation was predicted to be near adequate (score 3.95, where adequate = 4). At pHCa <5.55, higher available S resulted in a higher nodulation score (2.42) than in paddocks where S was deficient (score 0–1.97). These results suggest that improving the capacity of legumes to supply nitrogen should focus on addressing soil acidity and plant nutrition, specifically P and S.
20
Edis, R. B., D. Chen, G. Wang, D. A. Turner, K. Park, M. Meyer e C. Kirkby. "Soil nitrogen dynamics in irrigated maize systems as impacted on by nitrogen and stubble management". Australian Journal of Experimental Agriculture 48, n. 3 (2008): 382. http://dx.doi.org/10.1071/ea06098.
Testo completoAbstract (sommario):
The soil nitrogen (N) dynamics of an irrigated maize system in which stubble retention and stubble burned treatments were superimposed over treatments of varying N fertiliser rate were studied. The field site was near Whitton, New South Wales, Australia, and the work described here is part a life cycle analysis of greenhouse gas emissions from maize project. The objective of this part of the work was to quantify the fate of fertiliser N applied at the site. Field measurements of denitrification, mineral N content and recovery of 15N-labelled urea from microplots with and without ammonium thiosulfate were complimented with laboratory studies of denitrification and nitrous oxide (N2O) flux. Significantly (P < 0.05) more fertiliser N was recovered in the grain from the stubble incorporated treatment than the stubble burned treatment and there was greater recovery of fertiliser N in the soil at the end of the experiment in the stubble burned treatment. This may indicate that fertiliser N applied to the stubble burned system may be more exposed to soil-N transformations. The reason for the difference in uptake and soil residual is not clear but may be related to soil structure differences leading to less plant accessibility of N in the burned treatment. This difference may lead to more nitrous oxide emission from soil in the stubble burned treatments. Short-term (1 h) static chamber measurements in the field found a strong N-rate dependence of N2O emission rate for fertiliser rates between 0 and 300 kg N/ha. Inclusion of ammonium thiosulfate in the fertiliser formulation did not appear to have a significant impact on fertiliser N recovery.
21
Harries, Martin, Ken C. Flower e Craig A. Scanlan. "Sustainability of nutrient management in grain production systems of south-west Australia". Crop and Pasture Science 72, n. 3 (2021): 197. http://dx.doi.org/10.1071/cp20403.
Testo completoAbstract (sommario):
Balancing nutrient inputs and exports is essential to maintaining soil fertility in rainfed crop and pasture farming systems. Soil nutrient balances of land used for crop and pasture production in the south-west of Western Australia were assessed through survey data comprising biophysical measurements and farm management records (2010–15) across 184 fields spanning 14 Mha. Key findings were that nitrogen (N) inputs via fertiliser or biological N2 fixation in 60% of fields, and potassium (K) inputs in 90% of fields, were inadequate to balance exports despite increases in fertiliser usage and adjustments to fertiliser inputs based on rotations. Phosphorus (P) and sulfur (S) balances were positive in most fields, with only 5% returning losses >5 kg P or 7 kg S/ha. Within each of the three agroecological zones of the survey, fields that had two legume crops (or pastures) in 5 years (i.e. 40% legumes) maintained a positive N balance. At the mean legume inclusion rate observed of 20% a positive partial N budget was still observed for the Northern Agricultural Region (NAR) of 2.8 kg N/ha.year, whereas balances were negative within the Central Agricultural Region (CAR) by 7.0 kg N/ha.year, and the Southern Agricultural Region (SAR) by 15.5 kg N/ha.year. Hence, N budgets in the CAR and SAR were negative by the amount of N removed in ~0.5 t wheat grain, and continuation of current practices in CAR and SAR fields will lead to declining soil fertility. Maintenance of N in the NAR was achieved by using amounts of fertiliser N similar to other regions while harvesting less grain. The ratio of fertiliser N to legume-fixed N added to the soil in the NAR was twice that of the other regions. Across all regions, the ratio of fertiliser N to legume-fixed N added to the soil averaged ~4.0:1, a major change from earlier estimates in this region of 1:20 under ley farming systems. The low contribution of legume N was due to the decline in legume inclusion rate (now 20%), the low legume content in pastures, particularly in the NAR, and improved harvest index of lupin (Lupinus angustifolius), the most frequently grown grain legume species. Further quantifications of the effects of changing farming systems on nutrient balances are required to assess the balances more accurately, thereby ensuring that soil fertility is maintained, especially because systems have altered towards more intensive cropping with reduced legume production.
22
Angus, J. F., R. R. Gault, M. B. Peoples, M. Stapper e A. F. van Herwaarden. "Soil water extraction by dryland crops, annual pastures, and lucerne in south-eastern Australia". Australian Journal of Agricultural Research 52, n. 2 (2001): 183. http://dx.doi.org/10.1071/ar00103.
Testo completoAbstract (sommario):
The extraction of soil water by dryland crops and pastures in south-eastern Australia was examined in 3 studies. The first was a review of 13 published measurements of soil water-use under wheat at several locations in southern New South Wales. Of these, 8 showed significantly more water extracted by crops managed with increased nitrogen supply or growing after a break crop. The mean additional soil water extraction in response to break crops was 31 mm and to additional N was 11 mm. The second study used the SIMTAG model to simulate growth and water-use by wheat in relation to crop management at Wagga Wagga. The model was set up to simulate crops that produced either average district yields or the potential yields achievable with good management. When simulated over 50 years of weather data, the combined water loss as drainage and runoff was predicted to be 67 mm/year for poorly managed crops and 37 mm for well-managed crops. Water outflow was concentrated in 70% of years for the poorly managed crops and 56% for the well-managed crops. In those years the mean losses were estimated to be 95 mm and 66 mm, respectively. The third study reports soil water measured twice each year during a phased pasture–crop sequence over 6.5 years at Junee. Mean water content of the top 2.0 m of soil under a lucerne pasture averaged 211 mm less than under a subterranean clover-based annual pasture and 101 mm less than under well-managed crops. Collectively, these results suggest that lucerne pastures and improved crop management can result in greater use of rainfall than the previous farming systems based on annual pastures, fallows, and poorly managed crops. The tactical use of lucerne-based pastures in sequence with well-managed crops can help the dewatering of the soil andreduce or eliminate the risk of groundwater recharge.
23
Bell, Michael J., Wayne Strong, Denis Elliott e Charlie Walker. "Soil nitrogen—crop response calibration relationships and criteria for winter cereal crops grown in Australia". Crop and Pasture Science 64, n. 5 (2013): 442. http://dx.doi.org/10.1071/cp12431.
Testo completoAbstract (sommario):
More than 1200 wheat and 120 barley experiments conducted in Australia to examine yield responses to applied nitrogen (N) fertiliser are contained in a national database of field crops nutrient research (BFDC National Database). The yield responses are accompanied by various pre-plant soil test data to quantify plant-available N and other indicators of soil fertility status or mineralisable N. A web application (BFDC Interrogator), developed to access the database, enables construction of calibrations between relative crop yield ((Y0/Ymax) × 100) and N soil test value. In this paper we report the critical soil test values for 90% RY (CV90) and the associated critical ranges (CR90, defined as the 70% confidence interval around that CV90) derived from analysis of various subsets of these winter cereal experiments. Experimental programs were conducted throughout Australia’s main grain-production regions in different eras, starting from the 1960s in Queensland through to Victoria during 2000s. Improved management practices adopted during the period were reflected in increasing potential yields with research era, increasing from an average Ymax of 2.2 t/ha in Queensland in the 1960s and 1970s, to 3.4 t/ha in South Australia (SA) in the 1980s, to 4.3 t/ha in New South Wales (NSW) in the 1990s, and 4.2 t/ha in Victoria in the 2000s. Various sampling depths (0.1–1.2 m) and methods of quantifying available N (nitrate-N or mineral-N) from pre-planting soil samples were used and provided useful guides to the need for supplementary N. The most regionally consistent relationships were established using nitrate-N (kg/ha) in the top 0.6 m of the soil profile, with regional and seasonal variation in CV90 largely accounted for through impacts on experimental Ymax. The CV90 for nitrate-N within the top 0.6 m of the soil profile for wheat crops increased from 36 to 110 kg nitrate-N/ha as Ymax increased over the range 1 to >5 t/ha. Apparent variation in CV90 with seasonal moisture availability was entirely consistent with impacts on experimental Ymax. Further analyses of wheat trials with available grain protein (~45% of all experiments) established that grain yield and not grain N content was the major driver of crop N demand and CV90. Subsets of data explored the impact of crop management practices such as crop rotation or fallow length on both pre-planting profile mineral-N and CV90. Analyses showed that while management practices influenced profile mineral-N at planting and the likelihood and size of yield response to applied N fertiliser, they had no significant impact on CV90. A level of risk is involved with the use of pre-plant testing to determine the need for supplementary N application in all Australian dryland systems. In southern and western regions, where crop performance is based almost entirely on in-crop rainfall, this risk is offset by the management opportunity to split N applications during crop growth in response to changing crop yield potential. In northern cropping systems, where stored soil moisture at sowing is indicative of minimum yield potential, erratic winter rainfall increases uncertainty about actual yield potential as well as reducing the opportunity for effective in-season applications.
24
Cammarano, Davide, Glenn Fitzgerald, Bruno Basso, Deli Chen, Peter Grace e Garry O'Leary. "Remote estimation of chlorophyll on two wheat cultivars in two rainfed environments". Crop and Pasture Science 62, n. 4 (2011): 269. http://dx.doi.org/10.1071/cp10100.
Testo completoAbstract (sommario):
For this study we hypothesise that the use of canopy chlorophyll content index (CCCI) and crop greenness will be useful in assessing crop nutritional status and provide a robust management tool by growth stage DC30 for fertiliser application across multiple sites without being confounded by soil and biomass differences. The objectives of this study were: (i) to study the robustness of the CCCI and greenness as a measure of crop N content at two different locations, and (ii) to validate the model developed for crop nitrogen (N) determination. Data were collected from two rain-fed field sites cropped to wheat, one in Southern Italy (Foggia) and the other in the south-eastern wheat belt of Australia (Horsham). Data collection was conducted during the growing season in 2006–07 (December–June) for the Italian site and during the 2006 and 2007 (June–December) growing seasons for the Australian site. Measurements included crop biophysical properties (leaf area index (LAI), biomass, crop N concentration), hyperspectral remote sensing data, and SPAD (chlorophyll meter) determination. An independent dataset including SPAD, biomass, and remotely sensed data from Horsham (Australia) was used to test the validity of the model developed. Results showed that there is good correlation between SPAD and crop N content. The relationship between greenness (measured as LAI*SPAD) and CCCI was fitted with an exponential model and was not affected by biomass accumulation or soil reflectance (r2 = 0.85; y = 15.1e4.5424x; P < 0.001). When this model was tested on the independent dataset it yielded good results for the estimation of greenness (y = 1.22x − 54.87; r2 = 0.90; P < 0.001; root mean square error 32.2; relative error 15%). In conclusion, SPAD measurements combined with LAI could be used as a crop nutritional management tool by DC30 for fertiliser application across multiple sites.
25
Dear, B. S., J. M. Virgona, G. A. Sandral, A. D. Swan e S. Morris. "Changes in soil mineral nitrogen, nitrogen leached, and surface pH under annual and perennial pasture species". Crop and Pasture Science 60, n. 10 (2009): 975. http://dx.doi.org/10.1071/cp09026.
Testo completoAbstract (sommario):
Soil mineral nitrogen (N) profiles during the growing season and changes in total soil N and available N after 3–4 years were examined under 9 different pasture swards containing annual legumes, lucerne (Medicago sativa L.), or one of 4 perennial grasses at 2 sites representative of the low and medium rainfall belt of south-eastern Australia. The effect of the presence of phalaris (Phalaris aquatica L.) or lucerne on the spatial variation in surface pH was also measured. The 9 pastures were subterranean clover (Trifolium subterraneum L.), subterranean clover with annual weeds, yellow serradella (Ornithopus compressus L.), lucerne, phalaris, cocksfoot (Dactylis glomerata L.), lovegrass (Eragrostis curvula (Schrader) Nees), wallaby grass (Austrodanthonia richardsonii (Cashm.) H.P. Linder), and a mixture of lucerne, phalaris, and cocksfoot. All the perennial treatments were sown with subterranean clover. Available mineral N values in the surface 0.10 m of soil following summer rainfall were substantially higher in pure subterranean clover or serradella (Ornithopus compressus L.) swards (24–50 μg N/g) than those containing a mixture of subterranean clover and perennials (9–20 μg N/g). Apparent leaching of soil nitrate down the profile during winter was greatest in annual pasture treatments and least in swards containing perennials. Soil pH(CaCl2) at the 0–0.10 m depth varied with proximity to perennial plants and was significantly higher (+0.2–1.1 pH units) near the base of perennial plants than in gaps between the perennials or in annual-only swards. Available mineral N to 1.0 m before cropping at the end of the pasture phase was highest following subterranean clover (175–344 kg N/ha) and serradella (202–316 kg N/ha) at both sites. Available N was lowest (91–143 kg N/ha) following perennial grass–clover swards at the drier site where the annual legume content was lower, but perennial grass–clover swards produced larger soil N values (147–219 kg N/ha) at the higher rainfall site. Removal of the pasture in August–September compared with November in the year before cropping increased available N at the time of sowing by an average of 44% (51 kg N/ha) at the drier site and 43% (74 kg N/ha) at the wetter site. Incorporating perennial pasture species in swards was found to be advantageous in reducing nitrate leaching and preventing a decline in surface soil pH; however, available soil N to following crops could be lower if the annual legume content of perennial grass-based pastures declined due to competition from the perennial species.
26
Unkovich, Murray, Paul Sanford, John Pate e Mike Hyder. "Effects of grazing on plant and soil nitrogen relations of pasture-crop rotations". Australian Journal of Agricultural Research 49, n. 3 (1998): 475. http://dx.doi.org/10.1071/a97071.
Testo completoAbstract (sommario):
Plant and soil nitrogen (N) fluxes were assessed in subterranean clover (Trifolium subterraneum L.) based pastures set-stocked at 8 sheep per hectare (light grazing) or grazed at a much higher, but variable, intensity to maintain 1400 kg standing dry matter per hectare (intensive grazing) through the addition or removal of sheep. Pasture composition and biomass production, herbage N concentration, plant nitrate (NO-3) utilisation, and N2 fixation by clover were assessed at 3-weekly intervals over the growing season. Soil ammonium (NH+4) and NO-3 availability were assessed at similar intervals using soil coring and in situ incubation cores. Seasonal pasture yield under light grazing was 11·5 t dry matter/ha compared with 7·9 t/ha under intensive grazing, the difference being mostly attributable to reduced grass growth under intensive grazing. However, there was essentially no difference between the pastures in total N accumulation (300 kg N/ha in the lightly grazed and 302 kg N/ha in the intensively grazed pastures). The lesser dry matter production under intensive grazing was compensated for by higher N concentration and increased clover content of the sward, and faster clover growth late in the growing season. N2 fixation by clover under intensive grazing (153 kg N/ha) was slightly greater than under light grazing (131 kg N/ha). Proportional dependence of clover on N2 fixation (%Ndfa) was similar under intensive grazing (78%) and light grazing (84%), despite higher continued availability of soil mineral N under intensive grazing. Uptake of soil N by the grass component amounted to 147 kg N/ha under light grazing v. 96 kg N/ha in the intensively grazed pasture, and for the clover was 18 and 40 kg N/ha, respectively. Capeweed (Arctotheca calendula L.), a common weed of south-west Australian pastures, was extraordinarily active in absorbing, storing, and reducing soil NO-3, especially when subjected to intensive grazing. After the 3 years of the grazing trial, the pastures were cultivated and cropped to oats, triticale, and canola and the biomass and N uptake of each crop assessed. Intensive grazing in the previous pasture resulted in increased availability of soil mineral N in the subsequent cropping phase and accordingly augmented crop N uptake and eventual grain protein levels relative to crops following lightly grazed pasture. The study indicated that intensive grazing before cropping may offer a useful management tool for improving N nutrition and yields of non-leguminous crops in pasture-crop rotations under the conditions prevailing in the south-west of Australia.
27
Mayfield, A. H., e S. P. Trengove. "Grain yield and protein responses in wheat using the N-Sensor for variable rate N application". Crop and Pasture Science 60, n. 9 (2009): 818. http://dx.doi.org/10.1071/cp08344.
Testo completoAbstract (sommario):
Soil types, cereal crop growth and grain yields are typically variable across many paddocks in the cropping regions of South Australia. In this study the value of a variable rate nitrogen fertiliser application, using the Yara N-Sensor, was compared with the standard practice of a uniform application, at crop growth stage 31, on the grain yield and protein content of wheat. These comparisons were made using the same total amount of fertiliser in paired variable and uniform rate treatments in commercial crops at a total of 10 sites over two years in the medium to higher rainfall areas of the Mid North and Yorke Peninsula of South Australia. The mean increase in wheat grain yield for the variable rate treatment was only 40 kg/ha, or 0.8%, when compared with the uniform rate treatment averaged over these 10 sites and two years. Grain yield differences ranged from 160 kg/ha more to 60 kg/ha less for the variable rate treatment when compared with the uniform rate treatment. Wheat grain yields with the uniform treatments ranged from 2.53 t/ha to 5.68t/ha and with a mean grain yield of 4.24 t/ha. The mean wheat grain protein content with the variable rate treatment was 11.0%, compared with 10.5% with the uniform rate treatment, a relative increase of 5.1%. Where grain yield responses to the variable rate treatments were compared between different biomass areas within a paddock, the greatest grain yield increases to a variable rate of N compared with a uniform rate were in the areas with the lowest 20% of crop biomass whereas grain yield differences were negligible in areas with the highest 60% of crop biomass. These low biomass areas also had the greatest grain yield response to the applied post emergent nitrogen fertiliser when compared with areas with no post emergent nitrogen fertiliser. N-Sensor outputs (biomass and N-rate) were compared with measurements of plant biomass, N uptake (kg N/ha) and %N content at points of contrasting biomass and N-rate within paddocks. There was a high correlation between the N-Sensor biomass and N-rate values and actual plant biomass and N uptake but not with the %N content. Crop biomass maps made using sensors such as the N-Sensor could provide useful data layers, which in combination with other datasets such as grain yield maps or elevation maps, be used to produce zone maps for further analysis or for variable rate input treatments. The N-Sensor could also be used in some situations to map variations in weed biomass for possible site specific weed management.
28
Jones, R. B., M. Imsic, P. Franz, G. Hale e R. B. Tomkins. "High nitrogen during growth reduced glucoraphanin and flavonol content in broccoli (Brassica oleracea var. italica) heads". Australian Journal of Experimental Agriculture 47, n. 12 (2007): 1498. http://dx.doi.org/10.1071/ea06205.
Testo completoAbstract (sommario):
Broccoli (Brassica oleracea var. italica) heads are commonly consumed in the Western diet and frequent consumption is thought to help protect against certain cancers and cardiovascular disease. Broccoli heads contain relatively high levels of glucosinolates and flavonols, thought to be the key phytochemicals that contribute to the health benefits gained upon consumption. In this study, we investigated the effect of applied nitrogen (N) at either 0, 15, 30 or 60 kg/ha, or 30, 60, 90 or 150 kg/ha with applied sulfur (S) at 50 or 100 kg/ha on the glucosinolates glucoraphanin, glucobrassicin and progoitrin, and the flavonols quercetin and kaempferol in broccoli cv. Marathon florets. Trials were conducted in two sites in either heavy clay or sandy loam to also assess the effect of soil type on phytochemical content. Application rates were based around recommended N and S applications for this crop in south-east Australia. N applications over 30 kg/ha caused a decrease in the content of glucoraphanin (18–34%) and both flavonols (20–38%). Progoitrin content was not affected while glucobrassicin increased by up to 44% with N applications >30 kg/ha. S applications of 50 or 100 kg/ha had no significant effect on either glucosinolates or flavonols. Crop yield (fresh weight), however, was significantly depressed (up to 40%) by N applications below 60 kg/ha. Fresh weight was also significantly depressed in plants grown in heavy clay compared with plants grown in a sandy loam, and phytochemical content increased, possibly due to a concentration effect. Therefore, low N applications to optimise phytochemicals may be only commercially useful if growers are producing mini-broccoli heads, as levels required to optimise phytochemical content (<30 kg/ha) also caused a significant decline in yield.
29
Berger, J. D., K. H. M. Siddique e S. P. Loss. "Cool season grain legumes for Mediterranean environments: species × environment interaction in seed quality traits and anti-nutritional factors in the genus Vicia". Australian Journal of Agricultural Research 50, n. 3 (1999): 389. http://dx.doi.org/10.1071/a98098.
Testo completoAbstract (sommario):
Seed size and protein, sulfur (S), total phenolics, condensed tannins, and proteinase inhibitor concentrations were measured in 4 Vicia species (V. faba, V. sativa, V. ervilia, V. narbonensis) grown at up to 30 locations in the south-west of Western Australia. There was a species × environment interaction for all seed traits, and this was reflected in the relationships with environmental parameters and other seed traits within each species. For V. faba, it was difficult to account for the production of seed quality traits or antinutritional factors on the basis of descriptive environmental parameters such as climate or edaphic characteristics. The remaining species were more responsive to environmental factors measured throughout the study. Seed size was negatively associated with soil salinity in V. narbonensis and V. ervilia. Seed protein content was positively correlated with soil total nitrogen (N) and phosphorus (P) in V. sativa and V. ervilia, and also with electrical conductivity, pH, and exchangeable cations in V. ervilia. The S content of V. narbonensis seeds increased with increasing soil S availability, while the opposite occurred in V. ervilia and V. sativa. Total phenolics were positively associated with total N and P in V. sativa, and negatively correlated with soil clay content, S, and salinity in V. ervilia. Proteinase inhibitors in V. sativa were positively associated with soil salinity, while the opposite was the case in V. ervilia. Proteinase inhibitors in V. ervilia were also negatively correlated with pH, clay content, total N, and exchangeable cations, whereas the total N and exchangeable cations were associated with increasing proteinase inhibitors in V. narbonensis. These complex and contrasting relationships between antinutritional factors and environmental parameters suggest that the carbon: nutrient balance hypothesis, the pre-eminent paradigm used to predict plant resource allocation to N and C based defence, may not be applicable to the seeds of legumes. The agricultural significance of the species ´ environment interaction above depends on the seed characteristic in question. Increased S uptake by V. narbonensis relative to V. ervilia and V. sativa may advantage this species as a fodder crop, given that these species are targeted at alkaline, fine-textured soils where soil S availability is likely to be relatively high. However, in the seed of V. narbonensis and V. sativa, fluctuating concentrations of polyphenolics and condensed tannins occasionally reach the relatively high levels recorded in V. faba, and other anti-nutritional factors not withstanding, this may limit their palatability to monogastrics.
30
Conyers, M. K., J. E. Holland, B. Haskins, R. Whitworth, G. J. Poile, A. Oates, V. van der Rijt e E. Tavakkoli. "Sulfur and nitrogen responses by barley and wheat on a sandy soil in a semi-arid environment". Crop and Pasture Science 71, n. 10 (2020): 894. http://dx.doi.org/10.1071/cp20280.
Testo completoAbstract (sommario):
Soil testing guidelines for sulfur (S) under dryland cropping in south-eastern Australia are not well developed. Our objective was to assess the value of soil and tissue tests for S and nitrogen (N), because the two minerals frequently interact), in predicting S-deficient sites and hence increasing the probability of response to application of S (and N). Here, we report three proximal experiments in 2014–16 for barley (Hordeum vulgare L.) and wheat (Triticum aestivum L.) on a sandy soil in a semi-arid environment near Merriwagga in western New South Wales. The trials contained a factorial combination of four rates of each of applied N as urea and S as high-grade gypsum. Responses to S were obtained for dry matter (DM) quantity and nutrient content at flowering in 2014, but no grain-yield response was obtained in any year. DM response to applied S was obtained when the concentration of S in the DM was increased from 0.08% in barley and 0.09% in wheat without S application to 0.10–0.11% in both crops with S applied as gypsum. Because we obtained no grain-yield responses to applied S, the 0.10% S in grain was likely to have been adequate for both crops in these experiments. A pool of subsoil S was accessed during each season and this compensated for any DM deficiencies of S by the time of grainfill. Shallow soil tests (0–10 cm) for S can therefore indicate sufficiency but not necessarily deficiency; therefore, in grain-cropping areas, we recommend soil S tests on the same samples as used for deep N testing (to 60 cm) and that an S-budgeting approach be used following the soil tests. Furthermore, for marginal nutritional circumstances such as occurred in this study, the supporting use of N:S ratio is recommended, with values >17 in DM or grain likely to indicate S deficiency for both barley and wheat.
31
O'Neill, C. J., E. Humphreys, J. Louis e A. Katupitiya. "Maize productivity in southern New South Wales under furrow and pressurised irrigation". Australian Journal of Experimental Agriculture 48, n. 3 (2008): 285. http://dx.doi.org/10.1071/ea06093.
Testo completoAbstract (sommario):
Irrigation farmers in the Murray–Darling Basin of Australia are under considerable pressure to reduce the amount of water they use for irrigation, while sustaining production and profitability. Changing from surface to pressurised irrigation systems may provide some or all of these outcomes; however, little is known about the performance of alternative irrigation methods for broadacre annual crops in this region. Therefore, a demonstration site for comparing furrow, subsurface drip and sprinkler irrigation was established on a representative clay soil in the Coleambally Irrigation Area, NSW. The performance of maize (Zea mays L.) under the three irrigation systems was compared during the 2004–05 season. Subsurface drip irrigated maize out-performed sprinkler and furrow irrigated maize in terms of grain yield (drip 11.8 t/ha, sprinkler 10.5 t/ha, furrow 10.1 t/ha at 14% moisture), net irrigation water application (drip 5.1 ML/ha, sprinkler 6.2 ML/ha, furrow 5.3 ML/ha), net irrigation water productivity (drip 2.3 t/ML, sprinkler 1.7 t/ML, furrow 1.9 t/ML) and total water productivity (drip 1.7 t/ML, sprinkler 1.4 t/ML, furrow 1.3 t/ML). Thus, subsurface drip irrigation saved ~30% of the total amount of water (irrigation, rain, soil water) needed to produce the same quantity of grain using furrow irrigation, while sprinkler irrigation saved ~8% of the water used. The higher net irrigation with sprinkler irrigation was largely due to the lower soil water content in the sprinkler block at the time of sowing. An EM31 survey indicated considerable spatial soil variability within each irrigation block, and all irrigation systems had spatially variable water distribution. Yield variability was very high within all irrigation systems, and appeared to be more strongly associated with irrigation variability than soil variability. All irrigation blocks had large patches of early senescence and poor cob fill, which appeared to be due to nitrogen and/or water deficit stress. We expect that crop performance under all irrigation systems can be improved by improving irrigation, soil and N management.
32
Beecher, HG, JA Thompson, PE Bacon e BW Dunn. "Soil nitrogen supply to rice: crop sequence effects". Australian Journal of Experimental Agriculture 34, n. 7 (1994): 987. http://dx.doi.org/10.1071/ea9940987.
Testo completoAbstract (sommario):
The effect of cropping sequence on soil nitrogen (N) supply to a rice crop was investigated using an in situ incubation technique in a direct drill system on a red-brown earth soil in south-eastern Australia. The crop sequences were (i) a rice crop in each of the previous 4 summers, (ii) rice then 4 seasons of annual pasture (long pasture phase), (iii) rice, 2 winter cereal crops then 2 seasons of annual pasture (short pasture phase), and (iv) rice then 4 winter cereal crops. This study was undertaken in the fifth year of the crop sequence experiment, when all sequences had returned to rice. Within the rice crop, fertilised (160 kg N/ha) and unfertilised plots were established on the burnt stubble portion of the main crop sequence plots. Nitrogen uptake in unfertilised plots ranged from 79 kg N/ha in continuously cropped rice treatments to 165 kg N/ha in short pasture phase treatments. Application of 160 kg N/ha at permanent flood increased N uptake to 207 kg N/ha for the short pasture treatment. Crop biomass and tillering varied with cropping sequence and increased with fertiliser nitrogen application. Crop sequence had little effect on soil mineral N content during the growing season. However, total soil N mineralisation during the season varied with both crop sequence and fertiliser application. The continuous rice sequence mineralised 119 kg N/ha, whilst the long pasture phase sequence mineralised 246 kg N/ha. Fertiliser application increased mineralised N to 267 and 337 kg N/ha for continuous rice and short pasture phase treatments, respectively. Nitrogen mineralisation rate peaked (4 kg N/ha.day) some 40-50 days after permanent flood, coinciding with panicle initiation and the period of high N demand in the rice crop. Increased N availability after panicle initiation resulted in significantly higher grain yields. This work demonstrates that both the magnitude and timing of N supply affects the grain yield of the rice crop. Nitrogen supply is affected by the previous crop sequences. Practical implications are that pasture phase length of highly clover-dominant pastures could be reduced (from 4 to 2 years) and still provide similar contributions of N to succeeding rice crops; that continuous rice growing might achieve high yields similar to rice in rotation with legume pastures with the judicious application of fertiliser N; and that these N fertiliser applications may have to be quite high to achieve grain yields similar to rice in rotation with legume pastures.
33
Holford, I. C. R. "Soil phosphorus: its measurement, and its uptake by plants". Soil Research 35, n. 2 (1997): 227. http://dx.doi.org/10.1071/s96047.
Testo completoAbstract (sommario):
Phosphorus (P) is the most important nutrient element (after nitrogen) limiting agricultural production in most regions of the world. It is extremely chemically reactive, and more than 170 phosphate minerals have been identified. In all its natural forms, including organic forms, P is very stable or insoluble, and only a very small proportion exists in the soil solution at any one time. Plant-available P may be considered in either its quantitative or intensive dimension. The quantity of available P is time-specific and crop-specific, because it is the amount of P that will come into the soil solution and be taken up by the crop during its life cycle. The intensity of available P (availability) is most easily identified with its concentration in the soil solution. The soil property controlling the relationship between the solid phase P and its concentration in solution is known as the buffering capacity. The solid phase P involved in this relationship is only a small proportion of the total P, and is known as labile P. It is usually measured by isotopic exchange, but this exchangeable P component does not include the sparingly soluble compounds that also replenish the soil solution as its concentration is depleted by plant uptake. The buffering capacity is the ability of the soil solution to resist a change in its P concentration as P is removed by plant uptake or added in fertilisers or organic materials. Buffering capacity is synonymous with sorptivity, which is a preferable term in the context of the reactivity of P fertiliser with soil. It is usually measured from an adsorption isotherm. By fitting a suitable equation, such as the Langmuir, the total sorption capacity as well as the sorption strength can be determined. Both parameters are important in understanding P availability in soils. Buffering capacity has a major effect on the uptake of labile P because it is inversely related to the ease of desorption of solid phase P and its diffusion. Available P therefore is a direct function of the quantity of labile P and an inverse function of buffering capacity. This has been demonstrated in plant uptake studies. Similarly, the most effective methods of measuring available P (soil tests) are those which remove a proportion of labile P that is inversely related to buffer capacity. Soil tests which measure the concentration of P in solution actually measure availability rather than available P, and their efficacy on a range of soils will depend on the uniformity of the soils" buffer capacities. The most effective soil test usually consists of an anionic extractant. Acidic lactate or fluoride have been found most effective in New South Wales, on a wide range of soils, except calcareous soils which neutralise the acidic component (usually hydrochloric or acetic acid) of the extractant. Sodium bicarbonate (pH 8 · 5) has been found effective on calcareous soils and is widely used throughout the world. It has proved unreliable on NSW soils, and may need more thorough evaluation on non-calcareous soils in other parts of Australia.
34
Thomas, G. A., R. C. Dalal, E. J. Weston, K. J. Lehane, A. J. King, D. N. Orange, C. J. Holmes e G. B. Wildermuth. "Pasture - crop rotations for sustainable production in a wheat and sheep-based farming system on a Vertosol in south-west Queensland, Australia". Animal Production Science 49, n. 8 (2009): 682. http://dx.doi.org/10.1071/ea07170.
Testo completoAbstract (sommario):
Rainfed grain production, based on winter cereals, is marginal in south-west Queensland, Australia, because of low and variable rainfall and high evapotranspiration. Also, grain yield and grain quality have decreased as soil fertility, particularly soil nitrogen supply, has declined on older cropping lands. An option for improving soil N supply is to include legume-based pastures in rotation with winter cereals. The objective of this study was to determine the effects of short-term (18 months) legume pastures (annual medics and lucerne + annual medics), and longer term (3 years) mixed grass (Bambatsi panic) and legume (lucerne + annual medics) pasture phases on sheep production and on soil water and N supply and production of subsequent wheat crops on a grey Vertosol soil. Two separate phases of annual medics and lucerne + annual medics pastures produced mean total aboveground dry matter yield of 7.10 t/ha of annual medics and 5.80 t/ha of lucerne + annual medics over the 18-month periods. For two phases of the grass + legume pastures, mean total aboveground dry matter yield was 3.95 t/ha for grass and 8.19 t/ha for legume over 3 years. Over an 18-month period, sheep bodyweight gains and fleece weights were similar for the annual medics, lucerne + annual medics and grass + legume pastures and were approximately five times greater than those from native pasture as a result of the greater stocking rate possible on the sown pastures. Greater drying of the soil profile occurred following lucerne + annual medics and grass + legume pasture phases than continuous wheat, resulting in lower soil water content at sowing of wheat crops following these pasture phases on several occasions. Mean soil nitrate-N benefits before wheat sowing in the first year following termination of the 18-month annual medics, lucerne + annual medics, and the 3-year grass + legume pasture phases were 45, 44 and 42 kg N/ha, respectively. Grain N yields and gross margins of the first wheat crops following the 18-month annual medics, lucerne + annual medics, and the 3-year grass + legume pasture phases were similar in value to continuous wheat with ~60, 80, and 40–60 kg N/ha fertiliser applied at sowing, respectively. Improvements in grain N yield and gross margin were still evident in the fifth wheat crop following annual medics and lucerne + annual medics pastures and in the third wheat crop following grass + legume pasture, compared with continuous wheat without N fertiliser addition. Total gross margins from 1996 to 2005 were 1.6–2.5 times greater for the pasture–crop rotations than continuous wheat where no N fertiliser was applied to wheat. However, gross margins were greater in continuous wheat than in pasture–crop rotations where N fertiliser was applied to target prime hard grade grain protein in wheat. The 3-year grass + legume pasture phase showed potential to improve surface soil structure and water infiltration and to reduce decline in soil organic carbon concentration at 0–0.1 m depth, compared with continuous wheat cropping and shorter-term legume pasture phases.
35
Silsbury, JH. "Grain yield of wheat in rotation with pea, vetch or medic grown with three systems of management". Australian Journal of Experimental Agriculture 30, n. 5 (1990): 645. http://dx.doi.org/10.1071/ea9900645.
Testo completoAbstract (sommario):
Pea (Pisum sativum L. cv. Alma), vetch (Vicia sativa L. cv. Languedoc) and annual medic (Medicago truncatula Gaertn. cv. Paraggio) were grown at Brinkworth, South Australia, in 1987 in large (0.75 ha) plots and subjected to 3 systems of management: (i) ploughing in at flowering as a green manure crop, (ii) harvesting for grain and ploughing in the dry residues, and (iii) harvesting for grain and removing the residues. A wheat crop was sown over the whole area in the following season (1988) and the effects of type of legume and management on grain yield and grain protein content were measured. The management system imposed on the legume had a highly significant (P<0.01) effect on the grain yield of the following wheat crop, but there were no significant differences between the 3 legumes in their effects on wheat yield or on grain protein content. Ploughing in the legumes as a green manure crop at flowering added about 100 kg/ha more nitrogen (N) to the soil than allowing the legumes to mature, harvesting for seed, and removing residues. Incorporating the dry residues rather than removing them added about 26 kg N/ha. The green manure crop significantly increased subsequent wheat yield (by 49%; P<0.001) and protein content of the grain (by 13%; P<0.05) compared with the treatment in which the legumes were harvested for grain and all residues removed; incorporating the dry residues increased yield by 10%. It is concluded that the amount of N added during the legume phase in a rotation is more important than the kind of legume from which the N is derived. The occasional use of a dense legume crop as a green manure may rapidly add a large amount of N to a soil to be slowly exploited by following grain crops.
36
Dong, Ning, Iain Colin Prentice, Bradley J. Evans, Stefan Caddy-Retalic, Andrew J. Lowe e Ian J. Wright. "Leaf nitrogen from first principles: field evidence for adaptive variation with climate". Biogeosciences 14, n. 2 (30 gennaio 2017): 481–95. http://dx.doi.org/10.5194/bg-14-481-2017.
Testo completoAbstract (sommario):
Abstract. Nitrogen content per unit leaf area (Narea) is a key variable in plant functional ecology and biogeochemistry. Narea comprises a structural component, which scales with leaf mass per area (LMA), and a metabolic component, which scales with Rubisco capacity. The co-ordination hypothesis, as implemented in LPJ and related global vegetation models, predicts that Rubisco capacity should be directly proportional to irradiance but should decrease with increases in ci : ca and temperature because the amount of Rubisco required to achieve a given assimilation rate declines with increases in both. We tested these predictions using LMA, leaf δ13C, and leaf N measurements on complete species assemblages sampled at sites on a north–south transect from tropical to temperate Australia. Partial effects of mean canopy irradiance, mean annual temperature, and ci : ca (from δ13C) on Narea were all significant and their directions and magnitudes were in line with predictions. Over 80 % of the variance in community-mean (ln) Narea was accounted for by these predictors plus LMA. Moreover, Narea could be decomposed into two components, one proportional to LMA (slightly steeper in N-fixers), and the other to Rubisco capacity as predicted by the co-ordination hypothesis. Trait gradient analysis revealed ci : ca to be perfectly plastic, while species turnover contributed about half the variation in LMA and Narea. Interest has surged in methods to predict continuous leaf-trait variation from environmental factors, in order to improve ecosystem models. Coupled carbon–nitrogen models require a method to predict Narea that is more realistic than the widespread assumptions that Narea is proportional to photosynthetic capacity, and/or that Narea (and photosynthetic capacity) are determined by N supply from the soil. Our results indicate that Narea has a useful degree of predictability, from a combination of LMA and ci : ca – themselves in part environmentally determined – with Rubisco activity, as predicted from local growing conditions. This finding is consistent with a plant-centred approach to modelling, emphasizing the adaptive regulation of traits. Models that account for biodiversity will also need to partition community-level trait variation into components due to phenotypic plasticity and/or genotypic differentiation within species vs. progressive species replacement, along environmental gradients. Our analysis suggests that variation in Narea is about evenly split between these two modes.
37
Maier, NA, GE Barth, MN Bartetzko, JS Cecil e WL Chvyl. "Nitrogen and potassium nutrition of Australian waxflowers grown in siliceous sands. 1. Stem growth and yield responses". Australian Journal of Experimental Agriculture 36, n. 3 (1996): 355. http://dx.doi.org/10.1071/ea9960355.
Testo completoAbstract (sommario):
The effects of nitrogen (N) and potassium (K) on stem growth and yield responses of Australian waxflowers were investigated. Experiments were conducted in commercial plantings at 3 sites in South Australia. Plantings of Chamelaucium uncinatum cvv. Alba (2 sites) and Purple Pride (1 site) and a Chamelaucium hybrid (C. floriferum x C. uncinatum), known locally as Walpole wax (1 site), were 3-5 years old when the study began in 1990. Nitrogen and K were applied at rates up to 160 g N and 80 g K/plant.year. Application of N significantly (P<0.05) increased stem growth, with the magnitude varying considerably between sites and years. Increasing the rate of applied N from 0 to 80 or 160 g/plant.year increased mean tip-growth of flowering stems of cv. Alba by 47.7% at site 1 and 137.1% at site 3, and of Walpole wax by 144.2% at site 2. In contrast, the effect on cv. Purple Pride was minimal. Tip-growth also varied significantly (P<0.05) between sites. Applied K did not significantly affect stem growth at any site. Application of N significantly (P<0.05) increased the yield of 41-70 and >70 cm stems, and total stem yield at all sites with variation between years and cultivars. For example at site 2 increasing the applied N rate from 0 to 80 or 160 g/plant .year increased total stem yield by 13.9, 176.2 and 77.6% in 1991, 1992 and 1993, respectively. In contrast, the effect of applying K was inconsistent. Application of N significantly increased the weight of prunings at all sites and yield of prunings also varied between years. Applied K significantly affected the yield of prunings at site 3, where application of 80 compared with 0 g1plant.year decreased the yield by 17.9%. For all sites, the mean ratios between total stem weight and total biomass harvested were in the range 0.68-0.82. The effect of applied N was only significant at site 3, where the ratio decreased from 0.76 to 0.57 when the rate of applied N increased from 0 to 160 g/plant.year. The effect of K was not significant at any site. At sites 1 and 2, and for cv. Alba at site 3, application of 80 or 160 g N1plant.year decreased mean stem dry matter by 8.0, 9.3 and 11.0%, respectively. Stem dry matter content also varied significantly between years at all sites. The effect of applied K was only significant at site 3, where application of 80 g1plant.year reduced dry matter content by 5.3% compared with 34.2% for the nil rate. Based on data for all sites, stem fractionation showed that dry matter yields (as a percentage of total stem dry weight), were in the order, woody tissue (3 15-49.9%) > leaves (22.1-29.2%) > flowers (15.9-25.8%) > tip-growth (5.0-21.9%). The effect of applied K on the yield of the different stem parts was only significant (P<0.05) at site 1, where in 1991 yield of the tip-growth fraction decreased. We conclude that to develop effective N fertiliser strategies for waxflowers requires knowledge of (i) soil type, in particular residual N fertility; (ii) annual vegetative growth cycle (i.e. periods of growth flushing); (iii) harvest period; and (iv) flowering time. For cultivars or hybrids harvested when vegetative growth is negligible (e.g. winter) N nutrition can be optimised, while for those harvested during periods of vegetative flushing (e.g. September-November) lower rates of N should be applied to ensure tip-growth is not excessive. Although yield responses to applied K were inconsistent, we recommend 20 g K/plant.year to ensure that productivity is maintained over the 5-10 years flowering stems can be harvested from commercial plantings.
38
Kemp, D. R., D. L. Michalk e J. M. Virgona. "Towards more sustainable pastures: lessons learnt". Australian Journal of Experimental Agriculture 40, n. 2 (2000): 343. http://dx.doi.org/10.1071/ea99001.
Testo completoAbstract (sommario):
The Temperate Pasture Sustainability Key Program (TPSKP) was established across south-eastern Australia to test the hypotheses that an improved perennial grass content in pastures would result in fewer weeds, better water use (and hence lesser impacts on soil salinity), and lower soil acidification rates. Grazing tactics were seen as a means to enhance or maintain the perennial grass content. Soil and water sustainability experiments in summer and winter dominant rainfall environments showed fewer weeds, improvements in water use and less acidity under perennial versus annual grass pastures. Further work is needed to determine if these gains are sufficient to make perennial grass pastures sustainable in the long-term as some nitrate leakage still occurred at the winter rainfall site. Indicators were developed to rate the sustainability of treatments within experiments. A subset of these indicators was common across experiments and could readily be used by farmers to provide an initial assessment of the soil and water sustainability of their pasture systems. These are: the mineral nitrogen at the bottom of the root zone (40–60 cm); soil pH at the surface and bottom of the root zone and perennial grass content by species. Managing pastures through droughts is a critical aspect of grazing management in Australia. Experiments within the TPSKP demonstrated that perennial grasses survived during drought when maintained above critical lower biomass values. These values ranged from 0.5 to 1.5 t DM/ha depending upon species. Over all experiments, there was general support for the view that maintaining a higher level of biomass in pastures resulted in more sustainable systems. Twenty-three grazing experiments using an open communal grazing design showed that most perennial grasses were sensitive to grazing at some stage in their seasonal growth cycles. The exceptions were inconclusive for several reasons e.g. the grazing pressure may not have been high enough at those sites to elucidate any effects; they occurred where the perennial grass content was less than 10% or exceeded 70%, of the sward; or were confounded by interactions between species where the species under study was not dominant. After taking these exceptions into account, it was then possible to determine where grazing tactics could be expected to work. Species differed in their response to grazing. Some perennial grasses were more sensitive to grazing during periods of stress (e.g. dry summers) than when actively growing (e.g. cocksfoot), while the reverse applied with others (e.g. phalaris). Of the grasses sensitive to grazing when actively growing, sensitivity of some was largely confined to the reproductive period (e.g. perennial ryegrass). Across most experiments, continuous grazing resulted in either a decline in or no net benefit to, the perennial grass content. Microlaena stipoides was the only species to respond to increased grazing pressure — this only applied in spring. The experiments clearly showed that tactical rests were an important tool for grassland management. The effects recorded were predominantly expressed through impacts on vegetative growth and survival of existing plants. Short-term experiments and dry seasons did not enable recruitment processes to be studied. Within pastures, grazing tactics can influence many species. The challenge is to use the TPSKP outcomes to develop strategies that optimise the composition of these swards. Due to the short-term nature of these experiments the results were evaluated within a conservative framework and often simply on the absolute level of parameters. Techniques need to be developed to more effectively monitor the process (i.e. rates of change), rather than the consequences (i.e. ends). The information gained in this program needs to be incorporated into practical strategies for better management of pastures and tested at a commercial scale. The TPSKP was one of the largest, coordinated pasture programs ever attempted. Some major outcomes were the experience gained by a large number of grassland scientists in running such programs, the development and acceptance of standardised measurement protocols and a much stronger network among grazing systems scientists committed to achieving improved management systems.
39
Gupta, V. V. S. R., S. J. Kroker, M. Hicks, C. W. Davoren, K. Descheemaeker e R. Llewellyn. "Nitrogen cycling in summer active perennial grass systems in South Australia: non-symbiotic nitrogen fixation". Crop and Pasture Science 65, n. 10 (2014): 1044. http://dx.doi.org/10.1071/cp14109.
Testo completoAbstract (sommario):
Non-symbiotic nitrogen (N2) fixation by diazotrophic bacteria is a potential source for biological N inputs in non-leguminous crops and pastures. Perennial grasses generally add larger quantities of above- and belowground plant residues to soil, and so can support higher levels of soil biological activity than annual crops. In this study, the hypothesis is tested that summer-active perennial grasses can provide suitable microsites with the required carbon supply for N2 fixation by diazotrophs, in particular during summer, through their rhizosphere contribution. In a field experiment on a Calcarosol at Karoonda, South Australia, during summer 2011, we measured populations of N2-fixing bacteria by nifH-PCR quantification and the amount of 15N2 fixed in the rhizosphere and roots of summer-active perennial grasses. Diazotrophic N2 fixation estimates for the grass roots ranged between 0.92 and 2.35 mg 15N kg–1 root day–1. Potential rates of N2 fixation for the rhizosphere soils were 0.84–1.4 mg 15N kg–1 soil day–1 whereas the amount of N2 fixation in the bulk soil was 0.1–0.58 mg 15N kg–1 soil day–1. Populations of diazotrophic bacteria in the grass rhizosphere soils (2.45 × 106 nifH gene copies g–1 soil) were similar to populations in the roots (2.20 × 106 nifH gene copies g–1 roots) but the diversity of diazotrophic bacteria was significantly higher in the rhizosphere than the roots. Different grass species promoted the abundance of specific members of the nifH community, suggesting a plant-based selection from the rhizosphere microbial community. The results show that rhizosphere and root environments of summer-active perennial grasses support significant amounts of non-symbiotic N2 fixation during summer compared with cropping soils, thus contributing to biological N inputs into the soil N cycle. Some pasture species also maintained N2 fixation in October (spring), when the grasses were dormant, similar to that found in soils under a cereal crop. Surface soils in the rainfed cropping regions of southern Australia are generally low in soil organic matter and thus have lower N-supply capacity. The greater volume of rhizosphere soil under perennial grasses and carbon inputs belowground can potentially change the balance between N immobilisation and mineralisation processes in the surface soils in favour of immobilisation, which in turn contributes to reduced N losses from leaching.
40
Gardner, WK, RG Fawcett, GR Steed, JE Pratley, DM Whitfield, Hvan Rees e Rees H. Van. "Crop production on duplex soils in south-eastern Australia". Australian Journal of Experimental Agriculture 32, n. 7 (1992): 915. http://dx.doi.org/10.1071/ea9920915.
Testo completoAbstract (sommario):
The environment, duplex soil types and trends in crop production in South Australia, southern New South Wales, north-eastern and north-central Victoria, the southern Wimmera and the Victorian Western District are reviewed. In the latter 2 regions, pastoral industries dominate and crop production is curtailed by regular and severe soil waterlogging, except for limited areas of lower rainfall. Subsurface drainage can eliminate waterlogging, but is feasible only for the Western District where subsoils are sufficiently stable. The other regions all have a long history of soil degradation due to cropping practices, but these effects can now be minimised with the use of direct drilling and stubble retention cropping methods. A vigorous pasture ley phase is still considered necessary to maintain nitrogen levels and to restore soil structure to adequate levels for sustainable farming. Future productivity improvements will require increased root growth in the subsoils. Deep ripping, 'slotting' of gypsum, and crop species capable of opening up subsoils are techniques which may hold promise in this regard. The inclusion of lucerne, a perennial species, in annual pastures and intercropping at intervals is a technique being pioneered in north-central and western Victoria and may provide the best opportunity to crop duplex soils successfully without associated land degradation.
41
Chittleborough, D. J., J. W. Cox e D. P. Stevens. "Pathways of phosphorus, nitrogen, and carbon movement over and through texturally differentiated soils, South Australia". Soil Research 37, n. 4 (1999): 679. http://dx.doi.org/10.1071/sr98082.
Testo completoAbstract (sommario):
One method for preventing the degradation of water supplies through contamination with phosphorus (P), nitrate (NO3), and dissolved organic carbon (DOC) is to restrict movement of these contaminants from the catchment into water bodies. The purpose of the study was to quantify and characterise the proportion of NO3, P, and DOC moving from duplex soils by overland flow and through-flow on a sub-catchment scale, and to characterise soil properties that influence their movement. Two sites in the Adelaide Hills (South Australia) with contrasting duplex soils were instrumented to collect overland flow and through-flow from the soils A and B horizon. Each site contained 2 sub-catchments in close proximity. Sub-catchments were well defined by the natural topography sloping from hillcrest to a stream headwater. Soil type, especially the degree of texture contrast, the macroporosity, and the proportion of clay in the B horizon, had a large influence on the pathways of water, and therefore P, DOC, and NO3 movement. Environmentally significant concentrations of P (>0�1 mg/L) and NO3-N (>0�5 mg/L) moved overland and through these soils in 1997. High DOC loads (25 mg/L), which would also impact on water treatment costs, moved through some soils. Significant loading of P moved through and over soils in both dissolved (0�5 mg/L) and particulate (0�3 mg/L) forms. Consequently, through-flow cannot be ignored as a contributor to P in streams and both dissolved and particulate P must be measured under these conditions to define the full impact of P. The findings from this research have implications for research on catchment management to restrict DOC and nutrient movement into waterways.
42
Holland, Jonathan E., e Asim Biswas. "Predicting the mobile water content of vineyard soils in New South Wales, Australia". Agricultural Water Management 148 (gennaio 2015): 34–42. http://dx.doi.org/10.1016/j.agwat.2014.09.018.
Testo completo
43
Xu, ZH, JN Ladd e DE Elliott. "Soil nitrogen availability in the cereal zone of South Australia .1. Soil organic carbon, total nitrogen, and nitrogen mineralisation rates". Soil Research 34, n. 6 (1996): 937. http://dx.doi.org/10.1071/sr9960937.
Testo completoAbstract (sommario):
Assessments of soil nitrogen (N) availability were undertaken using soils sampled at 0-10 and 10-20 cm depths from 123 experimental sites where the responses of cereal crops to N fertilisers were tested, throughout the cereal zone of South Australia. Rates of N mineralisation and percentage N mineralisation, as determined by a laboratory aerobic incubation method, were related to soil properties. Mineralisable N (N mineralised during a Li-week incubation) of 0-10 cm soil varied from 14 to 121 kg N/ha with a median of 50 kg N/ha, and that of 10-20 cm soil, from 5 to 42 kg N/ha (median 19 kg N/ha). Mineralisable N in 0-10 cm soil accounted for 90% of total mineralisable N in 0-20 cm soil. The percentages of N mineralised were generally higher in 0-10 cm soil (0.8-12.5%, median 3.4%) than in 10-20 cm soil (0.4-8.3%, median 2.3%). Soil organic carbon (OC) and total N could be well estimated from each other, and fron! soil pH, bulk density, and held capacity, with coefficients of determination (R2) ranging from 0.64 to 0.78. Overall, either mineralisable N or percentage N mineralisation rate in the surface soils could be well estimated from soil OC, total N, C to N ratio, bulk density, field capacity, and pH (R2, 0.78-0.86 for mineralisable N, and 0.67-0.91 for percentage N mineralisation rate).
44
Norton, R. M., e N. G. Wachsmann. "Nitrogen use and crop type affect the water use of annual crops in south-eastern Australia". Australian Journal of Agricultural Research 57, n. 3 (2006): 257. http://dx.doi.org/10.1071/ar05056.
Testo completoAbstract (sommario):
The effect of management and crop selection on water use and profile drying was investigated using 2 series of experiments conducted in the Victorian Wimmera. The effect of applied nitrogen on growth and water use of canola was assessed from 3 field experiments on a Vertosol soil. Across these sites, 140 kg N/ha increased crop water use by a mean of 30 mm, and the biological response averaged 3.68 t/ha of shoot dry matter and seed yield increased by 73% from 1.46 to 2.52 t/ha. The additional nitrogen enabled roots to go deeper into the soil and also to extract water to higher tensions, but the increases in water use were far less than the growth and yield responses. Estimated average soil evaporation was 120 mm across these experiments, but ranged from 26 to 57% of total water use. It was concluded that increased crop vigour in response to applied nitrogen does increase total water use, but the main way that water-use efficiency increases is through reduced soil evaporation. In a second series of experiments, the growth, yield, and water use of wheat, canola, linseed, mustard, and safflower were compared across 4 sites with differing soil moisture contents. Wheat was the highest yielding crop at all sites. Mustard and canola produced similar amounts of biomass and seed yields, whereas linseed produced seed yields that were generally less than the brassica oilseeds. Safflower grew well and produced large amounts of biomass at all sites, but this increased growth did not necessarily translate into increased seed yields. Safflower yielded less seed than all other crops at the 2 dry sites, but yields were similar to canola at the wetter sites. On 2 drier sites, soil water extraction occurred to approximately 1 m for all crops, and all available water was used within that zone by all crops. Where the soil was wet beyond 1 m, safflower was able to extract water from deeper in the profile than the other crops and generated a soil water deficit of about 100 mm more than the other crops at maturity. This deficit persisted into the subsequent autumn–winter period. The potential of using safflower as a management option to extract water from deep in the profile, and so create a soil buffer, is discussed.
45
Banu, Nargis A., Balwant Singh e Les Copeland. "Microbial biomass and microbial biodiversity in some soils from New South Wales, Australia". Soil Research 42, n. 7 (2004): 777. http://dx.doi.org/10.1071/sr03132.
Testo completoAbstract (sommario):
Eight surface soils (0–15 cm) including 1 Ferrosol, 2 Tenosols, 2 Kurosols, 1 Sodosol, 1 Chromosol, and 1 Kandosol were collected from mainly pasture sites in New South Wales. The soils had different physico-chemical properties and there were some differences between the sites in climatic conditions. Soil microbial biomass carbon (MBC) was estimated by the chloroform-fumigation extraction method, and substrate utilisation patterns determined by the Biolog method were used to assess the amount, functional diversity, substrate richness and evenness, and community structure of the microorganisms in these soils. The amount of MBC (585 µg C/g) and the microbial diversity (H´ = 3.24) were high in soils that had high clay (33%), organic C (5.96%), total N (0.45%), free iron (7.06%), moisture content (50%), and cation exchange capacitiy (133.5 mmolc/kg). These soil properties, e.g. soil moisture (r2 = 0.72), organic C (r2 = 0.58), total N (r2 = 0.63), free iron (r2 = 0.44), and EC (r2 = 0.53), were positively correlated with MBC and microbial diversity index, whereas pH and sand and silt content showed negative correlations. The climatic factors (temperature and rainfall) had no significant influence on either MBC or diversity.
46
Valentine, S., P. Lewis, R. T. Cowan e J. DeFaveri. "The effects of high stocking rates on milk production from dryland and irrigated Mediterranean pastures". Animal Production Science 49, n. 2 (2009): 100. http://dx.doi.org/10.1071/ea07071.
Testo completoAbstract (sommario):
An experiment using herds of ~20 cows (farmlets) assessed the effects of high stocking rates on production and profitability of feeding systems based on dryland and irrigated perennial ryegrass-based pastures in a Mediterranean environment in South Australia over 4 years. A target level of milk production of 7000 L/cow.year was set, based on predicted intakes of 2.7 t DM/cow.year as concentrates, pasture intakes from 1.5 to 2.7 t/cow.year and purchased fodder. In years 1 and 2, up to 1.5 t DM/cow.year of purchased fodder was used and in years 3 and 4 the amounts were increased if necessary to enable levels of milk production per cow to be maintained at target levels. Cows in dryland farmlets calved in March to May inclusive and were stocked at 2.5, 2.9, 3.3, 3.6 and 4.1 cows/ha, while those in irrigated farmlets calved in August to October inclusive and were stocked at 4.1, 5.2, 6.3 and 7.4 cows/ha. In the first 2 years, when inputs of purchased fodder were limited, milk production per cow was reduced with higher stocking rates (P < 0.01), but in years 3 and 4 there were no differences. Mean production was 7149 kg/cow.year in years 1 and 2, and 8162 kg/cow.year in years 3 and 4. Production per hectare was very closely related to stocking rate in all years (P < 0.01), increasing from 18 to 34 t milk/ha.year for dryland farmlets (1300 to 2200 kg milk solids/ha) and from 30 to 60 t milk/ha.year for irrigated farmlets (2200 to 4100 kg milk solids/ha). Almost all of these increases were attributed to the increases in grain and purchased fodder inputs associated with the increases in stocking rate. Net pasture accumulation rates and pasture harvest were generally not altered with stocking rate, though as stocking rate increased there was a change to more of the pasture being grazed and less conserved in both dryland and irrigated farmlets. Total pasture harvest averaged ~8 and 14 t DM/ha.year for dryland and irrigated pastures, respectively. An exception was at the highest stocking rate under irrigation, where pugging during winter was associated with a 14% reduction in annual pasture growth. There were several indications that these high stocking rates may not be sustainable without substantial changes in management practice. There were large and positive nutrient balances and associated increases in soil mineral content (P < 0.01), especially for phosphorus and nitrate nitrogen, with both stocking rate and succeeding years. Levels under irrigation were considerably higher (up to 90 and 240 mg/kg of soil for nitrate nitrogen and phosphorus, respectively) than under dryland pastures (60 and 140 mg/kg, respectively). Soil organic carbon levels did not change with stocking rate, indicating a high level of utilisation of forage grown. Weed ingress was also high (to 22% DM) in all treatments and especially in heavily stocked irrigated pastures during winter. It was concluded the higher stocking rates used exceeded those that are feasible for Mediterranean pastures in this environment and upper levels of stocking are suggested to be 2.5 cows/ha for dryland pastures and 5.2 cows/ha for irrigated pastures. To sustain these suggested stocking rates will require further development of management practices to avoid large increases in soil minerals and weed invasion of pastures.
47
Hopmans, P., N. Collett e R. Bickford. "Effects of fire retardant on heathland soils in south-eastern Australia". Soil Research 45, n. 8 (2007): 607. http://dx.doi.org/10.1071/sr07040.
Testo completoAbstract (sommario):
A study was undertaken to assess the effects of fire retardant application, unmodified by heat of fire, on soil properties in 2 fire-prone heathland communities at Marlo and the Grampians in south-eastern Australia. Fire retardant (Phos-Chek D75-R at 0.144 g/L) was applied at rates of 0.5, 1.0, and 1.5 L/m2 and compared with control treatments of nil and 1.0 L/m2 of water. Monitoring of surface soils showed that pH at both sites decreased while soil salinity increased immediately after application followed by a rapid decline to pre-treatment values within 12 months. The impact of retardant on total carbon and nitrogen was minor and within the range of natural variation of C and N in surface soils at both sites. Levels of readily available or labile forms of N increased at both sites but declined rapidly to background values after 12 months. Applications of retardant progressively increased extractable P in the surface soil at Marlo, in contrast to the Grampians where a rapid increase was observed after two months followed by a decline after 12 months. These results showed a significant increase in labile P in the surface soil after 12 months and also indicated that a large proportion of the phosphate applied had leached into the subsoil. Likewise, fire retardant applied at the highest rate caused increases in labile sulfate after 2 months at both sites, followed by a rapid decline to background levels. It is expected that the elevated levels of soil phosphate in particular could have a long-term impacts on growth and composition of heathland vegetation known to be sensitive to elevated levels of phosphate in soil.
48
Evans, J. "An evaluation of potential Rhizobium inoculant strains used for pulse production in acidic soils of south-east Australia". Australian Journal of Experimental Agriculture 45, n. 3 (2005): 257. http://dx.doi.org/10.1071/ea03129.
Testo completoAbstract (sommario):
Profitability of the pulse industry relies considerably on crop nitrogen fixation because this process supplies greater than 60% of pulse crop nitrogen. Therefore the industry requires the most efficient Rhizobium symbioses and effective inoculation management. Re-appraisal of the recommended inoculant strain for field pea, SU303, in south-east Australia, was warranted by field evidence that SU303 failed to maximise grain yield at sites in Western Australia. Re-appraisal of the inoculant strain for faba bean and lentil, WSM1274, was warranted because of anecdotal evidence from Western Australia of associated crop failures. In addition, a glasshouse study in Western Australia reported greater dry matter production by faba bean and lentil inoculated with strains other than WSM1274. This paper reports trials comparing potential inoculant strains for field pea and faba bean in soils of south-east Australia. Comparisons are based on efficiency for nitrogen fixation, survival on seed and survival in soil. Additionally, because the pulse industry lacked comprehensive information to assist decision making on the need for recurring inoculation, relevant investigation of this issue is also reported. The results of 3 field experiments for efficiency for nitrogen fixation, over mildly (pHCa 5.0) to strongly (pHCa 4.3) acidic soil in south-east Australia supported replacing SU303 as the commercial inoculant. The efficiency for nitrogen fixation of WSM1274 on faba bean was not found to be inferior to alternative strains. However, its capacity for survival on seed at temperatures of 15°C and above, over a wide range of relative humidity, and perhaps its capacity for survival in acidic soil, was inferior. This provided additional evidence to justify the replacement of this inoculant strain that was agreed to by a national steering committee in 2001, based on the Western Australia reports, the early experiments in this study and those of a collaborative study in Victoria. Alternative inoculant strains to SU303 and WSM1274 were identified in the current study. Temperature and relative humidity conditions suitable for maintaining inoculant viability with extended storage of inoculated field pea and faba bean are also discussed. A survey of rhizobia surviving in soil was used to determine the time scale of persistence of Rhizobium leguminosarum bv. viciae and Bradyrhizobium sp. (Lupinus) in soils of the south-east. It was concluded that in soils of pH (CaCl2) <5.1, inoculation of field pea and faba bean should be routinely practiced; none of the strains of R. leguminosarum bv. viciae tested showed ability for survival in strongly acidic soil sufficient to obviate seed inoculation. It was further concluded that the absence of a legume host for lupin rhizobia for 4 or more years would also warrant reintroducing inoculant of B. sp. (Lupinus).
49
Paul, K. I., P. J. Polglase, A. M. O'Connell, J. C. Carlyle, P. J. Smethurst e P. K. Khanna. "Soil nitrogen availability predictor (SNAP): a simple model for predicting mineralisation of nitrogen in forest soils". Soil Research 40, n. 6 (2002): 1011. http://dx.doi.org/10.1071/sr01114.
Testo completoAbstract (sommario):
A new empirical model (SNAP) combines a simple laboratory measurement of the basal rate of N mineralisation with the modifying effects of daily temperature and water content to predict seasonal and annual rates of mineralisation of forest soils. Short-term (20-60-day) aerobic incubations of either undisturbed or bulked and mixed soil were found suitable for prediction of the basal rate of N mineralisation. Data from laboratory incubations of a range of soils were used to calibrate empirical relationships describing the effects of temperature (Tm) and water (Wm) on rates of N mineralisation. Submodels for predicting daily average temperature (STUF) and water content (SWUF) for up to 3 surface soil layers were developed and used to provide inputs to the Tm and Wm functions, respectively. Inputs required for SNAP are restricted to variables whose values are easily obtained. In addition to the amount of N mineralised during a short aerobic laboratory incubation, other soil properties required are bulk density, gravel and clay content, and upper and lower limits of soil water content. Climatic data required included daily air temperature, rainfall, and solar radiation. Other inputs are slope, leaf area index of the stand, and approximate mass and height of litter. Predicted rates of N mineralisation have been verified using data from 9 native forests, 12 radiata pine plantations, and 12 eucalypt plantations from across southern Australia. Despite the wide range of forest types, soil types, climatic regions, and management systems, predicted annual rates of N mineralisation were in close agreement with those observed in the field, regardless of whether daily soil temperature and water content were predicted (R2 = 0.76, P < 0.001, n�=�127) or observed (R2 = 0.78, P < 0.001, n = 68). Sensitivity analysis showed that it was most important to minimise analytical error in inputs used to calculate the basal rate of N mineralisation (i.e. soil temperature, water content, and N mineralised during laboratory incubation). The model was more sensitive to daily soil temperature than to daily soil water content.
50
Fillery, IR, e KJ McInnes. "Components of the fertiliser nitrogen balance for wheat production on duplex soils". Australian Journal of Experimental Agriculture 32, n. 7 (1992): 887. http://dx.doi.org/10.1071/ea9920887.
Testo completoAbstract (sommario):
In this paper, we review literature on the fate of fertiliser nitrogen (N) applied to duplex soils in wheat-growing regions of southern Australia, and discuss the contribution of specific N transformations to N loss. Duplex soils are characterised by the presence of soil material, within the rooting depth of crops, that possess hydraulic conductivities that are lower than those of overlying material. Denitrification and the transport of nitrate below rooting depth of crops are thought to be the chief causes of loss of fertiliser N and to contribute to poor grain yields. Ammonia volatilisation could contribute also to N loss. The fate of fertiliser N commonly applied to wheat in southern Australia has largely been evaluated using budgeting procedures using l5N, a stable isotope of N. Results from studies in south-eastem Australia, using red-brown earths, indicate that between 10 and 40% of applied 15N can be lost irrespective of time of application to wheat. Denitrification is believed to be the chief cause of loss of l5N. Similar studies on yellow duplex soils in Western Australia have shown fertiliser N loss to range from 70% to no loss of the l5N applied. The exact cause of N loss in Western Australian studies is unclear. There was circumstantial evidence for ammonia loss from surface-applied urea, and evidence of leaching of nitrates from this and other ammoniumbased fertilisers. The role of denitrification has not been clarified in Western Australian studies. In the majority of studies, recovery of 15N in aboveground biomass exceeded 40% of that applied. In addition, between 17 and 48% of applied 15N, of which 10-15% may be in root material, has been recovered in the soil organic matter pool. The predominance of the denitrification process in south-eastern Australian soils, and the inability to improve the efficiency of utilisation of 15N by delaying the time of application to wheat underscores the importance of controlling the nitrification process using inhibitors. Management options for Western Australian soils are less clear. Some agronomic experiments have demonstrated the advantage of delaying the application of fertiliser N to wheat to improve the efficiency of its utilisation. There is also evidence which suggests that N should be applied early in the growth cycle to promote tiller development and thereby increase the potential for grain yield.