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1
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.
2
Ewing, MA, AD Bathgate, RJ French e CK Revell. "The role of crop and pasture legumes in rotations on duplex soils". Australian Journal of Experimental Agriculture 32, n. 7 (1992): 971. http://dx.doi.org/10.1071/ea9920971.
Testo completoAbstract (sommario):
Duplex soils are prominent in southern Australia and are generally low in fertility. Their agricultural performance is, therefore, suboptimal in most circumstances without an exogenous source of nitrogen. This is often supplied by legumes which are grown in rotation with non-leguminous crops. Both crop and pasture legumes are now widely used in southern Australia and the contribution that they make to the non-legume phase of rotations is through nitrogen fixation and through other mechanisms such as cereal disease breaks. We use a mathematical programming model, MIDAS (Model of an Integrated Farming Dryland Agricultural System), to investigate the role of legumes in the low rainfall wheatbelt of Western Australia. The impact of legumes on farm profitability is assessed with a special focus on the contribution of legumes grown on a duplex soil. By using the model, the sensitivity of rotation choice on this duplex soil to changes in biological and economic parameters is explored. We conclude that crop legumes, in particular, have a firmly established role on sandy-surfaced duplex soils in low rainfall regions and that substantial increases in both the productivity and legume content of pasture would be required to outperform rotations which include crop legumes.
3
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.
4
Spain, AV. "Influence of environmental conditions and some soil chemical properties on the carbon and nitrogen contents of some tropical Australian rainforest soils". Soil Research 28, n. 6 (1990): 825. http://dx.doi.org/10.1071/sr9900825.
Testo completoAbstract (sommario):
Concentrations of carbon, total nitrogen, total phosphorus, soil pH, the sum of the exchangeable basic cations, clay and dithionite-extractable iron were examined in the surface soils of 72 rainforest sites from north-eastern tropical Queensland. Soils derived from basalt had higher levels of most of the above properties than those formed on other parent materials. Differences between the carbon status of soils formed from basalt and those formed from other parent materials may be related to the higher free iron levels and phosphorus status of the former group. Excluding the soils of basalt origin, both carbon and nitrogen are positively related to clay content. In contrast, within the soils of basaltic origin, carbon concentrations are negatively related to clay contents through interactions with free iron oxides. Separate univariate regression relationships were established between carbon and nitrogen concentrations and site temperature and precipitation for soils derived from basaltic and combined granitic and acid volcanic parent materials. Coefficients relating both nitrogen and carbon to temperature differed between these groupings. The importance of topography in controlling carbon levels is demonstrated in soils that are poorly drained or formed on ridges, while the importance of soil age is demonstrated by a juvenile soil formed on weakly weathered basalt.
5
Baldock, J. A., B. Hawke, J. Sanderman e L. M. Macdonald. "Predicting contents of carbon and its component fractions in Australian soils from diffuse reflectance mid-infrared spectra". Soil Research 51, n. 8 (2013): 577. http://dx.doi.org/10.1071/sr13077.
Testo completoAbstract (sommario):
Quantifying the content and composition of soil carbon in the laboratory is time-consuming, requires specialised equipment and is therefore expensive. Rapid, simple and low-cost accurate methods of analysis are required to support current interests in carbon accounting. This study was completed to develop national and state-based models capable of predicting soil carbon content and composition by coupling diffuse reflectance mid-infrared (MIR) spectra with partial least-squares regression (PLSR) analyses. Total, organic and inorganic carbon contents were determined and MIR spectra acquired for 20 495 soil samples collected from 4526 locations from soil depths to 1 m within Australia’s agricultural regions. However, all subsequent MIR/PLSR models were developed using soils only collected from the 0–10, 10–20 and 20–30 cm depth layers. The extent of grinding applied to air-dried soil samples was found to be an important determinant of the variability in acquired MIR spectra. After standardisation of the grinding time, national MIR/PLSR models were developed using an independent test-set validation approach to predict the square-root transformed contents of total, organic and inorganic carbon and total nitrogen. Laboratory fractionation of soil organic carbon into particulate, humus and resistant forms was completed on 312 soil samples. Reliable national MIR/PLSR models were developed using cross-validation to predict the contents of these soil organic carbon fractions; however, further work is required to enhance the representation of soils with significant contents of inorganic carbon. Regional MIR/PLSR models developed for total, organic and inorganic carbon and total nitrogen contents were found to produce more reliable and accurate predictions than the national models. The MIR/PLSR approach offers a more rapid and more cost effective method, relative to traditional laboratory methods, to derive estimates of the content and composition of soil carbon and total nitrogen content provided that the soils are well represented by the calibration samples used to build the predictive models.
6
Wong, M. T. F., e K. Wittwer. "Positive charge discovered across Western Australian wheatbelt soils challenges key soil and nitrogen management assumptions". Soil Research 47, n. 1 (2009): 127. http://dx.doi.org/10.1071/sr08098.
Testo completoAbstract (sommario):
Nitrogen management in Western Australia (WA) and in cropping areas elsewhere in Australia assumes that soil contains negligible or no positive charge and is therefore unable to retain nitrate against leaching. The amount of water needed to displace nitrate is thus assumed to be the drainable volume of water held by the soil (1 pore volume), and in sandy soils about 100 mm drainage is assumed to be required to displace nitrate by 1 m. The clay mineralogy of the highly weathered soils of the WA wheatbelt is dominated by kaolinite and iron and aluminium oxides. This mineralogy suggests likely occurrence of positive charge and anion exchange capacity (AEC), since these minerals can carry positive charge under normal acidic field situations. We measured AEC of soils sampled widely across the WA wheatbelt by independent leaching and batch equilibration methods of charge measurement. This showed widespread occurrence of positive charge and AEC in these soils. AEC ranged from 0 to 2.47 mmolc/kg and is linearly correlated with the potassium chloride or monocalcium phosphate extractable sulfate content of the soil. This correlation provides a rapid screening method to identify soils with positive charge. Application of ion-chromatographic theory showed that AEC has a large effect in delaying nitrate leaching by up to 12.5 pore volumes. The most highly charged soil (2.47 mmolc/kg) thus needed 12.5 times more water to displace nitrate than currently assumed. This potentially large delay in nitrate leaching affects the optimum amount and time of fertiliser application, rates of soil acidification attributed to nitrate leaching and the benefit of ameliorating subsoils to allow roots access to subsoil water and leached nitrate. It also calls into question the use of anions such as bromide to trace water flow and estimate recharge in these soils.
7
Moata, Melinda R. S., Ashlea L. Doolette, Ronald J. Smernik, Ann M. McNeill e Lynne M. Macdonald. "Organic phosphorus speciation in Australian Red Chromosols: stoichiometric control". Soil Research 54, n. 1 (2016): 11. http://dx.doi.org/10.1071/sr15085.
Testo completoAbstract (sommario):
Organic phosphorus (P) plays an important role in the soil P cycle. It is present in various chemical forms, the relative amounts of which vary among soils, due to factors including climate, land use, and soil type. Few studies have investigated co-variation between P types or stoichiometric correlation with the key elemental components of organic matter– carbon (C) and nitrogen (N), both of which may influence P pool structure and dynamics in agricultural soils. In this study we determined the organic P speciation of twenty Australian Red Chromosols soils, a soil type widely used for cropping in Australia. Eight different chemical forms of P were quantified by 31P NMR spectroscopy, with a large majority (>90%) in all soils identified as orthophosphate and humic P. The strongest correlations (r2 = 0.77–0.85, P < 0.001) between P types were found among minor components: (i) between two inositol hexakisphosphate isomers (myo and scyllo) and (ii) between phospholipids and RNA (both detected as their alkaline hydrolysis products). Total soil C and N were correlated with phospholipid and RNA P, but not the most abundant P forms of orthophosphate and humic P. This suggests an influence of organic matter content on the organic P pool consisting of phospholipid and RNA, but not on inositol P or the largest organic P pool in these soils – humic P.
8
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.
9
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.
10
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.
11
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.
12
McDonald, GK. "The contribution of nitrogen fertiliser to the nitrogen nutrition of rainfed wheat crops in Australia: a review". Australian Journal of Experimental Agriculture 29, n. 3 (1989): 455. http://dx.doi.org/10.1071/ea9890455.
Testo completoAbstract (sommario):
Very little nitrogen (N) fertiliser is applied to wheat crops in Australia. Currently, about 105 t of N fertiliser (less than 20% of Australia's total consumption) are used annually at an average rate of 2-3 kg Nha. This scant use of N fertiliser over much of the Australian wheat belt N is because the N derived from a legume-dominant pasture ley is thought to provide a wheat crop's N requirement. However, trends in the grain protein content of Australian wheat and some other indices of soil fertility suggest that legume-based pastures have not always been able to supply all the N required for adequate nutrition of the wheat crop and that there has been some occasional need for extra N from applications of fertiliser. Recent declines in the productivity and quality of pastures has further increased the need for supplementary applications of N fertiliser. The increase in grain legume production also has been partly based on the presumption that grain legumes contribute to the N economy of the following wheat crop. Many experiments throughout the wheat belt show a yield advantage of wheat grown after a grain legume, but these rotation trials also show that the level of productivity of the grain legume has little effect on the yield of the following wheat crop. A review of these experiments suggests that grain legumes, directly, contribute little to the N nutrition of a following wheat crop and their benefit may be from the legume acting as a disease break or providing the opportunity to control grassy weeds.
13
W. Arnold, G., M. Abensperg-Traun, R. J. Hobbs, D. E. Steven, L. Atkins, J. J. Viveen e D. M. Gutter. "Recovery of shrubland communities on abandoned farmland in southwestern Australia: soils, plants, birds and arthropods". Pacific Conservation Biology 5, n. 3 (1999): 163. http://dx.doi.org/10.1071/pc990163.
Testo completoAbstract (sommario):
Passive recovery of land formerly used for agricultural production may be an inexpensive and rapid method of ecosystem recovery, and may provide an alternative method to active revegetation. Passive recovery may also contribute to sustainable agriculture (soil salinity). For undisturbed and disturbed areas of the central wheatbelt of Western Australia, this paper reports the effects of farming history (clearing only, cultivation, duration of farming, and time since farming ceased) on the soil nutrient content, plant floristics (richness and composition) and structure, and the abundance, species richness and species composition of birds and arthropods. Only one site was cultivated for >6 years. We summarize as follows: (1) Previous clearing and cultivation has left no residual effects on the nitrogen or phosphorus content in the sandy soils. (2) There were no significant differences in terms of plant species richness but some differences in cover of woody plants, grass cover and plant species composition for farming history or time since farming ceased. (3) There were no significant differences in bird species richness but differences in species composition for time since farming ceased. (4) Arthropods showed few (and low) significant differences in their abundance, richness or species composition across different farming histories and time periods since farming ceased. Farming of these shrublands has left only minor changes in the composition and structure of the vegetation, and in the abundance, species richness and species composition of the passerine bird and arthropod assemblages. Abandoned parcels of land on the sandy soils which support shrubland may yield useful conservation benefits with relatively little input.
14
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.
15
Ye, Xiao Fei, Jun Hong Bai, Qiong Qiong Lu, Qing Qing Zhao e Jun Jing Wang. "Spatial Distribution of Phosphorus in Surface Soils of Wetlands with Different Plant Communities in the Yellow River Delta, China". Advanced Materials Research 726-731 (agosto 2013): 1383–86. http://dx.doi.org/10.4028/www.scientific.net/amr.726-731.1383.
Testo completoAbstract (sommario):
Spatial distribution characteristics of available phosphorus (AP) and total phosphorus (TP) in wetland soils withPhragmites australis,Suaeda salsaandTamarix chinnensiswere investigated and their influencing factors was also indentified using principal correspondence analysis for ordination in the Yellow River Delta of China. Our results showed that TP and AP contents in both sites withPhragmites australisandSuaeda salsa, and the horizontal distributions of AP content in three sites exhibited similar distribution characteristics to that of AP:TP ratios. Additionally, soil properties such as soil moisture, salinity, total nitrogen, total carbon and pH values were the important influencing factors of higher spatial variability of AP and TP.
16
Baldock, J. A., I. Wheeler, N. McKenzie e A. McBrateny. "Soils and climate change: potential impacts on carbon stocks and greenhouse gas emissions, and future research for Australian agriculture". Crop and Pasture Science 63, n. 3 (2012): 269. http://dx.doi.org/10.1071/cp11170.
Testo completoAbstract (sommario):
Organic carbon and nitrogen found in soils are subject to a range of biological processes capable of generating or consuming greenhouse gases (CO2, N2O and CH4). In response to the strong impact that agricultural management can have on the amount of organic carbon and nitrogen stored in soil and their rates of biological cycling, soils have the potential to reduce or enhance concentrations of greenhouse gases in the atmosphere. Concern also exists over the potential positive feedback that a changing climate may have on rates of greenhouse gas emission from soil. Climate projections for most of the agricultural regions of Australia suggest a warmer and drier future with greater extremes relative to current climate. Since emissions of greenhouse gases from soil derive from biological processes that are sensitive to soil temperature and water content, climate change may impact significantly on future emissions. In this paper, the potential effects of climate change and options for adaptation and mitigations will be considered, followed by an assessment of future research requirements. The paper concludes by suggesting that the diversity of climate, soil types, and agricultural practices in place across Australia will make it difficult to define generic scenarios for greenhouse gas emissions. Development of a robust modelling capability will be required to construct regional and national emission assessments and to define the potential outcomes of on-farm management decisions and policy decisions. This model development will require comprehensive field datasets to calibrate the models and validate model outputs. Additionally, improved spatial layers of model input variables collected on a regular basis will be required to optimise accounting at regional to national scales.
17
Orton, T. G., D. E. Allen e P. M. Bloesch. "Nitrogen mineralisation in sugarcane soils in Queensland, Australia: II. From laboratory to field-based prediction". Soil Research 57, n. 7 (2019): 755. http://dx.doi.org/10.1071/sr19032.
Testo completoAbstract (sommario):
Using Australian sugarcane regions as a case study, we present an approach for prediction of in-field nitrogen (N) mineralisation over a crop season. The approach builds on the statistical modelling applied in Allen et al. 2019, which demonstrated good predictive ability on data from a laboratory incubation study (an external R2 of 0.84 in a cross-validation exercise), and adjusts those mineralisation rates according to soil moisture and temperature factors. The required field soil temperature and moisture conditions were simulated using a mechanistic model for the response of soil conditions to input climate data. We investigate drivers of variability in the predicted in-season mineralised N, and compare predictions with currently implemented N fertiliser discounts, which are based on a relationship with soil organic carbon content. The main purpose of this paper is to illustrate the potential use of the results in Allen et al. (2019) for calculating predictions of in-season mineralised N that could be applicable under field conditions in the Australian sugarcane regions. A thorough test to properly validate predictions has not yet been conducted, but collecting data to do so should be the focus of further work.
18
Chen, W., R. W. Bell, R. F. Brennan, J. W. Bowden, A. Dobermann, Z. Rengel e W. Porter. "Key crop nutrient management issues in the Western Australia grains industry: a review". Soil Research 47, n. 1 (2009): 1. http://dx.doi.org/10.1071/sr08097.
Testo completoAbstract (sommario):
In the present paper, we review 4 topics that were identified through extensive consultation with stakeholders as issues of high impact and influence for the grains industry: improving soil testing and interpretation; role of fluid fertilisers in the Western Australian (WA) grains industry; using spatial and temporal information to improve crop nutrient management, particularly for nitrogen; and developing recommendations for managing emerging nutrient deficiencies. The key findings are summarised below. To further improve soil testing and interpretation, the review suggests that future research should focus on addressing soil sampling and interpretation questions, as they are important factors affecting the accuracy of fertiliser recommendations with changing cropping practices. There have been several studies to compare fluid with granular forms of P in WA, but the responses have not, so far, been consistent. More work may be needed to understand different crop response to fluid P fertiliser additions, particularly on low pH soils in WA. An understanding of the long-term performance of fluid P will also require an assessment of the residual value of fluid P compared with granular P under field conditions. Precision agriculture (PA) technology has potential to improve crop nutrient management and farm profitability in WA. The review indicates that understanding both spatial and temporal yield variation is critical for the successful adoption of PA technology by growers. The review also suggests that in WA, there is a need to explore the use of different layers of spatial information for determining management zones. In response to wide adoption of no-till and stubble retention cropping systems, increased use of fluid fertilisers together with advanced application technologies, and increased interest in cropping in the high rainfall zone, there is need to better understand growers’ practices and attitudes to crop nitrogen (N) management, and thus to better position research and extension activities. The review also suggests the need to evaluate new fertiliser products and site-specific N management concepts and develop N management practices for waterlogging-prone soils for improved N use efficiency in cereal production systems in WA. The negative balance of magnesium (Mg) observed in WA cropping systems, together with the information reviewed on factors affecting soil Mg content and crop response to Mg application across Australia, suggests that there is a need to evaluate the risk and impact of Mg deficiency on acidic sandy soils of WA.
19
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.
20
Duncan, Elliott G., Cathryn A. O’Sullivan, Margaret M. Roper, Mark B. Peoples, Karen Treble e Kelley Whisson. "Crop and microbial responses to the nitrification inhibitor 3,4-dimethylpyrazole phosphate (DMPP) in Mediterranean wheat-cropping systems". Soil Research 55, n. 6 (2017): 553. http://dx.doi.org/10.1071/sr16327.
Testo completoAbstract (sommario):
Nitrification inhibitors (NIs) such as 3,4,-dimethylpyrazole phosphate (DMPP), are used to suppress the abundance of ammonia-oxidising micro-organisms responsible for nitrification. In agriculture, NIs are used to retain soil mineral nitrogen (N) as ammonium to minimise the risk of losses of N from agricultural soils. It is currently unclear whether DMPP-induced nitrification inhibition can prevent losses of N from the light soils prevalent across the main rain-fed cropping regions of Western Australia, or whether it can improve the productivity or N uptake by broadacre crops such as wheat. Herein, we report on a series of glasshouse and field studies that examined the effect of applications of DMPP in conjunction with urea (as ENTEC urea; Incitec Pivot, Melbourne, Vic., Australia) on: (1) soil nitrification rates; (2) the abundance of ammonia-oxidising bacteria and archaea (AOB and AOA respectively); and (3) wheat performance (grain yield, protein content and N accumulation). A glasshouse study demonstrated that DMPP inhibited nitrification (for up to ~40 days after application) and reduced the abundance of AOB (by 50%), but had no effect on AOA abundance, wheat grain yield or protein content at any fertiliser N rate. Across six field experiments, DMPP also limited nitrification rates and reduced AOB abundance for approximately the first 40 days after application. However, by the end of the growing season, DMPP use had not increased soil mineral N resources or impaired AOB abundance compared with urea-only applications. In addition, DMPP had no effect on AOA abundance in any trial and did not improve crop performance in most trials.
21
Falkiner, RA, PK Khanna e RJ Raison. "Effect of superphosphate addition on N mineralization in some Australian forest soils". Soil Research 31, n. 3 (1993): 285. http://dx.doi.org/10.1071/sr9930285.
Testo completoAbstract (sommario):
Pinus radiata stands are reported to accumulate increased N on addition of phosphatic fertilizers. Field and laboratory studies were initiated to determine if addition of superphoshate increases soil N mineralization in forest soils. In a field experiment, application of 200 kg P ha-1 as superphosphate to trenched plots in a Pinus radiata stand increased accumulated soil mineral-N contents by 122% and 82% above the control on two occasions. Application of 500 kg P ha-1 as superphosphate either alone or in combination with lime (10 Mg ha-1) increased in situ soil net N mineralization in a dry sclerophyll eucalypt forest from 20.7 (control) to 28.3 (+P) and 30.2 (+P+lime) kg N ha-1 yr-1 20 cm-1. Uptake by the vegetation accounted for all of the mineralized nitrogen. In a 180 day laboratory incubation using undisturbed soil columns (0-20 cm) from nine forest sites, seven soils showed a positive response to superphosphate (100 kg P ha-1) addition, with increases in N mineralization ranging from 14% to 117%. The response of N mineralization to superphosphate addition was not related to initial soil organic C, total N or P content in the 0-20 cm layer. However, soil pH and organic C combined to account for 76% of the variation in N mineralization response (P < 0.01). In the 0-5 cm layer of untreated soils, soil organic P content could explain 71% of the variation in net N mineralization. Addition of superphosphate appears to increase N mineralization in several Australian forest soils and the improved availability of N will enhance tree growth rates. The mechanisms underlying the response are still poorly understood and thus also our ability to predict its significance for tree nutrition on specific forest sites.
22
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.
23
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.
24
Carlyle, J. Clive, Mark W. Bligh e EK Sadanandan Nambiar. "Woody residue management to reduce nitrogen and phosphorus leaching from sandy soil after clear-felling Pinus radiata plantations". Canadian Journal of Forest Research 28, n. 8 (1 agosto 1998): 1222–32. http://dx.doi.org/10.1139/x98-111.
Testo completoAbstract (sommario):
We studied the potential of woody residue management to reduce N and P leaching from sandy soils after clear-felling Pinus radiata D. Don. stands in southeastern Australia. Treatment variables were (i)branch diameter, (ii)branch mass, (iii)branch placement (surface or buried), and (iv)branch comminution. Treatments were applied to zero-tension lysimeters containing homogenized soil, forest floor, and green needles. Leachates from these treatments were collected weekly for 2 years and analysed for mineral N (Nm), soluble organic N, and total soluble P. Addition of 60 Mg·ha-1 of branch residue to the soil surface reduced Nm leaching by 13%, but the same quantity of buried branch reduced Nm leaching by 27%. Comminuting branches before burying further reduced Nm leaching. Much of the effect of placement, mass, and comminution on Nm leaching was related to differences in the surface area of branch material in contact with soil. Comminuting and burying branches reduced P leaching by 31%. An increase in branch N content after 2 years was linearly related to the reduction in Nm leached but accounted for only 23-48% of this reduction. Irrespective of treatment, there were linear relationships between the N and P concentrations in remaining material and the relative mass loss of wood and bark.
25
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
26
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.
27
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.
28
Chapman, Tamra F. "Comparison of soils and plants on the active and relic parts of a recolonised burrowing bettong (Bettongia lesueur) warren". Pacific Conservation Biology 21, n. 4 (2015): 298. http://dx.doi.org/10.1071/pc15016.
Testo completoAbstract (sommario):
The burrowing bettong (Bettongia lesueur) is a rat-kangaroo that digs while foraging and is the only marsupial to construct warrens and live communally in them. It previously occurred over a large part of Australia, but was extinct on the mainland by the early 1960s, before its role in ecosystem function could be understood. Bettongs, sourced from island and captive populations, were reintroduced as part of a rangeland restoration program at Matuwa (Lorna Glen) in central Western Australia. This study compared soil properties and plant productivity on the active and relic parts of a single warren to determine whether the presence of the bettongs was likely to be of benefit at the patch scale. Soil rock content, hydraulic conductivity, mineral nitrogen, phosphorus, potassium and sulfur were significantly higher for soils on the active part than on the relic part of the warren. Cotton bush (Ptilotus obovatus) shrubs were similar in size for the areas compared, but those growing on the active part of the warren had significantly more living tissue, greater leaf biomass and larger leaves, with higher moisture and nutrient content. These responses are indicative of access to additional mineral nutrients, probably derived from the urine and faeces of the bettongs. Only one warren was investigated in the present study and thus, this was a ‘patch’ level, unreplicated study. A broader, landscape-scale study is recommended, to compare relic warrens and active warrens with undisturbed sites, to confirm the hypotheses raised as a result of this study.
29
Loss, SP, GSP Ritchie e AD Robson. "Effect of lupins and pasture on soil acidification and fertility in Western Australia". Australian Journal of Experimental Agriculture 33, n. 4 (1993): 457. http://dx.doi.org/10.1071/ea9930457.
Testo completoAbstract (sommario):
An 'across the fence' comparison of farmer paddocks with nearby virgin bush sites was made at 3 locations, to measure the effects of lupins and subterranean clover based pastures on the chemical properties of the soil. Estimated rates of acidification in the 0-60 cm depth were 0.29-0.55 kmol H+/ha.year for wheat-lupin paddocks and 0.16-0.2 1 kmol H+/ha .year for pasture paddocks. A significant proportion of this acidification occurred below 20 cm, particularly in the lupin paddocks (up to 70% of the total). Severe water repellency had developed at 1 location that had produced 30 lupin crops with the occasional wheat crop. Despite these detrimental effects, lupins maintained soil mineral nitrogen and organic matter contents and electrical conductivities similar to those in pasture paddocks, even though the soils in the lupin rotations had been sown to wheat more frequently.
30
Frossard, Emmanuel, Nina Buchmann, Else K. Bünemann, Delwende I. Kiba, François Lompo, Astrid Oberson, Federica Tamburini e Ouakoltio Y. A. Traoré. "Soil properties and not inputs control carbon : nitrogen : phosphorus ratios in cropped soils in the long term". SOIL 2, n. 1 (29 febbraio 2016): 83–99. http://dx.doi.org/10.5194/soil-2-83-2016.
Testo completoAbstract (sommario):
Abstract. Stoichiometric approaches have been applied to understand the relationship between soil organic matter dynamics and biological nutrient transformations. However, very few studies have explicitly considered the effects of agricultural management practices on the soil C : N : P ratio. The aim of this study was to assess how different input types and rates would affect the C : N : P molar ratios of bulk soil, organic matter and microbial biomass in cropped soils in the long term. Thus, we analysed the C, N, and P inputs and budgets as well as soil properties in three long-term experiments established on different soil types: the Saria soil fertility trial (Burkina Faso), the Wagga Wagga rotation/stubble management/soil preparation trial (Australia), and the DOK (bio-Dynamic, bio-Organic, and “Konventionell”) cropping system trial (Switzerland). In each of these trials, there was a large range of C, N, and P inputs which had a strong impact on element concentrations in soils. However, although C : N : P ratios of the inputs were highly variable, they had only weak effects on soil C : N : P ratios. At Saria, a positive correlation was found between the N : P ratio of inputs and microbial biomass, while no relation was observed between the nutrient ratios of inputs and soil organic matter. At Wagga Wagga, the C : P ratio of inputs was significantly correlated to total soil C : P, N : P, and C : N ratios, but had no impact on the elemental composition of microbial biomass. In the DOK trial, a positive correlation was found between the C budget and the C to organic P ratio in soils, while the nutrient ratios of inputs were not related to those in the microbial biomass. We argue that these responses are due to differences in soil properties among sites. At Saria, the soil is dominated by quartz and some kaolinite, has a coarse texture, a fragile structure, and a low nutrient content. Thus, microorganisms feed on inputs (plant residues, manure). In contrast, the soil at Wagga Wagga contains illite and haematite, is richer in clay and nutrients, and has a stable structure. Thus, organic matter is protected from mineralization and can therefore accumulate, allowing microorganisms to feed on soil nutrients and to keep a constant C : N : P ratio. The DOK soil represents an intermediate situation, with high nutrient concentrations, but a rather fragile soil structure, where organic matter does not accumulate. We conclude that the study of C, N, and P ratios is important to understand the functioning of cropped soils in the long term, but that it must be coupled with a precise assessment of element inputs and budgets in the system and a good understanding of the ability of soils to stabilize C, N, and P compounds.
31
Frossard, E., N. Buchmann, E. K. Bünemann, D. I. Kiba, F. Lompo, A. Oberson, F. Tamburini e O. Y. A. Traoré. "Soil properties and not inputs control carbon, nitrogen, phosphorus ratios in cropped soils in the long-term". SOIL Discussions 2, n. 2 (21 settembre 2015): 995–1038. http://dx.doi.org/10.5194/soild-2-995-2015.
Testo completoAbstract (sommario):
Abstract. Stoichiometric approaches have been applied to understand the relationship between soil organic matter dynamics and biological nutrient transformations. However, very few studies explicitly considered the effects of agricultural management practices on soil C : N : P ratio. The aim of this study was to assess how different input types and rates would affect the C : N : P molar ratios of bulk soil, organic matter and microbial biomass in cropped soils in the long-term. Thus, we analysed the C, N and P inputs and budgets as well as soil properties in three long-term experiments established on different soil types: the Saria soil fertility trial (Burkina Faso), the Wagga Wagga rotation/stubble management/soil preparation trial (Australia), and the DOK cropping system trial (Switzerland). In each of these trials, there was a large range of C, N and P inputs which had a strong impact on element concentrations in soils. However, although C : N : P ratios of the inputs were highly variable, they had only weak effects on soil C : N : P ratios. At Saria, a positive correlation was found between the N : P ratio of inputs and microbial biomass, while no relation was observed between the nutrient ratios of inputs and soil organic matter. At Wagga Wagga, the C : P ratio of inputs was significantly correlated to total soil C : P, N : P and C : N ratios, but had no impact on the elemental composition of microbial biomass. In the DOK trial, a positive correlation was found between the C budget and the C to organic P ratio in soils, while the nutrient ratios of inputs were not related to those in the microbial biomass. We argue that these responses are due to differences in soil properties among sites. At Saria, the soil is dominated by quartz and some kaolinite, has a coarse texture, a fragile structure and a low nutrient content. Thus, microorganisms feed on inputs (plant residues, manure). In contrast, the soil at Wagga Wagga contains illite and haematite, is richer in clay and nutrients and has a stable structure. Thus, organic matter is protected from mineralization and can therefore accumulate, allowing microorganisms to feed on soil nutrients and to keep a constant C : N : P ratio. The DOK soil represents an intermediate situation, with high nutrient concentrations, but a rather fragile soil structure, where organic matter does not accumulate. We conclude that the study of C, N, and P ratios is important to understand the functioning of cropped soils in the long-term, but that it must be coupled with a precise assessment of element inputs and budgets in the system and a good understanding of the ability of soils to stabilize C, N and P compounds.
32
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.
33
Unkovich, Murray. "Nitrogen fixation in Australian dairy systems: review and prospect". Crop and Pasture Science 63, n. 9 (2012): 787. http://dx.doi.org/10.1071/cp12180.
Testo completoAbstract (sommario):
Quantitative measurement of N2 fixation has rarely been conducted in Australian dairy pastures. The available data indicate that annual N2 fixation rates in Australian dairy pastures are generally low, due to low pasture legume content. With typical legume contents of grazed pastures less than 30% of total pasture biomass production, annual N2 fixation in herbage is usually much less than 50 kg ha–1 year–1. Other factors which are likely to be able to contribute to increased N2 fixation input (rhizobia, mineral N management, soil acidity, soil water contents) will have little impact until such time as legume contents are increased. In contrast, for some hay systems, such as those using lucerne, N2 fixation input is shown to be high (200–300 kg ha–1 year–1). While pasture clover contents remain low there is little value in study or measurement of N2 fixation, nor in complex modelling, as N2 fixation will be of little quantitative importance. However, where legume contents, and thus potential N2 fixation are increased, there is scope for investigation into potential increases in N input from this source, which is invariably linked to fertiliser application, the management of grazing and the N returns in urine and dung. These are the major influences on sward N dynamics and legume N2 fixation. The inoculant rhizobia used for white clover in Australia (TA1) is likely to be suboptimal. Isolated in Tasmania in 1953 it has been shown to be inferior in N2 fixation compared with other strains on several occasions. Root pests and diseases are likely to be prevalent and impact directly on clover root growth and perhaps nodulation. Modelling is often used to describe the probable influence of management and/or climate on the operation of agricultural systems. Reliable modelling of N2 fixation requires capacity to integrate the effects of grazing and pasture composition on soil mineral N dynamics, the influence of this mineral N on nodulation and on suppression of N2 fixation, and environmental and management influences on soil rhizobial populations. Currently no models have demonstrated this capacity. At present, a suitably calibrated regression model is probably a good option for modelling N2 fixation in Australian dairy pastures. Environmental benefits ensuing from increasing N2 fixation and substituting this for fertiliser N are likely to be greater off-farm (reduced GHG emissions at site of fertiliser manufacture) than on, if current fertiliser management is optimal. Nevertheless substituting fixed N for fertiliser N would have modest environmental and feed efficiency benefits.
34
Anderson, WK, GB Crosbie e K. Lemsom. "Production practices for high protein, hard wheat in Western Australia". Australian Journal of Experimental Agriculture 35, n. 5 (1995): 589. http://dx.doi.org/10.1071/ea9950589.
Testo completoAbstract (sommario):
Field experiments were conducted at 18 sites over 4 years in the eastern and north-eastern wheatbelt of Western Australia where average annual rainfall is <400mm, to investigate suitable techniques for the production of high protein (>13%) wheat in an area that traditionally produces grain of a much lower average protein percentage. Wilgoyne yielded as well as, or better than, any of the cultivars accepted into the Special Hard (SH) grade in Western Australia but 5-10% less than cultivars suitable for the Australian Standard White (ASW) grade. Differences between cultivars were greatest at the optimum sowing time in late May. Lower yields in early May were attributed to water stress during early growth or to frost damage during grain filling. The addition of nitrogen (N) fertiliser to crops sown after 1 June was less effective in increasing grain yield and grain protein than N added to earlier sowings. Most crops that produced >13% protein followed medic or field peas. The addition of N fertiliser was seldom required to produce this concentration of protein in crops that followed medic or peas. Crops following pasture with a low legume content or wheat had lower grain protein concentrations. Friable red-brown earth soils in a medic or pea rotation were able to achieve the required grain protein, but other combinations were not extensively tested. From these experiments, cultivars with inherently small grains due to their propensity to produce high levels of small grain screenings (whole grain through a 2-mm, slotted sieve) may be less able to increase yields economically by increasing kernel numbers per unit area under conditions in Western Australia.
35
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.
36
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).
37
Smethurst, P. J., e E. K. S. Nambiar. "Effects of slash and litter management on fluxes of nitrogen and tree growth in a young Pinusradiata plantation". Canadian Journal of Forest Research 20, n. 9 (1 settembre 1990): 1498–507. http://dx.doi.org/10.1139/x90-198.
Testo completoAbstract (sommario):
The effects of slash and litter management practices on soil water and temperature, fluxes of mineral N, needle water potential, and tree nutrition and growth were studied in a young Pinusradiata D. Don plantation growing on a sandy Podzol in southeastern Australia. Treatments were slash and litter retained (SL), litter only retained (L), litter ploughed (LP), and slash and litter removed (SLR). Soils without slash or litter cover (LP and SLR) were up to 4 °C warmer on average than soils overlaid by slash or litter and were subjected to greater extremes of temperature. Treatments had relatively little effect on soil water content and needle water potential in trees. Carbon in surface soil increased from 1.14 to 1.83% after incorporation of litter by ploughing, but decreased to 1.37% during the next 40 months. Smaller but significant decreases in C also occurred in other treatments. LP and SLR led to the highest rates of N mineralization in the 1st year. During the first 3 years after clear-felling, rates of N mineralization increased in SL, L, and LP but decreased in SLR. During the 4th year, rates of N mineralization were low (20–30 kg N•ha−1•year−1) in all treatments. Over 4 years, 211, 170, 210, and 147 kg N•ha−1 were mineralized in treatments SL, L, LP, and SLR, respectively. Rates of mineralization and leaching were strongly correlated (R2 = 0.82) and leaching below 30 cm accounted for 75–85% of N mineralized irrespective of treatment. Incorporation of litter by ploughing doubled concentrations of mineral N during the first summer after planting and increased early tree growth. However, rates of N mineralization in the slash and litter treatments, which were high compared with potential rates of uptake, were weakly correlated with tree growth. Factors controlling N supply were of little consequence for tree growth during this early phase of plantation establishment.
38
Nolan, Rachael H., Tonantzin Tarin, Kendal A. Fairweather, James Cleverly e Derek Eamus. "Variation in photosynthetic traits related to access to water in semiarid Australian woody species". Functional Plant Biology 44, n. 11 (2017): 1087. http://dx.doi.org/10.1071/fp17096.
Testo completoAbstract (sommario):
Low soil water content can limit photosynthesis by reducing stomatal conductance. Here, we explore relationships among traits pertaining to carbon uptake and pre-dawn leaf water potential (as an index of soil water availability) across eight species found in semiarid central Australia. We found that as pre-dawn leaf water potential declined, stomatal limitations to photosynthesis increased, as did foliar nitrogen, which enhanced photosynthesis. Nitrogen-fixing Acacia species had higher foliar nitrogen concentrations compared with non-nitrogen fixing species, although there was considerable variability of traits within the Acacia genus. From principal component analysis we found that the most dissimilar species was Acacia aptaneura Maslin&J.E.Reid compared with both Eucalyptus camaldulensis Dehnh. and Corymbia opaca. (D.J.Carr & S.G.M.Carr)K.D.Hill&L.A.S.Johnson, having both the largest foliar N content, equal largest leaf mass per area and experiencing the lowest pre-dawn water potential of all species. A. aptaneura has shallow roots and grows above a hardpan that excludes access to groundwater, in contrast to E. camaldulensis and C. opaca, which are known to access groundwater. We conclude that ecohydrological niche separation is an important factor driving the variability of within-biome traits related to carbon gain. These observations have important implications for global vegetation models, which are parameterised with many of the traits measured here, but are often limited by data availability.
39
Asseng, S., G. C. Anderson, F. X. Dunin, I. R. P. Fillery, P. J. Dolling e B. A. Keating. "Use of the APSIM wheat model to predict yield, drainage, and NO3- leaching for a deep sand". Australian Journal of Agricultural Research 49, n. 3 (1998): 363. http://dx.doi.org/10.1071/a97095.
Testo completoAbstract (sommario):
High rates of drainage and leaching of nitrates in deep sands in Western Australia are contributing to groundwater recharge and soil acidification in this region. Strategies are being soughtto increase water and nitrogen (N) use in the legume-based cropping systems. Choice of appropriate management strategies is complicated by the diversity of soil types, the range of crops, and the inherent season to season variability. Simulation models provide the means to extrapolate beyond the bounds of experimental data if accurate predictions of key processes can be demonstrated. This paper evaluates the accuracy of predictions of soil water content, evapotranspiration, drainage, inorganic N content insoil, nitrate (NO-3) leaching, wheat growth, N uptake, and grain yields obtained from the Agricultural Production Systems Simulator (APSIM) model when this was initialised with appropriate information on soil properties and wheat varieties commonly grown on deep sands in the 500 mm rainfall zone west of Moora in Western Australia. The model was found to give good predictions of soil water content,evapotranspiration, deep drainage, and overall NO-3 leaching. Temporal changes in inorganic N insoil were simulated, although the small concentrations in soil inorganic N precluded close matching of paired observed and predicted values. Crop growth and N uptake were closely predicted up to anthesis, but a poor fit between observed and predicted crop growth and N uptake was noted postanthesis. Reasons for the discrepancies between modelled and observed values are outlined. The model was run with historical weather data (81 years) and different initial soil water and inorganic soil N profiles to assess the probability of drainage and NO-3 leaching, and the grain yield potentials for wheat grown on deep sands in the region west of Moora. Simulation showed that thesoil water and the soil inorganic N content at the beginning of each season had no effect on grain yield, implying that pre-seed soil NO-3 was largely lost from the soil by leaching. There was a 50% probability that 141 mm of winter rainfall could drain below 1·5 m and a 50% probability that 53 kgN/ha could be leached under wheat following a lupin crop, where initial soil water contents andsoil NO-3 contents used in the model were those measured in a deep sand after late March rainfall. Simulated application of N fertiliser at sowing increased both grain yield and NO-3 leaching. Splitting the N application between the time of sowing and 40 days after sowing decreased NO-3 leaching,increased N uptake by wheat, and increased grain yield, findings which are consistent with agronomic practice. The high drainage and leaching potential of these soils were identified as the main reasons why predicted yields did not approach the French and Schultz potential yield estimates based on 20 kg grain yield per mm of rainfall. When the available water was reduced by simulated drainage, simulated grain yields for the fertilised treatments approached the potential yield line.
40
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.
41
Reuter, Hendrik, Julia Gensel, Marcus Elvert e Dominik Zak. "Evidence for preferential protein depolymerization in wetland soils in response to external nitrogen availability provided by a novel FTIR routine". Biogeosciences 17, n. 2 (31 gennaio 2020): 499–514. http://dx.doi.org/10.5194/bg-17-499-2020.
Testo completoAbstract (sommario):
Abstract. Phragmites australis litters were incubated in three waterlogged anoxic wetland soils of different nutrient status for 75 d, and litter nitrogen (N) dynamics were analyzed by elemental analyses and Fourier transform infrared spectroscopy (FTIR). At the end of the incubation time, the N content in the remaining litter tissue had increased in most samples. Yet, the increase in N content was less pronounced when litters had been decomposed in a more-N-poor environment. FTIR was used to quantify the relative content of proteins in litter tissue and revealed a highly linear relationship between bulk N content and protein content. Changes in bulk N content thus paralleled and probably were governed by changes in litter protein content. Such changes are the result of two competing processes within decomposing litter: enzymatic protein depolymerization as a part of the litter breakdown process and microbial protein synthesis as a part of microbial biomass growth within the litter. Assuming microbial homeostasis, DNA signals in FTIR spectra were used to calculate the amount of microbial N in decomposed litter which ranged from 14 % to 42 % of the total litter N for all leaf samples. Microbial carbon (C) content and resultant calculated carbon use efficiencies (CUEs) indicate that microbial N in litter accumulated according to predictions of the stoichiometric decomposition theory. Subtracting microbial C and N contributions from litter, however, revealed site-dependent variations in the percentual amount of the remaining still-unprocessed plant N in litter compared to remaining plant C, an indicator for preferential protein depolymerization. For all leaf litters, the coefficient of preferential protein depolymerization (α), which relates N-compound depolymerization to C-compound depolymerization, ranged from 0.74–0.88 in a nutrient-rich detritus mud to 1.38–1.82 in Sphagnum peat, the most nutrient-poor substrate in this experiment. Preferential protein depolymerization from litter decomposing in Sphagnum peat leads to a gradual N depletion in the early phase of litter decomposition, which we propose as a preservation mechanism for vascular litter in Sphagnum peatlands.
42
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.
43
Schefe, Cassandra R., Kirsten M. Barlow, Nathan J. Robinson, Douglas M. Crawford, Timothy I. McLaren, Ronald J. Smernik, George Croatto, Ronald D. Walsh e Matt Kitching. "100 Years of superphosphate addition to pasture in an acid soil—current nutrient status and future management". Soil Research 53, n. 6 (2015): 662. http://dx.doi.org/10.1071/sr14241.
Testo completoAbstract (sommario):
Pasture-based animal production systems, which occupy a significant proportion of the landscape in Victoria, Australia, have historically been nutrient-limited, with phosphorus (P) often the most limiting nutrient. The Permanent Top-Dressed (PTD) pasture experiment was established in 1914 at the Rutherglen Research Station, Victoria, to investigate the management of this deficiency. The main objective of the PTD experiment was to demonstrate the value of adding P fertiliser at two rates to increase pasture productivity for lamb and wool production. We report on the status of the PTD soils after 100 years, investigating the long-term implications of continuous grazing and fertiliser management (0, 125 and 250 kg/ha of superphosphate every second year) of non-disturbed pasture. We investigated the long-term effects of P fertiliser on the forms and distribution of P and other relevant soil parameters. In the fertilised treatments, P has accumulated in the surface soils (0–10 cm) as both orthophosphate and organic P, with an Olsen P of 16–21 mg P/kg, which is non-limiting for pasture production. In the treatment with 250 kg superphosphate, there has also been movement of P down through the soil profile, probably due to the high sand content of the surface soil and the transfer through the profile of small quantities of water-soluble P and P bound to organic ligands. Over time, the site has continued to acidify (surface 0–10 cm); the soil acidity combined with aluminium (Al) concentrations in the fertilised treatments approach a level that should impact on production and where broadcast lime would be recommended. After 100 years of non-disturbed pasture, the surface soils of these systems would be in a state of quasi-equilibrium, in which the fertilised systems have high levels of carbon (C), nitrogen, P and exchangeable Al. The continued stability of this system is likely dependent upon maintaining the high C status, which is important to nutrient cycling and the prevention of Al phytotoxicity. There are two risks to this system: (i) the declining pH; and (ii) soil disturbance, which may disrupt the equilibrium of these soils and the bio-chemical processes that maintain it.
44
Petch, A., e RW Smith. "Effect of lupin management on the yield of subsequent wheat crops in a lupin-wheat rotation". Australian Journal of Experimental Agriculture 25, n. 3 (1985): 603. http://dx.doi.org/10.1071/ea9850603.
Testo completoAbstract (sommario):
Wheat was grown in a series of 1:1 rotation cycles with sweet lupins over 8 years on three sites in Western Australia. Grain yield of wheat was the main test used to compare five lupin management treatments with a control treatment, 'no-lupins'. The lupins were cut as for silage, cut as for hay, or harvested as mature grain, the stubble being burnt or removed in summer, or turned into the soil the next autumn. Nitrogen taken up in the lupins and in the wheat was measured, as well as soil mineral nitrogen in the top 10 cm in the final year. Lupin yield and nitrogen content within any year were similar over all treatments. As much nitrogen was removed in hay and silage as in mature lupins, but wheat yielded most grain after the 'silage' and 'hay' treatments, and least after 'no-lupins' or after the 'remove' and 'turn-in' stubble treatments. Nitrogen uptakes in young wheat plants point to treatment effects due to differences in nitrogen availability, but the treatments also caused different weed populations which at least partially affected wheat yields. Herbicide control of encroaching weeds in the lupins raised soil nitrate levels the following summer and increased subsequent wheat yields.
45
Smethurst, P. J., e E. K. S. Nambiar. "Distribution of carbon and nutrients and fluxes of mineral nitrogen after clear-felling a Pinusradiata plantation". Canadian Journal of Forest Research 20, n. 9 (1 settembre 1990): 1490–97. http://dx.doi.org/10.1139/x90-197.
Testo completoAbstract (sommario):
The effects of clear-felling and slash removal on the distribution of organic matter and nutrients, fluxes of mineral N, and soil water and temperature were studied in a 37-year-old Pinusradiata D. Don plantation, on a sandy Podzol in southeastern Australia. Slash, litter, and the top 30 cm of soil combined contained 1957 kg N•ha−1, of which slash and litter contained 12 and 25%, respectively. Therefore, loss of slash and litter due to burning or other intensive site preparation practices would substantially reduce the N capital at the site. During the first 18 months after clear-felling, soil water content in the clear-felled area was up to 50% higher than in the uncut plantation, but there were only minor differences in soil temperature. Slash removal decreased the water content of litter, but had little effect on the water content or temperature of the soil. In the uncut plantation, N mineralized in litter and soil was completely taken up by the trees. Following clear-felling, rates of N mineralization increased in litter after 4 months, and in soil after 12 months, but changes were less pronounced with slash removal. After clear-felling, increased mineralization and the absence of trees (no uptake) led to increased concentrations of mineral N in both litter and soil, 64–76% of which was leached below the 30 cm soil depth prior to replanting. Despite leaching, concentrations of mineral N after clear-felling remained higher than those in the uncut plantation for at least 3 years.
46
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.
47
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.
48
Miao, Z. H., J. A. Fortune e J. Gallagher. "The potential of two rough-seeded lupin species (Lupinus pilosus and L. atlanticus) as supplementary feed for sheep". Australian Journal of Agricultural Research 52, n. 6 (2001): 615. http://dx.doi.org/10.1071/ar99142.
Testo completoAbstract (sommario):
The rough-seeded lupins are better adapted to alkaline soils than the domesticated lupins currently in use in commercial agriculture in southern Australia. Lupinus pilosus and L. atlanticus are two species of rough-seeded lupins that are undergoing domestication, and could be very valuable for sheep as a supplementary feed. However, there is little information on the nutritive value of these lupins. Two experiments were conducted to evaluate the nutritive value of L. pilosus and L. atlanticus, compared with L. angustifolius, which is widely used as an animal feed in Australia. The results showed that the rough-seeded lupins examined had larger seeds, a greater proportion of seed coat in the whole seed, and a higher fibre content in the seed coat than domesticated lupins. Nitrogen (N) content in the kernel of the various lupin species was similar. The high fibre content in seed coat did not appear to limit the digestion of the seeds by sheep as demonstrated by the high potential degradability of seed dry matter (DM) for all lupin species. There were no significant differences betweenL. pilosus,L. atlanticus, andL. angustifolius as a supplementary feed provided at low levels in DM digestibility (DMD), apparent energy digestibility (AED), and N-balance, suggesting that L. pilosus and L. atlanticus could be used in place of L. angustifolius. AlsoL. atlanticus could be substituted for L. angustifolius at high levels of supplementation as there were no differences in DMD, AED, apparent N digestibility, and N-balance when these species were fed to sheep as a supplement to barley straw. Supplementation with lupin seed at 150 g/day significantly improved DM intake by 195 g/day, DMD by 8.7, and AED by 11.4 percentage units. However, a high level of lupin supplementation in a diet based on barley straw did not increase DMD and AED of the diet.
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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.
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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.