Articles de revues : « Crops and soils South Australia »

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Cartwright, B., BA Zarcinas et LR Spouncer. « Boron toxicity in South Australian barley crops ». Australian Journal of Agricultural Research 37, n^o 4 (1986) : 351. http://dx.doi.org/10.1071/ar9860351.

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Boron toxicity was identified in barley crops grown on a range of soils at 16 widespread locations in South Australia, and also at one site in western Victoria. The soils on which boron toxicity occurred included red-brown earths (Calcic Natrixeralf), calcareous earths (Xerollic Calciorthid and Calcic Paleorthid), and calcareous sands ('Petrocalcixerollic' Xerochrept). At one site the soil was a grey clay (Palexerollic Chromoxerert). The properties of some examples of normal and high-boron soils which were sampled in close proximity are discussed. For individual high-boron soil profiles it was possible to demonstrate statistically significant relationships between extractable boron and ESP, CEC and clay content. However, these relationships did not hold generally for comparisons between normal and high-boron soils. Boron concentrations in affected barley ranged from 56 mg/kg in mature straw to 323 mg/kg in whole tops at Feekes stage 10.1. In control samples the mean boron concentration was 22.8 mg/kg. The concentrations of other nutrient elements (P, K, S, Mg, Cu, Zn, Mn, Mo) were within normal ranges, and did not differ between control samples and plants with toxicity symptoms. Barley plants affected by the toxicity had increased concentrations of Na and Cl, and decreased concentrations of Ca compared with control plants. These effects were small, but statistically significant, and were consistent with the notion that the toxicity was associated with sodic soils. The findings extend our earlier work on boron toxicity at a single site, and demonstrate that the toxicity is widespread in South Australia.

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Humphries, A. W., X. G. Zhang, K. S. McDonald, R. A. Latta et G. C. Auricht. « Persistence of diverse lucerne (Medicago sativa sspp.) germplasm under farmer management across a range of soil types in southern Australia ». Australian Journal of Agricultural Research 59, n^o 2 (2008) : 139. http://dx.doi.org/10.1071/ar07037.

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The persistence of a diverse group of lucerne (Medicago sativa sspp.) germplasm was evaluated under farmer management across a range of acidic and neutral-alkaline soils at 8 sites in South and Western Australia. Dryland field trials were sown in parallel with commercial lucerne paddocks being grown in rotation with cereal crops, remaining unfenced and under management by the farmer for the life of the stand. The combined differences in soil type, grazing management, and low rainfall contributed to large differences in average lucerne persistence between sites in South Australia and Western Australia. After 3 years, plant frequency (a measure of plant density used to monitor persistence) averaged 17% (at least 17 plants/m2) on the strongly acidic soils in Western Australia and 30% on the neutral-alkaline soils in South Australia (at least 30 plants/m2). Differences in persistence were attributed to the combined stresses of soil pH, drought conditions, and grazing management. Genetic correlation analyses between sites failed to show any clear patterns in the performance of entries at each site, except for a high correlation between 2 South Australian sites in close proximity. Highly winter-active germplasm was less persistent than other winter activity groups, but was higher yielding when assessed in an additional trial at Katanning, WA. Highly winter-active lucerne (class 9–10) should continue to be recommended for short (2–4 year) phases in rotation with cereals, and winter-active groups (6–8) should be recommend for longer (4–7 year) phases in rotations. The results of this evaluation are also being used to identify broadly adapted, elite genotypes in the breeding of new lucerne cultivars for the southern Australian cropping districts.

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Reuter, DJ, CB Dyson, DE Elliott, DC Lewis et CL Rudd. « An appraisal of soil phosphorus testing data for crops and pastures in South Australia ». Australian Journal of Experimental Agriculture 35, n^o 7 (1995) : 979. http://dx.doi.org/10.1071/ea9950979.

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Data from more than 580 field experiments conducted in South Australia over the past 30 years have been re-examined to estimate extractable soil phosphorus (P) levels related to 90% maximum yield (C90) for 7 crop species (wheat, barley, oilseed rape, sunflower, field peas, faba beans, potato) and 3 types of legume-based pasture (subterranean clover, strawberry clover, annual medics). Data from both single-year and longer term experiments were evaluated. The C90 value for each species was derived from the relationship between proportional yield responsiveness to applied P fertiliser rates (determined as grain yield in crops and herbage yield in ungrazed pastures) and extractable P concentrations in surface soils sampled before sowing. Most data assessments involved the Colwell soil P test and soils sampled in autumn to 10 cm depth. When all data for a species were considered together, the relationship between proportional yield response to applied P and soil P status was typically variable, particularly where Colwell soil P concentration was around C90. When data could be grouped according to common soil types, soil surface texture, or P sorption indices (selected sites), better relationships were discerned. From such segregated data sets, different C90 estimates were derived for either different soil types or soil properties. We recommend that site descriptors associated with the supply of soil P to plant roots be determined as a matter of course in future P fertiliser experiments in South Australia. Given the above, we also contend that the Colwell soil P test is reasonably robust for estimating P fertiliser requirements for the diverse range of soils in the agricultural regions of the State. In medium- and longer term experiments, changes in Colwell soil P concentration were measured in the absence or presence of newly applied P fertiliser. The rate of change (mg soil P/kg per kg applied P/ha) appeared to vary with soil type (or soil properties) and, perhaps, cropping frequency. Relatively minor changes in soil P status were observed due to different tillage practices. In developing P fertiliser budgets, we conclude that a major knowledge gap exists for estimating the residual effectiveness of P fertiliser applied to diverse soil types under a wide range of South Australian farming systems.

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Turner, NC. « Crop production on duplex soils : an introduction ». Australian Journal of Experimental Agriculture 32, n^o 7 (1992) : 797. http://dx.doi.org/10.1071/ea9920797.

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Duplex or texture-contrast soils occur over about 60% of the agricultural areas of south-west Western Australia. Annual crops of wheat, barley, oats, and lupins predominate on these soils, grown in rotation with annual pastures. The climate is characterised by cool, wet winters and hot, dry summers. Crop production is restricted to the winter and spring and is limited by waterlogging in the wet winter months and by water shortage during grain filling in spring. Research on crop production on duplex soils has been undertaken for the past 8 years by a collaborative team from the CSIRO Dryland Crops andyoils Program and the Western Australian Department of Agriculture. This research has been focussed on 3 sites at which processes limiting crop production on duplex soils have been highlighted. This special issue was initiated to summarise that research and to put it in its regional and national perspective. Additionally, opportunity was taken to compare and contrast experiences both within Western Australia and throughout Australia, and to draw out management options for crop production on duplex soils.

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Sadras, Victor O., et John F. Angus. « Benchmarking water-use efficiency of rainfed wheat in dry environments ». Australian Journal of Agricultural Research 57, n^o 8 (2006) : 847. http://dx.doi.org/10.1071/ar05359.

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Attainable water-use efficiency relates attainable yield, i.e. the best yield achieved through skilful use of available technology, and seasonal evapotranspiration (ET). For wheat crops in south-eastern Australia, there is a common, often large gap between actual and attainable water-use efficiency. To evaluate whether this gap is only an Australian problem or a general feature of dry environments, we compared water-use efficiency of rainfed wheat in south-eastern Australia, the North American Great Plains, China Loess Plateau, and the Mediterranean Basin. A dataset of published data was compiled (n = 691); water-use efficiency (WUEY/ET) was calculated as the ratio between actual grain yield and seasonal ET. Maximum WUEY/ET was 22 kg grain/ha.mm. Average WUEY/ET (kg grain/ha.mm) was 9.9 for south-eastern Australia, 9.8 for the China Loess Plateau, 8.9 for the northern Great Plains of North America, 7.6 for the Mediterranean Basin, and 5.3 for the southern-central Great Plains; the variation in average WUEY/ET was largely accounted for by reference evapotranspiration around flowering. Despite substantial differences in important factors including soils, precipitation patterns, and management practices, crops in all these environments had similarly low average WUEY/ET, between 32 and 44% of attainable efficiency. We conclude that low water-use efficiency of Australian crops is not a local problem, but a widespread feature of dry environments. Yield gap analysis for crops in the Mallee region of Australia revealed low availability of phosphorus, late sowing, and subsoil chemical constraints as key factors reducing water-use efficiency, largely through their effects on soil evaporation.

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Bowmer, KH. « Atrazine persistence and toxicity in two irrigated soils of Australia ». Soil Research 29, n^o 2 (1991) : 339. http://dx.doi.org/10.1071/sr9910339.

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The persistence of atrazine in two contrasting irrigated soils from the Riverine Plain of south-eastern Australia was measured in the laboratory at three constant temperatures. Particularly at lower temperatures atrazine was more persistent, by an order of magnitude, than reported for soils overseas; but in two successive field experiments, encompassing both surface and incorporated applications of atrazine in the heavier soil, residues measured after about 7 months were within the range expected from the literature. The measured residues were 2-6 times smaller than predicted using a simulation model, probably reflecting volatilization and other losses which are not included in the model, but which are expected to be substantial at the extremely high soil surface temperatures observed in the field. Comparative measurements of aged residues in the heavy clay soil showed higher results from chemical analysis of acetonitrile-water soil extracts than by in situ glasshouse bioassay using oats and turnips, demonstrating that only one third of the extractable residue was available to crops. Comparison of soil-based and hydroponic assay using soybeans showed that this soil reduced the effective atrazine concentration in solution by at least 16-fold, but sensitive crops could still be damaged when grown in rotation after tolerant crops, or if irrigated with contaminated water.

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Fillery, IR, et KJ McInnes. « Components of the fertiliser nitrogen balance for wheat production on duplex soils ». Australian Journal of Experimental Agriculture 32, n^o 7 (1992) : 887. http://dx.doi.org/10.1071/ea9920887.

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In this paper, we review literature on the fate of fertiliser nitrogen (N) applied to duplex soils in wheat-growing regions of southern Australia, and discuss the contribution of specific N transformations to N loss. Duplex soils are characterised by the presence of soil material, within the rooting depth of crops, that possess hydraulic conductivities that are lower than those of overlying material. Denitrification and the transport of nitrate below rooting depth of crops are thought to be the chief causes of loss of fertiliser N and to contribute to poor grain yields. Ammonia volatilisation could contribute also to N loss. The fate of fertiliser N commonly applied to wheat in southern Australia has largely been evaluated using budgeting procedures using l5N, a stable isotope of N. Results from studies in south-eastem Australia, using red-brown earths, indicate that between 10 and 40% of applied 15N can be lost irrespective of time of application to wheat. Denitrification is believed to be the chief cause of loss of l5N. Similar studies on yellow duplex soils in Western Australia have shown fertiliser N loss to range from 70% to no loss of the l5N applied. The exact cause of N loss in Western Australian studies is unclear. There was circumstantial evidence for ammonia loss from surface-applied urea, and evidence of leaching of nitrates from this and other ammoniumbased fertilisers. The role of denitrification has not been clarified in Western Australian studies. In the majority of studies, recovery of 15N in aboveground biomass exceeded 40% of that applied. In addition, between 17 and 48% of applied 15N, of which 10-15% may be in root material, has been recovered in the soil organic matter pool. The predominance of the denitrification process in south-eastern Australian soils, and the inability to improve the efficiency of utilisation of 15N by delaying the time of application to wheat underscores the importance of controlling the nitrification process using inhibitors. Management options for Western Australian soils are less clear. Some agronomic experiments have demonstrated the advantage of delaying the application of fertiliser N to wheat to improve the efficiency of its utilisation. There is also evidence which suggests that N should be applied early in the growth cycle to promote tiller development and thereby increase the potential for grain yield.

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Xiong, X., F. Stagnitti, G. Allinson, N. Turoczy, P. Li, M. LeBlanc, M. A. Cann et al. « Effects of clay amendment on adsorption and desorption of copper in water repellent soils ». Soil Research 43, n^o 3 (2005) : 397. http://dx.doi.org/10.1071/sr04088.

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Copper is an important micronutrient and trace amounts are essential for crop growth. However, high concentrations of copper will produce toxic effects. Australia is increasingly developing production of crops in water repellent soils. Clay amendment, a common amelioration techniques used in Australia, has demonstrated agronomic benefits in increased crop or pasture production. The sorption and desorption of copper and the effect of clay treatment on copper behaviour in a water repellent soil collected from an experimental farm in South Australia is studied. We found that the water repellent soils amended with clay have an increased adsorption capacity of copper. Also the clay-amended soils had an increased ratio of specific sorption to total sorption of copper. The implications of this study to the sustainable agro-environmental management of water repellent soils is discussed.

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Hollaway, K. L., R. S. Kookana, D. M. Noy, J. G. Smith et N. Wilhelm. « Crop damage caused by residual acetolactate synthase herbicides in the soils of south-eastern Australia ». Australian Journal of Experimental Agriculture 46, n^o 10 (2006) : 1323. http://dx.doi.org/10.1071/ea05053.

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Grain growers in south-eastern Australia have reported unexpected crop failures with theoretically safe recropping periods for acetolactate synthase herbicides in alkaline soils. This experience has led to the concern that these herbicides may degrade very slowly in alkaline soils, and herbicide residues have at times been blamed for unexplained crop losses. To address this issue, we established 5 recropping trials across Victoria and South Australia with 5 acetolactate synthase herbicides (chlorsulfuron, triasulfuron, metsulfuron-methyl, imazethapyr, and flumetsulam). The herbicides were applied to separate plots in years 1, 2 or 3, and sensitive crop species were sown in year 4 to measure the impact of herbicide residues. We observed that the persistence of the sulfonylureas (chlorsulfuron, triasulfuron, metsulfuron-methyl) varied between herbicides, but all persisted longer in alkaline soils than in acid soils, and were, therefore, more likely to damage crops in alkaline soil. Imazethapyr persisted longer in clay soils than in sandy soils and was, therefore, more likely to damage crops in clay soils. All herbicides persisted longer when rainfall was below average. Canola was more sensitive to imazethapyr than either pea, lentil or medic, but was less sensitive to the sulfonylureas. In contrast, lentil and medic were the most sensitive to sulfonylureas. Despite some damage, we found that safe recropping periods could be predicted from the product labels in all but one situation. The sole exception was that metsulfuron-methyl reduced dry matter and yield of lentil and medic sown 10 months after application in a soil with pH 8.5. We hypothesise that the real cause of crop failure in many situations is not unusual herbicide persistence, but failure to take full account of soil type (pH and clay content including variation in the paddock) and rainfall when deciding to recrop after using acetolactate synthase herbicides.

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Unkovich, Murray, Therese McBeath, Rick Llewellyn, James Hall, Vadakattu VSR Gupta et Lynne M. Macdonald. « Challenges and opportunities for grain farming on sandy soils of semi-arid south and south-eastern Australia ». Soil Research 58, n^o 4 (2020) : 323. http://dx.doi.org/10.1071/sr19161.

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Sandy soils make up a substantial fraction of cropping land in low rainfall (<450 mm p.a.) south and south-eastern Australia. In this paper we review the possible soil constraints to increased production on these soils in this region. Many of these soils have a very low (<3%) clay content and suffer from severe water repellency, making crop establishment and weed control problematic. Crops which do emerge are faced with uneven soil wetting and poor access to nutrients, with crop nutrition constraints exacerbated by low fertility (soil organic matter < 1%) and low cation exchange capacity. Zones of high penetration resistance appear common and have multiple causes (natural settling, cementation and traffic induced) which restrict root growth to <40 cm. Crop water use and grain yield are therefore likely to be well below the water-limited potential. Water repellency is readily diagnosed and where apparent should be the primary management target. Repellency can be mitigated through the use of furrow and other sowing technologies, along with soil wetting agents. These techniques appear to be affected by site and soil nuances and need to be refined for local soils and conditions. Once crop establishment on water repellent soils has been optimised, attention could be turned to opportunities for improving crop rooting depth through the use of deep tillage or deep ripping techniques. The required ripping depth, and how long the effects may last, are unclear and need further research, as do the most effective and efficient machinery requirements to achieve sustained deeper root growth. Crop nutrition matched to the water-limited crop yield potential is the third pillar of crop production that needs to be addressed. Low soil organic matter, low cation exchange capacity, low biological activity and limited nutrient cycling perhaps make this a greater challenge than in higher rainfall regions with finer textured soils. Interactions between nutrients in soils and fertilisers are likely to occur and make nutrient management more difficult. While amelioration (elimination) of water repellency is possible through the addition of clay to the soil surface, the opportunities for this may be restricted to the ~30% of the sandy soils of the region where clay is readily at hand. The amounts of clay required to eliminate repellency (~5%) are insufficient to significantly improve soil fertility or soil water holding capacity. More revolutionary soil amelioration treatments, involving additions and incorporation of clay and organic matter to soils offer the possibility of a more elevated crop yield plateau. Considerable research would be required to provide predictive capacity with respect to where and when these practices are effective.

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Adcock, D., A. M. McNeill, G. K. McDonald et R. D. Armstrong. « Subsoil constraints to crop production on neutral and alkaline soils in south-eastern Australia : a review of current knowledge and management strategies ». Australian Journal of Experimental Agriculture 47, n^o 11 (2007) : 1245. http://dx.doi.org/10.1071/ea06250.

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Crop yield variability and productivity below potential yield on neutral and alkaline soils in the semiarid Mediterranean-type environments of south-eastern Australia have been attributed, in part, to variable rooting depth and incomplete soil water extraction caused by physical and chemical characteristics of soil horizons below the surface. In this review these characteristics are referred to as subsoil constraints. This document reviews current information concerning subsoil constraints typical of neutral and alkaline soils in south-eastern Australia, principally salinity, sodicity, dense soils with high penetration resistance, waterlogging, nutrient deficiencies and ion toxicities. The review focuses on information from Australia (published and unpublished), using overseas data only where no suitable Australian data is available. An assessment of the effectiveness of current management options to address subsoil constraints is provided. These options are broadly grouped into three categories: (i) amelioration strategies, such as deep ripping, gypsum application or the use of polyacrylamides to reduce sodicity and/or bulk density, deep placement of nutrients or organic matter to overcome subsoil nutrient deficiencies or the growing of ‘primer’ crops to naturally ameliorate the soil; (ii) breeding initiatives for increased crop tolerance to toxicities such as salt and boron; and (iii) avoidance through appropriate agronomic or agro-engineering solutions. The review highlights difficulties associated with identifying the impact of any single subsoil constraint to crop production on neutral and alkaline soils in south-eastern Australia, given that multiple constraints may be present. Difficulty in clearly ranking the relative effect of particular subsoil constraints on crop production (either between constraints or in relation to other edaphic and biological factors) limits current ability to develop targeted solutions designed to overcome these constraints. Furthermore, it is recognised that the task is complicated by spatial and temporal variability of soil physicochemical properties and nutrient availability, as well as other factors such as disease and drought stress. Nevertheless, knowledge of the relative importance of particular subsoil constraints to crop production, and an assessment of impact on crop productivity, are deemed critical to the development of potential management solutions for these neutral to alkaline soils.

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Anderson, WK, RJ French et M. Seymour. « Yield responses of wheat and other crops to agronomic practices on duplex soils compared with other soils in Western Australia ». Australian Journal of Experimental Agriculture 32, n^o 7 (1992) : 963. http://dx.doi.org/10.1071/ea9920963.

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A survey of experimental results relating crop management to grain yield was conducted for wheat and other crops on duplex and non-duplex soils in the wheatbelt of Western Australia. Increases in grain yield of wheat due to improved agronomic practices on duplex soils were almost as great as on other soils. Early sowing improved yield more on duplex soils than on other soils, but the response to applied nitrogen was more variable, possibly related to the reduced efficiency of uptake of applied nitrogen. The yield advantage for a semi-dwarf cultivar (Aroona) over a tall cultivar (Garnenya) was less (6%) on duplex soils than on other soils (29%). The optimum seed rate was 27% greater on duplex than on other soils. Increases in both grain yield and grain quality due to the application of potassium were large on 1 duplex soil. Water use efficiency in grain production was similar on duplex and other soils where seasonal water use did not exceed about 350 mm. At 1 location in the eastern wheatbelt, yields of wheat, barley, lupins and peas grown on a duplex soil were compared with yields on 2 other soils. Wheat was the most productive crop on the duplex soil, while barley yielded most on the other soils. All crops, except lupins, yielded less on the duplex soil. Experiments with 2 lupin cultivars grown on duplex and other soils on the south coast of Western Australia (average growing season rainfall >300 mm) showed that both cultivars yielded less on duplex soils, but 1 cultivar required slightly fewer plants to achieve its maximum yield on the duplex soils. This survey of experimental results in Western Australia shows that duplex soils are no less productive than other soils when results are averaged over all crops and locations. We conclude, however, that different management practices may be required to improve yields on duplex compared with other soils.

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Lamb, D. W. « The use of qualitative airborne multispectral imaging for managing agricultural crops - a case study in south-eastern Australia ». Australian Journal of Experimental Agriculture 40, n^o 5 (2000) : 725. http://dx.doi.org/10.1071/ea99086.

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Charles Sturt University has operated an airborne multispectral imaging system as a research support and management tool over south-eastern Australian crops since 1994. Our experiences have demonstrated the utility, timeliness and cost-effectiveness of qualitative multispectral imagery for monitoring and managing spatial variability in a range of agricultural crops, yet to date the technology remains underutilised in Australia. Images showing variations in the texture of soils in paddocks are a useful indicator of the location of different soil zones for soil sampling, and can assist in siting of treatment plots within paddocks. Multispectral imagery can be used for a synoptic assessment of early weed pressure in fallow paddocks or seedling crops. Locating variability in crop emergence and, later, canopy vigour and biomass, are all potentially means of undertaking precision farming without the capital investment associated with yield mapping. However, like any remote monitoring tool, follow-up ground-truthing must always be used to establish or confirm the causes of observed variability. The use of the technology as part of a greater data acquisition strategy is recommended.

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Bolan, NS, RE White et MJ Hedley. « A review of the use of phosphate rocks as fertilizers for direct application in Australia and New Zealand. » Australian Journal of Experimental Agriculture 30, n^o 2 (1990) : 297. http://dx.doi.org/10.1071/ea9900297.

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Field trials in New Zealand have shown that reactive phosphate rocks (RPRs) can be as effective as soluble P fertilisers, per kg of P applied, on permanent pastures that have a soil pH<6.0 (in water) and a mean annual rainfall >800 mm. Whereas RPRs such as North Carolina, Sechura, Gafsa and Chatham Rise have been evaluated on permanent pastures in New Zealand, most Australian field trials have examined unreactive PRs such as Christmas Island A and C grade, Nauru and Duchess, using annual plant species. Only in recent experiments has an RPR, North Carolina, been examined. Except on the highly leached sands in southern and south-western Australia, both reactive and unreactive PRs have shown a low effectiveness relative to superphosphate. In addition to chemical reactivity, other factors may contribute to the difference in the observed agronomic effectiveness of PRs in Australia and New Zealand. Generally, PRs have been evaluated on soils of lower pH, higher pH buffering capacity (as measured by titratable acidity) and higher P status in New Zealand than in Australia. Rainfall is more evenly distributed throughout the year on New Zealand pastures than in Australia where the soil surface dries out between rainfall events. Dry conditions reduce the rate at which soil acid diffuses to a PR granule and dissolution products diffuse away. Even when pH and soil moisture are favourable, the release of P from PR is slow and more suited to permanent pasture (i.e. the conditions usually used to evaluate PRs in New Zealand) than to the annual pastures or crops used in most Australian trials. Based on the criteria of soil pH<6.0 and mean annual rainfall >800 mm, it is estimated that the potentially suitable area for RPRs on pasture in New Zealand is about 8 million ha. Extending this analysis to Australia, but excluding the seasonal rainfall areas of northern and south-western Australia, the potentially suitable area is about 13 million ha. In New Zealand, many of the soils in the North and South Islands satisfy both the pH and rainfall criteria. However, suitable areas in Australia are confined mainly to the coastal and tableland areas of New South Wales and eastern Victoria, and within these areas the actual effectiveness of RPR will depend markedly on soil management and the distribution of annual rainfall. Further research on RPR use should be focused on these areas.

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Gupta, V. V. S. R., S. J. Kroker, M. Hicks, C. W. Davoren, K. Descheemaeker et R. Llewellyn. « Nitrogen cycling in summer active perennial grass systems in South Australia : non-symbiotic nitrogen fixation ». Crop and Pasture Science 65, n^o 10 (2014) : 1044. http://dx.doi.org/10.1071/cp14109.

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Non-symbiotic nitrogen (N2) fixation by diazotrophic bacteria is a potential source for biological N inputs in non-leguminous crops and pastures. Perennial grasses generally add larger quantities of above- and belowground plant residues to soil, and so can support higher levels of soil biological activity than annual crops. In this study, the hypothesis is tested that summer-active perennial grasses can provide suitable microsites with the required carbon supply for N2 fixation by diazotrophs, in particular during summer, through their rhizosphere contribution. In a field experiment on a Calcarosol at Karoonda, South Australia, during summer 2011, we measured populations of N2-fixing bacteria by nifH-PCR quantification and the amount of 15N2 fixed in the rhizosphere and roots of summer-active perennial grasses. Diazotrophic N2 fixation estimates for the grass roots ranged between 0.92 and 2.35 mg 15N kg–1 root day–1. Potential rates of N2 fixation for the rhizosphere soils were 0.84–1.4 mg 15N kg–1 soil day–1 whereas the amount of N2 fixation in the bulk soil was 0.1–0.58 mg 15N kg–1 soil day–1. Populations of diazotrophic bacteria in the grass rhizosphere soils (2.45 × 106 nifH gene copies g–1 soil) were similar to populations in the roots (2.20 × 106 nifH gene copies g–1 roots) but the diversity of diazotrophic bacteria was significantly higher in the rhizosphere than the roots. Different grass species promoted the abundance of specific members of the nifH community, suggesting a plant-based selection from the rhizosphere microbial community. The results show that rhizosphere and root environments of summer-active perennial grasses support significant amounts of non-symbiotic N2 fixation during summer compared with cropping soils, thus contributing to biological N inputs into the soil N cycle. Some pasture species also maintained N2 fixation in October (spring), when the grasses were dormant, similar to that found in soils under a cereal crop. Surface soils in the rainfed cropping regions of southern Australia are generally low in soil organic matter and thus have lower N-supply capacity. The greater volume of rhizosphere soil under perennial grasses and carbon inputs belowground can potentially change the balance between N immobilisation and mineralisation processes in the surface soils in favour of immobilisation, which in turn contributes to reduced N losses from leaching.

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Wong, M. T. F., R. W. Bell et K. Frost. « Mapping boron deficiency risk in soils of south-west Western Australia using a weight of evidence model ». Soil Research 43, n^o 7 (2005) : 811. http://dx.doi.org/10.1071/sr05022.

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The aim of this work was to develop a risk map for boron (B) deficiency in the grain cropping regions of Western Australia (WA), whilst avoiding the high costs associated with direct B measurements for an area as vast as the south-west of WA. The study firstly determined relationships between 0.01 m CaCl2-extractable soil B levels and readily available data on soil properties and parent materials for Reference Soils of south-west Australia and secondly assembled direct evidence of B deficiency risk from surveys of farmers’ crops and soils and from glasshouse experiments. Across 73 Reference Soils, there was a positive relationship between 0.01 m CaCl2-extractable soil B levels and clay (r 2 = 0.50) and pH (r 2 = 0.43) in the surface horizon. Soils containing <0.5 mg B/kg generally had <5% clay and pH CaCl2 <5.5. Plant and soil analysis surveys in farmers’ fields revealed 10–20% of fields had B levels below tentative critical levels. In a glasshouse experiment, B response in oilseed rape was obtained in 4 sandy acid soils, all developed on sandstone parent materials. From this prior evidence of B deficiency, spatial data layers for surface soil pH, subsurface pH, surface clay level, and geology in south-western Australia were weighted and combined using the Dempster-Shafer weight of evidence model to map B-deficiency risk. The weightings of evidence layers were revised to increase the correspondence between predicted areas of high risk and field areas with measured low B or B deficiency from a validation dataset. The model helps overcome the high cost associated with direct B measurements for risk mapping. A similar approach may have value for mapping risk of other deficiencies of relevance to agriculture.

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Gardner, WK, RG Fawcett, GR Steed, JE Pratley, DM Whitfield, Hvan Rees et Rees H. Van. « Crop production on duplex soils in south-eastern Australia ». Australian Journal of Experimental Agriculture 32, n^o 7 (1992) : 915. http://dx.doi.org/10.1071/ea9920915.

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The environment, duplex soil types and trends in crop production in South Australia, southern New South Wales, north-eastern and north-central Victoria, the southern Wimmera and the Victorian Western District are reviewed. In the latter 2 regions, pastoral industries dominate and crop production is curtailed by regular and severe soil waterlogging, except for limited areas of lower rainfall. Subsurface drainage can eliminate waterlogging, but is feasible only for the Western District where subsoils are sufficiently stable. The other regions all have a long history of soil degradation due to cropping practices, but these effects can now be minimised with the use of direct drilling and stubble retention cropping methods. A vigorous pasture ley phase is still considered necessary to maintain nitrogen levels and to restore soil structure to adequate levels for sustainable farming. Future productivity improvements will require increased root growth in the subsoils. Deep ripping, 'slotting' of gypsum, and crop species capable of opening up subsoils are techniques which may hold promise in this regard. The inclusion of lucerne, a perennial species, in annual pastures and intercropping at intervals is a technique being pioneered in north-central and western Victoria and may provide the best opportunity to crop duplex soils successfully without associated land degradation.

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Nevard, Timothy D., Donald C. Franklin, Ian Leiper, George Archibald et Stephen T. Garnett. « Agriculture, brolgas and Australian sarus cranes on the Atherton Tablelands, Australia ». Pacific Conservation Biology 25, n^o 4 (2019) : 377. http://dx.doi.org/10.1071/pc18081.

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Flocks of brolgas (Antigone rubicunda) and Australian sarus cranes (A. antigone gillae) congregate in cropping areas of the Atherton Tablelands in north Queensland, Australia, during the non-breeding months of May to December each year and sometimes come into conflict with farmers. The central part of the region has been declared a Key Biodiversity Area, largely because it is the only well known non-breeding area for the Australian sarus crane. We investigated spatial and temporal patterns of use of this landscape for foraging by the two species to determine how they might be affected by changes in cropping. Abundances of the species were positively correlated with each other over both time and space. Sarus cranes were nevertheless markedly more abundant on the fertile volcanic soils of the central Tablelands, whilst brolgas were more abundant on a variety of soils in outlying cropping areas close to roost sites, especially in the south-west of the region. Both species used a wide variety of crops and pastures but occurred at highest densities on ploughed land and areas from which crops (especially maize) had been harvested. In addition, brolgas were also strongly associated with early-stage winter cereals with volunteer peanuts from the previous crop. We conclude that maize and peanut crops are important as foraging sites for both species during the non-breeding season, a situation that requires management in the interest of both cranes and farmers, especially as cropping patterns intensify and agricultural technology changes. However, we also note that flocking on the Atherton Tablelands indicates that brolgas and sarus cranes are likely to be adaptable to change and able to take advantage of newly created cropping areas.

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Cox, JW, DJ Mcfarlane et RW Skaggs. « Field-evaluation of DRAINMOD for predicting waterlogging intensity and drain performance in South-Western Australia ». Soil Research 32, n^o 4 (1994) : 653. http://dx.doi.org/10.1071/sr9940653.

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Waterlogging is common on sloping duplex soils in south-western Australia and causes damage to non-irrigated cereal crops and pastures. The factors which affect the performance of surface seepage interceptor drains installed to reduce this waterlogging are complex because the soils are very variable and have preferred pathways for groundwater flow. We compared DRAINMOD's predictions with field measured waterlogging intensity and drain flow over 3 years near Mt Barker and Narrogin in Western Australia. DRAINMOD failed to accurately predict waterlogging intensities and drain flows because water can move through macropores which bypass the soil matrix. At Mt Barker, DRAINMOD overpredicted waterlogging intensity by between 120% in a wet year and 650% in a very dry year. Drain flows were underpredicted by 148% in the driest year. At Narrogin, DRAINMOD underpredicted waterlogging intensity each year (rainfall was below average each year) and drain flow in the driest two years. However, by increasing Ks of the topsoil and adjusting Ks of the subsoil clay, DRAINMOD predictions agreed with measured responses. DRAINMOD can be used to predict waterlogging intensities and drain flows in duplex soils in the >450 mm annual rainfall areas of south-western Australia provided adjustments are made to the field point-measured Ks. Reliability increases with increasing rainfall during the growing season.

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Davidson, J. A., M. Krysinska-Kaczmarek, C. J. Wilmshurst, A. McKay, Herdina et E. S. Scott. « Distribution and Survival of Ascochyta Blight Pathogens in Field-Pea-Cropping Soils of Australia ». Plant Disease 95, n^o 10 (octobre 2011) : 1217–23. http://dx.doi.org/10.1094/pdis-01-11-0077.

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Phoma koolunga, Didymella pinodes, and P. medicaginis var. pinodella were detected in DNA extracted from soil following field pea crops across four states in the southeastern and western regions of Australia. P. koolunga was commonly detected in soil from South Australia but rarely in other states whereas D. pinodes plus P. medicaginis var. pinodella were widespread in all regions tested. The quantity of DNA of these pathogens detected in soils prior to growing field pea was positively correlated with ascochyta blight lesions on field pea subsequently grown in infested soil in a pot bioassay and also on field pea in naturally infected field trials. The quantity of DNA of the soilborne pathogens was greatest following a field pea crop and gradually decreased in the following 3 years. The DNA tests were used to quantify the DNA of the pathogens in field pea plants sampled from naturally infected field trials in South Australia over two seasons. The combined results of DNA tests and pathogen isolation from the plants indicated that P. koolunga and D. pinodes were equally responsible for the ascochyta blight symptoms in the diseased trials, while P. medicaginis var. pinodella had a minor role in the disease complex.

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Hollaway, K. L., R. S. Kookana, D. M. Noy, J. G. Smith et N. Wilhelm. « Persistence and leaching of sulfonylurea herbicides over a 4-year period in the highly alkaline soils of south-eastern Australia ». Australian Journal of Experimental Agriculture 46, n^o 8 (2006) : 1069. http://dx.doi.org/10.1071/ea04221.

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The sulfonylurea herbicides are commonly used in the cereal belt of south-eastern Australia and there is concern that their persistence in alkaline soils is long enough to damage subsequent rotational crops such as legumes and oilseeds. In this study, we investigated leaching and persistence of 3 commonly used herbicides (chlorsulfuron, triasulfuron and metsulfuron-methyl) in alkaline soils of south-eastern Australia (pH range 7.4–8.6) for at least 4 years after treatment. In general, chlorsulfuron was predicted to persist for 3–5 years [time to degrade to 1% (DT99) of 33–63 months after treatment depending on the field site], triasulfuron for 1–3 years (DT99 of 13–37 months after treatment), and metsulfuron-methyl for less than 1 year (although data were insufficient for degradation estimates) after its application. However, this varied between sites and years of application. Although, the majority of residues remained in the top 20 cm of the soil profile throughout the study, leaching of a small fraction of the residue to deeper layers of the profiles (up to 1 m) was observed. Despite their slow rate of degradation, the herbicides did eventually dissipate, even in soils with very high pH (8.5). In most cases, the current product labels provide an adequate safety period to protect sensitive rotational crops from potential damage due to excessive persistence. However, in particular years at 3 of the 5 field sites, metsulfuron-methyl and triasulfuron persisted beyond the recommended recropping period (9 months for metsulfuron-methyl and 22 months for triasulfuron in soils up to pH 7.5 or 24 months in soils pH 7.6 and above). An accurate measurement of soil pH and its variability within the paddock is essential to minimise any subsequent crop damage by these herbicides.

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Li, G. D., K. R. Helyar, M. K. Conyers, B. R. Cullis, P. D. Cregan, R. P. Fisher, L. J. C. Castleman, G. J. Poile, C. M. Evans et B. Braysher. « Crop responses to lime in long-term pasture-crop rotations in a high rainfall area in south-eastern Australia ». Australian Journal of Agricultural Research 52, n^o 3 (2001) : 329. http://dx.doi.org/10.1071/ar00087.

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A long-term trial, known as ‘managing acid soils through efficient rotations’ (MASTER), commenced in 1992 to develop and demonstrate a cropping system that is economically viable on the highly acid soils of the traditional permanent pasture region in south-eastern Australia, so that their fertility is sustained or improved. There were 2 permanent pasture systems and 2 pasture–crop rotations, each with and without lime. This paper reports the effect of lime on crop production over the first cycle (6 years). On annual pasture–crop rotations, lime significantly increased the dry matter production at anthesis and grain yields of wheat (cv. Dollarbird) compared with the unlimed treatments. Averaged across years from 1992 to 1997 (excluding the severe drought year 1994), wheat crops produced 1.6 t/ha more grain on the limed treatments than on the unlimed treatments (3.6 v. 2.0 t/ha). On perennial pasture–crop rotations, the lime effects varied with crops grown at each phase and year. For example, despite being tolerant of acidity, oats (cv. Yarran) responded to lime in 1996. Likewise, triticale (cv. Abacus) responded to lime in 1997. Wheat (cv. Dollarbird) that is moderately tolerant to acidity responded to lime in phase 6 from 1992 to 1997 excluding 1994 (3.5 v. 1.7 t/ha). Acid-tolerant wheat varieties, triticale, and narrow-leaf lupins are considered the most viable crops for the soil and climatic conditions encountered in this high rainfall (5000—800 mm per annum) area of south-eastern Australia.

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Bolland, M. D. A., D. G. Allen et K. S. Walton. « Soil testing for phosphorus : comparing the Mehlich 3 and Colwell procedures for soils of south-western Australia ». Soil Research 41, n^o 6 (2003) : 1185. http://dx.doi.org/10.1071/sr02153.

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Soil samples were collected from 14 long-term field experiments in south-western Australia to which several amounts of superphosphate or phosphate rock had been applied in a previous year. The samples were analysed for phosphorus (P) by the Colwell sodium bicarbonate procedure, presently used in Western Australia, and the Mehlich 3 procedure, being assessed as a new multi-element test for the region. For the Mehlich procedure, the concentration of total and inorganic P in the extract solution was measured. The soil test values were related to yields of crops and pasture measured later on in the year in which the soil samples were collected.The Mehlich 3 procedures (Mehlich 3 total and Mehlich 3 inorganic soil test P values) were similar, with the total values mostly being slightly larger. For soil treated with superphosphate, for each year of each experiment: (i) Mehlich 3 values were closely correlated with Colwell values; and (ii) the relationship between plant yield and soil test P (the soil P test calibration) was similar for the Colwell and Mehlich 3 procedures. However, for soil treated with phosphate rock, the Colwell procedure consistently produced lower soil test P values than the Mehlich 3 procedure, and the calibration relating plant yield to soil test P was different for the Colwell and Mehlich 3 procedures, indicating, for soils treated with phosphate rock, separate calibrations are required for the 2 procedures. We conclude that for soils of south-western Australia treated with superphosphate (most of the soils), the Mehlich 3 procedure can be used instead of the Colwell procedure to measure soil test P, providing support for the Mehlich 3 procedure to be developed as the multi-element soil test for the region.

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Hollaway, K. L., R. S. Kookana, D. M. Noy, J. G. Smith et N. Wilhelm. « Persistence and leaching of imazethapyr and flumetsulam herbicides over a 4-year period in the highly alkaline soils of south-eastern Australia ». Australian Journal of Experimental Agriculture 46, n^o 5 (2006) : 669. http://dx.doi.org/10.1071/ea04223.

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Imazethapyr and flumetsulam are acetolactate synthase herbicides commonly used in the cereal belt of south-eastern Australia. As their labels recommend recropping periods of up to 34 months for imazethapyr and 24 months for flumetsulam, there are concerns that in some cases their persistence may damage subsequent rotation crops. This is the first major study in south-eastern Australia to investigate their leaching and persistence for up to 4 years after treatment. Imazethapyr persisted for more than 3 years at 2 sites and flumetsulam for more than 2 years at 3 sites. For imazethapyr, soil type (clay content) rather than soil pH seemed to be most important in determining persistence, with residues of 10% of applied imazethapyr predicted to persist for 24 months after treatment in clay soil and 5 months after treatment in sandy soil. The potential for leaching below our studied soil depth of 40 cm is of concern for imazethapyr but not for flumetsulam. The current labels appear to provide adequate information for safe recropping periods, but may be conservative for imazethapyr in sandy soils.

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Bailey, P., J.-L. Sagliocco, J. Vitou et D. Cooke. « Prospects for biological control of cutleaf mignonette, Reseda lutea (Resedaceae), by Baris picicornis and Bruchela spp. in Australia ». Australian Journal of Experimental Agriculture 42, n^o 2 (2002) : 185. http://dx.doi.org/10.1071/ea01059.

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In South Australia, Reseda lutea is abundant, invading pastures and crops on calcareous soils while in its native Mediterranean range it is uncommon in occurrence and is not reported as a weed of cultivated crops. Its invasive behaviour in South Australia may be attributed to vegetative growth of root fragments spread by cultivation, while propagation by seed is of minor importance. Surveys in Spain, Portugal, Morocco, France, Turkey and Israel indicated that agronomic differences, particularly depth of cultivation and seeding rates of cereals may explain why it is not a crop weed in these countries. Another difference is that plants in the region of origin have an associated fauna not present in Australia. These potential biological control agents include a root-boring weevil, Baris picicornis, flower- and seed-feeding urodontids, Bruchela suturalis and B. rufipes, and a leaf spot pathogen,Cercospora resedae. Baris picicornis was introduced from France and Turkey, under quarantine, to Australia but laboratory specificity-testing demonstrated that it could complete its life cycle on 2 commercially grown cultivars of Brassica rapa (choy sum and Chinese cabbage). Because of this, it is not proposed to release B. picicornis in Australia at present. Bruchela suturalis was also introduced into Australian quarantine from France but attempts to change its annual life cycle to Southern Hemisphere seasons were not successful, and a culture could not be established. Both Baris picicornis and Bruchela spp. remain promising agents, and further work on their introduction is justified by their potential for biological control of R. lutea.

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Li, Guangdi D., Rajinder P. Singh, John P. Brennan et Keith R. Helyar. « A financial analysis of lime application in a long-term agronomic experiment on the south-western slopes of New South Wales ». Crop and Pasture Science 61, n^o 1 (2010) : 12. http://dx.doi.org/10.1071/cp09103.

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Management of Acid Soils Through Efficient Rotations (MASTER) is a long-term agronomic experiment commenced in 1992. There were 3 fundamental treatment contrasts in this experiment: (a) annual systems v. perennial systems; (b) limed v. unlimed treatments; and (c) permanent pastures v. pasture–crop rotations. The soil was acidic to depth with pH (in CaCl2) below 4.5 and exchangeable Al above 40% at 0.10–0.20 m when the experiment started. Lime was applied every 6 years to maintain soil pHCa at 5.5 in the 0–0.10 m soil depth. A financial analysis was undertaken to estimate potential benefits and costs involved in liming acid soils on the south-western slopes of New South Wales, based on data from the MASTER experiment. The most important finding from the current study is that liming pastures on soils that have a subsurface acidity problem is profitable over the long-term for productive livestock enterprises. The pay-back period for liming pastures, grazed by Merino wethers, was 14 years for both annual and perennial pastures. More profitable livestock enterprises, such as prime lambs or growing-out steers, were estimated to reduce the pay-back period. This gives farmers confidence to invest in a long-term liming program to manage highly acid soils in the traditional permanent pasture region of the high-rainfall zone (550–800 mm) of south-eastern Australia. Results from the current study also confirmed that the total financial return from liming is greater if the land is suitable for operation of a pasture–crop rotation system. The positive cash flows generated from cropping in a relatively short time can significantly shorten the pay-back period for the investment in lime. But cropping without liming on soils with subsurface acidity was worse than grazing animals. Crop choice is crucial for the perennial pasture–crop rotation. Inclusion of high-value cash crops, such as canola or a wheat variety with high protein, would lead to a rise in the aggregate benefits over time as the soil fertility improved and soil acidity was gradually ameliorated.

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Nichols, P. G. H., M. J. Barbetti, G. A. Sandral, B. S. Dear, C. T. de Koning, D. L. Lloyd, P. M. Evans, A. D. Craig, P. Si et M. P. You. « Coolamon subterranean clover (Trifolium subterraneum L. var. subterraneum) ». Australian Journal of Experimental Agriculture 47, n^o 2 (2007) : 223. http://dx.doi.org/10.1071/ea05282.

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Coolamon is a mid-season to late-season flowering F4-derived crossbred subterranean clover of var. subterraneum, developed by the collaborating organisations of the National Annual Pasture Legume Improvement Program. It is a replacement for Junee and has been selected for release on the basis of its greater herbage production and persistence, and its resistance to both known races of clover scorch. Coolamon is recommended for sowing in Western Australia, New South Wales, Victoria, South Australia and Queensland. It is best suited to well-drained, moderately acidic soils in areas with a growing season of 6.5–8 months that extends into November. Coolamon is best suited to phase farming and permanent pasture systems. It can also be used in cropping rotations, but at least 2 years of pasture are required between crops. Coolamon has been granted Plant Breeders Rights in Australia.

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Chan, K. Y., C. G. Dorahy, S. Tyler, A. T. Wells, P. P. Milham et I. Barchia. « Phosphorus accumulation and other changes in soil properties as a consequence of vegetable production, Sydney region, Australia ». Soil Research 45, n^o 2 (2007) : 139. http://dx.doi.org/10.1071/sr06087.

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A survey of 34 farms covering the major soil types used for growing vegetables within the greater Sydney metropolitan region (New South Wales, Australia) was undertaken to determine the effect of vegetable production on soil chemical and physical properties. Comparison of farmed ‘vegetable’ v. unfarmed ‘reference’ sites revealed that the soils used for vegetable production had extremely high concentrations of total P, Colwell-P, and CaCl2-extractable P (mean 1205, 224, and 4.3 mg/kg in the 0–0.30 m layer, respectively). In the 0–0.30 m soil layer, mean bicarbonate-extractable P (Colwell-P) concentrations have increased to up to 44 times that of the unfarmed reference soils and exceed that required for adequate vegetable nutrition. Concentrations of P in the soil solution (CaCl2-P) were up to 230 times that of the unfarmed reference soils. Moreover, the vegetable soils had low total soil carbon concentrations (mean 14.1 g/kg in the 0–0.10 m layer, only 57% of the mean concentration of the reference soils). These soils exhibited extremely low structural stability, which is likely to reduce soil infiltration rates and increase the potential for runoff. Marked changes in soil pH, EC, and exchangeable cations (Ca, Mg, and K) were also observed as a consequence of vegetable production. All of these changes are a consequence of current management practices used in vegetable production, which include application of high rates of inorganic fertilisers and poultry manure, as well as excessive cultivation. Excessive accumulation of P, to at least 0.30 m depth, coupled with a loss of soil structural stability, is of particular environmental concern. Options such as adopting minimum tillage, in conjunction with using alternative inputs such as low P composts and cover crops, as a means of improving soil structure and reducing the extent of P accumulation in these soils require further investigation.

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Angus, J. F., A. F. van Herwaarden, D. P. Heenan, R. A. Fischer et G. N. Howe. « The source of mineral nitrogen for cereals in south-eastern Australia ». Australian Journal of Agricultural Research 49, n^o 3 (1998) : 511. http://dx.doi.org/10.1071/a97125.

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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.

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French, Robert J., et Bevan J. Buirchell. « Lupin : the largest grain legume crop in Western Australia, its adaptation and improvement through plant breeding ». Australian Journal of Agricultural Research 56, n^o 11 (2005) : 1169. http://dx.doi.org/10.1071/ar05088.

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Between 500 000 and 1 000 000 tonnes of narrow-leafed lupins (Lupinus angustifolius L.) are produced in Western Australia each year. It has become the predominant grain legume in Western Australian agriculture because it is peculiarly well adapted to acid sandy soils and the Mediterranean climate of south-western Australia. It has a deep root system and root growth is not reduced in mildly acid soils, which allows it to fully exploit the water and nutrients in the deep acid sandplain soils that cover much of the agricultural areas of Western Australia. It copes with seasonal drought through drought escape and dehydration postponement. Drought escape is lupin’s main adaptation to drought, and has been strengthened by plant breeders over the past 40 years by removal of the vernalisation requirement for flowering, and further selection for earlier flowering and maturity. Lupin postpones dehydration by several mechanisms. Its deep root system allows it to draw on water from deep in the soil profile. Lupin stomata close to reduce crop water demand at a higher leaf water potential than wheat, but photosynthetic rates are higher when well watered. It has been proposed that stomata close in response to roots sensing receding soil moisture, possibly at a critical water potential at the root surface. This is an adaptation to sandy soils, which hold a greater proportion of their water at high matric potentials than loamy or clayey soils, since the crop needs to moderate its water use while there is still sufficient soil water left to complete its life cycle. Lupin has limited capacity for osmotic adjustment, and does not tolerate dehydration as well as other crops such as wheat or chickpea. Plant breeding has increased the yield potential of lupin in the main lupin growing areas of Western Australia by 2–3 fold since the first adapted cultivar was released in 1967. This has been due largely to selecting earlier flowering and maturing cultivars, but also to improved pod set and retention, resistance to Phomopsis leptostromiformis (Kühn) Bubák, and more rapid seed filling. We propose a model for reproductive development in lupin where vegetative growth is terminated in response to receding soil moisture and followed by a period in which all assimilate is devoted to seed filling. This should allow lupin to adjust its developmental pattern in response to seasonal conditions to something like the optimum that mathematical optimal control theory would choose for that season. This is the type of pattern that has evolved in lupin, and the task of future plant breeders will be to fine-tune it to better suit the environment in the lupin growing areas of Western Australia.

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Brennan, R. F., M. D. A. Bolland et J. W. Bowden. « Potassium deficiency, and molybdenum deficiency and aluminium toxicity due to soil acidification, have become problems for cropping sandy soils in south-western Australia ». Australian Journal of Experimental Agriculture 44, n^o 10 (2004) : 1031. http://dx.doi.org/10.1071/ea03138.

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Nutrient omission experiments determined the cause of ‘waves’ of good and bad growth in wheat and barley crops following burning of swathed canola crop residues on acidified sandy soils in south-western Australia. Potassium deficiency, and molybdenum deficiency and aluminium toxicity induced by soil acidification, were identified as major problems. Burning canola swaths increased bicarbonate-extractable soil potassium by 20–100 mg/kg, and as measured in 0.01 mol/L CaCl2, increased soil pH by 0.3–0.8 of a pH unit and decreased aluminium extracted from soil by 1–6 mg/kg. These changes in soil chemistry were shown to be responsible for waves of better crop growth under the burnt swaths. Root lesion nematodes were shown not to be related to the problem.

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Hocking, P. J., et M. J. McLaughlin. « Genotypic variation in cadmium accumulation by seed of linseed, and comparison with seeds of some other crop species ». Australian Journal of Agricultural Research 51, n^o 4 (2000) : 427. http://dx.doi.org/10.1071/ar99124.

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The accumulation of cadmium (Cd) in plants is a health issue because a range of grain and vegetable crops can accumulate levels of Cd that are in excess of limits set by the World Health Organization and individual countries. Many Australian agricultural soils used to produce confectionery linseed have a history of intensive use of Cd-contaminated phosphatic fertilisers and this, combined with soil properties such as high chloride salinity, can result in enhanced availability of Cd to crops. We investigated genotypic variation in Cd accumulation in seed of 17 linseed and Linola (termed linseed) lines from Australia and elsewhere in a glasshouse study using a soil from southern Australia that had a history of the application of Cd-contaminated phosphatic fertiliser. Canola, Indian mustard, lupins, and wheat were also included in the study for comparison. Under the experimental conditions, Cd concentrations in seed of all but one of the linseed lines exceeded the maximum permitted concentration (MPC) of 250 µg/kg for confectionery linseed traded on the international market. There was a 2.3-fold variation in seed Cd concentrations between all the linseed lines (range, 233–545 µg/kg). Linseed lines from Australia and overseas were equally capable of accumulating Cd in seed. Brown-seeded and golden-seeded lines accumulated similar concentrations of Cd. Canola, Indian mustard, lupins, and wheat accumulated about 10-fold lower concentrations of Cd in seed than linseed, and did not exceed Australian or other MPCs. There was little difference in Cd concentrations between the seed and de-seeded capsules of linseed, but a large difference in Cd concentration between the seed and de-seeded fruit parts of the other crops. The mean seed to de-seeded fruit part Cd concentration ratio for linseed was 0.87 : 1 compared with a ratio of 0.35 : 1 for the other crops, suggesting that linseed has comparatively ineffective barriers discriminating against the transport of Cd to seed. Analysis of seed lots of confectionery linseed sampled from a grain receival depot showed that seed lots from farms in Victoria (range 140–560 µg Cd/kg) had 5-fold greater Cd concentrations than those from farms in New South Wales (range 20–160 µg/kg). This is presumably due to a more intensive history of the application of Cd-contaminated phosphatic fertiliser to pastures and crops in Victoria, as well as differences in environmental and soil conditions.

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Nuttall, J. G., et R. D. Armstrong. « Impact of subsoil physicochemical constraints on crops grown in the Wimmera and Mallee is reduced during dry seasonal conditions ». Soil Research 48, n^o 2 (2010) : 125. http://dx.doi.org/10.1071/sr09075.

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Subsoil physicochemical constraints can limit crop production on alkaline soils of south-eastern Australia. Fifteen farmer paddocks sown to a range of crops including canola, lentil, wheat, and barley in the Wimmera and Mallee of Victoria and the mid-north and Eyre Peninsula of South Australia were monitored from 2003 to 2006 to define the relationship between key abiotic/edaphic factors and crop growth. The soils were a combination of Calcarosol and Vertosol profiles, most of which had saline and sodic subsoils. There were significant correlations between ECe and Cl– (r = 0.90), ESP and B (r = 0.82), ESP and ECe (r = 0.79), and ESP and Cl– (r = 0.73). The seasons monitored had dry pre-cropping conditions and large variations in spring rainfall in the period around flowering. At sowing, the available soil water to a depth of 1.2 m (θa) averaged 3 mm for paddocks sown to lentils, 28 mm for barley, 44 mm for wheat, and 92 mm for canola. Subsoil constraints affected canola and lentil crops but not wheat or barley. For lentil crops, yield variation was largely explained by growing season rainfall (GSR) and θa in the shallow subsoil (0.10–0.60 m). Salinity in this soil layer affected lentil crops through reduced water extraction and decreased yields where ECe exceeded 2.2 dS/m. For canola crops, GSR and θa in the shallow (0.10–0.60 m) and deep (0.60–1.20 m) layers were important factors explaining yield variation. Sodicity (measured as ESP) in the deep subsoil (0.80–1.00 m) reduced canola growth where ESP exceeded 16%, corresponding to a 500 kg/ha yield penalty. For cereal crops, rainfall in the month around anthesis was the most important factor explaining grain yield, due to the large variation in rainfall during October combined with the determinant nature of these crops. For wheat, θa in the shallow subsoil (0.10–0.60 m) at sowing was also an important factor explaining yield variation. Subsoil constraints had no impact on cereal yield in this study, which is attributed to the lack of available soil water at depth, and the crops’ tolerance of the physicochemical conditions encountered in the shallow subsoil, where plant-available water was more likely to occur. Continuing dry seasonal conditions may mean that the opportunity to recharge soil water in the deeper subsoil, under continuous cropping systems, is increasingly remote. Constraints in the deep subsoil are therefore likely to have reduced impact on cereals under these conditions, and it is the management of water supply, from GSR and accrued soil water, in the shallow subsoil that will be increasingly critical in determining crop yields in the future.

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McBeath, T. M., M. J. McLaughlin, R. D. Armstrong, M. Bell, M. D. A. Bolland, M. K. Conyers, R. E. Holloway et S. D. Mason. « Predicting the response of wheat (Triticum aestivum L.) to liquid and granular phosphorus fertilisers in Australian soils ». Soil Research 45, n^o 6 (2007) : 448. http://dx.doi.org/10.1071/sr07044.

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Liquid forms of phosphorus (P) have been shown to be more effective than granular P for promoting cereal growth in alkaline soils with high levels of free calcium carbonate on Eyre Peninsula, South Australia. However, the advantage of liquid over granular P forms of fertiliser has not been fully investigated across the wide range of soils used for grain production in Australia. A glasshouse pot experiment tested if liquid P fertilisers were more effective for growing spring wheat (Triticum aestivum L.) than granular P (monoammonium phosphate) in 28 soils from all over Australia with soil pH (H2O) ranging from 5.2 to 8.9. Application of liquid P resulted in greater shoot biomass, as measured after 4 weeks’ growth (mid to late tillering, Feeks growth stage 2–3), than granular P in 3 of the acidic to neutral soils and in 3 alkaline soils. Shoot dry matter responses of spring wheat to applied liquid or granular P were related to soil properties to determine if any of the properties predicted superior yield responses to liquid P. The calcium carbonate content of soil was the only soil property that significantly contributed to predicting when liquid P was more effective than granular P. Five soil P test procedures (Bray, Colwell, resin, isotopically exchangeable P, and diffusive gradients in thin films (DGT)) were assessed to determine their ability to measure soil test P on subsamples of soil collected before the experiment started. These soil test values were then related to the dry matter shoot yields to assess their ability to predict wheat yield responses to P applied as liquid or granular P. All 5 soil test procedures provided a reasonable prediction of dry matter responses to applied P as either liquid or granular P, with the resin P test having a slightly greater predictive capacity on the range of soils tested. The findings of this investigation suggest that liquid P fertilisers do have some potential applications in non-calcareous soils and confirm current recommendations for use of liquid P fertiliser to grow cereal crops in highly calcareous soils. Soil P testing procedures require local calibration for response to the P source that is going to be used to amend P deficiency.

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Huang, Xiaodong, Peter Grace, Keith Weier et Kerrie Mengersen. « Nitrous oxide emissions from subtropical horticultural soils : a time series analysis ». Soil Research 50, n^o 7 (2012) : 596. http://dx.doi.org/10.1071/sr11100.

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Time series regression models were used to examine the influence of environmental factors (soil water content and soil temperature) on the emissions of nitrous oxide (N2O) from subtropical soils, by taking into account temporal lagged environmental factors, autoregressive processes, and seasonality for three horticultural crops in a subtropical region of Australia. Fluxes of N2O, soil water content, and soil temperature were determined simultaneously on a weekly basis over a 12-month period in South East Queensland. Annual N2O emissions for soils under mango, pineapple, and custard apple were 1590, 1156, and 2038 g N2O-N/ha, respectively, with most emissions attributed to nitrification. The N2O-N emitted from the pineapple and custard apple crops was equivalent to 0.26 and 2.22%, respectively, of the applied mineral N. The change in soil water content was the key variable for describing N2O emissions at the weekly time-scale, with soil temperature at a lag of 1 month having a significant influence on average N2O emissions (averaged) at the monthly time-scale across the three crops. After accounting for soil temperature and soil water content, both the weekly and monthly time series regression models exhibited significant autocorrelation at lags of 1–2 weeks and 1–2 months, and significant seasonality for weekly N2O emissions for mango crop and for monthly N2O emissions for mango and custard apple crops in this location over this time-frame. Time series regression models can explain a higher percentage of the temporal variation of N2O emission compared with simple regression models using soil temperature and soil water content as drivers. Taking into account seasonal variability and temporal persistence in N2O emissions associated with soil water content and soil temperature may lead to a reduction in the uncertainty surrounding estimates of N2O emissions based on limited sampling effort.

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Angus, J. F., R. R. Gault, M. B. Peoples, M. Stapper et A. F. van Herwaarden. « Soil water extraction by dryland crops, annual pastures, and lucerne in south-eastern Australia ». Australian Journal of Agricultural Research 52, n^o 2 (2001) : 183. http://dx.doi.org/10.1071/ar00103.

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The extraction of soil water by dryland crops and pastures in south-eastern Australia was examined in 3 studies. The first was a review of 13 published measurements of soil water-use under wheat at several locations in southern New South Wales. Of these, 8 showed significantly more water extracted by crops managed with increased nitrogen supply or growing after a break crop. The mean additional soil water extraction in response to break crops was 31 mm and to additional N was 11 mm. The second study used the SIMTAG model to simulate growth and water-use by wheat in relation to crop management at Wagga Wagga. The model was set up to simulate crops that produced either average district yields or the potential yields achievable with good management. When simulated over 50 years of weather data, the combined water loss as drainage and runoff was predicted to be 67 mm/year for poorly managed crops and 37 mm for well-managed crops. Water outflow was concentrated in 70% of years for the poorly managed crops and 56% for the well-managed crops. In those years the mean losses were estimated to be 95 mm and 66 mm, respectively. The third study reports soil water measured twice each year during a phased pasture–crop sequence over 6.5 years at Junee. Mean water content of the top 2.0 m of soil under a lucerne pasture averaged 211 mm less than under a subterranean clover-based annual pasture and 101 mm less than under well-managed crops. Collectively, these results suggest that lucerne pastures and improved crop management can result in greater use of rainfall than the previous farming systems based on annual pastures, fallows, and poorly managed crops. The tactical use of lucerne-based pastures in sequence with well-managed crops can help the dewatering of the soil andreduce or eliminate the risk of groundwater recharge.

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Ward, P. R., R. A. Lawes et D. Ferris. « Soil-water dynamics in a pasture-cropping system ». Crop and Pasture Science 65, n^o 10 (2014) : 1016. http://dx.doi.org/10.1071/cp14046.

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Pasture cropping is a farming system in which annual crops are sown into established perennial pastures. It may provide environmental benefits such as increased groundcover and reduced deep drainage, while allowing traditional crop production in the Mediterranean-style climate of south-western Australia. In this research, we investigated deep drainage and the temporal patterns of water use by a subtropical perennial grass, annual crops, and a pasture-cropping system over a 4-year period. Both the pasture and pasture-cropped treatments reduced deep drainage significantly, by ~50 mm compared with the crop treatment. Competition between the pasture and crop components altered patterns of average daily water use, the pasture-cropped treatment having the highest water use for July, August and September. Consequently, water-use efficiency for grain production was lower in the pasture-cropped plots. This was offset by pasture production, so that over a full 12-month period, water-use efficiency for biomass production was generally greater for the pasture-cropped plots than for either the pasture or crop monocultures. Pasture cropping may be a viable way of generating sustainable economic returns from both crop and pasture production on sandy soils of south-western Australia.

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Bell, M. J., P. W. Moody, G. R. Harch, B. Compton et P. S. Want. « Fate of potassium fertilisers applied to clay soils under rainfed grain cropping in south-east Queensland, Australia ». Soil Research 47, n^o 1 (2009) : 60. http://dx.doi.org/10.1071/sr08088.

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Negative potassium (K) balances in all broadacre grain cropping systems in northern Australia are resulting in a decline in the plant-available reserves of K and necessitating a closer examination of strategies to detect and respond to developing K deficiency in clay soils. Grain growers on the Red Ferrosol soils have increasingly encountered K deficiency over the last 10 years due to lower available K reserves in these soils in their native condition. However, the problem is now increasingly evident on the medium-heavy clay soils (Black and Grey Vertosols) and is made more complicated by the widespread adoption of direct drill cropping systems and the resulting strong stratification of available K reserves in the top 0.05–0.1 m of the soil profile. This paper reports glasshouse studies examining the fate of applied K fertiliser in key cropping soils of the inland Burnett region of south-east Queensland, and uses the resultant understanding of K dynamics to interpret results of field trials assessing the effectiveness of K application strategies in terms of K availability to crop plants. At similar concentrations of exchangeable K (Kexch), soil solution K concentrations and activity of K in the soil solution (ARK) varied by 6–7-fold between soil types. When Kexch arising from different rates of fertiliser application was expressed as a percentage of the effective cation exchange capacity (i.e. K saturation), there was evidence of greater selective adsorption of K on the exchange complex of Red Ferrosols than Black and Grey Vertosols or Brown Dermosols. Both soil solution K and ARK were much less responsive to increasing Kexch in the Black Vertosols; this is indicative of these soils having a high K buffer capacity (KBC). These contrasting properties have implications for the rate of diffusive supply of K to plant roots and the likely impact of K application strategies (banding v. broadcast and incorporation) on plant K uptake. Field studies investigating K application strategies (banding v. broadcasting) and the interaction with the degree of soil disturbance/mixing of different soil types are discussed in relation to K dynamics derived from glasshouse studies. Greater propensity to accumulate luxury K in crop biomass was observed in a Brown Ferrosol with a KBC lower than that of a Black Vertosol, consistent with more efficient diffusive supply to plant roots in the Ferrosol. This luxury K uptake, when combined with crops exhibiting low proportional removal of K in the harvested product (i.e. low K harvest index coarse grains and winter cereals) and residue retention, can lead to rapid re-development of stratified K profiles. There was clear evidence that some incorporation of K fertiliser into soil was required to facilitate root access and crop uptake, although there was no evidence of a need to incorporate K fertiliser any deeper than achieved by conventional disc tillage (i.e. 0.1–0.15 m). Recovery of fertiliser K applied in deep (0.25–0.3 m) bands in combination with N and P to facilitate root proliferation was quite poor in Red Ferrosols and Grey or Black Vertosols with moderate effective cation exchange capacity (ECEC, 25–35 cmol(+)/kg), was reasonable but not enough to overcome K deficiency in a Brown Dermosol (ECEC 11 cmol(+)/kg), but was quite good on a Black Vertosol (ECEC 50–60 cmol(+)/kg). Collectively, results suggest that frequent small applications of K fertiliser, preferably with some soil mixing, is an effective fertiliser application strategy on lighter clay soils with low KBC and an effective diffusive supply mechanism. Alternately, concentrated K bands and enhanced root proliferation around them may be a more effective strategy in Vertosol soils with high KBC and limited diffusive supply. Further studies to assess this hypothesis are needed.

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Xu, ZH, JN Ladd et DE Elliott. « Soil nitrogen availability in the cereal zone of South Australia .1. Soil organic carbon, total nitrogen, and nitrogen mineralisation rates ». Soil Research 34, n^o 6 (1996) : 937. http://dx.doi.org/10.1071/sr9960937.

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Assessments of soil nitrogen (N) availability were undertaken using soils sampled at 0-10 and 10-20 cm depths from 123 experimental sites where the responses of cereal crops to N fertilisers were tested, throughout the cereal zone of South Australia. Rates of N mineralisation and percentage N mineralisation, as determined by a laboratory aerobic incubation method, were related to soil properties. Mineralisable N (N mineralised during a Li-week incubation) of 0-10 cm soil varied from 14 to 121 kg N/ha with a median of 50 kg N/ha, and that of 10-20 cm soil, from 5 to 42 kg N/ha (median 19 kg N/ha). Mineralisable N in 0-10 cm soil accounted for 90% of total mineralisable N in 0-20 cm soil. The percentages of N mineralised were generally higher in 0-10 cm soil (0.8-12.5%, median 3.4%) than in 10-20 cm soil (0.4-8.3%, median 2.3%). Soil organic carbon (OC) and total N could be well estimated from each other, and fron! soil pH, bulk density, and held capacity, with coefficients of determination (R2) ranging from 0.64 to 0.78. Overall, either mineralisable N or percentage N mineralisation rate in the surface soils could be well estimated from soil OC, total N, C to N ratio, bulk density, field capacity, and pH (R2, 0.78-0.86 for mineralisable N, and 0.67-0.91 for percentage N mineralisation rate).

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Norton, R. M., et N. G. Wachsmann. « Nitrogen use and crop type affect the water use of annual crops in south-eastern Australia ». Australian Journal of Agricultural Research 57, n^o 3 (2006) : 257. http://dx.doi.org/10.1071/ar05056.

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The effect of management and crop selection on water use and profile drying was investigated using 2 series of experiments conducted in the Victorian Wimmera. The effect of applied nitrogen on growth and water use of canola was assessed from 3 field experiments on a Vertosol soil. Across these sites, 140 kg N/ha increased crop water use by a mean of 30 mm, and the biological response averaged 3.68 t/ha of shoot dry matter and seed yield increased by 73% from 1.46 to 2.52 t/ha. The additional nitrogen enabled roots to go deeper into the soil and also to extract water to higher tensions, but the increases in water use were far less than the growth and yield responses. Estimated average soil evaporation was 120 mm across these experiments, but ranged from 26 to 57% of total water use. It was concluded that increased crop vigour in response to applied nitrogen does increase total water use, but the main way that water-use efficiency increases is through reduced soil evaporation. In a second series of experiments, the growth, yield, and water use of wheat, canola, linseed, mustard, and safflower were compared across 4 sites with differing soil moisture contents. Wheat was the highest yielding crop at all sites. Mustard and canola produced similar amounts of biomass and seed yields, whereas linseed produced seed yields that were generally less than the brassica oilseeds. Safflower grew well and produced large amounts of biomass at all sites, but this increased growth did not necessarily translate into increased seed yields. Safflower yielded less seed than all other crops at the 2 dry sites, but yields were similar to canola at the wetter sites. On 2 drier sites, soil water extraction occurred to approximately 1 m for all crops, and all available water was used within that zone by all crops. Where the soil was wet beyond 1 m, safflower was able to extract water from deeper in the profile than the other crops and generated a soil water deficit of about 100 mm more than the other crops at maturity. This deficit persisted into the subsequent autumn–winter period. The potential of using safflower as a management option to extract water from deep in the profile, and so create a soil buffer, is discussed.

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Ryan, M. H., R. M. Norton, J. A. Kirkegaard, K. M. McCormick, S. E. Knights et J. F. Angus. « Increasing mycorrhizal colonisation does not improve growth and nutrition of wheat on Vertosols in south-eastern Australia ». Australian Journal of Agricultural Research 53, n^o 10 (2002) : 1173. http://dx.doi.org/10.1071/ar02005.

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Most crops host arbuscular mycorrhizal fungi (AMF). Canola and other brassicas are some of the few exceptions. This study examined AM fungal colonisation, uptake of phosphorus (P) and zinc (Zn), growth, and yield of wheat following brassicas and crops that host AMF in 5 crop-sequence experiments in southern New South Wales and Victoria. All experiments were on alkaline Vertosols, similar to soils in the northern wheatbelt on which low AM fungal colonisation of wheat following canola, or long-fallow, has been reported to induce poor crop growth. Soils with a broad range of extractable P concentrations were chosen. AM fungal colonisation of wheat was generally lower following brassicas than hosts of AMF, although this varied with year and location. The effect on wheat AM fungal colonisation levels did not vary between brassicas with differing levels and types of root glucosinolates. Low AM fungal colonisation did not affect early wheat growth, pre-anthesis P and Zn uptake, or yield. A positive relationship between AM fungal colonisation and grain Zn and P concentrations occurred in one experiment. High levels of colonisation by AMF did not protect crop roots from damage by root pathogens and high levels of pathogen damage made interpretation of results difficult in some instances. As these findings are consistent with results from an experiment on an acidic Kandosol in southern New South Wales, it appears farmers do not need to consider the degree to which wheat will be colonised by AMF when planning crop sequences in south-eastern Australia.

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Evans, J., NA Fettell, DR Coventry, GE O'Connor, DN Walsgott, J. Mahoney et EL Armstrong. « Wheat response after temperate crop legumes in south-eastern Australia ». Australian Journal of Agricultural Research 42, n^o 1 (1991) : 31. http://dx.doi.org/10.1071/ar9910031.

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At 15 sites in the cereal belt of New South Wales and Victoria, wheat after lupin or pea produced more biomass and had a greater nitrogen (N) content than wheat after wheat or barley; on average these crops assimilated 36 kg N/ha more. The improved wheat yield after lupin averaged 0 . 9 t/ha and after pea 0.7 t/ha, increases of 44 and 32% respectively. The responses were variable with site, year and legume. Soil available N was increased by both lupin and pea and the levels of surface inorganic N measured at the maturity of first year crops was often related to N in wheat grown in the following year. Of two possible sources of additional N for wheat after legumes, namely mineral N conserved in soil by lupin or pea (up to 60 kg N/ha) and the total N added in the residues of these legumes (up to 152 kg N/ha), both were considered significant to the growth of a following wheat crop. Their relative contribution to explaining variance in wheat N is analysed, and it is suggested wheat may acquire up to 40 kg N/ha from legume stubbles. Non-legume break crops also increased subsequent wheat yield but this effect was not as great as the combined effect of added N and disease break attained with crop legumes.

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Evans, J., A. M. McNeill, M. J. Unkovich, N. A. Fettell et D. P. Heenan. « Net nitrogen balances for cool-season grain legume crops and contributions to wheat nitrogen uptake : a review ». Australian Journal of Experimental Agriculture 41, n^o 3 (2001) : 347. http://dx.doi.org/10.1071/ea00036.

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The removal of nitrogen (N) in grain cereal and canola crops in Australia exceeds 0.3 million t N/year and is increasing with improvements in average crop yields. Although N fertiliser applications to cereals are also rising, N2-fixing legumes still play a pivotal role through inputs of biologically fixed N in crop and pasture systems. This review collates Australian data on the effects of grain legume N2 fixation, the net N balance of legume cropping, summarises trends in the soil N balance in grain legume–cereal rotations, and evaluates the direct contribution of grain legume stubble and root N to wheat production in southern Australia. The net effect of grain legume N2 fixation on the soil N balance, i.e. the difference between fixed N and N harvested in legume grain (Nadd) ranges widely, viz. lupin –29–247 kg N/ha (mean 80), pea –46–181 kg N/ha (mean 40), chickpea –67–102 kg N/ha (mean 6), and faba bean 8–271 kg N/ha (mean 113). Nadd is found to be related to the amount (Nfix) and proportion (Pfix) of crop N derived from N2 fixation, but not to legume grain yield (GY). When Nfix exceeded 30 (lupin), 39 (pea) and 49 (chickpea) kg N/ha the N balance was frequently positive, averaging 0.60 kg N/kg of N fixed. Since Nfix increased with shoot dry matter (SDM) (21 kg N fixed/t SDM; pea and lupin) and Pfix (pea, lupin and chickpea), increases in SDM and Pfix usually increased the legume’s effect on soil N balance. Additive effects of SDM, Pfix and GY explained most (R2 = 0.87) of the variation in Nadd. Using crop-specific models based on these parameters the average effects of grain legumes on soil N balance across Australia were estimated to be 88 (lupin), 44 (pea) and 18 (chickpea) kg N/ha. Values of Nadd for the combined legumes were 47 kg N/ha in south-eastern Australia and 90 kg N/ha in south-western Australia. The average net N input from lupin crops was estimated to increase from 61 to 79 kg N/ha as annual rainfall rose from 445 to 627 mm across 3 shires in the south-east. The comparative average input from pea was 37 to 47 kg N/ha with least input in the higher rainfall shires. When the effects of legumes on soil N balance in south-eastern Australia were compared with average amounts of N removed in wheat grain, pea–wheat (1:1) sequences were considered less sustainable for N than lupin–wheat (1:1) sequences, while in south-western Australia the latter were considered sustainable. Nitrogen mineralised from lupin residues was estimated to contribute 40% of the N in the average grain yield of a following wheat crop, and that from pea residues, 15–30%; respectively, about 25 and 15 kg N/ha. Therefore, it was concluded that the majority of wheat N must be obtained from pre-existing soil sources. As the amounts above represented only 25–35% of the total N added to soil by grain legumes, the residual amount of N in legume residues is likely to be important in sustaining those pre-existing soil sources of N.

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McDonald, G. K., J. D. Taylor, A. Verbyla et H. Kuchel. « Assessing the importance of subsoil constraints to yield of wheat and its implications for yield improvement ». Crop and Pasture Science 63, n^o 12 (2012) : 1043. http://dx.doi.org/10.1071/cp12244.

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Many of the soils in the Australian cereal belt have subsoils with chemical and physical properties that restrict root growth, which limits water use and yield. On alkaline sodic soils salinity, high pH, high available boron (B), deficiencies of zinc (Zn) and manganese (Mn) and high soil strength occur commonly and aluminium (Al) toxicity restricts root growth on acid soils. While the effects of individual subsoil constraints have been studied there is some debate about the relative importance to yield of the different soil stresses across the region. To address this issue yield variation among a set of 52 varieties of bread wheat was analysed using yield data from 233 trials conducted over 12 years. The trials were conducted in all mainland States but the majority were in South Australia and Western Australia. Each variety was characterised for its response to high B, high pH, Al toxicity, salinity, deficiencies in Zn and Mn and resistance to root lesion nematode (Pratylenchus neglectus), root growth through strong soil, seminal root angle, carbon isotope discrimination (CID) and maturity. This data was then used to examine the contribution of each trait to the genetic variation in yield at each of the 233 trials. The contribution of a specific trait to the genetic variation in yield at each site was used to infer the importance of a particular constraint to yield at that site. Of the traits linked to soil constraints, salinity tolerance, (measured by Na+ exclusion) was most often associated with genetic variation in grain yield (34% of all experiments), followed by tolerance to high Al (26%) and B tolerance (21%). Tolerance to low Zn and Mn were not consistently associated with yield variation. However, maturity was the trait that was most frequently associated with yield variation (51% of experiments), although the relative importance of early and late flowering varied among the States. Yield variation was largely associated with early flowering in Western Australia and the relative importance of late flowering increased as trials moved eastward into South Australia, Victoria and New South Wales. Narrow, rather than wide, seminal root angle was more commonly associated with high yield (25% of sites) and there was little evidence of any regional pattern in the importance of root angle. CID was important in 18% of trials with a low CID being most commonly associated with high yields. The yield advantage at sites where a trait contributed significantly to yield variation ranged from ~15% for Na+ exclusion and B tolerance to 4% for tolerance to high pH. The analysis has provided an assessment of the relative importance of a range of traits associated with adaptation to environments where subsoil constraints are likely to affect yield and has indicated patterns in the importance and effects of these traits that may be linked to regional variation in rainfall and soils.

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Bakker, D. M., G. J. Hamilton, D. J. Houlbrooke, C. Spann et A. Van Burgel. « Productivity of crops grown on raised beds on duplex soils prone to waterlogging in Western Australia ». Australian Journal of Experimental Agriculture 47, n^o 11 (2007) : 1368. http://dx.doi.org/10.1071/ea06273.

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Waterlogging of duplex soils in Western Australia has long been recognised as a major constraint to the production of agricultural crops and pastures. The work described in this paper examines the application of raised beds to arable land that is frequently waterlogged for the production of crops such as wheat, barley, field peas, lupins and canola. Raised beds are 138 cm wide, seed beds separated by 45 cm wide furrows 183 cm apart. These beds were made with a commercial bed former. Seven sites were selected across the south-eastern wheat belt of Western Australia with the experimental areas varying in size from 10 to 57 ha. These large sites were used to accommodate commercial farm machinery. Each site had raised beds formed with a commercial bedformer. The production from the bedded areas was compared with crops grown conventionally on flat ground under minimum tillage as the control. The experiments were established in 1997 and 1998 and the sites were monitored for a maximum of 5 years. In 11 of the 28 site-years of the experiments, grain yields on the raised beds were statistically significantly higher than the yield from crops grown on the control, with an average yield increase of 0.48 t/ha. Across the whole dataset, growing crops on raised beds did not produce significantly lower yields. Below average rainfall was received for much of the experimental period at several sites. Growing season rainfall had a large effect on grain yield and high rainfall over a period of 40 days after seeding significantly increased the grain yield difference between the raised bed and the control. These data indicate that the use of raised beds lead to higher grain yields when seasonal conditions are appropriate.

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Officer, S. J., R. D. Armstrong et R. M. Norton. « Plant availability of phosphorus from fluid fertiliser is maintained under soil moisture deficit in non-calcareous soils of south-eastern Australia ». Soil Research 47, n^o 1 (2009) : 103. http://dx.doi.org/10.1071/sr08090.

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Low soil moisture and phosphorus (P) deficiencies restrict grain production in south-eastern Australia. The effect of the soil moisture regime on the plant availability of P from fluid mono-ammonium phosphate (MAP) fertiliser was examined during vegetative growth of wheat and canola in P-responsive soils from the Wimmera, Mallee, and high rainfall zone (Glenelg) regions of Victoria. Three plant growth experiments were performed. In Experiment 1, wheat growth and P uptake increased synergistically as soil moisture increased above permanent wilting point (PWP) and as P rate increased. In Experiment 2, the uptake of P from MAP fertiliser of wheat growing under a soil moisture deficit was examined using radioactive (32P) labelling. A factorial design compared uptake from intact soil cores of 3 soil types (Vertosol, Sodosol, Chromosol), 2 depths of fertiliser placement (40 and 80 mm), and either 0 or 25 kg P/ha. Results showed distinct plant responses to both the presence and depth of MAP fertiliser. Banding MAP close to the seed was most efficient in terms of recovery of the fertiliser P, regardless of the soil moisture conditions. Soil moisture regime affected the plant uptake of soil P, rather than fertiliser P, with more soil P taken up by the plants when soil moisture increased. The plant availability of the residual MAP fertiliser in the soil was subsequently examined in Experiment 3. The availability of the residual MAP to canola seedlings was equivalent to 8 kg P/ha of freshly applied MAP. Following both crops (9 months), Colwell P values indicated no further residual MAP availability in soil that had been under the wet regime, and only a small residual value in soil from the dry regime. Banded application of fluid MAP close to the seed and into soil that is above PWP is recommended, even when a relatively dry season is expected, although the residual value to following crops may be limited.

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Pepper, Claire-Marie. « Understanding Sclerotinia Risks Associated with Growing Peanuts in the South Burnett Area ». Proceedings 36, n^o 1 (6 avril 2020) : 150. http://dx.doi.org/10.3390/proceedings2019036150.

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Sclerotinia Blight, caused by ascomycete fungal pathogen S. minor (Jagger), is a serious soil-borne disease of peanut crops within the South Burnett area in Queensland, Australia. The pathogen can infect root, stem and foliage tissues, forming characteristic fluffy white mycelial growth on stems leading to tissue wilting and necrosis. The disease can cause significant yield reductions and, in some cases, complete crop losses in peanut production. Outbreaks occur in cooler weather (under 18 °C) with high humidity levels (above 95%) as the higher humidity levels promote germination of sclerotia (Smith 2003, Maas, Dashiell et al. 2006). Therefore, knowledge of inoculum levels prior to sowing could enhance cropping systems through enhanced capacity to predict outbreaks. The South Australia Research and Development Institute (SARDI) offers a new soil test for Sclerotinia sp., called PreDictaB, available for farmers to asses inoculum levels pre-planting as a crop risk assessment tool. This project validated the accuracy of the PreDictaB test for Sclerotinia inoculum levels in the South Burnett soils, while gathering paddock and weather data to identify key characteristics linked to high risk of Sclerotinia Blight incidence to be transposed in a pre-season risk matrix model. Results demonstrated a close positive relationship between the level of Sclerotinia in the soil pre-planting and the paddock disease severity observed at harvest. The significance of the results for future research into potential management strategies is discussed. This new test has the potential to reduce the impact and presence of Sclerotinia in the field within the South Burnett region.

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Xu, R. K., D. R. Coventry, A. Farhoodi et J. E. Schultz. « Soil acidification as influenced by crop rotations, stubble management, and application of nitrogenous fertiliser, Tarlee, South Australia ». Soil Research 40, n^o 3 (2002) : 483. http://dx.doi.org/10.1071/sr00104.

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Soil acidification, as influenced by N fertiliser, stubble management, and crop rotations, was investigated using soil samples from a long-term rotation trial at Tarlee, South Australia. With the effects of combination of treatment inputs (wheat–lupin, stubble retention and N-fertiliser application), the pHCa (0–10 cm depth) declined from the starting value of 6.12 to 4.50 after a 14-year period. All of the treatments caused the soil pH to decrease. The mean acidification rates for the period 1978–1992 varied from 0.5 to 2.22 kmol H+/ha.year for different treatments. Although the rainfall at Tarlee (483 mm) is not sufficient to cause regular drainage events, it is likely that downward movement of NO3– in the soil profile has caused acidification in the surface soil. Also the retention of stubble caused more acidification than where there was regular stubble burning or removal. The acidification resulted in an increase in soil exchangeable Al and Mn and extractable Al and Mn, and the decrease in soil exchangeable base cations. The values for soluble Al (extracted in CaCl2) in 1992 were 1.58 and 2.45 mg/kg (0–10 cm depth) for the wheat–bean and wheat–lupin rotations, but the percentage of Al in the ECEC was low. It is not known whether this acidity has any impact on yields of field crops at this stage. But with soluble Al and the percentage of Al in ECEC increasing, it is possible that Al toxicity may occur in the high input-output cropping soils in South Australia. acidity, pH, aluminium, manganese.

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Pembleton, K. G., R. P. Rawnsley, J. L. Jacobs, F. J. Mickan, G. N. O'Brien, B. R. Cullen et T. Ramilan. « Evaluating the accuracy of the Agricultural Production Systems Simulator (APSIM) simulating growth, development, and herbage nutritive characteristics of forage crops grown in the south-eastern dairy regions of Australia ». Crop and Pasture Science 64, n^o 2 (2013) : 147. http://dx.doi.org/10.1071/cp12372.

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Pasture-based dairy farms are a complex system involving interactions between soils, pastures, forage crops, and livestock as well as the economic and social aspects of the business. Consequently, biophysical and farm systems models are becoming important tools to study pasture-based dairy systems. However, there is currently a paucity of modelling tools available for the simulation of one key component of the system—forage crops. This study evaluated the accuracy of the Agricultural Production Systems Simulator (APSIM) in simulating dry matter (DM) yield, phenology, and herbage nutritive characteristics of forage crops grown in the dairy regions of south-eastern Australia. Simulation results were compared with data for forage wheat (Triticum aestivum L.), oats (Avena sativa L.), forage rape (Brassica napus L.), forage sorghum (Sorghum bicolor (L.) Moench), and maize (Zea mays L.) collated from previous field research and demonstration activities undertaken across the dairy regions of south-eastern Australia. This study showed that APSIM adequately predicted the DM yield of forage crops, as evidenced by the range of values for the coefficient of determination (0.58–0.95), correlation coefficient (0.76–0.94), and bias correction factor (0.97–1.00). Crop phenology for maize, forage wheat, and oats was predicted with similar accuracy to forage crop DM yield, whereas the phenology of forage rape and forage sorghum was poorly predicted (R2 values 0.38 and 0.80, correlation coefficient 0.62 and –0.90, and bias correction factors 0.67 and 0.28, respectively). Herbage nutritive characteristics for all crop species were poorly predicted. While the selection of a model to explore an aspect of agricultural production will depend on the specific problem being addressed, the performance of APSIM in simulating forage crop DM yield and, in many cases, crop phenology, coupled with its ease of use, open access, and science-based mechanistic methods of simulating agricultural and crop processes, makes it an ideal model for exploring the influence of management and environment on forage crops grown on dairy farms in south-eastern Australia. Potential future model developments and improvements are discussed in the context of the results of this validation analysis.

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Siddique, KHM, et SP Loss. « Growth and seed yield of vetches (Vicia spp.) in south-western Australia ». Australian Journal of Experimental Agriculture 36, n^o 5 (1996) : 587. http://dx.doi.org/10.1071/ea9960587.

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The growth and seed yield of 5 vetch (Vicia) cultivars representing Vicia sativa, V. benghalensis and V. villosa were compared at 8 sites over 2 years in south-western Australia. The vetches showed considerable potential as grain and forage legume crops in the low to medium rainfall areas of the Western Australian cereal belt. Cultivars of V. sativa showed the most potential in terms of dry matter and seed yield, and on average across sites and seasons both Languedoc and Blanchefleur produced over 2.5 t/ha of dry matter at flowering: Machine-harvested seed yields were over 1.6 t/ha. Cultivars of V. benghalensis and V. villosa produced considerably less dry matter at flowering and had lower harvest index (0.14-0.42) and seed yield < 4 t/ha) when compared with the V. sativa cultivars, possibly due to their poor growth rates and delayed phenology. Early Purple, an early flowering and maturing selection from the V. benghalensis cultivar Popany, showed improved adaptation and seed yield at many low rainfall sites. Nevertheless, Languedoc, Blanchefleur and Early Popany are all considered late flowering (up to 126 days) compared with grain legumes adapted to this environment, and further improvement in vetch species could be achieved by selecting for more rapid development. Both soft-seededness and non-shattering pods should also be high priorities for vetch selection and/or breeding programs. It is concluded that vetch species may have a role in farming systems in Western Australia for the production of fodder, hay, grain or green manure while providing the other rotational benefits of legumes on fine-textured neutral to alkaline and shallow duplex soils where narrow-leafed lupin is poorly adapted.

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