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1
Petersen, E. H., e F. C. Hoyle. "Estimating the economic value of soil organic carbon for grains cropping systems in Western Australia". Soil Research 54, n. 4 (2016): 383. http://dx.doi.org/10.1071/sr15101.
Testo completoAbstract (sommario):
Soil organic carbon (SOC) has the potential to benefit soil function and fertility, and in agricultural production systems, it is considered integral to sustainable farming. We analyse the value of SOC in cropping systems of the south-west of Western Australia in terms of agronomic benefits from increasing productivity (through increased plant-available water-holding capacity) and reducing fertiliser use (due to increased mineralisation of nitrogen). We also present the potential value of SOC in terms of sequestration benefit if landholders were able to participate in a carbon-sequestration program. We estimate the marginal value of SOC (the value of a soil with more SOC, by 1 t C/ha, than a standard soil) to be AU$7.1–8.7/t C.ha.year, depending on rainfall zone and crop type. Approximately 75% of this value is the estimated sequestration value, 20% is the nitrogen-replacement value, and 5% is the estimated productivity improvement value. Over 50 years, this equates $130–160/t C.ha depending on the rainfall zone. These values are sensitive to variations in fertiliser and carbon prices. Our results imply this it is unlikely that the SOC benefits will drive practice change in the south-west of Western Australia.
2
Harries, Martin, Ken C. Flower e Craig A. Scanlan. "Sustainability of nutrient management in grain production systems of south-west Australia". Crop and Pasture Science 72, n. 3 (2021): 197. http://dx.doi.org/10.1071/cp20403.
Testo completoAbstract (sommario):
Balancing nutrient inputs and exports is essential to maintaining soil fertility in rainfed crop and pasture farming systems. Soil nutrient balances of land used for crop and pasture production in the south-west of Western Australia were assessed through survey data comprising biophysical measurements and farm management records (2010–15) across 184 fields spanning 14 Mha. Key findings were that nitrogen (N) inputs via fertiliser or biological N2 fixation in 60% of fields, and potassium (K) inputs in 90% of fields, were inadequate to balance exports despite increases in fertiliser usage and adjustments to fertiliser inputs based on rotations. Phosphorus (P) and sulfur (S) balances were positive in most fields, with only 5% returning losses >5 kg P or 7 kg S/ha. Within each of the three agroecological zones of the survey, fields that had two legume crops (or pastures) in 5 years (i.e. 40% legumes) maintained a positive N balance. At the mean legume inclusion rate observed of 20% a positive partial N budget was still observed for the Northern Agricultural Region (NAR) of 2.8 kg N/ha.year, whereas balances were negative within the Central Agricultural Region (CAR) by 7.0 kg N/ha.year, and the Southern Agricultural Region (SAR) by 15.5 kg N/ha.year. Hence, N budgets in the CAR and SAR were negative by the amount of N removed in ~0.5 t wheat grain, and continuation of current practices in CAR and SAR fields will lead to declining soil fertility. Maintenance of N in the NAR was achieved by using amounts of fertiliser N similar to other regions while harvesting less grain. The ratio of fertiliser N to legume-fixed N added to the soil in the NAR was twice that of the other regions. Across all regions, the ratio of fertiliser N to legume-fixed N added to the soil averaged ~4.0:1, a major change from earlier estimates in this region of 1:20 under ley farming systems. The low contribution of legume N was due to the decline in legume inclusion rate (now 20%), the low legume content in pastures, particularly in the NAR, and improved harvest index of lupin (Lupinus angustifolius), the most frequently grown grain legume species. Further quantifications of the effects of changing farming systems on nutrient balances are required to assess the balances more accurately, thereby ensuring that soil fertility is maintained, especially because systems have altered towards more intensive cropping with reduced legume production.
3
Dawes, W., R. Ali, S. Varma, I. Emelyanova, G. Hodgson e D. McFarlane. "Modelling the effects of climate and land cover change on groundwater recharge in south-west Western Australia". Hydrology and Earth System Sciences 16, n. 8 (14 agosto 2012): 2709–22. http://dx.doi.org/10.5194/hess-16-2709-2012.
Testo completoAbstract (sommario):
Abstract. The groundwater resource contained within the sandy aquifers of the Swan Coastal Plain, south-west Western Australia, provides approximately 60 percent of the drinking water for the metropolitan population of Perth. Rainfall decline over the past three decades coupled with increasing water demand from a growing population has resulted in falling dam storage and groundwater levels. Projected future changes in climate across south-west Western Australia consistently show a decline in annual rainfall of between 5 and 15 percent. There is expected to be a reduction of diffuse recharge across the Swan Coastal Plain. This study aims to quantify the change in groundwater recharge in response to a range of future climate and land cover patterns across south-west Western Australia. Modelling the impact on the groundwater resource of potential climate change was achieved with a dynamically linked unsaturated/saturated groundwater model. A vertical flux manager was used in the unsaturated zone to estimate groundwater recharge using a variety of simple and complex models based on climate, land cover type (e.g. native trees, plantation, cropping, urban, wetland), soil type, and taking into account the groundwater depth. In the area centred on the city of Perth, Western Australia, the patterns of recharge change and groundwater level change are not consistent spatially, or consistently downward. In areas with land-use change, recharge rates have increased. Where rainfall has declined sufficiently, recharge rates are decreasing, and where compensating factors combine, there is little change to recharge. In the southwestern part of the study area, the patterns of groundwater recharge are dictated primarily by soil, geology and land cover. In the sand-dominated areas, there is little response to future climate change, because groundwater levels are shallow and much rainfall is rejected recharge. Where the combination of native vegetation and clayey surface soils restricts possible infiltration, recharge rates are very sensitive to reductions in rainfall. In the northern part of the study area, both climate and land cover strongly influence recharge rates. Recharge under native vegetation is minimal and is relatively higher where grazing and pasture systems have been introduced after clearing of native vegetation. In some areas, the recharge values can be reduced to almost zero, even under dryland agriculture, if the future climate becomes very dry.
4
Thomas, Dean T., Roger A. Lawes, Katrien Descheemaeker e Andrew D. Moore. "Selection of crop cultivars suited to the location combined with astute management can reduce crop yield penalties in pasture cropping systems". Crop and Pasture Science 65, n. 10 (2014): 1022. http://dx.doi.org/10.1071/cp13436.
Testo completoAbstract (sommario):
Pasture cropping is an emerging farming-systems practice of southern Australia, in which winter grain crops are sown into an established stand of a winter-dormant, summer-growing perennial pasture. There is a pressing need to define times, locations and climates that are suitable for pasture cropping. To evaluate effects of management interventions, agro-environment, and possible interactions on crop and pasture productivity associated with pasture cropping, an AusFarm® simulation model was built to describe a pasture-cropping system based on annual crop and subtropical grass. The model was parameterised using data from field research on pasture cropping with barley cv. Buloke and a C4 subtropical grass, Gatton panic (Panicum maximum cv. Gatton), conducted at Moora, Western Australia. The simulation was run over 50 years using the historical climate data of five southern Australian locations (Cunderdin, Jerdacuttup, Mingenew, and Moora in Western Australia, and Karoonda in South Australia). Two wheat cultivars and one barley crop were considered for each location, to examine the impact of crop phenology on this farming system. Jerdacuttup and Moora favoured pasture cropping, with average barley-yield penalties of 10 and 12%. These locations were characterised by colder growing seasons, more plant-available water at anthesis, and more winter–spring rain. The cereal crops did not rely on stored soil moisture, growing instead on incident rain. The winter–spring growth of the Gatton panic pasture was highest at Mingenew. This generated a high yield penalty, 38% loss under pasture cropping, compared with the other locations. Changing the efficacy of a herbicide application to the pasture when the crop was sown had a strong effect on yield. Yield penalties at Moora and Mingenew reduced to 7 and 29%, respectively, when the proportion of live biomass killed by the herbicide was doubled. Utilisation of soil moisture by the Gatton panic pasture during summer and early autumn had little effect on subsequent grain yield, whereas reduced pasture growth during the winter–spring growing period had a substantial effect on crop yield. Pasture cropping can therefore succeed in agro-climatic regions where crops can be grown on incident rain and pasture growth is suppressed through low temperature or herbicide. Perennial pasture growth should be minimised during the crop growing period through the management of crop sowing date, nitrogen fertiliser application and C4 grass suppression to minimise the effect on stored soil water at crop anthesis.
5
Fisher, James, Peter Tozer e Doug Abrecht. "Livestock in no-till cropping systems - a story of trade-offs". Animal Production Science 52, n. 4 (2012): 197. http://dx.doi.org/10.1071/an11123.
Testo completoAbstract (sommario):
The trade-offs of incorporating livestock into no-till cropping systems were examined with respect to ground cover, water balance, nutrient cycling, pest management, whole-farm economics and farmer preferences. The hypothesis that livestock and no-till cropping enterprises may co-exist was investigated using a review of scientific literature and technical reports, information from farmer focus groups and an economic analysis based on case study data from farm consultants. The scientific review focussed on work from Australia, especially western and southern Australia, but also included research related to systems in northern New South Wales and southern Queensland and some related international work. The focus groups and case studies were from the cereal-sheep systems of western and southern Australia. It was concluded that the use of livestock in a no-till system is determined by the productive capacity of the land, the relative profitability of cropping and livestock, the management of herbicide-resistant weeds, sensitivity of soil to damage from grazing and trampling and the farmer’s passion, preference and willingness to apply increased management to livestock. Livestock are an important source of farm diversification and risk management. While net farm income tends to decline as the proportion of livestock increases, variation in net farm income also decreases, reducing volatility in revenue. Livestock need to comprise above 10–15% of net farm income to provide a positive impact on variability of return. Adaptation of mixed-farming systems through rotational grazing, temporary agistment of livestock or removal to non-cropping areas are all management options that may be utilised to remove or reduce potential negative impacts, improve integration and to realise triple-bottom-line gains.
6
Seymour, M. "Narbon bean (Vicia narbonensis) agronomy in south-western Australia". Australian Journal of Experimental Agriculture 46, n. 10 (2006): 1355. http://dx.doi.org/10.1071/ea04091.
Testo completoAbstract (sommario):
Narbon bean (Vicia narbonensis L.) shows promise as a fodder, green manure and grain crop in south-western Australia. This study examines the effect of time of sowing (2 experiments), plant density (3 experiments) and reaction to herbicides (4 experiments on tolerance to herbicides and 1 experiment on removing narbon bean from a wheat crop) in 10 separate field experiments sown at 4 locations in the mallee region of Western Australia from 1998 to 2001. Narbon bean was found to be unresponsive to changes in sowing date with yield maintained until the first week of June. The optimum plant density (90% of fitted maximum) for seed yield was found to be 31 plants/m2, equivalent to sowing rates in the range of 75–100 kg/ha. A wide range of herbicides applied either before sowing or immediately after sowing and before emergence had no significant effect on grain yield. These included simazine (750 g a.i./ha), cyanazine (1.25 kg a.i./ha) and diuron (500 g a.i./ha), which were applied immediately before sowing, and imazethapyr (29 g a.i./ha), which was applied after sowing, before emergence. Diflufenican (75 g a.i./ha) was found to be the only available option for post-emergence control of broadleaf weeds. The use of the non-selective herbicides glyphosate (450 g a.i./L) and Sprayseed 250 (paraquat 135 g a.i./L and diquat 115 g a.i./L) as post-emergence herbicides was found to be unpredictable at a range of application rates. Results ranged from a yield loss of 47% to a yield increase of 23%. In an experiment to test a range of herbicides for the selective control of narbon bean within a wheat crop, numerous herbicides were found to effectively remove volunteer narbon bean indicating that narbon bean is unlikely to become a weed in most cereal cropping systems.
7
Gupta, V. V. S. R., M. M. Roper e D. K. Roget. "Potential for non-symbiotic N2-fixation in different agroecological zones of southern Australia". Soil Research 44, n. 4 (2006): 343. http://dx.doi.org/10.1071/sr05122.
Testo completoAbstract (sommario):
Nitrogen fixation by symbiotic and non-symbiotic bacteria can be a significant source of nitrogen in cropping systems. However, contributions from non-symbiotic nitrogen fixation (NSNF) are dependent on available carbon in the soil and environmental conditions (soil moisture and temperature). In Australia, measurements of NSNF have been made in the field by quantifying nitrogenase activity. These studies have included determinations of the moisture and temperature requirements for NSNF and for crop residue decomposition that supplies carbon to NSNF bacteria. Other studies have determined the N input by NSNF using N budget calculations. These data together with information about carbon supply and environmental conditions were used to estimate potential NSNF in the cropping zones of southern Australia. Using the ArcviewGIS Spatial Analyst (v3.1), maps of Australia showing estimates of NSNF in different cropping zones as determined by rainfall and temperature or carbon availability were generated. In Western Australia (represented by Wongan Hills) and South Australia (represented by Avon), where summers are dry, estimates of NSNF were generally low (10–15 kg N/ha from January to June) due to limitations of soil moisture. In New South Wales, particularly in the north where summer rainfall patterns develop (represented by Gunnedah), the warm, moist conditions produced higher estimates of NSNF (totaling 32–38 kg N/ha from January to June). In this region, the majority of estimated NSNF occurred in January and February leading to the depletion of carbon supplies and reduced NSNF in autumn (March–June). Information about potential supplies of N from NSNF across the cropping zones should be useful for researchers to select and study areas that are most likely to benefit from NSNF. It should also help agronomists and extension officers explain changes in N status within paddocks or within specific farming systems and to provide more accurate advice on N fertiliser requirements, particularly in low-input farming systems.
8
Robertson, M. J., D. Gaydon, D. J. M. Hall, A. Hills e S. Penny. "Production risks and water use benefits of summer crop production on the south coast of Western Australia". Australian Journal of Agricultural Research 56, n. 6 (2005): 597. http://dx.doi.org/10.1071/ar04249.
Testo completoAbstract (sommario):
Summer crops grown during the summer fallow in a Mediterranean-type climate have the potential to produce out-of-season biomass and grain, increase water use, and reduce deep drainage. The potential effects of growing grain sorghum on components of the water balance, sorghum biomass and grain production, and yield of subsequent wheat crops were investigated by simulation using APSIM and long-term climate data from the Esperance district. Sorghum was simulated as part of 3 systems: (1) as an opportunity crop following wheat harvest, (2) as a fallow replacement after pasture removal and before entering a cropping phase, or (3) as a fallow replacement after a failed or waterlogged winter crop. Simulations were conducted for the period 1957–2003 at Myrup (mean annual rainfall 576 mm), Scaddan (408 mm), and Salmon Gums (346 mm). Sorghum was assumed to have a similar rooting depth to wheat. In order to gain confidence in using APSIM for these investigations, tests were initially conducted against field data involving summer and winter crops in sequence and measurements of soil water dynamics. Data sets also varied in summer rainfall, species (forage sorghum, grain sorghum, Japanese millet), and soil type (deep sand, and medium and shallow duplex). Overall, the simulations showed that incorporation of a sorghum crop increased transpiration by 10–30 mm/year, made the soil profile drier by a similar amount at wheat sowing, and consequently reduced deep drainage by 3–25 mm/year, depending upon cropping system and location. Long-term average drainage results were dominated by large episodes in wet years. The increased transpiration from the summer crop, although reducing drainage in wet years, could not eliminate drainage. Following wheat yields were reduced by an average of 200–400 kg/ha, corresponding to a reduction of 10% at wetter and 30% at drier locations. In the 2 fallow replacement systems, sorghum biomass was produced in nearly every simulated season. However, averaged over all seasons, sorghum grain production was much less reliable comprising only 10–20% of biomass. In the opportunity system, sorghum produced biomass in only 1 in 3 seasons at Salmon Gums and Scaddan and 1 in 2 at Myrup. Grain was produced in 1 in 5 seasons at all 3 locations, underlining the riskiness of this opportunity niche for summer crops in the Esperance district. Although summer cropping was shown to result in modest reductions in deep drainage, it also comes at a cost to wheat production. The largest effects on drainage and most reliable biomass production were seen in the systems where the summer crop was grown following pasture removal or a failed (waterlogged) winter crop. This research has also shown that recent farmer and researcher experiences of summer cropping are likely to be more favourably biased towards prospects for summer cropping than indicated by long-term simulations because of their longer-term perspective.
9
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 e M. P. You. "Coolamon subterranean clover (Trifolium subterraneum L. var. subterraneum)". Australian Journal of Experimental Agriculture 47, n. 2 (2007): 223. http://dx.doi.org/10.1071/ea05282.
Testo completoAbstract (sommario):
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.
10
Dalal, R. C., e K. Y. Chan. "Soil organic matter in rainfed cropping systems of the Australian cereal belt". Soil Research 39, n. 3 (2001): 435. http://dx.doi.org/10.1071/sr99042.
Testo completoAbstract (sommario):
The Australian cereal belt stretches as an arc from north-eastern Australia to south-western Australia (24˚S–40˚S and 125˚E–147˚E), with mean annual temperatures from 14˚C (temperate) to 26˚C (subtropical), and with annual rainfall ranging from 250 mm to 1500 mm. The predominant soil types of the cereal belt include Chromosols, Kandosols, Sodosols, and Vertosols, with significant areas of Ferrosols, Kurosols, Podosols, and Dermosols, covering approximately 20 Mha of arable cropping and 21 Mha of ley pastures. Cultivation and cropping has led to a substantial loss of soil organic matter (SOM) from the Australian cereal belt; the long-term SOM loss often exceeds 60% from the top 0–0.1 m depth after 50 years of cereal cropping. Loss of labile components of SOM such as sand-size or particulate SOM, microbial biomass, and mineralisable nitrogen has been even higher, thus resulting in greater loss in soil productivity than that assessed from the loss of total SOM alone. Since SOM is heterogeneous in nature, the significance and functions of its various components are ambiguous. It is essential that the relationship between levels of total SOM or its identif iable components and the most affected soil properties be established and then quantif ied before the concentrations or amounts of SOM and/or its components can be used as a performance indicator. There is also a need for experimentally verifiable soil organic C pools in modelling the dynamics and management of SOM. Furthermore, the interaction of environmental pollutants added to soil, soil microbial biodiversity, and SOM is poorly understood and therefore requires further study. Biophysically appropriate and cost-effective management practices for cereal cropping lands are required for restoring and maintaining organic matter for sustainable agriculture and restoration of degraded lands. The additional benefit of SOM restoration will be an increase in the long-term greenhouse C sink, which has the potentialto reduce greenhouse emissions by about 50 Mt CO2 equivalents/year over a 20-year period, although current improved agricultural practices can only sequester an estimated 23% of the potential soil C sink.
11
Dawes, W., R. Ali, S. Varma, I. Emelyanova, G. Hodgson e D. McFarlane. "Modelling the effects of climate and land cover change on groundwater recharge in south-west Western Australia". Hydrology and Earth System Sciences Discussions 9, n. 5 (10 maggio 2012): 6063–99. http://dx.doi.org/10.5194/hessd-9-6063-2012.
Testo completoAbstract (sommario):
Abstract. The groundwater resource contained within the sandy aquifers of the Swan Coastal Plain, south west Western Australia, provides approximately 60% of the drinking water for the metropolitan population of Perth. Rainfall decline over the past three decades coupled with increasing water demand from a growing population has resulted in falling dam storage and groundwater levels. Projected future changes in climate across south-west Western Australia consistently show a decline in annual rainfall of between 5 and 15%. There is expected to be a continuing reduction of diffuse recharge across the Swan Coastal Plain. This study aims to quantify the change in groundwater recharge in response to a range of future climate and land cover patterns across south-west Western Australia. Modelling the impact on the groundwater resource of potential climate change was achieved with a dynamically linked unsaturated/saturated groundwater model. A Vertical Flux Manager was used in the unsaturated zone to estimate groundwater recharge using a variety of simple and complex models based on land cover type (e.g. native trees, plantation, cropping, urban, wetland), soil type, and taking into account the groundwater depth. These recharge estimates were accumulated on a daily basis for both observed and projected climate scenarios and used in a MODFLOW simulation with monthly stress periods. In the area centred on the city of Perth, Western Australia, the patterns of recharge change and groundwater level change are not consistent spatially, or consistently downward. In the Dandaragan Plateau to the north-east of Perth there has been groundwater level rise since the 1970s associated with land clearing, and with rainfall projected to reduce the least in this area the groundwater levels are estimated to continue to rise. Along the coastal zone north of Perth there is an interaction between projected rainfall decline and legislated removal to pine forests. This results in areas of increasing recharge and rising water levels into the future despite a drying climate signal. To the south of Perth city there are large areas where groundwater levels are close to the land surface and not expected to change more than 1m upward or downward over the next two decades; it is beyond the accuracy of the model to conclude any definite trend. In the south western part of the study area, the patterns of groundwater recharge are dictated primarily by soil, geology and land cover. In the sandy Swan (northern boundary) and Scott Coastal Plains (southern boundary) there is little response to future climates, because groundwater levels are shallow and much rainfall is rejected recharge. The profile dries out more in summer but this allows more rainfall to infiltrate in winter. Until winter recharge is insufficient to refill the aquifers these areas will not experience significant falls in groundwater levels. On the Blackwood Plateau however, the combination of native vegetation and clayey surface soils that restrict possible infiltration and recharge mean the area is very sensitive to climate change. With low capacity for recharge and low storage in the aquifers, small reductions in recharge can lead to large reductions in groundwater levels. In the northern part of the study area both climate and land cover strongly influence recharge rates. Recharge under native vegetation is minimal and is relatively higher where grazing and pasture systems have been introduced after clearing of native vegetation. In some areas the low recharge values can be reduced to almost zero, even under dryland agriculture, if the future climate becomes very dry. In the Albany Area the groundwater resource is already over allocated, and the combination of existing permanent native vegetation with decreasing annual rainfall indicate reduced recharge. The area requires a reduction in groundwater abstraction to maintain the sustainability of the existing resource.
12
Hulugalle, N. R., T. B. Weaver, L. A. Finlay e V. Heimoana. "Soil organic carbon concentrations and storage in irrigated cotton cropping systems sown on permanent beds in a Vertosol with restricted subsoil drainage". Crop and Pasture Science 64, n. 8 (2013): 799. http://dx.doi.org/10.1071/cp12374.
Testo completoAbstract (sommario):
Long-term studies of soil organic carbon dynamics in two- and three-crop rotations in irrigated cotton (Gossypium hirsutum L.) based cropping systems under varying stubble management practices in Australian Vertosols are relatively few. Our objective was to quantify soil organic carbon dynamics during a 9-year period in four irrigated, cotton-based cropping systems sown on permanent beds in a Vertosol with restricted subsoil drainage near Narrabri in north-western New South Wales, Australia. The experimental treatments were: cotton–cotton (CC); cotton–vetch (Vicia villosa Roth. in 2002–06, Vicia benghalensis L. in 2007–11) (CV); cotton–wheat (Triticum aestivum L.), where wheat stubble was incorporated (CW); and cotton–wheat–vetch, where wheat stubble was retained as in-situ mulch (CWV). Vetch was terminated during or just before flowering by a combination of mowing and contact herbicides, and the residues were retained as in situ mulch. Estimates of carbon sequestered by above- and below-ground biomass inputs were in the order CWV >> CW = CV > CC. Carbon concentrations in the 0–1.2 m depth and carbon storage in the 0–0.3 and 0–1.2 m depths were similar among all cropping systems. Net carbon sequestration rates did not differ among cropping systems and did not change significantly with time in the 0–0.3 m depth, but net losses occurred in the 0–1.2 m depth. The discrepancy between measured and estimated values of sequestered carbon suggests that either the value of 5% used to estimate carbon sequestration from biomass inputs was an overestimate for this site, or post-sequestration losses may have been high. The latter has not been investigated in Australian Vertosols. Future research efforts should identify the cause and quantify the magnitude of these losses of organic carbon from soil.
13
Young, R. R., B. Wilson, S. Harden e A. Bernardi. "Accumulation of soil carbon under zero tillage cropping and perennial vegetation on the Liverpool Plains, eastern Australia". Soil Research 47, n. 3 (2009): 273. http://dx.doi.org/10.1071/sr08104.
Testo completoAbstract (sommario):
Australian agriculture contributes an estimated 16% of all national greenhouse gas emissions, and considerable attention is now focused on management approaches that reduce net emissions. One area of potential is the modification of cropping practices to increase soil carbon storage. Here, we report short–medium term changes in soil carbon under zero tillage cropping systems and perennial vegetation, both in a replicated field experiment and on nearby farmers’ paddocks, on carbon-depleted Black Vertosols in the upper Liverpool Plains catchment. Soil organic carbon stocks (CS) remained unchanged under both zero tillage long fallow wheat–sorghum rotations and zero tillage continuous winter cereal in a replicated field experiment from 1994 to 2000. There was some evidence of accumulation of CS under intensive (>1 crop/year) zero tillage response cropping. There was significant accumulation of CS (~0.35 Mg/ha.year) under 3 types of perennial pasture, despite removal of aerial biomass with each harvest. Significant accumulation was detected in the 0–0.1, 0.1–0.2, and 0.2–0.4 m depth increments under lucerne and the top 2 increments under mixed pastures of lucerne and phalaris and of C3 and C4 perennial grasses. Average annual rainfall for the period of observations was 772 mm, greater than the 40-year average of 680 mm. A comparison of major attributes of cropping systems and perennial pastures showed no association between aerial biomass production and accumulation rates of CS but a positive correlation between the residence times of established plants and accumulation rates of CS. CS also remained unchanged (1998/2000–07) under zero tillage cropping on nearby farms, irrespective of paddock history before 1998/2000 (zero tillage cropping, traditional cropping, or ~10 years of sown perennial pasture). These results are consistent with previous work in Queensland and central western New South Wales suggesting that the climate (warm, semi-arid temperate, semi-arid subtropical) of much of the inland cropping country in eastern Australia is not conducive to accumulation of soil carbon under continuous cropping, although they do suggest that CS may accumulate under several years of healthy perennial pastures in rotation with zero tillage cropping.
14
Dolling, P. J., S. Asseng, M. J. Robertson e M. A. Ewing. "Water excess under simulated lucerne - wheat phased systems in Western Australia". Australian Journal of Agricultural Research 58, n. 8 (2007): 826. http://dx.doi.org/10.1071/ar06048.
Testo completoAbstract (sommario):
The long-term effect of lucerne use, in reducing drainage of water below the root zone and runoff (water excess), has not been examined in south-western Australia (Western Australia). The main aims of the paper were to determine how the long-term mean water excess was influenced by the proportion of lucerne in the rotation and the length of the lucerne phase in relation to soil type and location. A simulation model was used to compare scenarios, drawing on historical weather data from 1957 to 2001. Simulations were performed for 2 locations (high and low rainfall) and 2 soil types (high and low water-holding capacity). Lucerne significantly and rapidly (within 2–3 years) reduces the long-term mean water excess in rotations consisting of 2–4 years of lucerne followed by 1–4 years of wheat compared with continuous wheat. For every 10% increase in the percentage of lucerne years in the total rotation length, the mean water excess decreased by 17–20 mm (7–9%) at Kojonup (high-rainfall site) and 7–8 mm (8–9%) at Buntine (low-rainfall site) compared with the water excess associated with continuous wheat at each location. The proportion of lucerne in the rotation had a greater effect on the water excess than the effect of different soil types. Variation in the water excess due to variation in rainfall was greater than the reduction in water excess due to lucerne. This makes the decisions about when to grow lucerne to reduce water excess difficult if livestock enterprises are less profitable than cropping enterprises. The simulations show that lucerne mean yearly biomass ranges from 4.5 to 6.9 t/ha at Kojonup and from 1.6 to 4.7 t/ha at Buntine, depending on soil type and stage of lucerne in the land use sequence. It is worth considering that lucerne has the potential to reduce subsequent wheat yields with removal in autumn.
15
Holland, J. E., T. H. Johnston, R. E. White e B. A. Orchard. "An investigation of runoff from raised beds and other tillage methods in the high rainfall zone of south-western Victoria, Australia". Soil Research 50, n. 5 (2012): 371. http://dx.doi.org/10.1071/sr11200.
Testo completoAbstract (sommario):
For many years, the poor physical and hydraulic properties of the soils in south-western Victoria have restricted crop production due to waterlogging. In this region of predominantly winter rainfall, raised beds have become popular with farmers to overcome these difficulties; however, little has been reported on the hydrology of raised beds compared with other tillage systems for cropping in the rain-fed environment of south-western Victoria. This study measured rainfall characteristics, runoff volumes, and soil properties such as the soil water content, bulk density, and hydraulic conductivity for three tillage treatments (raised beds, conventional cultivation, and deep cultivation) over 6 years on a Sodosol at a field site near Geelong, Victoria. Runoff was regressed against rainfall variables such as the amount per event, hours of rainfall, rainfall intensity, and maximum rainfall intensity to determine the significance of any differences between the treatments. The relationship between runoff and rainfall amount was best described with an exponential model. Raised beds significantly increased the amount of runoff relative to the other treatments when above-average rainfall was received, but there was little difference in runoff in years of below-average rainfall. No consistent effect of runoff on crop biomass was detected nor could any differences in runoff be attributed to differences in soil water content, hydraulic conductivity, and bulk density between treatments. The most important factor appeared to be the furrows between the raised beds, which acted as conduits for the flow of surface water during the larger storm events. During such events, runoff is an important hydrological process in cropping land in south-western Victoria.
16
Li, Guangdi D., Rajinder P. Singh, John P. Brennan e 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. 1 (2010): 12. http://dx.doi.org/10.1071/cp09103.
Testo completoAbstract (sommario):
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.
17
Young, Rick, Neil Huth, Steven Harden e Ross McLeod. "Impact of rain-fed cropping on the hydrology and fertility of alluvial clays in the more arid areas of the upper Darling Basin, eastern Australia". Soil Research 52, n. 4 (2014): 388. http://dx.doi.org/10.1071/sr13194.
Testo completoAbstract (sommario):
The impact of cropping on the hydrology and fertility of Vertosols in the northern Darling Basin (average annual rainfall >550 mm) has received much attention, together with the constraints placed on crop growth by naturally occurring subsoil salt stocks. These factors have not been quantified in the drier (450–550 mm), marginal cropping areas to the west. With widespread adoption of zero tillage technology and the potential for large increases in the capture and storage of rainfall in good seasons, mobilisation of salt could be exacerbated should crop water use be constrained by salt toxicity and/or nutrient deficiency. We investigated the size of salt stocks, historic deep drainage, and nutrient depletion under continuous cropping in the Grey and Brown Vertosols of the Walgett and Coonamble districts of north-western NSW. Soils collected from seven paired sites (cropped v. control native vegetation) showed chloride concentrations >500 mg/kg within 0–1.2 m, high exchangeable sodium percentage (~30%) at depth and deficiency in phosphorus, manganese and zinc. Soil total nitrogen decreased from an average stock of 4.9 t/ha at a rate of 0.008 t/ha.year under cropping within 0–0.1 m and soil carbon stocks decreased from 39 t/ha by 0.20 t/ha.year within 0–0.5 m.. Despite low rainfall, high evaporation and the large water-holding capacity of the cracking clays, there were significant downward shifts in chloride concentrations under cropping. Estimates of deep drainage under continuous cropping using chloride mass balance, chloride-front displacement and crop water-balance modelling with the Agricultural Production Systems Simulator (APSIM) generally agreed (range 0.1–2% of average annual rainfall). Simulations suggested that deep drainage may be increased 5–10-fold under zero-tillage winter cropping due to enhanced capture of rainfall by zero tillage compared with traditional practices. The associated flushing of salt from the root-zone together with correction of nutrient deficiency would enhance crop water use and productivity. Current methods indicate little storage in the subsoil for future deep drainage and that hydraulic conductivity is very low. Hence, the long-term effects of any increase in drainage rates, due to changes in cropping practices and/or climate, on the potential for salinisation of groundwater or transient water logging of the surface, are equivocal.
18
Belyaeva, Oxana N., Sally J. Officer, Roger D. Armstrong, Rob H. Harris, Ashley Wallace, Debra L. Partington, Kirsten Fogarty e Andrew J. Phelan. "Use of the agricultural practice of pasture termination in reducing soil N2O emissions in high-rainfall cropping systems of south-eastern Australia". Soil Research 54, n. 5 (2016): 585. http://dx.doi.org/10.1071/sr15307.
Testo completoAbstract (sommario):
Conversion of long-term pasture to cropping was investigated for its effects on nitrous oxide (N2O) emissions in a 2-year field experiment in the high-rainfall zone of south-western Victoria. Early termination (pasture terminated 6 months before sowing) followed by winter (ETw) and spring (ETs) crops and late termination (pasture terminated 1 month before sowing) followed by a winter crop (LTw) were compared with continuous, mown pasture (MP). Emissions of N2O were measured with an automated gas sampling and analysing system. Emissions from MP were the lowest throughout the study, resulting in annual losses of 0.13kg N2O-N ha–1 in the first and the second years of the experiment. N2O-N loss was 0.6kgha–1 from treatments without fallow in both years (LTw in 2013 and ETs in 2014). In the first year, annual losses from previous fallow in ETw and ETs plots were 7.1 and 3.6kg N2O-N ha–1, respectively. Higher annual N2O losses from treatments with fallow periods continued in the second year of the study and were 2.0 and 1.3kg N2O-N ha–1 from ETw and LTw treatments, respectively. High emissions were associated with N mineralisation and the accumulation of NO3-N in the soil during the extensive fallow period after early pasture termination or wheat harvest. Soil water content was a key factor influencing the temporal fluctuations in N2O emissions. Low emissions occurred when water-filled pore space was <30%, whereas high emissions occurred when it was >65%, suggesting that denitrification was the major source of N2O emission. Crop grain yield was not affected by the duration of fallow (and therefore timing of pasture termination) in the first year, but was lower (P<0.05) in the treatment without fallow in the second year. Terminating pasture late rather than early, thus reducing the length of the fallow period, is a practical way of reducing N2O emissions from mixed pasture–cropping systems.
19
Seymour, Mark, Jonathan H. England, Raj Malik, David Rogers, Andrew Sutherland e Allen Randell. "Effect of timing and height of defoliation on the grain yield of barley, wheat, oats and canola in Western Australia". Crop and Pasture Science 66, n. 4 (2015): 287. http://dx.doi.org/10.1071/cp13411.
Testo completoAbstract (sommario):
Winter cropping in Western Australia (WA) is dominated by spring-type cereals and canola (Brassica napus L.) with no vernalisation requirement that are sown in late autumn (late April and May). With limited earlier sowing opportunities for later maturing winter-type crops in early autumn, farmers aiming to obtain some benefit from the grazing of crops (i.e. dual-purpose) must consider the grazing potential of spring types sown in late autumn. The aim of this study was to develop grazing guidelines for spring-type crops in WA that will limit the potential for grain yield losses. In order to determine the recovery response of spring-type crops to grazing intensity and timing, 59 time-of-cutting × height-of-cutting experiments were conducted throughout the south-western region of WA in 2012. Experiments were conducted on spring types of wheat (Triticum aestivum L.), barley (Hordeum vulgare L.), canola and oats (Avena sativa L.). Multi-site analysis showed that treatments simulating high-intensity ‘crash’ grazing to ground level or to a height of 5 cm reduced grain yield unless conducted early in vegetative growth before reproductive stages. Treatments simulating ‘clip’ grazing by removing only the top 5–10 cm of crop foliage reduced grain yield to a lesser extent than crash grazing, and in several instances could extend the safe cutting period past hollow stem (Zadoks growth stage 30) and/or the end of July for cereals, or past mid-July for spring canola, provided the developing reproductive parts of all crops were not damaged. On average, the amounts of biomass removed by clip grazing without yield penalty were 0.4, 0.3, 0.5 and 0.3 t ha–1 for barley, wheat, oats and canola and were similar to those removed by earlier, safe crash grazing. These represent significant amounts of forage and suggest that clip grazing of spring-type crops may be an approach suited to WA cropping and grazing systems.
20
Hoffmann, Ary A., Andrew R. Weeks, Michael A. Nash, G. Peter Mangano e Paul A. Umina. "The changing status of invertebrate pests and the future of pest management in the Australian grains industry". Australian Journal of Experimental Agriculture 48, n. 12 (2008): 1481. http://dx.doi.org/10.1071/ea08185.
Testo completoAbstract (sommario):
The Australian grains industry is dealing with a shifting complex of invertebrate pests due to evolving management practices and climate change as indicated by an assessment of pest reports over the last 20–30 years. A comparison of pest outbreak reports from the early 1980s to 2006–07 from south-eastern Australia highlights a decrease in the importance of pea weevils and armyworms, while the lucerne flea, Balaustium mites, blue oat mites and Bryobia mites have increased in prominence. In Western Australia, where detailed outbreak records are available from the mid 1990s, the relative incidence of armyworms, aphids and vegetable weevils has recently decreased, while the incidence of pasture cockchafers, Balaustium mites, blue oat mites, redlegged earth mites, the lucerne flea and snails has increased. These changes are the result of several possible drivers. Patterns of pesticide use, farm management responses and changing cropping patterns are likely to have contributed to these shifts. Drier conditions, exacerbated by climate change, have potentially reduced the build-up of migratory species from inland Australia and increased the adoption rate of minimum and no-tillage systems in order to retain soil moisture. The latter has been accompanied by increased pesticide use, accelerating selection pressures for resistance. Other control options will become available once there is an understanding of interactions between pests and beneficial species within a landscape context and a wider choice of ‘softer’ chemicals. Future climate change will directly and indirectly influence pest distributions and outbreaks as well as the potential effectiveness of endemic natural enemies. Genetically modified crops provide new options for control but also present challenges as new pest species are likely to emerge.
21
Evans, J., A. M. McNeill, M. J. Unkovich, N. A. Fettell e 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. 3 (2001): 347. http://dx.doi.org/10.1071/ea00036.
Testo completoAbstract (sommario):
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.
22
Turner, Neil C., e Senthold Asseng. "Productivity, sustainability, and rainfall-use efficiency in Australian rainfed Mediterranean agricultural systems". Australian Journal of Agricultural Research 56, n. 11 (2005): 1123. http://dx.doi.org/10.1071/ar05076.
Testo completoAbstract (sommario):
Mediterranean environments are characterised by hot, dry summers and cool, wet winters. The native vegetation in Mediterranean-climatic regions is predominantly perennial shrubs and trees intermixed with annual forbs. In south-western Australia, the spread of agriculture has seen the well adapted perennial vegetation replaced by rainfed annual crops and pastures. This has increased waterlogging and secondary salinity, thereby causing loss of productivity in ~10% of the cleared land area. To reduce deep drainage and make the agricultural systems environmentally sustainable requires the re-introduction of perennial vegetation in the form of belts of trees or shrubs, and phase-farming systems with perennials such as lucerne replacing annual pastures between the cropping years. To be economically viable, agricultural productivity needs to increase by at least 3% per annum. Yields of dryland wheat, the predominant crop in the Mediterranean agricultural regions of Australia, have increased at ~1%/year for the century preceding the 1980s and since then by nearly 4%/year. Increases have arisen from both genotypic and agronomic improvements. Genotypic increases have arisen from selection for earliness, early vigour, deep roots, osmotic adjustment, increased transpiration efficiency, improved disease resistance, and an improved harvest index from high ear weight (grain number) at flowering and high assimilate storage and remobilisation. Agronomic increases have arisen from early sowing that has been enabled by minimum tillage, increased fertiliser use, especially nitrogen, weed control, and rotations to improve weed control, minimise disease risk, and increase nitrogen availability. Evidence is presented suggesting that the rapid increase in yield of wheat in the last two decades has likely arisen from the rapid adoption of new technologies. For productivity to be maintained in the face of the increasing requirement to be environmentally sustainable will be a challenge and will require better integration of breeding and agronomy.
23
Whalley, R. D. B., J. N. Price, M. J. Macdonald e P. J. Berney. "Drivers of change in the Social-Ecological Systems of the Gwydir Wetlands and Macquarie Marshes in northern New South Wales, Australia". Rangeland Journal 33, n. 2 (2011): 109. http://dx.doi.org/10.1071/rj11002.
Testo completoAbstract (sommario):
The Murray–Darling Basin is a Social-Ecological System (SES) of major importance to Australia and includes extensive wetland areas in the north-western parts of New South Wales. The Gwydir Wetlands and the Macquarie Marshes are the particular focus of this paper. These two wetland SES have undergone five successive adaptive cycles (phases) since they were first visited by Europeans in the early 19th century and the ecological, economic and social drivers initiating each transformation to a new cycle are described and analysed. The arrival of the European settlers with their domestic livestock rapidly displaced the Indigenous SES and the wetlands were extensively grazed; during wet periods the livestock were moved out of the wetlands and moved back in as the water receded. More recent land-use changes resulted from the building of major dams to enable storage of water for use in irrigated agriculture. A consequence of dam construction and water use has been a reduction in the frequency and extent of flooding, which has allowed many parts of the wetlands to be continually grazed. Furthermore, as machinery capable of cultivating the very heavy textured soils became available, dryland cropping became a major enterprise in areas of the floodplain where the likelihood of flooding was reduced. With the reduction in flooding, these wetland sites have been seriously degraded. The final phase has seen the invasion by an exotic weed, lippia [Phyla canescens (Kunth) Greene], which is a perennial that grows mat-like between other species of plants and spreads to produce a virtually mono-specific stand. The domestic livestock carrying capacity of the land becomes more or less zero and the conservation value of the wetlands is also dramatically decreased. Therefore, we suggest that lippia should be classed as an ecosystem engineer that has caused the latest transformation of these wetland SES and suggest research directions to investigate how they can be managed to revert to a state in which lippia is no longer dominant.
24
Davies, C. L., D. L. Waugh e E. C. Lefroy. "Variation in seed yield and its components in the Australian native grass Microlaena stipoides as a guide to its potential as a perennial grain crop". Australian Journal of Agricultural Research 56, n. 3 (2005): 309. http://dx.doi.org/10.1071/ar04204.
Testo completoAbstract (sommario):
This research investigated the potential to domesticate an Australian native grass (Microlaena stipoides) to produce a perennial grain crop. Perennial grain crops offer a new solution to the long-standing problems of salinity and soil erosion associated with conventional cropping systems based on annual plants. Seed yield and its components (culm number, spikelet number per culm, seed set, seed weight) were measured in 46 accessions of Microlaena stipoides (microlaena, meadow or weeping rice grass) from Western Australia and New South Wales to quantify potentially useful variation in the species. A high degree of variability was found to exist, with a 20-fold range in seed yield (0.1–2.4 g/plant), 5-fold range in seed weight (129–666 mg per 100 seeds), 2-fold range in spikelet number (14–30 per culm), 8-fold range in seed set (12–98%), and a 5-fold range in culm number (11–59 per plant). Seed yield was positively and significantly (P < 0.05) correlated with culm number, seed set, and seed weight (r > 0.55 for all). No correlation was found between seed yield and spikelet number per culm (r = –0.14). The range in seed yield and its components suggests that there is sufficient variation within microlaena to make selections for higher yielding lines. This variation will enable breeders to exploit genetic diversity more efficiently and identify useful accessions for further work. High priority traits for future work include synchronous maturity and resistance to shattering.
25
Oliver, Y. M., E. C. Lefroy, R. Stirzaker e C. L. Davies. "Deep-drainage control and yield: the trade-off between trees and crops in agroforestry systems in the medium to low rainfall areas of Australia". Australian Journal of Agricultural Research 56, n. 10 (2005): 1011. http://dx.doi.org/10.1071/ar04213.
Testo completoAbstract (sommario):
In the dryland cropping areas of southern Australia, at risk from dryland salinity, tree belts can improve water management by taking up water unused by crops, with the risk that crop yield will be reduced through competition. As there are few direct markets for tree products grown in the medium to low rainfall areas, the design of agroforestry systems becomes important in reducing the trade-off in crop yield. This study examined some factors that influence the trade-off between crop yield and deep-drainage control in order to develop design guidelines for medium to low rainfall agroforestry. Twenty-one sites in the grain-growing region of Western Australia and southern New South Wales were surveyed over 2 years for crop yields, tree leaf area index, and estimated recharge, providing data from 32 tree–crop interfaces on the relative influence of environmental factors and farming system characteristics on the trade-off between water management and crop yield. The factors most strongly correlated with higher yields were water-gaining sites, orientation that provided shelter from southerly to north-westerly (S, SW, W, NW) winds, and tree age (<10 years). The factors most strongly correlated with the area of cropped land protected against deep drainage were tree age (>10 years), lighter soil types, and low rainfall (<400 mm). Economic analysis of the trade-off required to produce a particular deep-drainage reduction target produced 3 groups of sites: (1) those where trees resulted in a gross margin increase of $15/ha and an estimated deep-drainage reduction of 52% (n = 3), (2) those with a gross margin loss of $49/ha and estimated deep-drainage reduction of 47% (n = 11), and (3) those with a gross margin loss of $163/ha and a deep-drainage reduction of 37% (n = 18). None of the 3 sites in the first group were in the most favourable class in both years, highlighting the vulnerability of a relatively fixed farming system to climate variability.
26
McGrath, S. R., R. Behrendt, M. A. Friend e A. D. Moore. "Utilising dual-purpose crops effectively to increase profit and manage risk in meat production systems". Animal Production Science 61, n. 11 (2021): 1049. http://dx.doi.org/10.1071/an20495.
Testo completoAbstract (sommario):
Dual-purpose cropping (sowing crops with the intention of both grazing them during vegetative growth and harvesting grain thereafter) has become a widespread farming practice in southern Australia. This synopsis paper integrates research from a multi-institutional research project conducted at three nodes located near Hamilton (south-western Victoria), Wagga Wagga (southern NSW) and Canberra (ACT), and sets out 11 principles for the effective utilisation of dual-purpose crops in meat production systems to increase profit and manage risk. Dual-purpose crops can be used to overcome feed quality gaps in late summer–autumn or feed quantity gaps in late autumn/winter. They provide large quantities of high-quality forages for grazing in summer, autumn and winter and can provide a substantial contribution to the annual number of grazing days on a farm. Utilisation of the high-quality dry matter provided by dual-purpose crops is most effective when directed at young growing stock for sale or future reproduction rather than reproducing adult ewes. For example, sale weight of yearlings per ewe was increased by 16% in systems at the Canberra node when dual-purpose crops were prioritised for grazing by weaners. Wool production was also increased in systems that included grazing of dual-purpose crops. Grazing crops in winter does not necessarily reduce supplementary feeding costs for winter or spring lambing. Modelling suggests that inclusion of dual-purpose crops does not substantially change the optimum time of lambing for sheep meat systems. Financial analysis of the experimental data from the Canberra node showed that although cash expenses per hectare were increased in the crop-grazing systems, the overall profitability of those systems over the life of the experiment was greater by AU$207/ha.year than that of the pasture-only system. Factors driving improved profitability included income from grain, higher income from meat and wool, and lower supplementary feeding costs. However, increasing the area sown to crop from 10% to 30% of the farm area in this Southern Tablelands system appeared to increase risk. In south-western Victoria, spring-sown canola carried risk similar to or less than other options assessed to achieve ewe-lamb mating weight. It is likely that at least part of the reduction in risk occurs through the diversification in income from the canola produced as part of the system. It was concluded that the grazing of cereal and canola crops for livestock production can be profitable and assist in managing risk.
27
Chapman, D. F., D. Beca, J. Hill, J. Tharmaraj, J. L. Jacobs e B. R. Cullen. "Increasing home-grown forage consumption and profit in non-irrigated dairy systems. 4. Economic performance". Animal Production Science 54, n. 3 (2014): 256. http://dx.doi.org/10.1071/an13186.
Testo completoAbstract (sommario):
The profitability of dairy farm systems in southern Australia is closely related to the amount of pasture grown and consumed on-farm by dairy cows. However, there are doubts regarding the extent to which gains in feed supply from perennial ryegrass pasture can continue to support productivity growth in the industry. A farmlet experiment was conducted in south-western Victoria for 4 years (June 2005–May 2009), comparing a production system based on the use of forage species that complement perennial ryegrass in their seasonal growth pattern (‘Complementary Forages’, or CF) with a well managed system solely based on perennial ryegrass pasture (‘Ryegrass Max’, or RM). The forage base in CF included perennial ryegrass with a double-cropping rotation of winter cereal grown for whole-crop silage, followed by a summer brassica for grazing on 15% of farmlet area, a summer-active pasture based on tall fescue (on average 20% of farmlet area), perennial ryegrass oversown with short-rotation ryegrasses (average 16% of farmlet area) and summer brassica crops used in the process of pasture renovation (average 5% of farmlet area). The stocking rate was 2.2 and 2.8 cows/ha on RM and CF, respectively. Both systems were profitable over the 4 years of the experiment, with the modified internal rate of return over 4 years being 14.4% and 14.7% for the RM and CF farmlets, respectively. The coefficient of variation (%) of annual operating profit over 4 years was higher for the CF farmlet (56% and 63% for RM and CF, respectively). A severe drought in one of the 4 years exposed the more highly stocked CF system to greater supplementary feed costs and business risk. By comparison, the RM system performed consistently well across different seasons and in the face of a range of milk prices. The very small gain in profit from CF, plus the associated higher risk, makes it difficult to endorse a substantial change away from the traditional RM feed supply to greater reliance on summer-grown forages on non-irrigated dairy farms in southern Australia, as implemented in this experiment.
28
Asseng, S., G. C. Anderson, F. X. Dunin, I. R. P. Fillery, P. J. Dolling e B. A. Keating. "Use of the APSIM wheat model to predict yield, drainage, and NO3- leaching for a deep sand". Australian Journal of Agricultural Research 49, n. 3 (1998): 363. http://dx.doi.org/10.1071/a97095.
Testo completoAbstract (sommario):
High rates of drainage and leaching of nitrates in deep sands in Western Australia are contributing to groundwater recharge and soil acidification in this region. Strategies are being soughtto increase water and nitrogen (N) use in the legume-based cropping systems. Choice of appropriate management strategies is complicated by the diversity of soil types, the range of crops, and the inherent season to season variability. Simulation models provide the means to extrapolate beyond the bounds of experimental data if accurate predictions of key processes can be demonstrated. This paper evaluates the accuracy of predictions of soil water content, evapotranspiration, drainage, inorganic N content insoil, nitrate (NO-3) leaching, wheat growth, N uptake, and grain yields obtained from the Agricultural Production Systems Simulator (APSIM) model when this was initialised with appropriate information on soil properties and wheat varieties commonly grown on deep sands in the 500 mm rainfall zone west of Moora in Western Australia. The model was found to give good predictions of soil water content,evapotranspiration, deep drainage, and overall NO-3 leaching. Temporal changes in inorganic N insoil were simulated, although the small concentrations in soil inorganic N precluded close matching of paired observed and predicted values. Crop growth and N uptake were closely predicted up to anthesis, but a poor fit between observed and predicted crop growth and N uptake was noted postanthesis. Reasons for the discrepancies between modelled and observed values are outlined. The model was run with historical weather data (81 years) and different initial soil water and inorganic soil N profiles to assess the probability of drainage and NO-3 leaching, and the grain yield potentials for wheat grown on deep sands in the region west of Moora. Simulation showed that thesoil water and the soil inorganic N content at the beginning of each season had no effect on grain yield, implying that pre-seed soil NO-3 was largely lost from the soil by leaching. There was a 50% probability that 141 mm of winter rainfall could drain below 1·5 m and a 50% probability that 53 kgN/ha could be leached under wheat following a lupin crop, where initial soil water contents andsoil NO-3 contents used in the model were those measured in a deep sand after late March rainfall. Simulated application of N fertiliser at sowing increased both grain yield and NO-3 leaching. Splitting the N application between the time of sowing and 40 days after sowing decreased NO-3 leaching,increased N uptake by wheat, and increased grain yield, findings which are consistent with agronomic practice. The high drainage and leaching potential of these soils were identified as the main reasons why predicted yields did not approach the French and Schultz potential yield estimates based on 20 kg grain yield per mm of rainfall. When the available water was reduced by simulated drainage, simulated grain yields for the fertilised treatments approached the potential yield line.
29
Bell, Michael J., Philip W. Moody, Geoffrey C. Anderson e Wayne Strong. "Soil phosphorus—crop response calibration relationships and criteria for oilseeds, grain legumes and summer cereal crops grown in Australia". Crop and Pasture Science 64, n. 5 (2013): 499. http://dx.doi.org/10.1071/cp12428.
Testo completoAbstract (sommario):
Australian cropping systems are dominated by winter cereals; however, grain legumes, oilseeds and summer cereals play an important role as break crops. Inputs of phosphorus (P) fertiliser account for a significant proportion of farm expenditure on crop nutrition, so effective fertiliser-use guidelines are essential. A national database (BFDC National Database) of field experiments examining yield responses to P fertiliser application has been established. This paper reports the results of interrogating that database using a web application (BFDC Interrogator) to develop calibration relationships between soil P test (0–10 cm depth; Colwell NaHCO3 extraction) and relative grain yield. Relationships have been developed for all available data for each crop species, as well as for subsets of those data derived by filtering processes based on experiment quality, presence of abiotic or biotic stressors, P fertiliser placement strategy and subsurface P status. The available dataset contains >730 entries but is dominated by data for lupin (Lupinus angustifolius; 62% of all P experiments) from the south-west of Western Australia. The number of treatment series able to be analysed for other crop species was quite small (<50–60 treatment series) and available data were sometimes from geographic regions or soil types no longer reflective of current production. There is a need for research to improve information on P fertiliser use for key species of grain legumes [faba bean (Vicia faba), lentil (Lens culinaris), chickpea (Cicer arietinum)], oilseeds [canola (Brassica napus), soybean (Glycine max)] and summer cereals [sorghum (Sorghum bicolor), maize (Zea mays)] in soils and farming systems reflecting current production. Interrogations highlighted the importance of quantifying subsurface P reserves to predict P fertiliser response, with consistently higher 0–10 cm soil test values required to achieve 90% maximum yield (CV90) when subsurface P was low (<5 mg P/kg). This was recorded for lupin, canola and wheat (Triticum aestivum). Crops grown on soils with subsurface P >5 mg/kg consistently produced higher relative yields than expected on the basis of a 0–10 cm soil test. The lupin dataset illustrated the impact of improving crop yield potentials (through more effective P-fertiliser placement) on critical soil test values. The higher yield potentials arising from placement of P-fertiliser bands deeper in the soil profile resulted in significantly higher CV90 values than for crops grown on the same sites but using less effective (shallower) P placement. This is consistent with deeper bands providing an increased and more accessible volume of profile P enrichment and supports the observation of the importance of crop P supply from soil layers deeper than 0–10 cm. Soil P requirements for different species were benchmarked against values determined for wheat or barley (Hordeum vulgare) grown in the same regions and/or soil types as a way of extrapolating available data for less researched species. This approach suggested most species had CV90 values and ranges similar to winter cereals, with evidence of different soil P requirements in only peanut (Arachis hypogaea – much lower) and field pea (Pisum sativum – slightly higher). Unfortunately, sorghum data were so limited that benchmarking against wheat was inconclusive.
30
Bell, Michael J., Wayne Strong, Denis Elliott e Charlie Walker. "Soil nitrogen—crop response calibration relationships and criteria for winter cereal crops grown in Australia". Crop and Pasture Science 64, n. 5 (2013): 442. http://dx.doi.org/10.1071/cp12431.
Testo completoAbstract (sommario):
More than 1200 wheat and 120 barley experiments conducted in Australia to examine yield responses to applied nitrogen (N) fertiliser are contained in a national database of field crops nutrient research (BFDC National Database). The yield responses are accompanied by various pre-plant soil test data to quantify plant-available N and other indicators of soil fertility status or mineralisable N. A web application (BFDC Interrogator), developed to access the database, enables construction of calibrations between relative crop yield ((Y0/Ymax) × 100) and N soil test value. In this paper we report the critical soil test values for 90% RY (CV90) and the associated critical ranges (CR90, defined as the 70% confidence interval around that CV90) derived from analysis of various subsets of these winter cereal experiments. Experimental programs were conducted throughout Australia’s main grain-production regions in different eras, starting from the 1960s in Queensland through to Victoria during 2000s. Improved management practices adopted during the period were reflected in increasing potential yields with research era, increasing from an average Ymax of 2.2 t/ha in Queensland in the 1960s and 1970s, to 3.4 t/ha in South Australia (SA) in the 1980s, to 4.3 t/ha in New South Wales (NSW) in the 1990s, and 4.2 t/ha in Victoria in the 2000s. Various sampling depths (0.1–1.2 m) and methods of quantifying available N (nitrate-N or mineral-N) from pre-planting soil samples were used and provided useful guides to the need for supplementary N. The most regionally consistent relationships were established using nitrate-N (kg/ha) in the top 0.6 m of the soil profile, with regional and seasonal variation in CV90 largely accounted for through impacts on experimental Ymax. The CV90 for nitrate-N within the top 0.6 m of the soil profile for wheat crops increased from 36 to 110 kg nitrate-N/ha as Ymax increased over the range 1 to >5 t/ha. Apparent variation in CV90 with seasonal moisture availability was entirely consistent with impacts on experimental Ymax. Further analyses of wheat trials with available grain protein (~45% of all experiments) established that grain yield and not grain N content was the major driver of crop N demand and CV90. Subsets of data explored the impact of crop management practices such as crop rotation or fallow length on both pre-planting profile mineral-N and CV90. Analyses showed that while management practices influenced profile mineral-N at planting and the likelihood and size of yield response to applied N fertiliser, they had no significant impact on CV90. A level of risk is involved with the use of pre-plant testing to determine the need for supplementary N application in all Australian dryland systems. In southern and western regions, where crop performance is based almost entirely on in-crop rainfall, this risk is offset by the management opportunity to split N applications during crop growth in response to changing crop yield potential. In northern cropping systems, where stored soil moisture at sowing is indicative of minimum yield potential, erratic winter rainfall increases uncertainty about actual yield potential as well as reducing the opportunity for effective in-season applications.
31
Robertson, Michael, Andrew Bathgate, Andrew Moore, Roger Lawes e Julianne Lilley. "Seeking simultaneous improvements in farm profit and natural resource indicators: a modelling analysis". Animal Production Science 49, n. 10 (2009): 826. http://dx.doi.org/10.1071/an09008.
Testo completoAbstract (sommario):
Natural resource indicators are used by catchment management organisations as targets for land use management. However, the nature of the trade-off function between natural resource management (NRM) outcomes and whole-farm profit is ill-defined, and varies between regions and according to the particular NRM indicator considered. Defining this function will assist catchment management organisations and farmers to evaluate the achievability of particular targets, and help determine the size of economic incentives required to offset any expected loss in farm profit associated with meeting targets. We addressed this issue by modelling representative farm businesses in two mixed farming regions (southern New South Wales and the central wheatbelt of Western Australia). The Agricultural Production Systems Simulator (APSIM) and GRAZPLAN farming systems models were linked and used to generate values of four NRM indicators (water leakage, nitrate leaching, groundcover and soil organic carbon change) for a wide range of crop–pasture rotations. The NRM indicator values were then incorporated into the Model of an Integrated Dryland System (MIDAS) whole-farm economic model to define the relationship with farm profit and farm cropping percentage. For some circumstances and indicators, the resulting trade-off functions were relatively flat; a wide range of enterprise mixes can lead to the same NRM outcomes but significant gains in the indicators may not be possible using current rotation options. For others, significant improvements could be achieved but at a substantial loss in whole-farm profit (through the selection of less profitable rotations). There were also examples where simultaneous gains in indicators and farm profit were possible. This analysis demonstrates an approach by which biophysical simulation models of the farming system can be linked to linear-programming representations of farming enterprises, and provides a method for deriving relationships between NRM targets and economic performance.
32
D'Emden, F. H., e R. S. Llewellyn. "No-tillage adoption decisions in southern Australian cropping and the role of weed management". Australian Journal of Experimental Agriculture 46, n. 4 (2006): 563. http://dx.doi.org/10.1071/ea05025.
Testo completoAbstract (sommario):
Adoption of no-tillage sowing systems has increased rapidly in many Australian grain growing regions over the past decade. The extent of herbicide resistant weed populations in these regions has also increased over the same period. A survey of growers in the South and Western Australian cropping regions was conducted to identify opportunities for more effective tillage and weed-related extension. Trends in sowing system use are determined, as are growers’ perceptions of the long-term effects of no-tillage on herbicide costs, herbicide resistance, and soil erosion. The results suggest a major expansion in the adoption of no-tillage sowing in most South Australian cropping regions over the next 5 years, although growers expect increased herbicide costs in no-tillage systems and an increased risk of herbicide resistance. Herbicide resistance and weed control issues are the main reasons given for reducing no-tillage use. A key research and extension challenge is to develop and implement weed management strategies that are able to sustain long-term no-tillage use in a cropping environment where growers place a high value on the soil and production benefits of no-tillage, but over-reliance on herbicides can rapidly lead to resistance in major crop weeds.
33
Scanlon, Timothy T., e Greg Doncon. "Rain, rain, gone away: decreased growing-season rainfall for the dryland cropping region of the south-west of Western Australia". Crop and Pasture Science 71, n. 2 (2020): 128. http://dx.doi.org/10.1071/cp19294.
Testo completoAbstract (sommario):
The shift in Indian Ocean sea surface temperatures in 1976 led to a change in rainfall for the broad-scale winter annual grain cropping and pasture region in the south-west of Western Australia (the WA wheatbelt). Agriculture in the eastern part the WA wheatbelt was particularly sensitive to the change in rainfall because it is a marginal area for agronomic production, with low rainfall before changes in sea surface temperature. A second shift in sea surface temperature occurred in 2000, but there has been no analysis of the resulting impact on rainfall in the eastern WA wheatbelt. An analysis of rainfall pre- and post-2000 was performed for sites in the eastern WA wheatbelt in three groups: 19 sites in the west, 56 central, and 10 east. The analysis found a decline in growing-season rainfall (i.e. April–October), especially during May–July, post-2000. Rainfall declines of 49.9 mm (west group), 39.1 mm (central group) and 28.0 mm (east group) represented respective losses of 20.1%, 17.4% and 14.2% of growing-season rainfall. Increases in out-of-season rainfall in the respective groups of 31.0, 33.6, and 50.7 mm (57.8%, 60.8% and 87.6%) meant that annual rainfall changes were smaller than growing-season losses. The west and central groups lost 17.5 and 6.16 mm annual rainfall, whereas the east group gained 15.6 mm. Analysis of wheat yield indicated reductions of 13.5% (west) and 9.90% (central) in the eastern WA wheatbelt; the small group of east sites had a potential yield gain of 8.9% arising from the increased out-of-season rainfall. Further, increased out-of-season rainfall will exacerbate weed and disease growth over the summer fallow.
34
Gibson, N., G. J. Keighery, M. N. Lyons e B. J. Keighery. "Threatened plant communities of Western Australia. 2 The seasonal clay-based wetland communities of the South West". Pacific Conservation Biology 11, n. 4 (2005): 287. http://dx.doi.org/10.1071/pc050287.
Testo completoAbstract (sommario):
The communities of seasonal clay-based wetlands of south-west Australia are described. They are amongst the most threatened In Western Australia. It is estimated that >90% of the original extent of these communities has been cleared for agriculture, and the remaining areas, despite largely occurring in conservation reserves, are threatened by weed invasion and rising saline groundwater. Thirty-six taxa are identified as claypan specialists occurring in six floristic communities. Composition was strongly correlated with rainfall and edaphic factors. The most consistent attribute shared between the seasonal clay-based wetlands of south-west Australia, and the analogous vernal pools systems of California, Chile, and South Africa was the widespread conversion of these wetlands to agricultural systems. The south-west Australia wetlands had a richer flora, different lifeform composition, higher species richness but fewer claypan specialists than the vernal pools of California. The dissimilarity in the regional floras and vegetation types from which the pool floras were recruited explain these differences.
35
Sudmeyer, R. A., D. J. M. Hall, J. Eastham e M. A. Adams. "The tree - crop interface: the effects of root pruning in south-western Australia". Australian Journal of Experimental Agriculture 42, n. 6 (2002): 763. http://dx.doi.org/10.1071/ea02012.
Testo completoAbstract (sommario):
This paper examines the effect severing lateral tree roots (root pruning) has on crop and tree growth and soil water content at 2 sites in the south-west of Western Australia. Crop and tree growth and soil water content were assessed in a Pinus pinaster windbreak system growing on 0.45–1.00 m of sand over clay, and crop growth was assessed adjacent to Eucalyptus globulus windbreaks growing on 4–5 m of sand. Crop yield was depressed by 23–52% within 2.5 times the tree height (H) of unpruned pines and by 44% within 2.5 H of pruned eucalypts. Depressed yields made cropping uneconomical within 1.5 H of the eucalypts and 1 H of the pines. Root pruning most improved crop yields where lateral tree roots were confined close to the soil surface and decreased in effectiveness as the depth to confining layer (clay) increased. Crop losses within 2.5 H of the pines were reduced from 39 to 14% in the year the trees were root pruned and were 25% 1 year after root pruning. Subsequent root pruning of the eucalypts did not improve crop yield. While root pruning severed lateral pine roots, tree growth was not significantly reduced. The principal cause of reduced crop yield near the trees appeared to be reduced soil moisture in the area occupied by tree roots. Competition for nutrients and light appeared to have little effect on crop yield. Root pruning can spatially separate tree and crop roots where the tree roots are confined close to the surface, and significantly improve crop yields without reducing tree growth.
36
Sherwood, John E., Jim M. Bowler, Stephen P. Carey, John Hellstrom, Ian J. McNiven, Colin V. Murray-Wallace, John R. Prescott et al. "The Moyjil site, south-west Victoria, Australia: chronology". Proceedings of the Royal Society of Victoria 130, n. 2 (2018): 32. http://dx.doi.org/10.1071/rs18005.
Testo completoAbstract (sommario):
An unusual shell deposit at Moyjil (Point Ritchie), Warrnambool, in western Victoria, has previously been dated at 67±10 ka and has features suggesting a human origin. If human, the site would be one of Australia’s oldest, justifying a redetermination of age using amino acid racemisation (AAR) dating of Lunella undulata (syn. Turbo undulatus) opercula (the dominant shellfish present) and optically stimulated luminescence (OSL) of the host calcarenite. AAR dating of the shell bed and four Last Interglacial (LIG) beach deposits at Moyjil and Goose Lagoon, 30 km to the west, confirmed a LIG age. OSL analysis of the host sand revealed a complex mixing history, with a significant fraction (47%) of grains giving an early LIG age (120–125 ka) using a three-component mixing model. Shell deposition following the LIG sea-level maximum at 120–125 ka is consistent with stratigraphic evidence. A sand layer immediately below the shell deposit gave an age of ~240 ka (i.e. MIS 7) and appears to have been a source of older sand incorporated into the shell deposit. Younger ages (~60–80 ka) are due to bioturbation before calcrete finally sealed the deposit. Uranium/thorium methods were not applicable to L. undulata opercula or an otolith of the fish Argyrosomus hololepidotus because they failed to act as closed systems. A U–Th age of 103 ka for a calcrete sheet within the 240 ka sand indicates a later period of carbonate deposition. Calcium carbonate dripstone from a LIG wave-cut notch gave a U–Th age of 11–14 ka suggesting sediment cover created a cave-like environment at the notch at this time. The three dating techniques have collectively built a chronology spanning the periods before and after deposition of the shell bed, which occurred just after the LIG sea-level maximum (120–125 ka).
37
Wong, M. T. F., R. W. Bell e K. Frost. "Mapping boron deficiency risk in soils of south-west Western Australia using a weight of evidence model". Soil Research 43, n. 7 (2005): 811. http://dx.doi.org/10.1071/sr05022.
Testo completoAbstract (sommario):
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.
38
Borger, Catherine P. D., Abul Hashem e Shahab Pathan. "Manipulating Crop Row Orientation to Suppress Weeds and Increase Crop Yield". Weed Science 58, n. 2 (giugno 2010): 174–78. http://dx.doi.org/10.1614/ws-09-094.1.
Testo completoAbstract (sommario):
Crop rows oriented at a right angle to sunlight direction (i.e., east–west within the winter cropping system in Western Australia) may suppress weed growth through greater shading of weeds in the interrow spaces. This was investigated in the districts of Merredin and Beverley, Western Australian (latitudes of 31° and 32°S) from 2002 to 2005 (four trials). Winter grain crops (wheat, barley, canola, lupines, and field peas) were sown in an east–west or north–south orientation. Within wheat and barley crops oriented east–west, weed biomass (averaged throughout all trials) was reduced by 51 and 37%, and grain yield increased by 24 and 26% (compared with crops oriented north–south). This reduction in weed biomass and increase in crop yield likely resulted from the increased light (photosynthetically active radiation) interception by crops oriented east–west (i.e., light interception by the crop canopy as opposed to the weed canopy was 28 and 18% greater in wheat and barley crops oriented east–west, compared with north–south crops). There was no consistent effect of crop row orientation in the canola, field pea, and lupine crops. It appears that manipulation of crop row orientation in wheat and barley is a useful weed-control technique that has few negative effects on the farming system (i.e., does not cost anything to implement and is more environmentally friendly than chemical weed control).
39
Islam, MR, MM Haque e MM Rahman. "Studies on seafood production systems in the South-west Region of Bangladesh". Journal of the Bangladesh Agricultural University 15, n. 1 (11 agosto 2017): 123–32. http://dx.doi.org/10.3329/jbau.v15i1.33537.
Testo completoAbstract (sommario):
The present study was conducted to understand existing production system of shrimp and prawn (seafood) with gher1 farming in the south-western region of Bangladesh from January to March 2014. Three gher farming clusters in three Upazilas of Bagerhat district were selected to carry out this study to assess the fact above using focus group discussion, key informant interview, questionnaire survey, physical observation, and literature review. The study revealed that gher farming system has changed the cropping patterns dramatically. This diversified farming system produces prawn, carp fish, boro paddy, and vegetable in the field where only single crop of paddy was cultivated. Gher dikes were used to produce vegetables, fruits and the central part for rice cultivation. Whereas the whole water body (during monsoon) and canals (during dry season) were used to culture finfish and prawn. Farmers were mainly found to use commercial feed with a rare amount of homemade feed because of the availability of commercial feed. Most of their investment goes for buying feed, PL and were found to take loan with high interest from banks or depot owners. Decreased salinity due to siltation in Mongla river resulted in increased overall production. The evidence presented in the study confirms that gher farming system impacting positively in the south-west region of Bangladesh.J. Bangladesh Agril. Univ. 15(1): 123-132, January 2017
40
Halse, S. A., J. K. Ruprecht e A. M. Pinder. "Salinisation and prospects for biodiversity in rivers and wetlands of south-west Western Australia". Australian Journal of Botany 51, n. 6 (2003): 673. http://dx.doi.org/10.1071/bt02113.
Testo completoAbstract (sommario):
Saline water was common in south-west Western Australian aquatic systems prior to land-clearing because most streams and wetlands were ephemeral and evapo-concentrated as they dried, and there were high concentrations of stored salt in groundwater and soil profiles. Nevertheless, a 1998 review of salinity trends in rivers of south-west Western Australia showed that 20-fold increases in salinity concentrations had occurred since clearing in the medium-rainfall zone (300–700 mm). More recent data confirm these trends and show that elevated salinities have already caused substantial changes to the biological communities of aquatic ecosystems. Further substantial changes will occur, despite the flora and fauna of the south-west being comparatively well adapted to the presence of salinity in the landscape. Up to one-third of wetland and river invertebrate species, large numbers of plants and a substantial proportion of the waterbird fauna will disappear from the wheatbelt, a region that has high biodiversity value and endemism. Increased salinities are not the only threat associated with salinisation: increased water volumes, longer periods of inundation and more widespread acidity are also likely to be detrimental to the biota.
41
Evans, J., C. Wallace, N. Dobrowolski, I. Pritchard e B. Sullivan. "Requirement of field pea for inoculation with Rhizobium and lime pelleting in soils of Western Australia". Australian Journal of Experimental Agriculture 33, n. 6 (1993): 767. http://dx.doi.org/10.1071/ea9930767.
Testo completoAbstract (sommario):
The requirement of field pea (Pisum sativum) for seed inoculation with Rhizobium and for lime pelleting of inoculated seed was investigated in field experiments in the south-west of Western Australia, especially at locations where inoculated field pea had been grown 2 years previously. At most sites with previous pea cropping, the nodulation, total dry matter and nitrogen, and grain yield of pea were not improved by seed inoculation or lime pelleting. At these sites soil populations of R. leguminosarum by. viciae at sowing were >103/g soil. Responses to inoculation were measured at sites where the soil was very acidic [pH(CaCl2) <4.5], or mildly acidic (to pH 4.9) and of light texture (>90% sand + gravel), or where pea had not grown previously. There were fewer rhizobia at sowing at these locations. Lime pelleting was not generally required to maximise field pea growth or yield, but yield was affected by the inoculant Rhizobium strain.
42
Gou, Yu, Hui Chen, Wei Wu e Hong-Bin Liu. "Effects of slope position, aspect and cropping system on soil nutrient variability in hilly areas". Soil Research 53, n. 3 (2015): 338. http://dx.doi.org/10.1071/sr14113.
Testo completoAbstract (sommario):
Human activities and topography are main factors affecting soil nutrient variation. However, the relationships between these factors are both site- and scale-specific. In hilly areas of south-western China, the dominant cropping systems are rice, vegetables, oranges, Chinese red pepper and maize–sweet potato intercropping. In the present study, slope position (valley, low slope, flat slope, middle slope, upper slope, ridge) and aspect (north, east, south, west) were derived to investigate the relationships among cropping system, terrain, and soil nutrients at county scale. Crops were mainly planted at middle or flat slope positions. Rice and orange plants were evenly distributed across the aspects whereas vegetables were mostly planted on the northern aspect. Red pepper and maize–sweet potato plants were mainly grown on the western and southern aspects. Rice sites had higher contents of organic matter and available nitrogen (N) and lower contents of available phosphorus (P) and available potassium (K). For dryland cropping systems, vegetable sites had higher contents of organic matter, available N, and available P. Red pepper sites had higher contents of available K. Contents of organic matter and available N were generally higher at lower landscape positions. Contents of available K were higher at lower and flat slope positions. Contents of available P were higher at higher landscape positions. Contents of organic matter and available N were higher on the northern and eastern, and lower on the western aspects. Contents of available P were higher on the western and lower on the northern aspects. No significant differences were found for available K across the aspects. Classification tree algorithms indicated that relative importance of the variables on soil nutrient variation was in the order: (i) cropping system, (ii) slope position, and (iii) aspect.
43
Michael, Pippa J., Paul B. Yeoh e John K. Scott. "The current and future projected distribution of Solanum hoplopetalum (Solanaceae): an indigenous weed of the south-western Australian grain belt". Australian Journal of Botany 60, n. 2 (2012): 128. http://dx.doi.org/10.1071/bt11242.
Testo completoAbstract (sommario):
The factors determining the distribution of the Western Australian endemic Solanum hoplopetalum Bitter & Summerh. (Solanaceae) were assessed because it was identified as a potential weed risk to Australian cropping regions, including under climate change scenarios. Incubation at constant temperatures determined daily plant growth rates and plants required 1380 degree-days above a threshold of 12.4°C to complete growth to flowering. From this and published information on the plant’s biology, we developed a mechanistic niche model using CLIMEX. The model projection for current climates produced a highly significant match to known distribution records. Spatially, the lower south-west and areas eastwards to South Australia, western New South Wales and southern parts of the Northern Territory were climatically suitable for growth of S. hoplopetalum. However, by 2070 the area under risk decreases, with the projected distribution under climate change contracting southwards. We hypothesise that climatic extremes and edaphic factors, possibly high soil pH, may be major factors determining the current distribution of S. hoplopetalum. Containment on the southern edge of the current distribution, interstate quarantine and local eradication in new areas of invasion are recommended as management options to combat the potential for this native weed to spread.
44
S. Watkins, R. ""Payneham Vale": integrated whole farm Planning". Pacific Conservation Biology 9, n. 1 (2003): 65. http://dx.doi.org/10.1071/pc030065.
Testo completoAbstract (sommario):
IN 1908, Ron's grandfather, Issac Gray, took up an uncleared block of land 15 km north of Frankland in the south-west of Western Australia (see Fig. 1, Hobbs 2003). During that time he ran a few cattle in the bush and clearing of the native woodlands of Wandoo (white gum) Eucalyptus wandoo, J arrah E. marginata and Marri (Redgum) E. calophylla was slow and tedious. Ron's parents took over the farm in 1947, and with the advent of the bulldozer, clearing of Watkin's property and surrounding district began in earnest during the 1950s. Clearing continued as fast "as money permitted", until almost the last natural vegetation was knocked down in 1978 (Fig. 1). Annual pastures with some cropping (for supplementary feed) were the main source of fodder for sheep and cattle.
45
Hodgkin, Ernest P., e Patrick Hesp. "Estuaries to salt lakes: Holocene transformation of the estuarine ecosystems of south-western Australia". Marine and Freshwater Research 49, n. 3 (1998): 183. http://dx.doi.org/10.1071/mf96109.
Testo completoAbstract (sommario):
When the estuaries of south-western Australia were first flooded by the Holocene marine transgression about 7000 years before present (BP), most were enclosed by limestone barrier dunes. Coastal sand drift built bars and flood-tide deltas in the narrow entrances, but until about 3500 years BP the estuaries remained tidal-dominated systems with a diverse marine–estuarine fauna. Now the bars/deltas so obstruct the small tides that estuary water is fresh in winter and marine to hypersaline in summer; the estuaries are river-flow-dominated systems and the ecosystems are characterised by a restricted euryhaline estuarine biota. Some estuaries are still permanently open, their bars/deltas never close, and some are seasonally open, their bars open with river flow in winter and close in summer. Other estuaries are normally closed, their bars remain closed for several years and break with episodic flood flow, or are permanently closed coastal salt lakes with bars that never or rarely break: they can become grossly hypersaline and may dry up altogether. An hypothesis to explain this Holocene transformation of the estuaries attributes it principally to sedimentary processes in an environment where river flow is highly seasonal, tides are microtidal, there was a fall in sea level, and there are differences in the volume and periodicity of flow and the degree of shelter to the entrances from the prevailing south-west winds and swell.
46
Hitchcock, Garrick. "Cross-border trade in Saratoga fingerlings from the Bensbach River, south-west Papua New Guinea". Pacific Conservation Biology 12, n. 3 (2006): 218. http://dx.doi.org/10.1071/pc060218.
Testo completoAbstract (sommario):
Saratoga Scleropages jardinii (Saville-Kent 1892) is a popular aquarium and sportsfish native to southern New Guinea and northern Australia. In recent years the people of the Bensbach River area in Papua New Guinea's Western Province have been harvesting wild fingerlings for sale across the nearby international border in Indonesia's Papua Province. From there the fish are sold to dealers in other parts of Asia. The species is protected by law in Indonesia, and subject to various regulations in Australia. In Papua New Guinea there are no controls on its exploitation. Uncontrolled harvesting of fingerlings from the Bensbach and other river systems in south New Guinea has had negative impacts on local fisheries, and led to a decline in the Australian export trade in wild-caught and farm-bred Saratoga.
47
McLeod, M. K., G. D. Schwenke, A. L. Cowie e S. Harden. "Soil carbon is only higher in the surface soil under minimum tillage in Vertosols and Chromosols of New South Wales North-West Slopes and Plains, Australia". Soil Research 51, n. 8 (2013): 680. http://dx.doi.org/10.1071/sr13032.
Testo completoAbstract (sommario):
Reduced carbon stock levels in Australian soil due to cropping provide a significant opportunity for carbon sequestration, and the recent initiative to consider soil carbon in domestic emissions trading requires a scientific assessment of soil carbon levels under a range of cropping soil management practices. Some of the previous research in southern and western New South Wales (NSW) showed that the rate of carbon decline in cropping soils is slowed under minimum tillage when the stubble is also retained. However, such comparison is rare in the NSW North-West Slopes and Plains region, particularly on the red soils (Chromosols) which are one of the major soil types in the region. We surveyed 50 dryland Chromosols, 72 dryland Vertosols, and 25 irrigated Vertosols on commercial farms across this region to examine the effects of conventional tillage, minimum tillage, and irrigation on total soil organic carbon. Samples of 0.1 m segments to 0.3 m depth were analysed for total organic carbon and other soil properties. Mid-infrared scans were used to predict the particulate, humus, and resistant soil organic carbon fractions. Bulk density was used to calculate total organic carbon stock for each segment, and equivalent soil mass (ESM) for 0–0.3 m. In Vertosols, for 0–0.3 m ESM, total organic carbon and particulate organic carbon were not different between management practices, whereas humic organic carbon and resistant organic carbon were consistently lower under conventional tillage. However, in 0–0.1 m, total organic carbon was greater under minimum tillage (15.2 Mg ha–1) than conventional tillage (11.9 Mg ha–1) or irrigation (12.0 Mg ha–1), reflecting less soil surface disturbance under minimum tillage. In Chromosols, only total organic carbon was higher under minimum tillage than conventional tillage in the 0–0.3 m ESM (39.8 v. 33.5 Mg ha–1) and in 0–0.1 m (19.7 v. 16.9 Mg ha–1). The strong influences of rainfall, temperature, bulk density, texture, and management history on soil carbon stocks suggested that these environmental and management factors require further consideration when gauging soil carbon sequestration potential under current and novel tillage practices in key regional locations.
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Harries, Martin, Geoffrey C. Anderson e Daniel Hüberli. "Crop sequences in Western Australia: what are they and are they sustainable? Findings of a four-year survey". Crop and Pasture Science 66, n. 6 (2015): 634. http://dx.doi.org/10.1071/cp14221.
Testo completoAbstract (sommario):
A survey was conducted of commercial broadacre paddocks in the south-west cropping zone of Western Australia from 2010 to 2013. In total, 687 paddock years of data were sampled from 184 paddocks. The land use of each paddock was recorded together with measurements of weed density, the incidence of soilborne pathogen DNA, and soil inorganic nitrogen (nitrate and ammonium). The dynamics of these biophysical variables were related to the crop and pasture sequences employed. Wheat was the most frequent land use (60% of paddock years), followed by canola and pasture (12% each), and lupins and barley (6% each). Four crop species, wheat, canola, barley and lupins, accounted for 84% of land use. By region, wheat, canola, barley and lupin accounted for 90% of land use in the Northern Agricultural Region (NAR), 83% in the Central Agricultural Region (CAR) and 78% in the Southern Agricultural Region (SAR). Conversely, pasture usage in the SAR was 21%, compared with 12% in the CAR and 7% in the NAR. Over the surveyed paddocks, weed density, soilborne pathogens and soil N were maintained at levels suitable for wheat production. The inclusion of land uses other than wheat at the frequency reported maintained the condition of these biophysical variables.
49
Rhind, S. G., e J. S. Bradley. "The effect of drought on body size, growth and abundance of wild brush-tailed phascogales (Phascogale tapoatafa) in south-western Australia". Wildlife Research 29, n. 3 (2002): 235. http://dx.doi.org/10.1071/wr01014.
Testo completoAbstract (sommario):
Body size and growth data were gathered on 387 wild brush-tailed phascogales captured between 1992–1997 in south-western Australia. This marsupial has not previously been studied in Western Australia. Compared with Victorian phascogales, those in the south-west (single region) are typically 20–30% smaller in mass, smaller in skeletal measurements, and sexual size dimorphism is less. Habitat quality was correlated with body size and the largest phascogales were found in swamp/gully systems. These findings suggest food is a normally limiting resource for this species in the south-west environment. Additionally, a significant decrease in growth and size occurred during a drought year (1994), and growth of young seemed restricted during dependency. Maternal mortality appeared high during late lactation as orphaned, unweaned young were encountered in nest boxes. In 1995 adult males were 25% less in mass than usual; females 15% less. Population decline followed and by 1996 capture rates were 1/3 of that typically found for the time of year. Recovery was not apparent until two years after drought (early 1997). In this food-limited environment phascogale populations appear particularly vulnerable to annual fluctuations in rainfall.
50
Tennant, D., G. Scholz, J. Dixon e B. Purdie. "Physical and chemical characteristics of duplex soils and their distribution in the south-west of Western Australia". Australian Journal of Experimental Agriculture 32, n. 7 (1992): 827. http://dx.doi.org/10.1071/ea9920827.
Testo completoAbstract (sommario):
Duplex soils are widespread in Western Australia and occupy about 60% of the south-west agricultural area. The physical and chemical properties of these soils reflect their origin as erosional surfaces of old laterite profiles and the predominance of underlying, quartz-rich, granitic materials. The resulting combination of high contents of quartz sand, kaolin clay, and iron and aluminium oxides has important consequences on water-holding capacity, fertility, nutrient leaching, phosphate fixation, anion and cation exchange capacity, and buffering capacity. These soils are generally held to have a number of physical and chemical problems. Among these, low fertility and low permeability of the clay B horizon have greatest effect. While data on the chemical properties of these soils are limited, significant data sets on the physical properties of duplex soils are available from several studies of catchment hydrology. These studies reflect concern with runoff, waterlogging, and the development of secondary salinisation. Depth to clay varies from 5 to >100 cm. The shallower depths (10-40 cm) predominate and, in medium and high rainfall areas, combine with low permeability in the clay to result in widespread waterlogging. Commonly, the sand surface can be hardsetting and can have high strength from structural decline, from the presence of cementing agents, and from traffic effects. Sodicity is widespread and has effects on hardsetting in the A horizon and on permeability of the B horizon. Management strategies are available to treat some of these problems, but generally, much has yet to be done to develop sustainable agricultural systems on these soils.