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Context: Spring-sown forage brassicas are commonly used to fill feed gaps in high-rainfall temperate livestock systems, but they have wider potential as an autumn-sown forage in drier environments within Australia's crop–livestock zone. Aims: We modelled the production potential of autumn-sown forage brassicas grown in diverse environments and tested their ability to alter the frequency and magnitude of feed gaps. Methods: Long-term production potential was simulated in APSIM for four forage brassica genotypes, compared with forage wheat and dual-purpose canola across 22 diverse agro-climatic locations. For seven regions, the change in frequency and magnitude of forage deficits from adding forage brassicas to representative forage–livestock systems was predicted. Key results: Across locations, median yields of forage brassicas ranged from 7 to 19 t DM/ha, and their annual metabolisable-energy yield was higher than that of forage wheat at most sites and nearly always exceeded dual-purpose canola. Forage brassicas performed better than forage wheat in later-sowing events (late April to early May) and maintained growth and quality later into spring. At five of the seven regions, adding 15% of farm forage area to forage brassicas reduced the frequency and magnitude of feed deficits by 35–50% and 20–40%, respectively. However, they were less beneficial where winter–spring feed gaps are uncommon. Conclusions: We demonstrated that autumn-sown forage brassicas can be reliable and productive contributors to the feed base in drier environments and are a suitable alternative to forage cereals. Implications: Forage brassicas can help reduce feed gaps and improve livestock production in a range of production systems spanning Australia's crop–livestock zone. Long-term simulation modelling showed that autumn-sown forage brassicas can serve as a reliable and valuable forage source in drier environments across Australia's crop–livestock zone. They have a long grazing window and stable production across a range of sowing dates and environments. Integrating forage brassicas into the existing feed base can reduce the frequency and magnitude of on-farm feed deficits in livestock production systems. They can also allow for a safe increase in stocking rates and reduce the need for supplementary feed. [ABSTRACT FROM AUTHOR]

Context: The winter feed gap is a common problem for livestock grazing systems worldwide, and changes to climate have made these deficits more unpredictable and extreme. Dual-purpose crops are an important tool in many southern Australian mixed crop–livestock systems to help fill the winter feed gap. Providing more reliable feed over winter can remove feed constraints and allow for earlier lambing in autumn with potential whole-farm system benefits. Aims: We simulated a whole-farm livestock enterprise in the Agricultural Production Systems Simulator (APSIM) to examine the implications of spring- and autumn-lambing systems relying on a standard pasture-only feedbase compared with a farm where 25% of its grazed area is allocated to dual-purpose crops. Methods: Twelve simulations were run across four locations in New South Wales, Australia, that varied in climatic conditions (both rainfall total and distribution) including two lambing systems (spring vs autumn) × two feedbase types (100% pasture vs 75% pasture and 25% dual-purpose crops) × three stocking densities. Key results: For autumn-lambing systems, integrating dual-purpose crops helped to fill the winter feed gap and reduced supplement demand on average by ~28% compared with a pasture-only system. Compared with the standard pasture-only spring-lambing system, integrating dual-purpose crops into spring- and autumn-lambing systems more than doubled gross margin returns due to economic grain yield and lower supplement demand. A shift from spring- to autumn-lambing facilitated by dual-purpose crops also led to better reproductive performance of ewes in the subsequent year. In higher-rainfall, cooler environments, autumn-lambing systems with dual-purpose crops had the highest system gross margins, lowest economic risk and allowed for a safe increase in stocking density. In lower-rainfall, warmer environments, integration of dual-purpose crops into spring-lambing systems returned marginally higher gross margins than for the autumn-lambing system, but differences were less apparent at high stocking density. In lower-rainfall environments, dual-purpose crops helped to mitigate some of the economic risk, but the benefits were less clear. Conclusions: We show dual-purpose crops can help fill the winter feed gap and support earlier lambing in autumn across a range of environments, especially in higher-rainfall cooler environments, with significant improvements in total farm gross margins. Implications: Integrating dual-purpose crops will enable farmers to change their livestock system to mitigate their risks, reduce supplementary feeding and capitalise on other potential benefits, such as improved marketing and avoiding animal health problems. Whole-farm simulation modelling suggests that integrating dual-purpose crops of wheat and canola to 25% of the farm decreases the winter feed gap and facilitates autumn-lambing systems across environments. Spring- and autumn-lambing systems with dual-purpose crops achieved more than double the farm gross margins compared with the standard spring-lambing, pasture-only system. In higher-rainfall, cooler environments, autumn-lambing systems with dual-purpose crops returned higher gross margins due to grain production and lower supplement demand, but in lower-rainfall, warmer environments, spring-lambing systems were still more profitable. [ABSTRACT FROM AUTHOR]

In many areas of Australia's mixed farming zone, cropping rotations are dominated by cereals and some areas have few suitable broadleaf alternatives. Forage brassicas are widely used in high rainfall livestock systems, but this study shows that several genotypes offer an alternative to forage oats in drier environments within Australia's mixed farming zone. We compared a diverse set of forage brassica genotypes sown in autumn and winter with benchmark species, principally oats, across 10 experimental site-years. In both early (800-1300 growing degree days after sowing) and late (1600-2100 growing degree days after sowing) grazing windows, several forage brassica genotypes had forage production similar or superior to oats and dual-purpose canola. Many forage brassica genotypes produced higher yields of metabolisable energy (ME) and crude protein (CP), particularly in the late grazing window. In the early grazing window, Rival and Green globe turnips and HT-R24 forage rape consistently produced ~15% above the site mean for all productivity measures, whereas kale produced ~40% less than the site mean. In the late grazing window, oats produced the greatest amount of edible biomass (~44% higher than the site mean); however, Goliath and HT-R24 forage rapes, Pallaton raphanobrassica and dual-purpose canola had the highest yields of ME and CP (~16% higher than the site mean). Green globe turnip, Hunter leafy turnip and Regal kale produced ~22% less than the site mean in this late grazing window. Multi-environment analyses revealed no genotype x environment interactions within the early grazing window. In the late grazing window, there were several genotypic adaptations, particularly for Pallaton, which performed better in low-medium production environments than the other genotypes. We show that forage brassicas offer superior yields of ME and CP, indicating that they may be better able to meet the energy and protein demands of grazing livestock than forage oats. [ABSTRACT FROM AUTHOR]

Forage brassicas are currently widely used in temperate–humid livestock systems; however, they offer potential to diversify crop rotation and forage options in the drier, mixed crop–livestock zone of Australia. A literature review highlighted that in these hotter and more arid environments, forage brassicas are more likely to fit as autumn-sown forage crop where they offer an energy-rich, highly digestible feed source that could be used during periods of low production and nutritive value of other forage sources. However, brassicas can also accumulate several anti-nutritional compounds that require gradual introduction to livestock diets, thereby reducing potential health risks and optimising animal performance. Preliminary experimental and commercial evaluations in subtropical Australia found high production of some forage brassica genotypes (>5 t DM/ha with growth rates of 50–60 kg DM/ha.day), comparable or superior to widely used forage cereal or forage legume options. Several forage brassicas showed moderate to high resistance to the root-lesion nematode, Pratylenchus thornei , and hence are likely to provide break-crop benefits compared with susceptible species (e.g. wheat). Together, this evidence suggests that forage brassicas have significant potential for wider use in crop–livestock farming systems in Australia. However, research is needed to identify genotypic adaptation and to match different forage brassica genotypes to production environments or system niches, especially some of the new genotypes that are now available. There is also a need to develop regionally-relevant recommendations of agronomic and grazing management that optimise forage and animal production, and mitigate potential animal health risks. Forage brassicas are widely used to provide high-quality forage in temperate, high-rainfall livestock systems but are rarely used in crop–livestock systems in drier regions. We find that forage brassicas have several attributes suited to wider use in crop rotations, and preliminary experiments demonstrate favourable productivity compared with other forage options. This work demonstrates the wider potential and research needs for forage brassicas to be used throughout Australia's mixed crop–livestock systems. [ABSTRACT FROM AUTHOR]

Understanding the implications of replacing fallows with cover crops on plant-available water (PAW) and soil mineral nitrogen (N) and their carry-over effects on subsequent cash crops is critical for understanding their potential for ecological intensification in water-limited environments. We modelled the impacts of different cover crop functional types over historical climate to predict how climate variability influences soil water and N acquisition and subsequent availability to a maize crop in a dryland farming system of subtropical Australia. Following local validation of simulation models (APSIM) with 3-site-years of field data, 70 years of crop-fallow rotations were simulated comparing conventional fallow against a diverse range of cover crops comprising monocultures and mixtures of grass vs. legume vs. brassica. Cover crops consistently reduced soil water and mineral N at maize sowing compared to conventional fallow. In dry to normal precipitation years, this induced a maize yield penalty of up to − 18% relative to fallow, primarily due to reduced water availability. In wet years, increased in maize grain yield (+4%) was predicted following legume and grass-associated cover crop mixtures with concomitant reductions in N leaching and soil surface runoff of up to 40%. Cash crop yields following grass-cover crops were more stable and carried lower downside risks; multi-species (grass-legume-brassica) cover crop mixtures carried higher yield penalties and greater downside risks due to high biomass accumulation and high soil water extraction. These long-term predictions in water-limited environments indicate that increasing cover crop complexity by using mixtures with diverse functional traits can lead to a greater risk of yield losses and increased yield instability unless they are managed differently to monoculture cover crops. Therefore, for successful integration of cover crops into dryland agroecosystems, cover crops should be considered as a flexible choice grown under favourable precipitation and economic scenarios rather than for continuous fallow replacement. • Applied APSIM to assess potential dryland fallow replacement cover crop options. • Cover crops reduced yields by 12% relative to fallow in dry to normal years. • Predicted yield gains in wet years following fababean and multi-species mixture. • Dryland cover crops should be considered as an opportunistic practice. [ABSTRACT FROM AUTHOR]

Understanding the quantity and timing of labour to fulfill the goals of different cropping systems or crop rotations is critical, but poorly quantified and understood in many agricultural systems, including the grain-growing regions of eastern Australia. Yet, labour supply and demands are important considerations for farmers and can significantly influence their agronomic management and decisions to adopt modified crop rotation systems. Here, we investigated the extent to which crop rotation systems, that differed in their intensity (i.e. the proportion of time when crops were growing), and diversity (i.e. the range of crops grown) influence labour requirements and labour productivity. We used the Agricultural Production Systems sIMulator (APSIM) to simulate a set of different crop rotations and combined the output with farmer survey data and expert knowledge derived from farm advisers to compute the labour inputs for key crop operations (i.e. sowing, spraying, harvesting). This information was used to calculate the labour required and the timing of this demand for each cropping system. We showed that as the cropping intensity increases the labour demand also increases, and vice versa. However, only small differences in labour demands were identified between systems with differing crop diversity (i.e. range of crops grown). Thus, when it comes to labour demands, crop diversity is less critical than cropping intensity. Labour demand was highly seasonal, with peaks around the intense operations of sowing and harvesting. These peak demands constrained the area that could be managed by a unit of labour, particularly as the cropping intensity increased. Further, this analysis highlights that the most profitable systems may not necessarily be the most efficient in terms of labour productivity (i.e. return per unit of labour). This analysis shows that when labour is limiting, labour demands and especially peak periods may contribute to a farmer's choice of cropping systems, adding to other critical factors like risk aversion and profit maximisation. The analysis contributes to the literature on the role of labour in the context of influencing the implementation and adoption of what are seemingly more productive or profitable farming systems. In particular, the results demonstrate how labour as a critical farm resource (i.e. its quantity, seasonality and timing, and productivity) can influence the design of crop rotations. [Display omitted] • Many cropping systems in Australia are being modified by altering their intensities and crop diversity, but their labour demands are unknown. • Crop rotations with distinct intensity and diversity are simulated in APSIM to estimate their labour demands, seasonality, and economic returns. • Altering cropping intensity had stronger influence on labour demands and returns than changing the crop diversity in the rotation. • Labour demands between rotations is not substantial to influence a farmers decision on adopting alternative or modified cropping sequences. • Findings contribute to the growing discussion on the role of labour for the design and potential feasibility of innovative cropping systems. [ABSTRACT FROM AUTHOR]

Highlights: [•] Mixing crops and livestock helps Australian farmers manage climate, price and soil variability. [•] Recent crop–livestock innovations can improve farm productivity, sustainability and reduce risk. [•] Potential for grazing dual-purpose cereal and canola crops or sacrificially grazing crops is unrealised. [•] Perennial pasture phases in grain crop rotations can provide multiple farm benefits. [•] Systems growing mixtures of crops and pastures and to utilise novel pasture species are evolving. [ABSTRACT FROM AUTHOR]

Abstract: Australia has a long history of mixed farming. This paper examines the integration of Australian cropping and livestock production from three perspectives: as a factor in land use change, a consequence of individual management practices and a means of meeting farmers’ multiple objectives. Since about 1995, the proportion of cropped land has increased on Australian cropping farms while livestock numbers have decreased. Land use in the north-eastern, central and south-western regions of the cropping zone have diverged. Despite these changes, mixed farms still dominate Australia’s broadacre farming regions. Previous accounts of the dimensions in which farming enterprises are integrated can be simplified for Australian broadacre agriculture. For most purposes it is sufficient to consider a nested set of four integration options: “specialization” (not integrated organizationally), “separation” (integrated organizationally only), “rotation” (integrated organizationally and spatially, but not temporally) and “synchronization” (integrated in all three dimensions). We illustrate these integration options with a short survey of agronomic practices that affect crop–livestock integration. We review the farmer objectives that enterprise integration can meet and the constraints that limit it, seeking to balance social, economic and agronomic factors. We use a dynamic simulation model to make a first quantification of the economic risk reduction provided by enterprise diversification. Constraints imposed by limited labour, capital, and management attention cannot be overlooked; this is especially relevant in Australia where labour is increasingly in short supply. We characterize our surveyed set of agronomic practices with respect to the farmer objectives they affect. We find that farmers generally have the option of meeting a particular objective through different practices that affect different dimensions of integration. Practices that result in closer integration in time and space generally require greater management attention; practices that do not integrate in space typically require an increase in external inputs. History suggests that current commodity price ratios may be sufficient to slow or reverse the overall land use trend away from livestock production. In the longer term, forecast increases in worldwide demand for meat, energy costs and soil resource constraints will all encourage Australian cropping farmers to maintain mixed systems; however reduced availability of labour relative to capital will push land use toward specialized systems. Valuing the benefits and costs associated with differing degrees of enterprise integration is a major research challenge that will require insightful application of both biophysical and economic models. [Copyright &y& Elsevier]

Failing grain crops are sometimes sacrificed for grazing by mixed farmers, a decision involving a complex range of factors. This simulation study used two APSIM (Agricultural Production Systems Simulator)-based approaches to investigate the circumstances under which more revenue might be obtained by sacrificing a wheat crop for grazing rather than harvesting it for grain in Western Australia's grainbelt. First, we developed a simple partial budget calculation to estimate and compare revenue from grain or grazing alternatives using data for grain yield and standing biomass at flowering. This was simulated for a factorial of soil types and locations varying in mean annual rainfall. We then simulated wheat quality and livestock production on spring wheat grazed at different stages of crop development and at a range of stocking rates. Dynamic simulations of grazing showed that livestock production increased as grazing was delayed; stocking rate had little impact at this time. Grazing earlier necessitated lighter stocking rates but surprisingly had little benefit for animal performance. Partial budgets showed that under average commodity prices, grazing a wheat crop could be more profitable 40-75% of the time on poorer soil types in lower rainfall environments. In these situations, by tactically grazing when grain yield is below a critical level economic returns could be increased by more than A$50/ha in 30-40% of years and over the long term average revenues could be increased by A$30/ha.year. This critical grain yield ranged from 1.3 to 1.7 t/ha on shallow gravel soil and 1.9 to 2.2 t/ha on a deep sand. In higher rainfall environments and on better soil types grazing was rarely a better option unless livestock prices were high relative to grain. This approach, combining crop simulation with partial budgets, was useful for developing simple management rules for a complex system. Overall, the findings of this study suggest that making tactical use of a wheat crop for forage in situations with low grain yield prospects is a major opportunity to increase profitability and help respond to climate variability in mixed farms in many areas of the Western Australian wheatbelt. [ABSTRACT FROM AUTHOR]

A central concern of the Grain & Graze research, development and extension program has been improving the management of the feedbase on mixed farms through addressing 'feed gaps' -- times of year during which the supply of forage is insufficient to meet livestock demand. In this review, we use the available data on pasture growth and quality, supplemented by modelling results, to describe the characteristic timing of feed gaps across the Australian cereal-livestock zone. Feedbase interventions studied during the Grain & Graze program have mainly addressed the supply side of the feed balance equation. We review these studies, paying particular attention to the time scale of the variability in the feed balance that each intervention is intended to address. We conclude that grazing of cereals (either dual-purpose or forage crops) is the most promising means of alleviating winter feed gaps in regions where they are important. Reducing feed gaps in summer by relying on unpredictable summer rainfall events will increase year-to-year variability in forage production and will therefore require more flexible livestock management systems to exploit it. The use of forage shrubs offers a practical tool for increasing the predictability of summer and autumn feed supply, but given their moderate capacity for providing additional metabolisable energy it remains important to carefully manage livestock over autumn and to manage the herbaceous inter-row pasture. Feed gaps mainly arise from an interaction between biology and economics. We find, however, that the options studied in the Grain & Graze program for addressing feed gaps require either greater complexity in pasture and grazing management or more opportunistic livestock trading; they therefore come at a cost to the manager's limited decision-making time. Times with feed gaps are also times when particular natural resource management risks (especially erosion) need to be managed. Supply-side interventions to relieve feed gaps will generally use more soil water, which will often have positive effects on natural resource management outcomes. [ABSTRACT FROM AUTHOR]

Dorycnium hirsutum and D. rectum are perennial legumes which may have potential for use as pastures for the control of groundwater recharge in southern Australia. Little is known about the quality of the forage of Dorycnium species for grazing livestock or how these species respond to cutting. The effect of cutting height on plant survival, production of dry matter (DM), the proportion of leaf, edible stem (approximately <5 mm diameter) and woody stem in the DM and the nutritive value of the edible components was investigated. Biomass above five cutting-height treatments (uncut, ground level, 5–8 cm, 10–15 cm and 15–30 cm above ground level) was removed at 8-week intervals from plots of D. hirsutum and D. rectum from September 2002 to July 2003. In both species, plants subjected to lower cutting height treatments produced less DM above the height of the cut than those cut at higher heights. DM production declined over time in all treatments. Plants cut to ground level failed to regrow after the second harvest in D. hirsutum and the fourth harvest in D. rectum. Thus, these Dorycnium species were susceptible to high severity defoliations at 8-week intervals. Negligible inedible woody stem was present in regrowth of both species after 8 weeks but D. hirsutum regrowth had a higher proportion of leaf (0·72) than D. rectum (0·56). Plants left uncut accumulated a large proportion of inedible woody stem in the DM (0·69 in both species) by July 2003, particularly at the base of the plant. Edible DM from regrowth of D. hirsutum and D. rectum had crude protein (CP) concentrations of 120 and 150 g kg−1 DM; dry matter digestibility (DMD) values of 0·45 and 0·58; organic matter digestibility (OMD) values of 0·50 and 0·64; neutral-detergent fibre (NDF) concentrations of 370 and 290 g kg−1 DM; and acid-detergent fibre (ADF) concentrations of 260 and 210 g kg−1 DM, respectively. Medicago sativa, grown under similar conditions, had higher digestibility values (0·63 DMD and 0·66 OMD) and similar CP concentrations to D. rectum (140 g kg−1 DM), but higher concentrations of NDF and ADF (410 and 290 g kg−1 DM). Leaf material from both Dorycnium species had a higher nutritive value than edible stems, with DMD and OMD values of leaf of D. rectum being 0·68 and 0·74 respectively. Uncut plants had a much lower nutritive value of edible DM than the regrowth from cut treatments; older material was also of a lower nutritive value. The relatively low nutritive value of even the young regrowth of Dorycnium species suggests that forage quality is a major limitation to its use. Forage of Dorycnium species could be used during periods when other sources of forage are in short supply but infrequent grazing it is likely to produce forage of a low nutritive value. [ABSTRACT FROM AUTHOR]

Pulses have emerged as important rotation crops in Australia. Some are in demand in agricultural production systems due to their high potential market value, because of their roles as grain or forage crops, their nitrogen fixation capability, and because they provide a disease break or improve soil health. While several pulse crops have been identified for winter-season cropping, there are few adapted legumes apart from mungbean that are appropriate for dryland summer cropping. Currently, short-duration crops of mungbean are commonly used, but yields are highly variable and susceptible to drought. Here, we propose that cowpea has the potential to become an alternative rotation crop in dryland summer cropping zones, providing a competitive and profitable alternative pulse crop option where its drought tolerance could enable better performance under inconsistent in-crop rainfall. We demonstrate that cowpea has nutritional properties and putative uses that could prove valuable in emerging plant-based protein and aquaculture markets. [ABSTRACT FROM AUTHOR]

Background: Many Australian native legumes grow in arid and nutrient-poor environments. Yet few Australian herbaceous legumes have been investigated for domestication potential. This study compared growth and reproductive traits, grain yield and seed composition of 17 native Australian legumes with three commercial grain legumes., Results: Seed yields of seven native legumes were > 40% of Cicer arietnum, with highest seed yields and harvest indices in Glycine sp. (14.4 g per plant, 0.54 g g(-1) ) and Lotus cruentus (10.2 g per plant, 0.65 g g(-1) ). Five native species flowered earlier than field pea (Pisum sativa) (109 days), though many were slower to flower and set seed. Largest seeds were found in Glycine canescens (17 mg), with seed of other native species 14 times smaller than commercial cultivars. Seed composition of many native legumes was similar to commercial cultivars (200-330 g protein kg(-1) dry weight (DW), 130-430 g dietary fibre kg(-1) DW). Two Cullen species had high fat content (>110 g kg(-1) DW) and Trigonella sauvissima had the highest crude protein content (370 g kg(-1) DW)., Conclusion: The seed composition and reproductive traits of some wild native Australian legumes suggest they could offer potential as grain crops for soils and environments where the current grain legumes are uneconomic. Further evaluation of genetic diversity, especially for seed size, overall productivity, and reproductive development is needed., (Copyright © 2011 Society of Chemical Industry.)