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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 19tDM/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.

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 × 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.

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.

Integration of tropical forage legumes into cropping systems may improve subsequent crop nitrogen (N) supply, but removal of legume biomass for forage is likely to diminish these benefits. This study aimed to determine: (i) under irrigated conditions, the potential N inputs that can be provided by different tropical forage legumes to a subsequent cereal crop; and (ii) the residual N benefits once fodder had been removed. Available soil mineral N following tropical forage legumes lablab (Lablab purpureus), centro (Centrosema pascuorum), butterfly pea (Clitoria ternatea) and burgundy bean (Macroptilium bracteatum) and grain legume soybean (Glycine max) was compared with a maize (Zea mays) control when legume biomass was retained or cut and removed (phase 1). An oat (Avena sativa) cover crop was then grown to ensure consistent soil-water across treatments (phase 2), followed by a maize grain crop (phase 3) in which N uptake, biomass production and grain yield were compared among the phase 1 treatments. To determine N-fertiliser equivalence values for subsequent maize crop yields, different rates of fertiliser (0–150kg urea-N/ha) were applied in phase 3. Retained biomass of butterfly pea, centro and lablab increased phase 3 unfertilised maize grain yield by 6–8t/ha and N uptake by 95–200kgN/ha compared with a previous cereal crop, contributing the equivalent of 100–150kg urea-N/ha. When legume biomass was cut and removed, grain yield in the phase 3 maize crop did not increase significantly. When butterfly pea, centro and lablab biomass was retained rather than removed, the maize accumulated an additional 80–132kgN/ha. After fodder removal, centro was the only legume that provided N benefits to the phase 3 maize crop (equivalent of 33kg urea-N/ha). Burgundy bean did not increase subsequent crop production when biomass was either retained or removed. The study found that a range of tropical forage legumes could contribute large amounts of N to subsequent crops, potentially tripling maize grain yield. However, when these legumes were cut and removed, the benefits were greatly diminished and the legumes provided little residual N benefit to a subsequent crop. Given the large N trade-offs between retaining and removing legume biomass, quantification of N inputs under livestock grazing or when greater residual biomass is retained may provide an alternative to achieving dual soil N–fodder benefits.

Several new and existing short-term forage legumes could be used to provide nitrogen (N) inputs for grain crops in subtropical farming systems. The fixed-N inputs from summer-growing forage legumes lablab (Lablab purpureus), burgundy bean (Macroptilium bracteatum) and lucerne (Medicago sativa) and winter-growing legume species snail medic (Medicago scutellata), sulla (Hedysarum coronarium) and purple vetch (Vicia benghalensis) were compared over several growing seasons at four locations in southern Queensland, Australia. Available soil mineral N and grain yield of a following cereal crop were compared among summer-growing legumes and forage sorghum (Sorghum spp. hybrid) and among winter-growing legumes and forage oats (Avena sativa). In the first year at all sites, legumes utilised the high initial soil mineral N, with <30% of the legume N estimated to have been derived from atmospheric N2 (%Ndfa) and legume-fixed N <30kg/ha. In subsequent years, once soil mineral N had been depleted, %Ndfa increased to 50–70% in the summer-growing legumes and to 60–80% in winter-growing legumes. However, because forage shoot N was removed, rarely did fixed N provide a positive N balance. Both lablab and burgundy bean fixed up to 150kgN/ha, which was more than lucerne in all seasons. Prior to sowing cereal grain crops, soil nitrate was 30–50kg/ha higher after summer legumes than after forage sorghum. At one site, lablab and lucerne increased the growth and yield of a subsequent grain sorghum crop by 1.4t/ha compared with growth after forage sorghum or burgundy bean. Of the winter-growing legumes, sulla had the highest total N2 fixation (up to 150kgN/ha.year) and inputs of fixed N (up to 75kgN/ha), and resulted in the highest concentrations of soil N (80–100kgN/ha more than oats) before sowing of the following crop. Wheat protein was increased after winter legumes, but there was no observed yield benefit for wheat or grain sorghum crops. New forage legume options, lablab, burgundy bean and sulla, showed potential to increase N supply in crop rotations in subtropical farming systems, contributing significant fixed N (75–150kg/ha) and increasing available soil N for subsequent crops compared to non-legume forage crops. However, high soil mineral N (>50kgN/ha) greatly reduced N2 fixation by forage legumes, and significant N2 fixation only occurred once legume shoot N uptake exceeded soil mineral N at the start of the growing season. Further work is required to explore the impact of different management strategies, such as livestock grazing rather than harvesting for hay, on the long-term implications for nutrient supply for subsequent crops.

Interest is growing in the potential to expand cropping into Australia’s high-rainfall zone (HRZ). Dual-purpose crops are suited to the longer growing seasons in these environments to provide both early grazing for livestock and later regrow to produce grain. Grain yield and grazing potential of wheats of four different maturity types were simulated over 50 years at 13 locations across Australia’s HRZ, and sowing date, nitrogen (N) availability and crop density effects were explored. Potential grazing days on wheat were obtained by simulating sheep grazing crops to Zadoks growth stage Z30 at 25 dry sheep equivalents (DSE)/ha. Optimal sowing dates for each maturity type at each location were matched to the flowering window during which risk of frost and heat stress was lowest. Overall, we found significant national potential for dual-purpose use of winter wheat cultivars across Australia’s HRZ, with opportunities identified in all regions. Simulated mean wheat yields exceeded 6t/ha at most locations, with highest mean grain yields (8–10t/ha) in southern Victoria, and lower yields (5–7t/ha) in the south-west of Western Australia (WA) and central and northern New South Wales (NSW). Highest grazing days were from winter cultivars sown early (March–mid-April), which could provide 1700–3000 DSE-days/ha of grazing across HRZ locations; this was 2–3 times higher than could be obtained from grazing spring cultivars (200–800 DSE-days/ha). Sowing date was critical to maximise both grazing and grain yield potential from winter cultivars; each 1-week delay in sowing after 8 March reduced grazing by 200–250 DSE-days/ha and grain yield by 0.45t/ha. However, in Mediterranean climates, a lower frequency of early sowing opportunities before mid-April (<30% of years) is likely to limit the potential to use winter cultivars. Prospects to graze shorter season spring cultivars that fit later sowing windows require further examination in south-west WA, the slopes of NSW and southern Queensland.

Recent expansion of cropping into Australia’s high-rainfall zone (HRZ) has involved dual-purpose crops suited to long growing seasons that produce both forage and grain. Early adoption of dual-purpose cropping involved cereals; however, dual-purpose canola (Brassica napus) can provide grazing and grain and a break crop for cereals and grass-based pastures. Grain yield and grazing potential of canola (up until bud-visible stage) were simulated, using APSIM, for four canola cultivars at 13 locations across Australia’s HRZ over 50 years. The influence of sowing date (2-weekly sowing dates from early March to late June), nitrogen (N) availability at sowing (50, 150 and 250kgN/ha), and crop density (20, 40, 60, 80 plants/m2) on forage and grain production was explored in a factorial combination with the four canola cultivars. The cultivars represented winter, winter×spring intermediate, slow spring, and fast spring cultivars, which differed in response to vernalisation and photoperiod. Overall, there was significant potential for dual-purpose use of winter and winter×spring cultivars in all regions across Australia’s HRZ. Mean simulated potential yields exceeded 4.0t/ha at most locations, with highest mean simulated grain yields (4.5–5.0t/ha) in southern Victoria and lower yields (3.3–4.0t/ha) in central and northern New South Wales. Winter cultivars sown early (March–mid-April) provided most forage (>2000 dry sheep equivalent (DSE) grazing days/ha) at most locations because of the extended vegetative stage linked to the high vernalisation requirement. At locations with Mediterranean climates, the low frequency (<30% of years) of early sowing opportunities before mid-April limited the utility of winter cultivars. Winter×spring cultivars (not yet commercially available), which have an intermediate phenology, had a longer, more reliable sowing window, high grazing potential (up to 1800 DSE-days/ha) and high grain-yield potential. Spring cultivars provided less, but had commercially useful grazing opportunities (300–700 DSE-days/ha) and similar yields to early-sown cultivars. Significant unrealised potential for dual-purpose canola crops of winter×spring and slow spring cultivars was suggested in the south-west of Western Australia, on the Northern Tablelands and Slopes of New South Wales and in southern Queensland. The simulations emphasised the importance of early sowing, adequate N supply and sowing density to maximise grazing potential from dual-purpose crops.

Grassland production systems contribute 40% to Australia’s gross agricultural production value and utilise >50% of its land area. Across this area, diverse systems exist, but these can be broadly classified into four main production systems: (i) pastoral grazing, mainly of cattle at low intensity (i.e. <0.4 dry sheep equivalents/ha) on relatively unimproved native rangelands in the arid and semi-arid regions of northern and central Australia; (ii) crop–livestock systems in the semi-arid zone where livestock graze a mixture of pastures and crops that are often integrated; (iii) high-rainfall, permanent pasture zone in the coastal hinterland and highlands; and (iv) dairy systems covering a broad range of environments and production intensities. A notable trend across these systems has been the decline in sheep numbers and the proportion of income from wool, with beef cattle or sheep meat increasingly important. Although there is evidence that most of these systems have lifted production efficiencies over the past 30 years, total factor productivity growth (i.e. change in output relative to inputs) has failed to match the decline in terms of trade. This has renewed attention on how research and development can help to increase productivity. These industries also face increasing scrutiny to improve their environmental performance and develop sustainable production practices. In order to improve the efficiency and productivity of grassland production systems, we propose and explore in detail a range of practices and innovations that will move systems to new or improved states of productivity or alter efficiency frontiers. These include: filling gaps in the array of pastures available, either through exploring new species or improving the adaptation and agronomic characteristics of species currently sown; overcoming existing and emerging constraints to pasture productivity; improving livestock forage-feed systems; and more precise and lower cost management of grasslands. There is significant scope to capture value from the ecological services that grasslands provide and mitigate greenhouse gas emissions from livestock production. However, large reductions in pasture research scientist numbers (75–95%) over the past 30 years, along with funding limitations, will challenge our ability to realise these potential opportunities.

Biomass production, soil water extraction, and water-use efficiency (WUE, kg dry matter (DM)/ha.mm growing-season water use) of tropical, summer-growing and temperate, winter-growing forage legumes suited to short-term rotations with crops were compared over several growing seasons in southern Queensland. Tropical legumes lablab (Lablab purpureus cvv. Highworth and Endurance), burgundy bean (Macroptillium bracteatum cvv. Cardarga/Juanita mix), and butterfly pea (Clitoria ternatea cv. Milgara) were compared with forage sorghum (Sorghum spp. cv. Silk and cv. Sugargraze). Temperate legumes snail medic (Medicago scutellata cv. Sava), lucerne (Medicago sativa cv. UQL-1), sulla (Hedysarum coronarium cv. Wilpena), and purple vetch (Vicia benghalensis cv. Popany) were compared with forage oats (Avena sativa cv. Taipan/Genie). Production and WUE of winter legumes was highly variable, with oats producing more biomass than the legumes, except in 2009 where oat establishment was poor. In years with good establishment, WUE of oats (14–28kg DM/ha.mm), snail medic (13–25kg DM/ha.mm), and sulla (12–20kg DM/ha.mm) were similar, but the production and WUE of vetch were generally lower (6–14kg DM/ha.mm). Sulla dried the soil profile by 60–100mm more than the annual species, but less than lucerne. Summer legumes, burgundy bean, and lablab performed similarly, although always produced less biomass and had lower WUE than forage sorghum. Lucerne extracted more water and maintained a drier profile by 70–150mm and had lower WUE (<10kg DM/ha.mm) than burgundy bean or lablab (9–30kg DM/ha.mm). Of the legumes tested, burgundy bean and lablab seem the most likely to be profitably integrated into subtropical cropping systems. Further evidence of the rotational benefits provided by these legumes is required before they will be favoured over the perceived reliability and higher productivity of annual grass-type forages.

Perennial wheat could improve grain production systems in Australia by rectifying many environmental problems such as hydrological imbalance, nutrient losses, soil erosion, and declining soil carbon and soil health. There are also potential direct production benefits from reduced external inputs, providing extra grazing for livestock in mixed farming systems, as well as benefits for whole-farm management which may offset lower grain yields. In addition to universal issues of domestication and breeding of perennial wheat, specific challenges for perennial wheat in Australia’s dryland systems will include tolerance of water deficit and poor soil environments, and the risks of hosting foliar pathogens over summer. Temperate perennial forage grasses could indicate the potential distribution and traits required in perennial wheat adapted to more arid environments (e.g. summer dormancy). Several Australian native and exotic perennial relatives of wheat could also provide sources of disease resistance, and tolerance of soil acidity, drought, salinity and waterlogging. Still, several farming systems could accommodate perennial wheat with inconsistent persistence in some environments. While developing perennial wheat will be challenging, there is significant opportunity in Australia for perennial wheat to diversify current cropping options. The risks may be minimised by staged investment and interim products with some immediate applications could be produced along the way.

Dryland salinity in southern Australia has been caused by inadequate water use by annual crops and pastures. The purpose of this study was to compare the water use of annual pastures and Medicago sativa L. (lucerne) with Dorycnium hirsutum (L.) Ser., a potential new perennial forage species. The soil water dynamics under bare ground, annual legume-, lucerne-, and D. hirsutum-based pastures were compared at 2 sites in the low- (Merredin) and medium- (New Norcia) rainfall wheatbelt of Western Australia between September 2002 and February 2005.  Soil under D. hirsutum was drier than under annual pastures by 8?23mm in Year 1, 43?57mm in Year 2, and 81mm in Year 3. Lucerne used little additional water (<19mm, n.s.) compared with D. hirsutum and profile soil water content was similar under both species throughout the experiment. At Merredin, annual pastures used water to a depth of 1.0m, whereas under both D. hirsutum and lucerne in the first 3 years after establishment the successive maximum depth of water use was 1.0, 1.8, and 2.2m. At New Norcia, additional soil water was extracted by lucerne and D. hirsutum at depths <1.0m and no difference between treatments was detected below 1.0m. Biomass of D. hirsutum pasture harvested in autumn contained minimal annual components and was 15?50% of that produced by lucerne- or annual legume-based pastures. D. hirsutum and lucerne plant density declined each summer (25?80%), but D. hirsutum density was lower than lucerne due to poorer establishment. Nonetheless, the comparable water use of lucerne and D. hirsutum suggests that D. hirsutum could make reductions in recharge similar to those of lucerne in the Western Australian wheatbelt.

Interest is growing in the potential to expand cropping into Australia's high-rainfall zone (HRZ). Dual-purpose crops are suited to the longer growing seasons in these environments to provide both early grazing for livestock and later regrow to produce grain. Grain yield and grazing potential of wheats of four different maturity types were simulated over 50 years at 13 locations across Australia's HRZ, and sowing date, nitrogen (N) availability and crop density effects were explored. Potential grazing days on wheat were obtained by simulating sheep grazing crops to Zadoks growth stage Z30 at 25 dry sheep equivalents (DSE)/ha. Optimal sowing dates for each maturity type at each location were matched to the flowering window during which risk of frost and heat stress was lowest. Overall, we found significant national potential for dual-purpose use of winter wheat cultivars across Australia's HRZ, with opportunities identified in all regions. Simulated mean wheat yields exceeded 6t/ha at most locations, with highest mean grain yields (8–10t/ha) in southern Victoria, and lower yields (5–7t/ha) in the south-west of Western Australia (WA) and central and northern New South Wales (NSW). Highest grazing days were from winter cultivars sown early (March–mid-April), which could provide 1700–3000 DSE-days/ha of grazing across HRZ locations; this was 2–3 times higher than could be obtained from grazing spring cultivars (200–800 DSE-days/ha). Sowing date was critical to maximise both grazing and grain yield potential from winter cultivars; each 1-week delay in sowing after 8 March reduced grazing by 200–250 DSE-days/ha and grain yield by 0.45t/ha. However, in Mediterranean climates, a lower frequency of early sowing opportunities before mid-April (30% of years) is likely to limit the potential to use winter cultivars. Prospects to graze shorter season spring cultivars that fit later sowing windows require further examination in south-west WA, the slopes of NSW and southern Queensland.