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CONTEXT: Summer crops are exposed to heat and drought stresses at critical stages during and after flowering, and their intensity and frequency are likely to increase with climate change. Agronomic stress avoidance offers the opportunity to temporally separate critical crop stages from heat and drought events, though it might require sowing cold sensitive summer crops early in late winter into colder than recommended soil temperatures. There is a need to understand how cold is too cold to sow summer crops early in late winter as well as what are the yield benefits and risks. OBJECTIVE: Here we quantify the likely benefits and trade-offs of sowing sorghum, a summer cereal, early in late winter as an adaptation to the increased frequency and intensity of heat and water stresses during flowering and grain filling.

Take home message • Nitrogen derived from atmosphere (Ndfa) in mungbean crops is strongly influenced by the amount of mineral soil nitrates that are available at planting. There is an almost linear decline in N2 fixation as soil nitrates increase in the top 60cm of the profile. • Mungbean and chickpea crops can access and utilise soil nitrate N in the top 60cm as efficiently as cereal crops. This raises implications for nitrate N supply in crops following these pulse crops. • Mungbeans planted in long fallow situations will create a soil nitrate N deficit as N2 fixation rates cannot replace the amount of soil nitrate being exported in grain. Circumstantial evidence suggests that chickpeas may be similar.

Take home messages The nitrogen (N) fertiliser demand for cereal cropping systems can increase due to two factors: 1. A reduction in the amount of soil organic N mineralised due to the continued decline of natural capital (soil organic carbon and total nitrogen) that occurs under cropping; and 2. An increased crop N demand due to higher yield potentials resulting from optimising other components of the cropping system. The amount of biological N fixation by pulse crops (chickpea/mungbean) is related to the crop yield and biomass and the availability of soil mineral N from mineralisation or carry-over of residual fertiliser. Where deep phosphorus (P) and potassium (K) application increases chickpea biomass (and grain yield), there is generally more N fixed. While some of this is re-exported in grain, the greater residue return means more N is carried forward to the next crop. Growers have a selection of fertiliser N management practices that have differing strengths and weaknesses – it is not a one-size-fits-all model for CQ (or northern region) farming systems. The 4R framework allows choice of rate, source, time and place for any nutrient applied to be implemented suiting each growers’ preferences, with on-going research addressing several themes in regional Qld.

Winter sown sorghum reduces the impact of heat and water stresses around flowering and increases cropping intensity, though, achieving uniform plant establishment remains challenging. Sowing sorghum in winter will require crops to uniformly germinate and emerge in soils which are cooler than the recommended >16ºC minimum daily temperature, during the driest time of the year. Prolonged emergence periods and reduced total emergence can decrease canopy uniformity with negative impacts on yield, crop management and cropping system intensity. Acceptable establishment percentages (>80%) were achieved for some site by seedlot combinations, though large differences in establishment rate between seedlots were observed. The differences in seedlot emerge rate were related to final establishment. This calls for seed vigour testing, novel seed production technologies, management of seedbed hydrothermal conditions and breeding programs for cold tolerance.

Early sown sorghum is a viable alternative for the Liverpool Plains of NSW. It is currently unknown if the longer vegetative period created by sowing into sub-optimal soil temperatures could affect water productivity. Water use was measured on an early (Agitator) and a late (MR Buster) maturing hybrid, sown in early and late spring and summer in 2018 and 2019 at 30, 60 (standard practice) and 120 thousand plants/ha. Crops sown very early into cooler soil conditions had lower water use than those sown at early and normal sowing times. There was a significant impact of time of sowing on grain yield, which was seasonally dependent. Water productivity for MR Buster was higher when grown at 30,000 plants/ha compared to the standard density and higher density. For Agitator, earlier sowing reduced water productivity. The potential of early sowing to increase yield and water productivity of sorghum needs assessment under additional seasons and environmental conditions.

Researching the management (M) of genotypes (G) in agronomic experimentation is essential to help farmers maximise grain yield, though the approach is complicated by interactions emerging from changing environmental (E) factors across sites and seasons. Available statistical methods for modelling the G×E interaction are limited as they do not provide a functional understanding of how environmental factors influence the G×E interaction, nor assess how different management practices (M) influence the G×E interaction. A predictive linear mixed model is proposed that incorporates site/season-specific environmental covariates into a standard G×E interaction framework. The model is extended to include continuously varying agronomic management practices whilst allowing for non-linear trait responses and complex variance structures. The methodology was applied to a multi-environment data set associated with GRDC’s optimising sorghum agronomy program. The analysis identified key environmental drivers and management strategies that explained the G×E×M interaction, enhancing the biological understanding of the analysis results and allowing for the development of more robust recommendations for agronomic practices.

The efficiency of soil water accumulation during fallow periods, and the availability of that soil water for use by crops are key drivers of northern farming system productivity and profitability. In 2015 seven farming systems experiments were established from central Queensland to central New South Wales to answer the question; Can system performance be improved by modifying farming systems in the northern grains region? To assess this soil water dynamics were monitored under different farming systems, along with soil nitrogen, pathogens, crop biomass, grain yield and variable costs, as measures of system performance. Analysis of soil water accumulation during the fallows and its subsequent use by sorghum, wheat and chickpea crops, showed a cost to all crops for converting biomass to grain yield. This cost was least for chickpea (50 mm), followed by wheat (100 mm) and highest for sorghum (150 mm), and should be deducted from crop water use to calculate water-use-efficiency (WUE). The WUE was lowest for pulse crops (10 kg/mm), but sorghum and wheat returned the same WUE (17 kg/mm). Northern growers typically store plant-available-water (PAW) in the fallow as a buffer against variable quantity and timing of in-crop rainfall. Crops produced a better than average WUE when planted with at least 60 mm PAW in a high in-crop rainfall season, or 120 mm of PAW with low in-crop rainfall.

The idea that “Yield is King” fails to acknowledge that what matters most to farmers is farm profits and risk, rather than yield. This is because decisions made in one season will affect options and crop performance over the next few years. Therefore, quantifying the longer-term impacts of innovation adoption is important. We used the Agricultural Production Simulation model (APSIM) to simulate and investigate the implications of adopting rain-fed winter sown sorghum in the Australian northern grains region. Results indicate that within a crop rotation early-planted sorghum will tend to decrease median sorghum crop yields but increase the following winter crop yields. This appears to have a marginal economic effect in Breeza and Dalby but encouraging results in Emerald. The inclusion of chickpea within the rotation increased returns in the best seasons with little change to downside risks in poor seasons.

History shows that transformational changes in agriculture are rarely associated with the adoption of single innovations. It has been argued that transformative changes in agriculture have usually resulted from the incremental adoption of complementary technologies, and result in ongoing increases in yield from improvements from breeding and agronomy – though gains in productivity remain piece meal, insufficient and primarily confused with adoption processes. Here we propose that there is a role and need to design research that aims to be more transformative, likely to have larger than the ongoing or incremental gains, and that can be achieved in shorter periods of time. This argument is discussed by summarising the results of a four-year cross-agency research program conducted across Eastern Australia that tested crop designs of winter sown sorghum (WSS). The innovation is a systems adaptation with the potential to produce gains in productivity and farmer profits beyond what is the incremental or ongoing yield gain – though impact will still be dependent on adoption rates.

Grain sorghum yield is often reduced by heat and water stress during critical growth stages around anthesis when planted in the traditional sowing window. Sorghum sown during late winter or early spring can flower before these stresses develop, though reduced plant establishments due to sub optimal soil temperatures and the likelihood of frost damage need to be managed. Two years of experiments at Mungindi, Moree and the Liverpool Plains in Northern NSW compared sowing time effect on plant establishment, date of anthesis and grain yield. Sorghum can be established in sub-optimal temperatures (<16°C) if seedbed moisture is available but losses of 10-30% need to be factored into sowing rates. The overlap between flowering and heat stress was minimised by ‘winter’ or early spring sowing. Grain yield was maintained or improved by planting earlier compared to traditional sowing times.

Take home message Shorter season, faster maturing crops can leave residual surface water from unutilised late season rain and/or residual deep water due to shallower roots and quicker maturity Legumes such as lentils, fababeans, field pea, and chickpea often leave 20-40 mm extra residual soil water compared to canola and winter cereals Higher residual water may not remain at sowing of next crop – fallow efficiency differences between crops and seasons can influence this – e.g. low cover after legumes For summer crops, mungbean typically leaves 20mm more residual water than sorghum/maize while cotton leaves 20mm less (i.e. mungbean > sorghum/maize > cotton) Early-sown, slower maturing crops (e.g. early sown winter crops) can dry the profile deeper (>2m) and utilise deep stored soil to support higher yield in dry springs. The legacy of drier soil may warrant changes to crop sequence and management to avoid yield penalties Extra residual water at sowing can increase grain yield of subsequent crops when water is limited during the critical period for yield determination so the marginal WUE (i.e. extra yield per mm of extra soil water available) can be very high (>60kg/ha/mm) As the value of the residual water is seasonally dependent, understanding how management (crop choice, sowing dates, N management) can be adjusted to capture value from such legacies across a sequence of crops is the goal of current farming systems research.

Take home message • While summer crops offer rotational options in the farming system, choose the correct crop to match your available soil water and crop history • Sorghum is a reliable performer often exceeding other options in terms of $ returned per mm used • Cotton and maize require higher water availability and produce less reliable WUE ($/mm). However, cotton has legacy impacts on water availability for subsequent crops that should be considered • Mungbean can produce higher $/mm in low water availability situations (<200 mm of rain + soil water). Repeated sowings of mungbeans are likely to induce yield reductions due to disease • Sorghum crops sown with > 150 mm of plant available water will maximise crop WUE and profitability. Every extra mm at sowing could be worth as much as $35-70 extra return/ha • Higher density sorghum crops may provide greater crop competition against weeds and potential upside yield benefits in good season. We have seen limited legacy benefits (e.g. improved ground cover) or costs (e.g. greater soil water/nutrient extraction) for soil water or nutrient availability.

Take home messages • Match optimal flowering period to growing environment to maximise grain yield potential. • One variety doesn’t fit all; there are no commercially available varieties that are broadly adapted across a wide range of sowing times or growing environments. • Optimising variety phenology and sowing time combinations achieves grain yield stability across a wide sowing window. • Probability of sowing opportunities will influence variety choice and sowing time decisions.

Take home messages • Large gaps in profitability are possible between the best and worst systems – differences of $92-494/ha per year were found between systems at each site • Intensity is the major factor driving good/poor economic performance of the farming system - more so than crop choice. Matching intensity to environmental potential seems to be the most important lever to optimise farming system profitability • Increasing crop intensity increased costs and risks, but potentially higher crop income wasn’t realised over the dry run of seasons and hence has produced lower gross margins than more conservative systems • Lower crop intensity had lower system gross returns, but because of lower inputs and costs may achieve a more favourable return on investment at lower risk when there are limited planting opportunities. These systems have achieved lower gross margins than the baseline system in all but one comparison • Increasing legume frequency has the potential to capitalise on favourable legume prices but using long-term prices has rarely exceeded gross margins of baseline systems • Increasing nutrient supply incurred higher costs and required favourable seasonal conditions to increase grain yields and gross margins – this rarely occurred over the experimental years (excluding Trangie 2016 and Emerald 2017 where significant crop responses were obtained) • Systems involving crops with higher price variability (e.g. pulses, cotton) had limited downside risk but increased upside opportunities of higher economic returns. Even when comparing recent and long-term grain prices, the relative profitability ranking of systems rarely changed • Selecting a crop system is a long-term decision with unknown future yield and prices, hence choose systems that maximise system productivity and resilience, rather than responding to current commodity prices.

Take home message • Integrated weed management has performed better than the Baseline system across most of the indices measured as part of the farming systems trial • Additional biomass production has not correlated with additional yield, relative to other systems using the same crop rotation • The improved performance has come at a nutritional cost which will need to be managed if implemented on a broader scale.

Identifying optimum combinations of genotype (G) and agronomic management (M) i.e. crop design, to match the environment (E) i.e. site and expected seasonal conditions, is a useful concept to maximise crop yields and farmers’ profits. However, operationalising the concept requires practitioners to understand the likelihood of different E outcomes and GxM combinations that would maximise yields while managing risks. Here we propose and demonstrate an analysis framework to inform crop designs (GxM) at the time of sowing of a dryland maize crop, that combines data sets from multi-environment field experimentation and crop simulation modelling, and that accounts for risk preference. A network of replicated, G by M on-farm and on-research station trials (n = 10), conducted across New South Wales and Queensland, Australia, over three seasons (2014–2016) was collected. The trials consisted of combinations of commercial maize hybrids, sown at a range of plant densities and row configurations producing site average yields (Environment-yield) that varied between 1576 and 7914 kg ha−1. Experimental data were used to test the capacity of APSIM-Maize 7.10 to simulate the experimental results, and to in-silico create a large synthetic data set of multi-E (sites x seasons) factorial combination of crop designs. Data mining techniques were applied on the synthetic data set, to derive a probabilistic model to predict the likely Environment-yield and associated risk from variables known at sowing, and to derive simple “rules of thumb” for farmers that discriminate high and low yielding crop designs across the lower, middle and upper tercile of the predicted Environment-yields. Four risk profiles are described, a “Dynamic” (i.e. each year the farmer would adopt a crop design based on the predicted Environment-yield tercile and corresponding “rules of thumb”), “High rewards seeker” (i.e. each year the farmer would adopt the crop design that optimises yield for the higher tercile of Env

Take home messages • Grain legumes have utilised soil mineral nitrogen (N) to the same extent as cereal crops and have higher N export which often offsets N fixation inputs • Additional applied N reduced the depletion of background soil mineral N status at most sites; we are recovering a high percentage (>50%) in soil mineral pool. • Application of ~50 t/ha of compost or manure (10 t/ha OC) coupled with N fertiliser rates for 90th percentile yield potential has dramatically increased the soil mineral N in four years • Decreasing cropping frequency has reduced N export and so stored more N over the longer fallows, which has reduced N fertiliser requirements for following crops • Long fallows are mineralising N and moving N down the soil profile even under some very dry conditions • Most excess N is not lost in the system rather it is moved down the soil profile for future crops • The marginal WUE of crops (i.e. the grain yield increase per extra mm of available water) is lower when crops have less than 100 mm prior to planting. Hence, waiting until soil moisture reaches these levels is critical to maximise conversion of accumulated soil moisture into grain • The previous crop influences the efficiency of fallow water accumulation with winter cereals > sorghum > pulses. Long fallows are also less efficient than shorter fallows (<8 months). This has implications for assuming how much soil moisture may have accumulated during fallows.

The efficiency of soil water accumulation during fallow periods, and the availability of that soil water for use by crops are key drivers of northern farming system productivity and profitabilityIn 2015 seven farming systems experiments were established from Central Queensland to Central NSW. Soil water, nitrogen and pathogens were regularly monitored along with crop biomass, grain yield and variable costs, as measures of system performance. A baseline cropping system, representing current commercial practice was established and tested against other systems with higher and lower crop intensity, higher crop diversity, greater inclusion of legumes in the rotation and higher fertiliser inputs. A key driver of northern farming system productivity and profitability is soil water accumulation during fallows periods for use by subsequent crops. We found that winter cereals and sorghum had the highest fallow efficiency (median 0.26), ahead of chickpeas (0.14) and canola (0.19). Short (4-8 months) and long (9-18 months) fallows following wheat had similar fallow efficiency, however lower fallow efficiency was recorded for sorghum stubble with longer fallows (0.33 vs 0.22) Changing cropping intensity had the greatest impact on fallow efficiencies, with increases in Higher intensity systems (0.37) and decreases in Lower intensity systems (0.16) relative to the Baseline (0.22). Varying fallow length has shown increased grain yield and water-use-efficiency for longer fallows, however rainfall use efficiency and gross margin/mm has favoured a 4-6 month fallow. Profitability favours a moderate intensity, with 0.8-1 crops/year providing the greatest return per mm of rainfall. Introduction The efficiency of soil water accumulation during fallow periods, and the availability of that soil water for use by crops are key drivers of northern farming system productivity and profitability. Fallow water is stored and used as a buffer for more reliable grain production in highly variable rai

Take home messages Winter sowing sorghum didn’t penalise yields in eight trials sites from Liverpool plains to Central Queensland and across two seasons In dryland cropping, winter sown sorghum provides additional sowing opportunities, reduces the chances of heat stress, and increases the chances of double cropping a winter crop In irrigated cropping, ratooned winter sown sorghum can compete with cotton on profits and is less risky Commercially available hybrids can successfully germinate and emerge in cooler soils than previously recommended, though the seed must be tested for vigour at low temperatures Sorghum seedlings can withstand mild frost, though so far, we haven’t been able to frost kill a crop, meaning that frost risk is unknown.

Farming systems are currently underperforming in terms of yield, due to challenges that include declines in soil fertility, herbicide resistant weeds and increasing soil pathogens. Farming system changes will have to be made to maintain and improve productivity into the future. In 2015 research began, supported by the Grains Research Development Corporation, with experiments established at seven locations throughout Queensland and northern New South Wales. These experiments will assess the impact of nine farming systems across numerous parameters, including system production and economics, resource use efficiency, pathogen loads/populations, weed populations and soil health. Interim results indicate that differences in cumulative yields and gross margins are mainly driven by crop choice. These results will be tracked over a five to 10 year timeframe, when systems performance will be evaluated against all parameters at the conclusion of the project in 2019. Ideally, the project will continue until 2024 to fully assess the expected long-term differences between the systems in the study.

Farming systems are currently underperforming in terms of yield, due to challenges that include declines in soil fertility, herbicide resistant weeds and increasing soil pathogens. Farming system changes will have to be made to maintain and improve productivity into the future. In 2015 research began, supported by the Grains Research Development Corporation, with experiments established at seven locations throughout Queensland and northern New South Wales. These experiments will assess the impact of nine farming systems across numerous parameters, including system production and economics, resource use efficiency, pathogen loads/populations, weed populations and soil health. Interim results indicate that differences in cumulative yields and gross margins are mainly driven by crop choice. These results will be tracked over a five to 10 year timeframe, when systems performance will be evaluated against all parameters at the conclusion of the project in 2019. Ideally, the project will continue until 2024 to fully assess the expected long-term differences between the systems in the study.