Lindsay W Bell 1, Andrew Zull2, Darren Aisthorpe2, David Lawrence2, Andrew Verrell3, Jon Baird3, Andrew Erbacher2, Jayne Gentry2, Greg Brooke3 and Kaara Klepper4
1 CSIRO Agriculture and Food, Toowoomba Qld 4350, Lindsay.Bell@csiro.au
2 Department of Agriculture and Fisheries, Queensland
3 New South Wales Department of Primary Industries
Farming systems experiments were undertaken across multiple sites spanning Australia’s northern grains region. A regional baseline of local current best practice was compared with several cropping system strategies that varied in cropping intensity (i.e. number of crops sown/yr), crop choices and nutrient application strategy. Crop yields, inputs and soil water dynamics were monitored in each system over 3.5 years to calculate the system water use efficiency (WUEsystem), i.e. the $ gross margin per mm of system water use (rainfall + change in soil water). Large gaps in profitability were found between the best and worst systems at each site ($200-700 per year between systems). Increasing crop intensity increased costs and either reduced or equalled the system water use efficiency (WUE) compared to the baseline systems at most sites. A promising lever to enhance farming system profitability is therefore, adjusting crop intensity to environmental potential. Increasing grain legume frequency achieved similar profitability and system WUE as the baseline. Increasing crop diversity and growing alternative crops increased costs but also profitability at some sites by managing diseases or weeds. Increasing nutrient supply incurred higher costs and as yet has rarely increased system profitability. Additional nutrients only increased system WUE when one crop in the sequence experienced > median rainfall (i.e. Trangie & Emerald).