Michael Moodie1, Nigel Wilhelm2, Peter Telfer2 and Todd McDonald1
1 Moodie Agronomy, PO Box 10189, Mildura, Victoria, 3502, firstname.lastname@example.org
2 South Australian Research & Development Institute, PO Box 397, Adelaide, South Australia 5001
At the end of the millennium drought, broad-leaved crops made up a very small proportion of the sown crops in the low rainfall (LR) regions of south-eastern Australia. However, the productivity and profitability of these intensive cereal cropping sequences was declining due to increasing agronomic constraints. Furthermore, the impact of broad-leaved crops on subsequent cereal productivity had been rarely tested in these LR regions and farmers regarded them as risky to grow and were uncertain about their system benefits. To address this uncertainty, replicated trials were conducted in paddocks where locally important agronomic constraints such as grass weeds, soil borne diseases and declining soil fertility were reducing the yields of cereal crops. Each trial comprised 19 unique crop sequences which included both one and two-year break phases in 2011 and/or 2012 followed by wheat in 2013 and 2014. Each trial also maintained a continuous wheat treatment for the four years of the trial as a benchmark to assess the impact of the other crop sequences. Cumulative break crop benefits were generally in the order of 0.5 – 1.5 t/ha of extra grain yield in subsequent wheat crops and as high as 2 t/ha, findings that are comparable with break crop benefits reported in higher rainfall regions in southern Australia. The inclusion of break phases also improved the overall profitability of the crop sequence, providing that at least one of the break phases was profitable. The profitability of the four-year crop sequence was improved by up to $100/ha per year when a break crop was included, relative to maintaining continuous wheat.