r.harrison@murdoch.edu.au

Wheat gluten is one of the most important proteins on the planet, but its end-use qualities are determined by the amount of nitrogen biosynthesised in the grain. Input-intense cereal production has a heavy reliance on nitrogen supplied from ammoniacal fertilisers. This practice can contribute up to 50% of the on-farm emissions of greenhouse gasses in agriculture.

Despite increasing rates of application of synthetic nitrogen to cereals, wheat grain protein levels, in developed nations, have been frequently failing to reach the premium grade required by the bread-making market. We hypothesized that wheat grain protein could be increased by growing the cereal on legume residues which are rich in biologically fixed N.

This approach was compared against growing wheat with fertiliser nitrogen in different cropping rotations in a dryland Mediterranean climate over 2-4 years, on different soil types. Wheat grown after both leguminous and non-leguminous treatments received low, medium and high rates of urea to indicate if forage legumes can provide sufficient nitrogen for sustainable wheat production.

At all sites and years studied we discovered that wheat grains produced following a year of forage legumes had significantly higher protein levels than when grown after non-leguminous crops in rotation. These results were achieved in combination with a reduction in on-farm emissions (by over 200 kg/ha of CO2) without compromising yield, as indicated by emissions accounting.

In summary, incorporating suitable forage legumes in dryland farming systems enables wheat production with increased proteins and low emission intensity to promote both economic and environmental sustainability.