Crop growth, yield and water use in long fallow and continuous cropping sequences in the Victorian mallee

Abstract

The agronomic implications of substituting mustard (Brassica juncea) for long (winter) fallows were investigated in a 6-year field experiment by comparing 2 cropping sequences (fallow–wheat–pea v. mustard–wheat–pea) in the semi-arid Victorian mallee. Production and water use of wheat, pea and mustard were measured. Grain yields ranged from 0.1 to 2.4 t/ha for wheat (mean 1.72 t/ha after fallow and 1.22 t/ha after mustard); from 0 to 0.6 t/ha (mean 0.22 t/ha) for mustard and from 0 to 1.4 t/ha (mean 0.8 t/ha) for field pea, strongly reflecting variable seasonal conditions (in-crop rainfall range from 84 to 231 mm). Mustard was shown to be a potential replacement for long fallow producing additional yield benefit (mustard + wheat) in one year. However, under drought conditions it introduces severe penalties to wheat growth and yield compared with the traditional fallow cropping system. Further, mustard did not affect water use, growth, or yield of the second crop after wheat (in our case field pea). This study highlights a conflict between developing farming systems that are productive, environmentally and socially acceptable under variable weather conditions and yet uphold the regional need to reduce dependence on fallowing. Further analyses of weather patterns and other crop choice strategies are needed to help develop better management strategies for the mallee region of Australia.