Weed Suppression and Performance of Grain Legumes Following an Irrigated Rice Crop in Southern Australia

Abstract

Post-rice irrigated soils offer several potential advantages for the growth of subsequen crops, but Australian producers have often been reluctant to grow grain legumes immediatel following a rice crop due to physico-chemical constraints. A field experiment was thus conducted t explore the potential for producing grain legumes following rice in comparison to those followin a fallow during 2012 and 2013. Two grain legumes, field pea and faba bean, were sown 5, 7 an 12 weeks after rice harvest in 2013 at Yanco, NSW, and plant growth indicators and grain yield wer compared. Early sowing of field pea following rice gave the best outcome, with plants flowerin three weeks earlier and yielding 1330 kg ha-1more grain than after fallow. In contrast, faba bea yield was 35 kg ha-1 less after rice than after fallow across the three sowing dates. Higher pea yiel was consistent with the early emergence of seedlings, higher light interception and overall greate plant growth following rice. Post-rice crops also had 10-fold less weed infestation than crops in similarly-established fallow treatment and, thus, required far less weed management. Legume crop sown at the later seeding date had significantly reduced (50%-60%) yields compared to those of th first two sowings; this is most likely a reflection of reduced temperatures and day lengths experience during vegetative and reproductive growth phases.