Root distribution and yield responses of wheat/maize intercropping to alternate irrigation in the arid areas of northwest China

A field experiment was conducted to investigate the effects of alternate irrigation (AI) on root distribution and yield of wheat (Triticum aestivum L.)/maize (Zea mays L.) intercropping system during the period of 2007-2009 in an oasis of arid north-west China. Five treatments, i.e. sole wheat with conventional irrigation (W), sole maize with alternate irrigation (AM), sole maize with conventional irrigation (CM), wheat/maize intercropping with alternate irrigation (AW/M), and wheat/maize intercropping with conventional irrigation (CW/M). The results showed that root growth was significantly enhanced by alternate irrigation (AI), root weight density (RWD), root length density (RLD) and root-shoot ratios (R/S) in AI treatments were all higher than those in conventional irrigation (CI) treatments. Moreover, intercropped wheat and maize also had a greater root development at a majority of soil depths than wheat and maize in monoculture. In three years, AW/M always achieved the highest total seed yield under different treatments. Higher yield and reduced irrigation resulted in higher water use efficiency (WUE) for the AW/M treatment. Our results suggest that AI should be a useful water-saving irrigation method on wheat/maize intercropping in arid oasis field where intercropping planting is decreased because of limited water resource.