Yang Qiliang

Effects of regulated deficit irrigation and nitrogen rate on use of water and nitrogen in maize root-zone soil

Regulated deficit irrigation is a new water-saving irrigation method and technique that may affect use of water and nitrogen. The object of this study was to explore the effects of water deficit at growth stages (seedling, jointing and heading) and levels of nitrogen (N) fertilizer (NH, 0.30 N g/kg dry soil; NL, 0.15 N g/kg dry soil; NN, 0 N g/kg dry soil) on use of water and N in root-zone soil. Pot experiment of maize [Zea mays (L.) cv. Hudan No. 16, a local variety] with six replications was conducted about water deficit stage and N rate. The effect of regulated deficit irrigation and N rate on dynamics of NO3− in root-zone soil and availability of water and N was studied. Results showed that NO3− was determined by N rate; the dynamics of NO3− in root-zone soil was affected by irrigation amount and N uptake at four growth stages. Soil NO3− in middle and lower layers of RDI lay between that of sustained low and high water, and there was a positive correlation between NO3− in middle and lower layers and N rate at the end of heading stage. N rate and water deficit stage had a notably significant effect on accumulation of dry mass and total N. Results showed that water deficit at jointing stage affected mass accumulation the greatest, then water deficit at seedling stage, and water deficit at heading stage was the lowest. The treatment of NH and water deficit at seedling stage had the maximum water use efficiency (WUE); the treatment of high nitrogen (NH) had the maximum total nitrogen accumulation, which was 2.54–3.23 times of that under non-nitrogen (NN).The N apparent use efficiency under RDI and low nitrogen (NL) was bigger than 30%, which was 6.6% more than that under RDI and NH. The best coupling treatment was water deficit at heading stage and NL.