Effects of regulated deficit irrigation and nitrogen nutrition on validity of water and nitrogen in maize rootzone soil

The objective of this study was to explore the effects of regulated deficit irrigation and nitrogen nutrition on validity of water and nitrogen in maize rootzone soil with pot experiment. The influence of regulated deficit irrigation and nitrogen nutrition on dynamics of NO3--N in rootzone soil and validity of water and nitrogen were studied. Results showed that soil NO3--N content was determined by N rate, and the dynamics of NO3--N in rootzone soil was affected by irrigation amount and nutrient uptake in each growing stage. Soil NO3--N contents in middle and lower soil layer of regulated deficit irrigation were at between that of low and high irrigation amount of normal irrigation, and there was a positive correlation between the content of NO3--N in middle and lower soil layer and N rate at the end of heading stage. N rate and water deficit period had a notably significant effect on accumulative dry matter and total nitrogen. Water deficit at jointing stage affected accumulative dry matter mostly, followed by that at seedling stage, and the least at heading stage. The treatment with high nitrogen rate and water deficit at seedling stage had the maximum water use efficiency; the treatment with high nitrogen rate had the maximum total nitrogen accumulation, which was 2.54-3.23 times of that in the treatment of zero nitrogen. The nitrogen apparent using efficiency under regulated deficit irrigation and low nitrogen was greater than 30%, which was 6.6% more than that under regulated deficit irrigation and high nitrogen. The best coupling treatment was water deficit at heading stage and low nitrogen.