Effects of methodical nitrogen-water distribution management on water and nitrogen use efficiency of rice

China Abstract: This study included three split-plot designed experiments. Experiments 1 and 2 were conducted in two fields with varied soil fertility and consistent treatment. Two rice varieties (Dexiang 4103, high NUE; Yixiang 3724, low NUE) were set as main plot. The sub-plot contained six nitrogen-water management modes (farmer’s usual management, FU; nitrogen-water coupling management, NWC; methodical nitrogen-water distribution management, MNWD; and their respective nitrogen-free controls). The main plot of Exp.3 was two high NUE varieties (Dexiang 4103, Fyou 498) and two low NUE varieties (Yixiang 3724, Chuanyou 6203); FU, NWC, and MNWD assembled the sub-plot. MNWD adopted the method of increasing frequency and re-ducing quantity, thus the nitrogen application rate was reduced by 20% compared with NWC and FU, the irrigation water amount was reduced by 20% to 25% compared with NWC, and smoothly and its ear bearing tiller percentage was higher. Compared with NWC and FU, the photo assimilation before anthesis MNWD had less, dry matter transportation before anthesis and high accumulation of assimilate after anthesis. The grain yield of MNWD was similar to that of NWC, while 8.77%–14.18% higher than that of FU. Correlation analysis showed that the dry weight of roots in 10–20 cm and 20–30 cm soil layers were significantly and positively correlated with nitrogen recovery efficiency (NRE), nitrogen agronomy efficiency (NAE), irrigation water production efficiency (IWPE) and water production efficiency (WPE). MNWD had a large amount of root system distributed in the soil layer below 10 cm, which was conducive to the improvement of water and nitrogen utilization efficiency. Compared with NWC and FU, MNWD increased NRE by 8.07%–11.99% and 20.72%–30.78%, NAE by 17.44%–27.38% and 96.47%–101.42%, IWPE by 23.34%–36.67% and 76.54%–117.38%, WPE by 8.41%–17.66% and 32.23%–65.29%, respectively.