Biomass accumulation and distribution, yield formation and water use efficiency responses of maize (Zea mays L.) to nitrogen supply methods under partial root-zone irrigation

Facing with the scarcity of water resource and irrational fertilizer use, it is highly important to supply plants with water and fertilizer in a coordination pattern to improve yield with high water use efficiency (WUE). A field experiment was conducted in 2012 and 2014 to investigate the effect of N supply methods on biomass accumulation and distribution, yield components and WUE of maize (Zea mays L.) under different partial root-zone irrigations in the Hexi corridor of Northwest China. Three irrigation methods included alternate furrow irrigation (AI), fixed furrow irrigation (FI) and conventional furrow irrigation (CI). Three N supply methods included alternate N supply (AN), fixed N supply (FN) and conventional N supply (CN), were applied in combination with each irrigation method. Leaf area index (LAI), shoot biomass and root length density at different growth stages, yield components, biomass distribution in different shoot organs and WUE of maize were determined. Results showed that, LAI at the R₁, R₂ and R₄ stages, shoot biomass at the R₆ stage, grain yield, harvest index (HI) and WUE of maize were significantly increased by AN or CN compared to FN in each irrigation method as well as by AI compared to CI and FI in each N supply method. Compared to CI coupled with CN (CICN), AI coupled with AN or CN (AIAN or AICN) significantly increased the LAI, shoot biomass, grain yield and WUE of maize. The biomass distribution proportion in kernel and contribution rate of the biomass transfer from other shoot organ to grain were also increased by AIAN and AICN, resulting in significantly higher HI. These increased shoot biomass accumulation and WUE were related to the enhanced LAI and root growth. AIAN and AICN also achieved a greater kernels number per cob and 1000-kernel weight compared to CICN. Thus, AI coupled with CN or AN are proposed as a better pattern of irrigation and nitrogen application with positive regulative effects on shoot biomass accumulation and distribution and WUE in the Hexi Corridor area of Northwest China and other regions with similar environments. These results can also provide a basis for in-depth understanding of the mechanism of biomass accumulation and growth responses to nitrogen supply methods.