Effects of irrigation method and ratio of organic to inorganic nitrogen on yield and water use of rice

A pot experiment was carried out to study the effects of irrigation method and ratio of organic to inorganic nitrogen (N) on rice growth, yield components and water use of rice. There were three irrigation methods, controlled irrigation (CIR), intermittent irrigation (IIR) and flooding irrigation (FIR), and three ratios of organic to inorganic N, 60% inorganic N+40% organic N (F1), 80% inorganic N+20% organic N (F2), 100% inorganic N (F3). The results show that compared to FIR treatment, the irrigation amount are reduced by 31.3% and 15.9% during the whole growth stages of rice under the CIR and IIR treatments, respectively, and the rice yields are reduced by 31.9% and 15.9%. Therefore, water use efficiencies (WUE) of rice are not enhanced. Compared to F3, rice yields of F1 and F2 are increased by 20.1% and 14.2%, and under the FIR treatment, WUEs of F1 and F2 are enhanced by 37.3% and 25.5%, respectively. Path analysis shows that number of productive ear, grains per ear and thousand kernel weights are the main components of rice yield in different irrigation methods and ratios of organic to inorganic N treatments. The principal component analysis shows that under the same total N application, 40% inorganic N could decrease irrigation water and increase rice yield in the IIR treatment appropriately.