Effects of water deficit and potassium fertilizer application on the grain yield, yield components and bending moment of rice (Oryza sativa L.) var. Tarom Mahalli

In order to investigate the effects of water deficit at different growth stages of rice and potassium application on yield, yield components and bending moment of rice a split plot field experiment was carried out based on a randomized complete block design with three replications at Nour city in 2009. The main plots were irrigation halting at four levels including irrigation halting at the initiation, middle and end of tillering and at full heading stages, and sub plots were potassium application at four levels including 0, 30, 60 and 90 kg K.h-1. The results showed that irrigation halting at full heading stage decreased significantly tiller numbers per hill, fertile tillers per hill, panicle numbers per m2, 1000 grain weight and grain yield (489.50 g.m-2). The highest number of panicles per m2, grain yield (540.20 g.m-2) and biological yield (1329 g.m-2) were obtained when irrigation halting at the middle tillering stage was used. By increasing potassium application, traits like panicle length, panicle number per m2, 1000 grain weight and grain yield, biological yield and harvest index were rised by 10.48, 12.81, 5.28, 16.39, 6.06 and 10%, respectively. Whereas, plant height and fourth inter node bending moment had been decreased 1.33 and 8.49%, respectively. Except the plant height, other traits were not significant for the interaction effects of irrigation halting and potassium rates. The maximum plant height was observed for the interaction effect of middle tillering stage and control (0 kg K.ha-1). Therefore, at the full heading stage, rice is very sensitive to irrigation halting because of decreasing grain yield and yield component.