EFFECT OF NITROGEN AND HARVEST GRAIN MOISTURE ON HEAD RICE YIELD

In rice (Oryza sativa L.) production, both grain yield and milling quality play an important role in determining the grower's income. Nitrogen input is essential in maintaining a desirable yield, but its effect on rice milling quality is less clear. This study examined optimal N input for rice milling quality and the combined effect of N and grain moisture at harvest on both grain yield and head rice yield. Experiments were conducted in California at the Rice Experiment Station, Butte County, on three cultivars (S201, M201, and L202) during the 1987 and 1988 growing seasons to determine the effects and optimum levels of N and grain moisture at harvest on milling quality. Results showed that the optimal harvest grain moisture to produce the maximum head rice yield depended on the levels of N applied and ranged between 220 and 270 g kg(-1) for S201, 210 to 270 g kg(-1) for M201, and 200 to 250 g kg(-1) for L202. The optimal N level for maximum head rice yield was 125 kg ha(-1) for S201, 112 kg ha(-1) for M201, and 130 kg ha(-1) for L202. These optimum N rates fell within the lower half region of the required N for 0.95 confidence of producing the maximum grain yield. Thus, optimum N inputs for head rice yields are also likely to produce maximum grain yields for the cultivars studied. These findings will greatly simplify the management requirement on N application for California rice farming.