Effect of high day-time temperature on rice quality under different panicle nitrogen treatments

Effect of high day-time temperature (HDT) on rice quality under different panicle nitrogen levels was investigated using japonica rice (Oryza sativa cv. Wuyujing3). There was significant difference in the effect of HDT among different nitrogen levels. HDT resulted in decreased milling quality, milled rice rate and head rice rate. Among the nitrogen treatments, effect of medium nitrogen treatment was largest, followed by low and high nitrogen treatment. For appearance quality, medium nitrogen treatment also exhibited the largest effect, while low nitrogen treatment showed the least. Grain chalkiness rate and grain chalkiness increased in all nitrogen treatments. Low and medium nitrogen treatments had lower brown rice rate and grain length to width ratio, but high nitrogen treatment had higher ones. Grain protein content increased with HDT regardless of nitrogen treatment. By contrast, the influence of HDT on amylose content varied with nitrogen treatments. Medium nitrogen treatment had higher amylose content whereas low and high nitrogen treatments had lower one. In addition, filled grain rate and grain weight was declined in all nitrogen treatments under HDT, with medium treatment having the lowest values. We concluded that suitable N application could effectively alleviate the negative impact of high temperature on the rice quality and yield.