Abstract:

Many studies on the sensibility of grain filling to nitrogen application at full panicle stage in rice have been conducted, with a lot of differences in results. Perhaps, it is related to different nutrition levels of nitrogen in plant at full panicle stage, on which there have been few studies. In this paper, the relationship between the efficient amount of nitrogen application for grain filling (NAGF) and the source-sink structure at full panicle stage was investigated with “Ⅱ-you 602”, a combination of mid-season hybrid rice under different amounts of nitrogen application in basic fertilizer, tillering fertilizer, and NAGF, expecting to establish a theoretical basis for efficient nitrogen application in high yield rice cultivation. There was highly significant correlation between the effect of yield increase by NAGF and nutrition level of plant. The efficient amount of NAGF depended on SPAD values of the first leaf from top, leaf nitrogen content, and total No. of spikelets per m² at full panicle stage. There were highly significant negative correlations between the efficient amount(y, kg ha^-1) of NAGF and SPAD values (x) of the first leaf from top at full panicle stage, y = －30.7980x + 1340.9 and R² = 0.9114. When the SPAD value of the first leaf from top at full panicle stage was over 43.5, as a critical diagnosing index in rice production, NAGF was not necessary.

Key words: Mid-season hybrid rice, Nitrogen application for grain filling, Efficient applying amount, SPAD value