Effects of Sowing Date on Japonica Rice Quality in South Henan

Based on the experiment with 5 japonica varieties and 5 sowing dates,the appropriate sowing date of japonica rice in south Henan was discussed by the rice quality. The results showed that as the sowing date was postponed,the percentage of brown rice,milled rice rate of 5 japonica varieties showed an increase trend,but the chalkiness,chalky rate and chalkiness size showed a significant decrease trend.The coefficients of variation of grain length and length-width ratio were small,gel consistence of 5 japonica varieties of the second( May 10) or the third( May 25) sowing date was the maximum value. The amylose content and alkali spreading value of different sowing dates made a great difference,but there was no significant regular change. The result of fuzzy probability method showed that the rice quality of 5japonica varieties was increased as the sowing date postponed,and the rice quality of the fourth( June 9)or fifth( June 24) sowing date was the best,indicating that appropriately postponing the sowing date was beneficial for the improvement of rice quality.