氮肥施用期及施用量对稻米品质的影响

通过连续3a的试验发现；齐穗期喷施尿素溶液能改善稻米加工品质，适当提高直链淀粉含量，延长胶稠度，但对垩白发生有一定促进作用，早稻早季种植形成较优米质的最佳氮肥用量大于晚季种植，增氮的同时应注意选择垩白小的品种，以扬其改善加工，蒸煮，营养品质之长，避增加垩白之短，重施基肥吻合早季种植水稻生育期短，灌浆快的特点，使其尽早吸收，充分利用氮素营养，故能形成较优的米质，而重施穗肥吻合晚季种植水稻生育期长，灌浆平缓的特点，在生育后期集中向籽粒供氮，利于优良米质的形成，施氮时期及施氮量调控优质稻米的形成与适应不同类型品种或不同季节水稻的生长发育特点有关，但伴随加工，蒸煮，营养等品质改善的同时，垩白总是增加，因此选择小晋白品种是运用氮肥调控米质的基础，各米质指标中，加工品质与垩白受影响最大，直链淀粉含量，胶稠度受影响次之，粒长及粒形受影响较小，糊化温度几乎不受影响，施氮越多，施用时期越晚，蛋白质含量越高，但由于国家标准中未涉及蛋白质含量与米质的关系，因此对米质的影响是好是坏有待进一步研究。

Effects of Applying Time and Quantity of Nitrogen Fertilizer on Rice Quality

The grinding quality could be improved by spraying urea solution during ripening period, meanwhile the amylose content was improved and gel consistency was extended while the chalkiness was increased. The fine quantity of nitrogen for the best quality of early rice planted in early season was more than those planted in lately season. Using the strong point of improving grinding, cooking and nutrition quality, avoiding the weak point of increasing chalkiness, little chalkiness variety should be selected while adding the quantity of nitrogen. Heavy basis fertilizer was best for the quality of rice planted in early season because it coincided with its characters while heavy spike fertilizer was best for the quality of rice planted in lately season coinciding with its characters. Adjusting the quality of rice by applying time and quantity of nitrogen was correlated with whether it could be coincided with the characters of different varieties or seasons. Little chalkiness variety was the basic element of adjusting quality of rice by nitrogen because chalkiness always increase while the polishing of grinding, cooking and nutrition quality increase. The variations of grinding quality and chalkiness, amylose content and gel consistency, length and shape of grain were decreased in turn. Gelatinization temperature almost did not change. The more nitrogen or later applying time of nitrogen, the higher protein content. As the quality standard of staple grain of China has no stipulation for rice protein content, whether the increasing of protein content is better or bad for quality of rice need further research.