The Study Of Sensitivity Differences Of Nitrogen Application In Different Double Cropping Rice Types And Its Mechanism

In the condition of field experiment, the rice which was selective breed or introducedin the double cropping rice area of South China in the past years are chosen. Throughsetting different nitrogen levels, study the sensitivity differences of nitrogen application indifferent types of double cropping rice and the mechanism.3different nitrogen levels wereset as follows, early season rice use0（N0）,120kg/hm（2N1）,180kg/hm（2N2），late seasonrice use0（N0）,120kg/hm（2N1），220kg/hm（2N3）.The results of the study are as follows:（1） The heading and maturity stage of different varieties of rice both delayed with theincrease of nitrogen application. So it was in the whole growth period.The ricedidn’t lodge in the condition of no nitrogen. While different varieties of ricelodged inordinately in the condition of medium and high nitrogen.（2） The amount of nitrogen application influenced on the dry matter producion ofrice，yield and yield components and compare hybrid rice with conventional rice,the sensitivities of the hybrid rice is more strong. As the amount of nitrogenapplication increased, the yields of most varieties increased. The increase ofnitrogen application improved the nitrogen content in the stem, foliage and spikewhich could promote the dry matter and nitrogen accumulation in full headingespecially from tillering to full heading. The increase rate of early season rice bynitrogen application is diffent, Luliangyou996and Ganxin203is largeer thanothers and sensitive to nitrogen fertilizer, Zhe733and7055have the smallestincrease rate and least sensitive to nitrogen fertilizer; The increase rate of lateseason rice by nitrogen application is diffent, Wuyou308and Fengyou299islargeer than others and sensitive to nitrogen fertilizer, M112and Jinyou998havethe smallest increase rate and least sensitive to nitrogen fertilizer.（3） The amount of nitrogen application influenced on the quality of rice. With theincreasing of nitrogen application, rate of brown rice, milled rice and head riceimproved. This increasing had no obvious influence on the grain length, grainwidth, length-width ratio. However, the chalkiness rate, chalkiness area anddegree reduced obviously with this increasing. But the degree of nitrogenapplication on quality improving is different in various types of rice.（4） The sensitivities of nitrogen application in different types of rice are different.The sensitivities of the hybrid rice is more strong which is related to root activity,photosynthesis, activity of nitrogen metabolism enzyme and so on.