The Effect Of N Management On The Rice Yield And N Efficiency Of Rice Variety Daohuaxiang

Nitrogen(N) nutrient is one of the major controllable factors to obtain high rice yield. It has long been focused to achieve high grain yield with little pollution by reasonable fertilizing. Rice varieties Daohuaxiang is the main cultivars of the first accumulated temperature zone in Heilongjiang Province, covering 80% percent of rice seeding areas. Few researches have bening maked on the relationships between N management and Daohuaxiang rice yield and N efficiency. We conducted a field experiment to determin soil inorganic N content change, N content of aboveground part, N uptake, rice yield and N efficiencies at different base-tiller and panicle N fertilizer rates. The main results were as follows:N moved to deeper layer as the N fertilizer raised. Base-tiller fertilizer rates had significant positive correlation(R2>0.9) with the inorganic N content of soil surface layer(0-4cm). The growth rate of soil inorganic N(2-4cm) reached the maximum of 84%(N3) and 215%(N5) in the 13th day after tiller fertilizing; Growth rate of soil inorganic N of 0-2cm soil layer reached 41%(N3) and 118%(N5). Soil inorganic N content of 4-6cm significantly increased at high rate of base-tiller fertilizer(N5), while the others had no significant change. Panicle fertilizer showed little effection on soil inorganic Ncontent of the top soil. The relationships between N content of surface soil and maximum tillering and panicle number showed positive correlation and curve relation, respectively. Higher soil N content at early stage went against to increase panicle number.Increasing N fertilizer help increase N content of rice plant. Treatments of enhansive base-tiller fertilizer N increased by 2%-20% of leaf N content compared to control at jointing stage. At tillering stage, N content of rice leaves and the maximum tillering showed positive correlation(R2=0.66-0.69). Leaf N content increased significantly as the panicle fertilizer increase wihile the base-tiller fertilizer stayed at rice late growth stage. N content of rice leaves reached the maximum of 1.42% in 23days after heading at the rate of 55 kg N/ha base-tiller fertilizer and 60 kg N/ha panicle fertilizer. Leaf SPAD could react N content of leaves,the relationship between leaf N content and SPAD had positive correlation(R=0.470,0.446) at tillering and jointing stage.Proper amount N fertilizer could help improve rice N nutrition. Before heading, rice N accumulation added with increasing rate of base-tiller fertilizer at the same panicle fertilizer rate. Compared to control treatment, the growth rate of N accumulation at 55 and 85 kg N/ha base-tiller rates reached 75%-113% and 59%-101% at tillering and heading stage, respectively. More N uptaken by rice plant when increase the panicle fertilizer rate while the base-tiller stayed the same. At mature, rice N accumulation reached the maximum of 112.55 kg/ha at the N rate of 55 kg/ha base-tiller fertilizer and 40 kg/ha panicle fertilizer. Increasing base-tiller and panicle fertilizer rates did not improve the totle N accumulation at this level. N accumulation at mature had a significant positive correlation(R2=0.886) with rice yield. It is a successive process for rice plant uptaking N, and ensure proper accumulating rates of each stage is important to obtain high rice yield.In some rate, increase base-tiller fertilizer help increase rice panicle number, but rice grain number per spike and seed setting rate decreased at the excess base-tiller N rate. Increasing panicle rate could decrease seed stting rate but help increase panicle number. Compared to apply 55 kg N/ha base-tiller fertilizer, increase and decrease 30 kg N/ha base-tiller N respectively reduced the rice yield at 4% and 10% at the same panicle fertilizer rate. While at the same base-tiller N rate, increase and decrease 20 kg N/ha panicle fertilizer reduced 0.4% and 5% rice yield respectively to 40 kg N/ha. Rice yield reached the maximum of 8.97 t/ha at the rate of 55 kg N/ha base-tiller fertilizer and 40 kg N/ha panicle fertilizer. After made a comprehensive analysis of the highest yield application, economically optimal yield application, maximum tillering and panicle number, we conclude that the optimum N application for Daohuaxiang varieties is:55-65 kg N/ha base-tiller fertilizer,35-40 kg N/ha panicle fertilizer and 95-105 kg N/ha total N rates.