氮肥运筹对水稻农学效应和氮素利用的影响

Agronomic responses to nitrogen application and nitrogen utilization in rice fields

通过田间试验,以不同氮肥量级为参照,结合关键生育期叶片叶绿素含量（SPAD值）指导氮肥施用,以探明潜江地区水稻关键生育期的氮肥适宜用量。结果表明,在施N 90~180 kg/hm2之间水稻产量差异不显著,当超过N 180 kg/hm2,产量降低。根据水稻产量（y）和施氮量（x）拟合得出一元二次关系式：y=-0.0728x2＋22.335x＋6811.5,R2=0.9442。结合当年水稻价格,肥料投入费用等计算出水稻的经济效益（y）和施氮量（x）之间的函数式：y=-0.134x2＋37.097x＋12533-M,R2=0.9331;由此得出经济效益最大时水稻的施氮量是N 138 kg/hm2。该施氮量下水稻的氮肥表观利用率、农学利用率和氮肥偏生产力可保持在40.9%、11.5 kg/kg和63.2 kg/kg,与完全依据SPAD值指导关键生育期的氮肥施用量相近似（N 140 kg/hm2）,保证了水稻最大的经济效益,同时也保持了较高的氮肥利用率,降低氮素表观损失。

Field experiments were conducted to explore the optimum N application rate based on agronomic responses to different N application rates,and the leaf SPAD values at the critical growth stages were measured for guiding the N management practices in the Qianjiang region.The results indicate that there are no significant differences in grain yield when N application rates range from 90 to 180 kg/ha,while grain yield is decreased when N rate is over 180 kg/ha.The equation between grain yield of rice and N application rate is established： y=-0.0728x2＋22.335x＋6811.5,R2=0.9442.Then the economic optimum nitrogen rate（EONR）,138 kg/ha,is evaluated in the study area by the equation between economic benefit of rice and N application rate（y=-0.134x2＋37.097x＋12533-M,R2=0.9331） based on the input of N fertilizer and output of grain yield,and the N recovery efficiency,agronomic efficiency and N partial factor productivity are 40.9%,11.5 kg/kg and 63.2 kg/kg,respectively.The produced N application rate（140 kg/ha） guided by SPAD values at the critical growth stages is matched perfectly with EONR under the maximum economic benefit,higher nitrogen use efficiency and low nitrogen apparent loss.