尿素不同分施比例对稻田表层水中氮素动态变化特征的研究

Study on the dynamics of nitrogen in surface water of paddy field as affected by different splitting application ratio of urea

采用具有独立灌排系统的田间试验研究了尿素不同分施比例对稻田表层水中氮素的影响。结果表明：表层水中总氮质量（TN）与施氮量成正相关，水稻不同生育期施肥田面水中总氮质量变化趋势为拔节肥〉分蘖肥〉基肥。TN浓度在施肥1d后达到最大，4d后降低了50％以上，之后则缓慢减小；铵态氮（NH4-N）最大值出现在施肥后2d；硝态氮（NO3-N）浓度变化缓慢，在整个水稻生育期中没有突出的峰值出现，施肥3-4d后浓度最高，之后逐渐减小。由于硝态氮浓度远远小于铵态氮或总氮浓度，因此控制稻田氮素流失应主要监测TN和NH4-N，而且重点应防止施氮后1周内产生径流。

A field case study with independent irrigation system was conducted to elucidate the effect of nitrogen in surface water of paddy field as affected by different splitting application ratios of urca. The results showed that the total nitrogen mass （TN） in the surface water was closely correlated to the rates of urea applied and followed a trend of TN at the elongation stage 〉 that at the filleting stage 〉 that at the transplanting after urea was applied. TN reached its peak values 1 d after fertilizer applicatlon,reduced to less than 50 % 4 d later and continued to diminishing thereafter. The variation of ammonium nitrogen （NH4-N） contents during the rice growing period had a similar trend as TN but with a delayed peak value occurred 2 d after urea application. The change in concentration of nitrate nitrogen （ NO3-N） was relatively fiat,without any significant peaks observed. Its high values showed up at 3 -4 d after fertilizer application and then gradually declined. Because the content of NO3-N was very small compared to NH4-N or TN in the surface water of the paddy field,the content of NH4-N or TN could be used as the main indexes for monitoring the water pollution from the paddy field,particularly within the first week after N application when water flooding from the field should be avoided as possible.