两种土壤不同施氮水平对稻田系统的氮素利用及环境效应影响

在非完全淹水稻田中,研究了不同施氮水平分次施氮对植株氮吸收、土壤中氮素的积累和渗漏水氮素污染的影响,结果发现:水稻植株氮积累量随施氮水平的增加迅速提高,但施氮超过225kg/hm2后,水稻吸氮基本保持不变;土壤中的氮累积情况表明,小于75kg/hm2的施氮不利于土壤肥力的保持,超过225kg/hm2后土壤氮累积严重;渗漏水平均含氮浓度与施氮水平密切相关,相关系数为0.943。分次施氮的效果表明,植株吸氮高峰集中在拔节期至孕穗期,土壤氮累积在基肥施后迅速增加,渗漏水含氮量的高峰集中在每次施肥后的小段时间内,特别是基肥施后达到其最大值。这说明通常施用占总施氮量50%以上的稻田基肥可能是引起土壤氮累积、流失和地下水污染的重要原因,应宜减少。

Effect of Different Nitrogen Application Levels on Nitrogen Utilization of Paddy Field System and Environment Impact Under Two Soils

The paper studied the nitrogen dynamic in rice-soil-leakage water system under different N application levels based on split supply in paddy rice field. The result showed that N uptake of rice increased quickly with the N application up to (225) kg/hm~2, and N uptake amount changed little when the applied nitrogen were more than 225 kg/hm~2. Nitrogen accumulation dynamic in soil showed that the long-term fertility for rice crop growth could not be sustained under 75 kg/hm~2 N application, but when N supply exceeded 225 kg/hm~2, a lot of surplus nitrogen was accumulated in soil. There was significant correlation between nitrogen applied levels with average total N concentration of the leakage water andcoefficient is 0.943. The period of booting stage to grain-filling stage is an important time for rice nitrogen uptake. N accumulation in soil increased quickly and the peak of N content in leakage water appeared after basal nitrogen applied, which implied that basal nitrogen fertilizer being more than 50% of the total applied amount may be the main reason leading to soil nitrogen accumulation and water pollution.