太湖地区水稻追肥的氨挥发损失和氮素平衡

采用密闭室通气法和¹⁵N 微区试验, 对太湖地区水稻不同生育期追施氮肥的氨挥发损失、水稻对氮肥的吸收利用和土壤氮素残留情况进行了研究。结果表明, 氨挥发损失主要发生在施肥后1 周内, 峰值出现在施肥后1~2 d, 氨挥发速率变化与田面水NH₄⁺-N 浓度变化规律一致, 分蘖肥和穗肥氨挥发损失率分别为16.7%和6.3%; 水稻分蘖肥的作物氮素利用率低于穗肥, 分别为36.7%和49.6%, 主要原因是穗肥的氨挥发损失较少,并且更易于向籽粒转移; 2 次追施氮肥的表观损失率分别为52.8%和40.7%; 在土壤中残留肥料氮为10.6%, 大都集中在0~20 cm 土壤中, 耕层以下较少。本结果表明, 在水稻孕穗时期施氮肥有利于提高氮肥利用效率、减少氮肥损失, 主要体现在穗肥拥有较低的氨挥发损失率和较高的籽粒利用率。

Ammonia volatilization and nitrogen balance after topdressing fertilization in paddy fields of Taihu Lake region

Ammonia volatilization, N fertilizer fate and soil residual nitrogen at different rice growth stages were investigated via continuous air-flow enclosure method and field ¹⁵N micro-plot experiment in gley paddy soils in Taihu Lake region. Results showed that ammonia volatilization occurred within one week and peaked in 1~2 days after fertilization. The rate of ammonia volatilization changed with NH₄⁺-N concentration in surface water. Ammonia volatilization loss from surface water respectively accounted for 16.7% and 6.3% of fertilizers applied at tillering and booting stages. Nitrogen use efficiency of rice plant was 36.7% and 49.6% of applied fertilizers at tillering and booting stages, respectively. This was mainly due to less ammonia volatilization after booting fertilization, which was more readily transferred to grains. In the two topdressing fertilization, apparent rate of nitrogen loss were 52.8% and 40.7% of applied N fertilizer respectively. About 10.6% of applied N fertilizer remained in the soil, which was mostly concentrated in the 0~20 cm soil layer. This showed that fertilization in booting stage could improve N use efficiency and reduce N loss. This was because of low ammonia volatilization loss and high utilization of fertilizers by grain of panicles during this period.