海南花岗岩砖红壤15N示踪尿素氮的去向

应用^15N示踪技术,研究海南花岗岩砖红壤蕹菜栽培条件下尿素氮的去向.结果表明：在该试验条件下,蕹菜吸收尿素氮的比例随着施氮量的增加而减少,吸收率在22.50%～43.84%之间,平均吸收率为33.32%,施氮量为2.696 kg/（0.09m^2）（300kg/hm^2）时,蕹菜的产量、干重和氮肥利用率最佳;土壤残留量随着施氮量的增加而增加,残留率在24.25%～47.28%之间,平均残留率为32.68%,残留在土壤中的肥料氮80%以上都分布在0～40 cm土层中,无机氮主要是NH4^＋-N,施氮量越大,在40cm以下土层中残留尿素氮所占的比例越大;尿素氮的损失率在30.22%～39.55%之间,平均损失率为34%,其中挥发损失率在0.78%～28.10%之间,平均挥发损失率为19.11%.

Study on the Behaviors of Urea-N in Latosol from Granite in Hainan with Isotope 15N

Experiments were carried out with 15N-urea tracer to study the behavior s of urea-N under the cultural conditions of water convolvulus in latosol from g ranite in Hainan. The utilization rate of nitrogen fertilizer by the water convo lvulus was found to decrease with the increase of N application rate, ranging fr om 22.5 % to 43.84 %, being 33.32 % on average. The yield and the dry weight of water convolvulus and the utilization rate of nitrogen fertilizer were optimum w hen the N fertilizer was applied at a rate of 2.696 g/0.09 m2 (300 kg/hm2). The residual N in the soil increased with the application rate of the N fertilizer. The soil residual N rates were found to range from 24.25 % to 47.28 %, 32.68 % o n average. More than 80 % of the residual N was distributed in the soil layers o f 0~40 cm. The main form of the soil residual N was ammonium nitrogen. The nitro gen losses of fertilizer N were in the range of 30 %~40 % (34 % on average). The losses mainly resulted from ammonia volatilization, within the range of 0.72 %~ 28.1 % (19.11 % on average).