海南花岗岩砖红壤^(15)N示踪尿素氮的去向

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

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2.696kg/(0.09m2)(300kg/hm2)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￣40cm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%。

Experiments were carried out with ^15N-urea tracer to study the behaviors of urea-N under the cultural conditions of water convolvulus in latosol from granite in Hainan. The utilization rate of nitrogen fertilizer by the water convolvulus was found to decrease with the increase of N application rate, ranging from 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 when the N fertilizer was applied at a rate of 2.696 g/0.09 mE （300 kg/hm^2）. 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 % on average. More than 80 % of the residual N was distributed in the soil layers of 0-40 cm. The main form of the soil residual N was ammonium nitrogen. The nitrogen 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）.