尿素在潮土中淋溶和转化特征研究

LEACHING AND TRANSFORMATION OF UREA IN FLUVO-AQUIC SOILS

采用不同灌溉水量和施N量,研究了尿素在潮土中的淋溶和转化特征。结果表明,在小麦返青期结合灌溉施尿素后,NH4+-N在40cm以上土层中积累,不会产生深层淋溶。而土层中NO3--N含量有较大变化,相同灌溉水量下,施N量越大,NO3--N向下层淋溶越深;相同施N量下,灌溉水量越大,NO3--N也有淋溶越深的趋势。在麦季,即使在超过当地的施N量(N180kg/hm2)和灌溉水量(750m3/hm2)条件下,收获时所有处理的NO3--N主要积累在130cm以上的土层中,NO3--N淋溶深度不超过130cm,不会产生对地下水的污染。

A field plot experiment was conducted and rate were main factors affecting leaching and transformation showed that water irrigation rate and nitrogen application of urea in fluvo-aquic soil. It was easily transformed into NH4^＋-N and NO3^--N when urea was applied into the soil at turning-green stage of winter wheat treated with irrigation. NH4^＋-N accumulated only in 0 - 40 cm layer and did not go down with leaching into deeper layers. However, NO3^--N concentration varied sharply in the soil profile. When the irrigation rates were the same, the more N was applied, the deeper NO3--N went down in the profile, and when the N application rates were the same, the higher the irrigation rate was, the deeper NO3--N was leached down in the profile. Even though the irrigation and nitrogen application exceeded the usual rate （750 m^3/hm^2and N 180 kg/hm^2, respectively）, NO3^--N accumulated in the soil layer 0 - 130 cm, and never went down beyond 130 cm in all treatments when the crop was ready for harvest. So during the wheat growing season N application will not contaminated the underground water.