蓄水多坑灌施下尿素在土壤中的运移转化特性

Transport and Transformation of Urea in Soil under Multiple-pit Irrigation

为提高蓄水多坑灌施尿素条件下土壤氮素利用率和保护生态环境,通过室内蓄水多坑(土箱半径40 cm,高120 cm,蓄水坑半径16 cm,深度60 cm)物理模型试验,研究了蓄水多坑灌施下尿素在土壤中的运移转化特性。结果表明,土壤水分主要分布在地表以下20~80 cm,0~10 cm土层土壤含水率较小,同一土壤深度处蓄水坑壁附近土壤含水率大于0通量面处土壤含水率;同一土壤深度蓄水坑壁附近土壤尿素态氮量大于0通量面处的尿素态氮量,尿素的水解在9 d内基本完成,第7天水解最快,尿素水解与时间存在良好的对数函数关系;土壤铵态氮主要集中在40~60 cm土层土壤中,且r=20 cm处的量高于0通量面处的;而土壤硝态氮的分布趋势与铵态氮相反,随时间的延长,0通量面和r=20 cm处的土壤铵态氮质量分数均在40~60 cm和60~80 cm增幅较大,而土壤硝态氮质量分数表现出在90~100 cm湿润锋处增幅最大。

In order to improve nitrogen use efficiency in multiple-pit-storage fertigation and protect ecological systems, we experimentally investigated the movement and transformation of urea in laboratory using six plexi- glass boxes filled with soils. The pits were placed at the four comer of each box, and the movement of water and urea from the pit to the soil was measured. The results showed that the water was found mainly in the depth of 20-80 cm and the soil in 0-10 cm depth was relatively dry. At the same depth, water content in the proximity of the pit was higher than that in soil outside the zero-flux plane. The urea distributed mainly in soil proximal the pit and water content in soil outside the zero-flux plane was much lower than that inside the plane. Urea hydrolysis was completed in nine days and its hydrolyzing rate peaked seven day after the irrigation commenced. The hydro- lysis rate decreased with time in a power law. The ammonia distributed mainly in 40-60 cm depth, and its concen- tration at 20 cm from the pit was higher than that in soil outside the zero-flux plane. The spatial distribution of ni- trate was opposite to that of ammonia. The ammonia showed a bigger increase in depths of 40-60 cm and 60-80 cm at 20 cm from the pits and zero flux plane, but the nitrate increased faster in 90-100 depth.