降雨对不同土地利用类型土壤水氮变化特征的影响

以2018年6—10月降雨条件下园地、林地、荒草地、坡耕地和裸地的标准径流小区为研究对象,裸地为对照,通过研究降雨对园地、林地、荒草地、坡耕地和裸地的土壤含水率、总氮、硝态氮和铵态氮含量与土层深度和时间的变化特征,经野外试验数据统计分析,提出降雨对园地、林地、荒草地、坡耕地和裸地土壤含水率、总氮、硝态氮和铵态氮含量与土层深度和时间变化特征的影响。结果表明:降雨增加园地、林地、荒草地、坡耕地和裸地土壤含水率,加速土壤总氮、硝态氮和铵态氮水解转化硝化和反硝化速度,影响土壤含水率、总氮、硝态氮和铵态氮含量,降雨与土壤含水率、总氮、硝态氮、铵态氮呈显著相关性(P0.05)。降雨条件下园地、林地、荒草地、坡耕地和裸地的土壤含水率随土层深度增大而增大,土层深度100 cm处土壤含水率最大,分别为30.34%,27.67%,24.98%,24.03%和21.95%,总氮随土层深度增大呈先增大后减小,在土层深度为60 cm土壤总氮含量最大,分别为1.02,0.99,0.90,0.86,0.75 g/kg,硝态氮和铵态氮含量随土层深度增大而减小,在土层深度为100 cm硝态氮和铵态氮含量均最小,其中硝态氮含量分别为9.01,7.89,7.25,6.10,5.22 mg/kg,铵态氮含量分别为9.41,9.14,6.40,5.38,4.37 mg/kg。土壤含水率随时间的延长先减小后增大又减小,呈正余弦变化趋势,8月土壤含水率最大,分别为22.97%,22.01%,19.87%,19.03%和17.98%,总氮随时间的延长先增大后减小,8月总氮最大,分别为1.09,1.01,0.94,0.84,0.76 g/kg,硝态氮和铵态氮含量随时间的延长而逐渐减少,6月硝态氮和铵态氮含量均最大,其中硝态氮含量分别为13.40,12.37,11.20,10.39,8.67 mg/kg,铵态氮含量分别为18.89,17.02,14.54,12.02,8.36 mg/kg。不同土地利用类型土壤含水率、总氮、硝态氮和铵态氮平均值与土层深度和时间关系由大到小依次为园地、林地、荒草地、坡耕地和裸地,研究结果为农田土壤水肥流失控制和养分利用提供理论技术支持。

Effects of Rainfall on Soil Water and Nitrogen Change Characteristics Under Different Land Uses

Under the rainfall from June to October, 2018, the standard runoff plots in garden land, forest land, grassland, farmland and bare land were taken as research object, with the bare land as the control. The soil moisture contents, total nitrogen, nitrate nitrogen and ammonium nitrogen contents in different soil depth and time were studied in garden land, forest land, grass land, farmland and bare land. Through statistical analysis of field test data, the effects of rainfall on soil water and nitrogen change characteristics under different land uses were proposed. The results showed that the rainfall increased soil moisture content in garden land, forest land, grassland, farmland and bare land and accelerated soil total nitrogen, nitrate nitrogen and ammonium nitrogen hydrolysis conversion of nitrification and denitrification rate, affected the soil moisture contents, total nitrogen, nitrate nitrogen and ammonium nitrogen contents. The rainfall had significant correlations (P<0.05) with soil moisture contents, total nitrogen, nitrate nitrogen, ammonium nitrogen. Under rainfall, soil moisture content increased with the soil depth in garden land, forest land, grassland, farmland and bare land. At soil depth of 100 cm, soil moisture content was the largest, which were 30.34%, 27.67%, 24.98%, 24.03% and 21.95%, respectively. Total nitrogen contents increased first and decreased then with the increasing soil depth, and at the soil depth of 60 cm, soil total nitrogen was the largest, which were 1.02, 0.99, 0.90, 0.86 and 0.75 g/kg, respectively. Nitrate nitrogen and ammonium nitrogen contents decreased with the increasing soil depth. The nitrate nitrogen and ammonium nitrogen contents at soil depth of 100 cm were the smallest, among which the nitrate nitrogen was 9.01, 7.89, 7.25, 6.10, 5.22 mg/kg, and the ammonium nitrogen was 9.41, 9.14, 6.40, 5.38, 4.37 mg/kg, respectively. With the time, soil moisture contents decreased first, then increased, and then decreased at last, showing a positively cosine changing trend. Soil moisture contents was the largest in August, which were 22.97%, 22.01%, 19.87%, 19.03% and 17.98% respectively. Total nitrogen first increased and then decreased with time, with the largest in August, which were 1.09, 1.01, 0.94, 0.84 and 0.76 g/kg, respectively. Nitrate nitrogen and ammonium nitrogen contents reduced gradually with time. Soil nitrate nitrogen and ammonium nitrogen contents were larger in June. Soil nitrate contents were 13.40, 12.37, 11.20, 10.39, 8.67 mg/kg, ammonium nitrogen 18.89, 17.02, 14.54, 12.02, 8.36 mg/kg, respectively. The relationships between average soil moisture contents, total nitrogen, nitrate nitrogen and ammonium nitrogen contents and soil depth and time in different land uses were following as:garden > woodland > grassland > sloping land > bare land. This study could provide theoretical and technical support for soil water and fertilizer loss control and nutrient utilization in farmland.