紫色土区坡耕地玉米季地表径流及其氮素流失特征

研究川中丘陵紫色土区坡耕地玉米全生育期地表径流及其氮素流失特征,以期为坡耕地氮素流失预测和有效防控提供理论依据。采用人工模拟降雨与微小区(1 m×2 m)相结合的方法,降雨强度设置为1.0,1.5,2.0mm/min,分别在玉米苗期、拔节期、抽雄期和成熟期进行人工模拟降雨。结果表明:玉米全生育期地表径流量及其氮素流失量随降雨强度的增加而增加。不同降雨条件下,玉米全生育期地表径流总量表现为苗期显著高于其它生育期。玉米拔节期地表径流中氮素平均流失浓度高达16.36mg/L;地表径流中氮素平均流失量在玉米苗期最高,为10.24mg/m~2,而抽雄期仅为2.97mg/m~2。玉米苗期地表径流中铵态氮流失量最大,成熟期地表径流中硝态氮流失量最大,抽雄期硝态氮和铵态氮流失量均最小;玉米全生育期地表径流中硝态氮为氮素流失的主要形态,占总氮的77.98%~97.85%。玉米拔节期氮素流失浓度最高,而苗期为氮素输出负荷量最大,苗期和拔节期地表径流中氮素流失易造成地表水体富营养化,可通过控制基肥、追肥的施入量和增加地表覆盖度减少氮素流失。

Characteristics of Runoff and Nitrogen Loss in Sloping Cropland of Purple Soil during Corn Growing Season

The characteristics of runoff and nitrogen loss in sloping cropland of purple soil during corn growth stages were carried out to provide a theoretical basis for the prediction and effective prevent of nitrogen loss in sloping cropland. Simulated rainfall combined with runoff plot experiments (1 m×2 m) was employed during each corn growth stage, including seedling stage, elongation stage, tasseling stage and maturity stage. The rainfall intensities were set as 1.0 mm/min, 1.5 mm/min and 2.0 mm/min. The results indicated that the runoff in soil surface and nitrogen loss increased with the increasing rainfall intensity during corn growth stages. Total runoff in the seedling stage was significantly higher than that in other growth stages. The average concentration of nitrogen loss in the elongation stage was up to 16.36 mg/L. The average amounts of nitrogen loss obtained the maximum value of 10.24 mg/m2 at the seedling stage, and the minimum value of 2.97 mg/m2 at the tasseling stage. For the nitrogen forms, ammonium nitrogen and nitratenitrogen accounted the greatest part of nitrogen loss at seedling stage and maturity stage of corn, respectively, and the loss of ammonium nitrogen and nitratenitrogen was the least at the tasseling stage of corn. During the whole growth stages of corn, nitratenitrogen was the main nitrogen form in the runoff of surface soil and accounted 77.98%~97.85% of the total nitrogen loss. The concentration of nitrogen loss was the highest in the elongation stage, and the nitrogen loss amount was the greatest in the elongation stage of corn. Nitrogen loss in the seeding and elongation stage of corn could easily lead to the eutrophication in waters. Thus, it was necessary to cut the application of base fertilizer and top dressing of nitrogen, and increase vegetation cover to reduce nitrogen loss in runoff.