淮北平原区农田降雨径流氮磷流失特征

降雨径流是农田氮磷流失的重要载体和通道,研究排水过程中氮磷元素的流失规律对于优化农业管理和保护水生态环境具有重要意义。文章基于农田原位观测方法,开展自然降雨条件下淮北平原典型区域农田径流排水试验研究,解析农田降雨径流特征及不同用地类型的氮磷输出规律。结果表明:4次径流过程的径流强度变化整体上呈单峰增长趋势,且径流方法中改进的SCS-CN(soil conservation service curve number)模型能有效模拟当地农田降雨径流深;不同用地类型间氮磷输出质量浓度和输出形态差异明显,总氮(total nitrogen, TN)和总磷(total phosphorus, TP)流失质量浓度从大到小顺序为玉米地、花生地、果园地;氮的输出形态主要为无机氮,而磷的输出形态不统一,玉米地和花生地主要为颗粒态磷,果园地为溶解态磷;农田径流氮磷计量比处于适合藻类生长范围,且TN、TP质量浓度均值显著高于《地表水环境质量标准》V类水标准。

Rainfall runoff is an important carrier and channel for the loss of nitrogen and phosphorus in farmland. Studying the loss of nitrogen and phosphorus in the drainage process is of great significance to optimize agricultural management and protect the water ecological environment. Based on the in situ farmland observation method and the conditions of natural rainfall, tests on the farmland runoff drainage in a typical area of the Huaibei Plain were conducted to analyze the characteristics of farmland rainfall runoff and the output of nitrogen and phosphorus of different types of land. The results show that the runoff intensity of the four runoff processes exhibits a single-peak growth trend as a whole, and the improved soil conservation service curve number (SCS-CN) model can effectively simulate the depth of the rainfall runoff in the local farmland. The differences between the output concentrations and output forms of the nitrogen and phosphorus of different types of land are obvious, and the concentrations of total nitrogen (TN) and total phosphorus (TP) loss decrease in the following order: corn field, peanut field, and orchard. The output form of nitrogen is mainly inorganic nitrogen, while the output form of phosphorus is not uniform. Particulate phosphorus (PP) is the main form in corn and peanut fields, whereas dissolved phosphorus (DP) is predominant in the orchard. The stoichiometric ratio of nitrogen and phosphorus is conducive to algae growth, and the average concentrations of the TN and TP are significantly higher than Class V water standards in Environmental Quality Standards for Surface Water.