冀南地区农田氮磷流失模拟降雨试验研究

农田氮磷养分流失是我国农业面源污染的主要污染源,为了研究冀南地区农田氮磷流失特征,本文采用人工模拟降雨大田试验的方法,测定施肥前后裸地农田地表径流与壤中流氮磷流失量,分析径流中不同形态氮磷的流失规律。结果表明:地表径流与壤中流的产流存在明显差异,地表径流产流过程波动明显,壤中流流量变化较为平缓并具有一定的滞后性,且在总径流量中的比例较小,两次试验分别占9.0%与13.1%;径流中氮素浓度在产流初期较高,随后迅速衰减,产流后0～35 min是累积氮流失量较快的时段;产流中可溶性氮的输出以硝氮为主,占累积流失量的71.0%～99.7%,且硝氮的流失极易受水文因素的影响;磷元素在径流中的含量较低,多以颗粒态存在,并且随着产流时间的延长,壤中流逐渐成为磷流失的主要途径;累积产流量与累积氮、磷流失量之间可分别用线性拟合与幂函数拟合,拟合优度分别在0.99与0.97以上,存在显著相关关系。研究结果表明,冀南地区农田在降雨之后氮磷流失量巨大且呈现一定规律性,适宜氮肥施用量与控制产流前期养分流失是防控当地农业非点源污染的有效途径。

Experimental study of simulated rainfall on nitrogen and phosphorus loss from farmland in Southern Hebei Province, China

Nitrogen and phosphorus nutrient loss in farmland is the major pollution source for agricultural non-point source pollution in China. A field experiment using artificial simulated rainfall was carried out to study the characteristics of nitrogen and phosphorus loss through surface runoff and interflow in farmland in southern Hebei Province. The results showed that, there was a remarkable difference between characteristics of surface runoff and interflow. The process of surface runoff fluctuated noticeably. The interflow changed more subtly and with a certain hysteresis, and its proportion of the total runoff was smaller, accounting for 9.0% and 13.1% in the two tests that were conducted. The concentration of nitrogen in the runoff was higher in the early stage of runoff production and then decayed rapidly. The first 35 min after runoff generation was the period of most rapid loss of accumulated nitrogen. The output of soluble nitrogen in the runoff was primarily nitrate nitrogen, accounting for 71.0% to 99.7% of the cumulative loss, and the loss of nitrate nitrogen was highly susceptible to hydrological factors. The content of phosphorus in the runoff was lower, mostly in the form of particles in the soil, and with the extension of runoff time, interflow gradually became the primary means of phosphorus loss. There is a significant correlation between cumulative runoff and cumulative loss of nitrogen and phosphorus, which can be fitted by linear fitting and power function, respectively, and the goodness of fit was above 0.99 and 0.97, respectively. The results show that the loss of nitrogen and phosphorus after rainfall in farmland in southern Hebei is huge and show a certain regularity. An effective way to prevent and control local agricultural non-point source pollution is therefore by suitable application of nitrogen fertilizer and controlling nutrient loss in the early stage of runoff generation.