洱海北部地区不同轮作农田氮、磷流失特性研究

Characteristics of nitrogen and phosphorus loss in various crop rotation systems in northern watershed of Erhai Lake

为明确洱海北部地区不同轮作模式下农田氮、磷流失特性,客观评价环境污染风险。试验在洱海北部地区沿弥苴河和罗时江流域的7个乡镇进行。采用定点取样与实地调研相结合的方法进行多点重复监测,调查不同轮作模式、轮作周期内田面水和沟渠水的氮、磷含量变化情况,研究不同轮作模式下氮、磷污染的负荷及其影响因素。结果表明,田面水中,不同轮作模式下氮素的流失差异显著且以水溶态为主,可溶性氮浓度以大蒜-水稻模式最高,油菜-水稻模式最低,其它轮作模式居中分布;降雨径流氮流失量以大蒜-水稻模式最高。磷素流失总量偏低,且以泥沙结合态为主,轮作模式间无显著差异。田面水质劣于沟渠水,田面水对沟渠水存在不同程度增荷作用;农田水对沟渠水总氮和总磷的增荷率分别为73%和82%,其中追肥是导致农田水对沟渠水增荷的关键因素。本研究中,大蒜-水稻是洱海流域农田氮、磷流失风险最高的种植模式;蚕豆-水稻比大蒜-水稻模式减少氮素流失风险38%。因此,应综合考虑环境效益和经济效益,合理安排种植结构,为洱海流域种植结构调整、控制农田面源污染提供参考。

Nitrogen and phosphorus losses of surface runoff in various crop rotation systems in north of lake Erhai watershed were researched for the risk evaluation and putting countermeasures for the nonpoint pollution from agricultural source.Pollution loads of nitrogen and phosphorus were studied in four typical crop rotation systems by using the influencing factors,by analyzing the content variation dynamic of nitrogen and phosphorus in surface water of farmland and ditch water in 7 townships of northern lake Erhai watershed.The results show that the water soluble nitrogen is main loss of runoff water,and the contents of nitrogen have significantly contrast in farmland surface water of different crop rotation systems.The contents in garlic-rice mode are significantly higher than those of the other rotation systems,and the basic trend is： garlic-rice higher than ryegrass-rice,ryegrass-rice higher than fava bean-rice,and fava bean-rice higher than rape-rice.However,the contents of phosphorus in farmland surface water are lower systems,and have no significant differences under various crop rotation.The particulate phosphorus is main loss of runoff.Generally,the contents of nitrogen and phosphorus in surface water are higher than those in the ditch water,respectively.The content of total nitrogen in surface water is higher than that of ditch water（about 73% increase）,and the content of total phosphorus in surface water is higher than that of ditch water（about 82% increase） in this study.Fertilization in the crop growth period is one of mainly reason for the high concentrations of nitrogen and phosphorus in surface water.In this study,the loss amount of nitrogen in the garlic-rice system is the highest,the loss amount of nitrogen under the vicia faba-rice system is reduced by 38% compared with that of the garlic-rice system.So,we suggest that reasonable cropping system could be established on the basis of considering the environmental and economic benefits,and it will provide some references on readjusting cropping system and controlling nonpoint pollution.