宁夏引黄灌区稻田氮磷流失特征初探

在宁夏引黄灌区选择相对封闭灌排体系作为试验监测区,通过2年在作物灌溉期间对试验监测区的灌排水中氮磷的跟踪监测,研究了该区域氮、磷流失,分析了支渠灌溉水、支沟排水中的氮磷动态变化规律。研究表明：2006年种稻区的氮磷流失明显高于2007年的稻旱区,稻区氮的流失负荷15.2kg·hm-2,磷的流失负荷6.9kg·hm-2;稻区比稻旱区氮磷流失严重,稻区总氮变幅在0.32～8.22mg·L-1,总磷变幅在0.012～0.921mg·L-1,均超过水体富营养化指标;稻区支沟排水中氮磷组分变化与稻旱区一致,氮都是以硝态氮为主,磷以溶解性总磷和颗粒磷为主,支沟排水中的硝态氮动态变化与总氮变化一致,颗粒磷与总磷动态变化一致,均为前期颗粒磷含量较高,中后期较低,可溶性总磷与之相反;灌溉前期支沟排水中氮磷流失严重的几个时期,均是在各种作物施肥7～10d后,尤其氮、硝态氮流失严重,后期支沟排水中氮磷流失是由于传统的不合理的灌溉形成的地表径流,将灌溉水养分含量迁移到排水中,造成支沟排水氮磷流失加重。结合宁夏引黄灌区的自然条件、耕作方式等因素,综合分析了宁夏引黄灌区在作物灌溉期间非点源污染产生过程及污染特点,为该地区非点源污染管理和控制提供科学依据。

Preliminary study on nitrogen and phosphorus loss in Yellow River irrigated paddy field of Ningxia

A relatively closed Yellow River irrigation-drainage system of Ning Xia area was chosen as an experimental monitoring pilot.The nitrogen and phosphorus in irrigation water and drainage water were separately tracked and monitored from 2006 to 2007. Having study on nitrogen and phosphorus loss in this specific area,and analysis N,P dynamic change in both irrigation and drainage water of branch canals. The study shows that：N,P loss in rice areas（IRA）of 2006 was obviously higher than dry-rice area（IDRA）of 2007.The load of nitrogen and phosphorus were 15.2 and 6.9 kg·hm-2,respectively in IRA;N,P loss in IRA was much more severely than IDRA.Total-N（TN）and Total-P（TP）content in IRA,which both surpassed the eutrophication risk index,were ranged from 0.32 to 8.22 mg·L-1 and 0.012～0.921 mg·L-1respectively;N,P components change in IRA branch canals drainage was the same as IDRA.In IRA,nitrogen was mainly based on Nitrate-N,while phosphorous based on dissolved TP and particulate P;Nitrate-N dynamic change in branch drainage was in line with TN.And particulate-P dynamic change was consistent with TP,among that particulate-P content showed higher in the beginning,while lower in mid and late term.However,soluble TP was contrary with particulate P;At the begging of branch drainage,N and P serious loss periods were all in 7～10 days after fertilization,especially nitrate-N loss significantly.Yet,N,P loss in the ending was due to unreasonable irrigation runoff,which moved N,P nutrient into drainage water and caused N,P loss much more seriously. The paper considered Ning Xia Yellow River irrigated areas’natural terms,farming patterns and etc factors,and analyzed non-point source pollution emerge,development procedure and characteristics,for providing a scientific basis of non-point source pollution management measures in Ning Xia Yellow River irrigation areas.