Sophocleous Marios, Townsend Margaret A, Vocasek Fred, Ma Liwang, Kc Ashok
Kansas Geological Survey, University of Kansas, 1930 Constant Ave., Lawrence, KS 66047, USA.
J Environ Qual. 2009 Apr 27;38(3):1286-301. doi: 10.2134/jeq2008.0318. Print 2009 May-Jun.
The use of treated wastewater for irrigation of crops could result in high nitrate-nitrogen (NO(3)-N) concentrations in the vadose zone and ground water. The goal of this 2-yr field-monitoring study in the deep silty clay loam soils south of Dodge City, Kansas, was to assess how and under what circumstances N from the secondary-treated, wastewater-irrigated corn reached the deep (20-45 m) water table of the underlying High Plains aquifer and what could be done to minimize this problem. We collected 15.2-m-deep soil cores for characterization of physical and chemical properties; installed neutron probe access tubes to measure soil-water content and suction lysimeters to sample soil water periodically; sampled monitoring, irrigation, and domestic wells in the area; and obtained climatic, crop, irrigation, and N application rate records for two wastewater-irrigated study sites. These data and additional information were used to run the Root Zone Water Quality Model to identify key parameters and processes that influence N losses in the study area. We demonstrated that NO(3)-N transport processes result in significant accumulations of N in the vadose zone and that NO(3)-N in the underlying ground water is increasing with time. Root Zone Water Quality Model simulations for two wastewater-irrigated study sites indicated that reducing levels of corn N fertilization by more than half to 170 kg ha(-1) substantially increases N-use efficiency and achieves near-maximum crop yield. Combining such measures with a crop rotation that includes alfalfa should further reduce the accumulation and downward movement of NO(3)-N in the soil profile.
使用经处理的废水灌溉农作物可能会导致包气带和地下水中的硝酸盐氮(NO₃-N)浓度升高。在堪萨斯州道奇城以南深厚粉质粘壤土上进行的这项为期两年的田间监测研究,目的是评估二级处理后的废水灌溉玉米中的氮如何以及在何种情况下到达下方高平原含水层的深层(20 - 45米)地下水位,以及如何采取措施将这个问题最小化。我们采集了15.2米深的土壤岩心以表征物理和化学性质;安装了中子探针进样管来测量土壤含水量,并安装了负压测渗仪定期采集土壤水样本;对该地区的监测井、灌溉井和生活井进行采样;并获取了两个废水灌溉研究地点的气候、作物、灌溉和施氮量记录。利用这些数据和其他信息运行根区水质模型,以确定影响研究区域氮素流失的关键参数和过程。我们证明,NO₃-N迁移过程导致包气带中氮的大量积累,且下方地下水中的NO₃-N含量随时间增加。对两个废水灌溉研究地点的根区水质模型模拟表明,将玉米施氮量减半以上至170千克·公顷⁻¹,可大幅提高氮素利用效率并实现接近最大作物产量。将这些措施与包括苜蓿在内的作物轮作相结合,应能进一步减少土壤剖面中NO₃-N的积累和向下移动。