Soil nitrogen balance under wastewater management: field measurements and simulation results.
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.
Sophocleous
Marios
M
Kansas Geological Survey, University of Kansas, 1930 Constant Ave., Lawrence, KS 66047, USA. marios@kgs.ku.edu
Townsend
Margaret A
MA
Vocasek
Fred
F
Ma
Liwang
L
Kc
Ashok
A
D000383:Agriculture; D003198:Computer Simulation; D008956:Models, Chemical; D009584:Nitrogen / Q000032:analysis*; D012722:Sewage; D012987:Soil / Q000032:analysis*; D018505:Waste Management; D014874:Water Pollutants, Chemical / Q000032:analysis*
D012722:Sewage; D012987:Soil; D014874:Water Pollutants, Chemical; D009584:Nitrogen