Nitrate and chloride loading to groundwater from an irrigated north-central U.S. sand-plain vegatable field.
Groundwater pollution and associated effects on drinking water have increased with the expansion of irrigated agriculture in north-central U.S. sand plains. Controlling this pollution requires an ability to measure and predict pollutant loading by specific agricultural systems. We measured NO3 and Cl loading to groundwater beneath a Wisconsin central sand plain irrigated vegetable field using both a budget method and a new monitoring-based method. By relying on frequent monitoring of shallow groundwater, the new method overcomes some limitations of other methods. Monitoring-based and budget methods agreed well, and indicated that loading to groundwater was 165 kg ha(-1) NO3-N and 111 kg ha(-1) Cl for sweet corn (Zea mays L.) in 1992, and 228 kg ha(-1) NO3-N and 366 kg ha(-1) Cl for potato (Solanum tuberosum L.) in 1993. Nitrate N loading was 56 to 60% of available N, or 66 to 70% of fertilizer N. Sweet corn NO3 loading was about typical for this region, but potato NO3 loading was probably 50% greater than typical because heavy rains provoked extra fertilizer application. Our results imply that typical NO3-N loading would be 119 kg ha(-1) for sweet corn and 203 kg ha(-1) for potato, even with strict adherence to University Extension fertilizer recommendations. To keep average groundwater NO3-N within the 10 mg L(-1) U.S. drinking water standard, each irrigated vegetable field would need to be offset by five to eight times as much land supplying NO3-free groundwater recharge.
Stites
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W
Central Wisconsin Groundwater Center, Univ of Wisconsin, Stevens Point 54481, USA. wstites@coredcs.com
Kraft
G J
GJ
D000383:Agriculture; D002712:Chlorides / Q000032:analysis*; D005308:Fertilizers; D005544:Forecasting; D008962:Models, Theoretical; D009566:Nitrates / Q000032:analysis*; D011891:Rain; D012989:Soil Pollutants / Q000032:analysis*; D014675:Vegetables; D014872:Water Movements; D014873:Water Pollutants / Q000032:analysis*; D014881:Water Supply
D002712:Chlorides; D005308:Fertilizers; D009566:Nitrates; D012989:Soil Pollutants; D014873:Water Pollutants