Water Quality in Walnut Creek Watershed: Nitrate‐Nitrogen in Soils, Subsurface Drainage Water, and Shallow Groundwater

作者：Cindy A. Cambardella, Tom B. Moorman, Dan B. Jaynes, Jerry Lee Hatfield, Tim B. Parkin, William W. Simpkins, Douglas L. Karlen · 发表于：Journal of Environmental Quality · 年份：1999 · DOI：10.2134/jeq1999.00472425002800010003x · 被引用次数：193 · 研究领域：Soil and Water Nutrient Dynamics、Hydrology and Watershed Management Studies、Groundwater and Isotope Geochemistry

Abstract Nonpoint source contamination of surface and groundwater resources with nitrate‐N (NO3‐N) has been linked to agriculture across the midwestern USA. A 4‐yr study was conducted to assess the extent of NO3‐N leaching in a central Iowa field. Water flow rate was monitored continuously and data were stored on an internal datalogger. Water samples for chemical analysis were collected weekly provided there was sufficient flow. Twelve soil cores were collected in spring, early summer, mid‐summer, and after harvest for each of the 4 yr. Nitrate‐N concentrations in shallow groundwater exhibited temporal trends and were higher under Clarion soil than under Okoboji or Canisteo soil. Denitrification rates were two times higher in Okoboji surface soil than in Clarion surface soil and the highest denitrificafion potential among subsurface sediments was observed for deep unoxidized loess. Soil profile NO3‐N concentrations decreased with depth and were the same below 30 cm for fertilized corn (Zea mays L.) and soybean (Glycine max L. Merr.). Nitrate‐N concentrations in subsurface drainage water exceeded 10 mg L−1 for 12 mo and were between 6 and 9 mg L−1 for 32 mo during the 4‐yr study. The temporal pattern of NO3‐N concentrations in subsurface drainage water was not related to the timing of fertilizer N application or the amount of fertilizer N applied. Total NO3‐N losses to subsurface drains were greatest in 1993 (51.3 kg ha−1) and least in 1994 (4.9 kg ha−1). Most of the subsurfac...