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United States Department of Agriculture

Agricultural Research Service

Title: Effects of Near-Surface Hydrologic Conditions on Nitrate and Phosphorus Losses in Surface Runoff

Authors
item Zheng, F - INST SOIL & WATER CONSV.
item Huang, Chi Hua
item Norton, Lloyd

Submitted to: Journal of Environmental Quality
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 2, 2002
Publication Date: January 1, 2004
Citation: Zheng, F., Huang, C., Norton, L.D. 2004. Effects of near-surface hydrologic conditions on nitrate and phosphorus losses in surface runoff. Journal of Environmental Quality. 33:2174-2182(2004).

Interpretive Summary: Excessive nutrients, i.e., phosphorous (P) and nitrate-nitrogen (N), in surface water bodies that accelerate eutrophication of lakes and streams and cause environmental concerns have been attributed to runoff from agricultural field. Extensive efforts have been devoted to determine conditions that cause P and N losses, including status of soil fertility, plant uptake, timing and formulation of fertilizers, and manures, etc. However, surface hydrologic condition that may significantly affect P/N movement on the landscape has not yet been quantified. A laboratory study was designed to evaluate the hydrologic effects on P and N losses in surface runoff from soil pans under simulated rainfall. Experimental variables included rates of fertilizer input and different near-surface hydrologic conditions: free drainage (FD), saturation (SA), and artesian seepage (SP). Results showed that total N losses from SA and SP conditions ranged 57 to 100 and 1082 to 1006 times greater for low and high fertilizer inputs, respectively, as compared to the FD condition. Similarly, dissolved P losses from SA and SP averaged 5 to 10 times greater than those from the FD condition. These results demonstrate that soil saturation and artesian seepage condition has a significant contribution to chemical transport. Efforts need to be focused on understanding landscape conditions and processes that trigger hillslope seepage. Our findings will impact those working on soil conservation and erosion control with a better understanding on how excessive moisture accelerates nutrient transport and the implementation of drainage schemes to mitigate this problem.

Technical Abstract: Phosphorous (P) and nitrate-nitrogen (N) in runoff from agricultural fields are key contributors to nonpoint-source pollution and can accelerate eutrophication of lakes and streams. Extensive efforts have been made to determine conditions that cause P and N losses. However, the effects of surface hydrologic condition that may contribute significant P/N movement on the landscape has not yet been quantified. A laboratory study was designed to evaluate the hydrologic effects on P and N losses in surface runoff from soil pans under simulated rainfall. Experimental variables included three rates of fertilizer input, i.e., control, low (P: 40, N: 100 kg ha-1) and high (P: 80, N: 200 kg ha-1), and three near-surface hydrologic conditions: free drainage (FD), saturation (SA), and artesian seepage (SP). Results showed that total N losses from SA and SP conditions ranged 57 to 100 and 1082 to 1006 times greater, respectively, as compared to the FD condition. Similarly, dissolved P losses from SA and SP averaged 5 to 10 times greater than those from the FD condition. Total nutrient loading, i.e., concentration times total runoff volume, showed the same magnitude difference among different hydrologic treatments. These results demonstrate that artesian seepage condition has a significant contribution to the water quality problem and efforts need to be focused on understanding landscape conditions and processes that trigger hillslope seepage and developing proper control strategies.

Last Modified: 10/22/2014
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