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United States Department of Agriculture

Agricultural Research Service

Research Project: REDUCING NITRATE LOSSES FROM AGRICULTURAL FIELDS WITH SUBSURFACE DRAINAGE Project Number: 3625-12130-005-00
Project Type: Appropriated

Start Date: Dec 22, 2006
End Date: Sep 30, 2009

Objective:
1. Evaluate the impact of water table management on nitrate losses and crop yield in subsurface drained agricultural fields. (Contributes to Problem Area #3, Drainage Water Management Systems, Products #1 and #4 of the NP 201 Action Plan.) a. Measure the changes in NO3 concentration and load leaving a water table managed field and the fate of the water and N retained within the field, including their impact on crop yields. b. Quantify a partial N balance for a water table management system to determine if the system is accumulating or losing N. c. Examine the relationship between organic N compounds and crop N uptake in soils subjected to water table management. d. Refine and use agricultural systems models to predict the impact of water table management on crop yield, hydrology, and water quality in tile-drained fields for the different climate and soil conditions in the Midwest Corn Belt. 2. Compare the effectiveness of two small grain winter cover crop systems and in-field wood-chip bioreactors in reducing nitrate losses to subsurface drainage systems in agricultural fields. (Contributes to Problem Area #6, Water Quality Protection Systems, Products #1 and #4 of the NP 201 Action Plan, and Objective 2b secondarily contributes to Problem Area #3, Drainage Water Management Systems, Product #1 of the NP 201 Action Plan.) a. Measure the change in NO3 concentration and load leaving plots with cover crops or in-field wood chip bioreactors and their impacts on crop yields. b. Quantify a partial N and water balance for a corn-soybean rotation with and without cover crops (associated with the subsurface drainage system) to determine how this practice reduces N leaching. c. Examine the relationship between organic N compounds and plant N uptake in soils with and without cover crops. d. Refine and use agricultural system models to predict the impact of cover crops on crop yield, hydrology, and water quality in tile-drained fields under the different climate and soil conditions in the Midwest Corn Belt.

Approach:
For objective one, a five-year field study at several sites will evaluate the effectiveness of water table management on nitrate losses and crop yield in subsurface drained agricultural fields. Essentially, the outlets for subsurface drains in corn-soybean production fields will be raised to within 0.30 m of the surface from harvest until March 15 each year, lowered to 1.2 m from March 15 to June 1, and then raised to 0.60 m from June 1 to harvest. Measurements will be taken of crop growth, N uptake, and yield; nitrate concentration and load in drainage water; N inputs and outputs; soil organic and inorganic N compounds; and percolation, drainage, and lateral flow. The agricultural systems model, Root Zone Water Quality Model, will be parameterized to account for the impact of water table management on crop yield, hydrology, and water quality in the tile-drained experimental field. The model will then be used to predict the impact of water table management under different management scenarios, locations, and climate variations. For objective two, a five year field study will compare the effectiveness of two small grain winter cover crop systems and in-field wood-chip bioreactors in reducing nitrate losses to subsurface drainage systems in agricultural fields. An oat and a rye small grain winter cover crop will be planted each in a subsurface drained corn-soybean field. Additionally, in other treatment plots trenches filled with wood chips will parallel subsurface drainage tiles, such that water moving to the tiles will pass through the wood chip trenches. Measurements will be taken of crop growth, N uptake, and yield; nitrate concentration and load in drainage water; N inputs and outputs; soil organic and inorganic N compounds; and percolation, drainage, and lateral flow. The agricultural systems model, Root Zone Water Quality Model, will be parameterized to account for the impact of cover crops on crop yield, hydrology, and water quality in the tile-drained experimental field. The model will then be used to predict the impact of oat and rye winter cover crops under different management scenarios, locations, and climate variations.

Last Modified: 9/22/2014
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