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Title: Best Nitrogen Management Practices Can Reduce the Potential Flux of Nitrogen Out of the Arkansas Delta

Author
item SHUMWAY, CAL - Arkansas State University
item Delgado, Jorge
item BUNCH, THEODIS - Natural Resources Conservation Service (NRCS, USDA)
item HANSEN, LEROY - Economic Research Serivce (ERS, USDA)
item RUBAUDO, MARC - Economic Research Serivce (ERS, USDA)

Submitted to: Soil Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/1/2011
Publication Date: 3/12/2012
Citation: Shumway, C., Delgado, J.A., Bunch, T., Hansen, L., Rubaudo, M. 2012. Best Nitrogen Management Practices Can Reduce the Potential Flux of Nitrogen Out of the Arkansas Delta. Soil Science. 177:198-209.

Interpretive Summary: This study demonstrated that the NLEAP-GIS 4.2 NTT model is capable of assessing different cropping systems during different years and simulating the effects of management on residual soil nitrate accurately in the Arkansas Mississippi Delta region. The evaluations show that there is a need to account for high initial residual nitrate in the soil. The results also show that there is potential to use soybeans and cotton to lower the nitrate leaching potential caused by lower residual soil nitrate after harvest and/or lower nitrate leaching potential during the growing season. The addition of cotton and/or soybean into the rotation can potentially reduce the flux of nitrogen out of these systems if they are incorporated into a corn rotation. Due to the aforementioned environmental concern of nitrogen from this region being transported to the Gulf of Mexico, there is a great need to cut down on this flux of nitrogen starting at the field level, and to increase nitrogen use efficiencies. We recommend other practices such as the use of cover crops in addition to the cotton and soybean rotation. Cover crops can be planted after corn, where, without cover crops, nitrate can leave the soil after harvest, or after cotton to keep the soil cover. The NTT evaluations show that by implementing BMPs, reductions in nitrogen losses can be achieved in the Arkansas Delta. Improving BMPs in this watershed could help decrease direct and indirect emissions of N2O.

Technical Abstract: It has been reported that nitrogen losses in the Arkansas Delta can contribute to the flux of nitrogen into the Mississippi River Basin, which can in turn contribute to the nitrate load that the hypoxia problem in the Gulf of Mexico has been attributed to. Developing effective methods of reducing these nitrogen losses requires the development and validation of robust, new assessment tools that can be used to quickly evaluate management practices and their effects on the environment in terms of potential nitrogen losses and other factors. The recently developed concept of trading nitrogen in air and water quality markets can be used in conjunction with field studies to assess the potential benefits of nitrogen management. Field studies were conducted in 2008 and 2009 to collect data to test the new NLEAP and its ability to simulate nitrate dynamics for different cropping systems grown in three different locations in the Arkansas Delta. Simulation by the NLEAP conducted for cotton, soybean and corn grown in the Arkansas Delta showed that the model was able to accurately simulate the effects of management on residual soil nitrate (P < 0.01). The simulation showed that the residual nitrate can range from about 10 to 240 kg NO3-N ha-1 in the top 1.5 m of soil, in agreement with measured values. Additionally, long-term NLEAP analysis showed that rotations of soybeans into corn systems significantly reduced emissions of N2O across this region and reduced NO3-N leaching losses at the field level.