Using SWAT-MEA to determine optimal placement of crop management systems under no-till

Authors: CRAM, ANA - University Of Texas - El Paso; Moriasi, Daniel; Verser, Jerry - Alan; TABOADA, HEIDI - University Of Texas - El Paso; ESPIRITU, JOSE - University Of Texas - El Paso

Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/17/2021
Publication Date: 2/28/2022
Citation: Cram, A.C., Moriasi, D.N., Verser, J.A., Taboada, H., Espiritu, J. 2022. Using SWAT-MEA to determine optimal placement of crop management systems under no-till. Agronomy Journal. 114:1115-1127. https://doi.org/10.1002/agj2.20996.
DOI: https://doi.org/10.1002/agj2.20996

Interpretive Summary: Research has commonly reported benefits of no-till including reducing soil erosion. However, as farmers adopt the recommended no-till farming system there is a need for knowledge on how to best use cropland within the Fort Cobb Reservoir watershed (FCREW) in order to minimize environmental impacts on soil and water quality resources while maximizing crop yields. We used the Management Optimization Tool for Soil and Water Assessment Tool (SWAT-MOT) to determine optimal spatial placement of soybeans, winter wheat, grain sorghum, upland cotton, and peanuts cropping systems under no-till. This involved identifying optimal coverage area and application locations for each of these cropping systems to minimize nitrogen, phosphorus, and sediments while maximizing crop yields. Some modifications were made to enable application of the SWAT-MOT in the FCREW and the tool was able to identify optimal placement of the cropping systems. Results showed that under optimal placement, converting to no-till reduced nitrogen, phosphorus, and sediments by 45%, 32%, and 65%, respectively, while maintaining yields. Overall, the modified SWAT-MOT has potential for use as a tool to determining optimal placement of multiple cropping systems to minimize environmental impacts while maintaining crop yields. These results contribute to the goals of the Conservation Effects Assessment Project (CEAP) and Long-Term Agroecosystem Research (LTAR) network USDA initiatives.

Technical Abstract: No-till is one of the common conservation practices implemented in the Fort Cobb Reservoir watershed (FCREW) located in central Oklahoma to improve soil and water resources while ensuring sustainable crop production. In this study, we used the recently developed Management Optimization Tool for the Soil and Water Assessment Tool model (SWAT-MOT) to determine the optimal spatial placement of cropping systems when converting from conventional tillage to no-till in the FCREW. A previously calibrated and validated SWAT model for the FCREW for conventionally tilled land under winter wheat, sorghum, and peanuts cropping system was used. The objective functions for this study were maximizing crop yield ranks while minimizing sediment, total phosphorus (TP), and total nitrogen (TN) yield loads. Four modifications made in the SWAT-MOT in order to achieve the defined goal of this study include an automated process of conversion from conventional to no-till, ability to use crop yield ranks in the optimization process and to sum up species of N and P to TN and TP, and creation of a public domain standalone executable. Results indicated that converting from conventionally tilled to no-till system under optimal placement of crop management systems reduced TN, TP, and sediment yield rates by 45%, 32%, and 65%, respectively, while crop yields were in the same order of magnitude. Overall, this case study shows that the SWAT-MOT was able to successfully identify optimal placement of crop management systems under no-till system and can be used for decision-making.