An integrated tool for cost-effectively applying nutrient management practices for corn, soybeans, and wheat

Authors: LIU, YAOZE - State University Of New York- College Of Environmental Science And Forestry; LI, SIYU - State University Of New York- College Of Environmental Science And Forestry; NGUYEN, ANH - State University Of New York- College Of Environmental Science And Forestry; ENGEL, BERNARD - Purdue University; CHEN, JINGQIU - Florida A & M University; Flanagan, Dennis; GUO, TIAN - Purdue University; LI, FAWEN - Tianjin University; REN, DONGYANG - China Agricultural University; LIU, CHENGXU - Purdue University

Submitted to: Science of the Total Environment
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/19/2024
Publication Date: 10/31/2024
Citation: Liu, Y., Li, S., Nguyen, A.H., Engel, B.A., Chen, J., Flanagan, D.C., Guo, T., Li, F., Ren, D., Liu, C. 2024. An integrated tool for cost-effectively applying nutrient management practices for corn, soybeans, and wheat. Science of the Total Environment. https://doi.org/10.1016/j.scitotenv.2024.177110.
DOI: https://doi.org/10.1016/j.scitotenv.2024.177110

Interpretive Summary: Surface runoff and sediment losses from farm fields can also carry pollutants such as nitrogen, phosphorus, and pesticides. In particular, losses of dissolved and sediment-bound phosphorus (P) from fertilizers or manures can be transported far off-site to distant rivers and lakes causing problems such as eutrophication and harmful algal blooms, that can produce toxins deadly to humans and other animals. This has recently been a large issue in Lake Erie, from runoff and pollutants entering it from the Maumee River. This region of the country (northwestern Ohio, southeastern Michigan, and northeastern Indiana) is also largely agricultural lands with high productivity. One of the ways to minimize losses of P and other nutrients is to use nutrient management, which evaluates existing soil levels of these chemicals and recommends the needed types and amounts of fertilizers, application method, time of application, and fertilizer placement that maximizes crop productivity and/or profit and minimizes potential losses and environmental impacts. In this research we developed a computer modeling tool that evaluates various land management practices, nutrient management strategies, and effects on potential pollutant losses and practice economics. The tool, called SWAT-COST-NM, was applied to a small watershed area in northeastern Indiana, where measured data on runoff and nutrient losses were available to validate baseline information, and various practice and nutrient management scenarios could be evaluated. We tested the baseline conditions and 25 alternative scenarios to simulate production of corn, soybeans, and winter wheat. Both single nutrient management practices and combined practices were evaluated, and we found that the best option to reduce potential P losses while slightly increasing profitability was a combined practice scenario that applied all P fertilizers at 20% below original rates and used all subsurface applications. This research impacts scientists, students, extension agents, conservation agency personnel, farmers, and others looking for tools to determine ways to reduce nutrient losses while maintaining profitability. This new computer simulation program is another tool now available to assist in planning ways to reduce loss of pollutants to off-site water bodies.

Technical Abstract: In recent years, the issue of harmful algal blooms (HABs) in the western basin of Lake Erie has become critical - primarily triggered by phosphorus losses from cropland in the Maumee River watershed (with major crops of corn, soybeans, and wheat). Implementing agricultural best management practices (BMPs) is crucial to reduce excess nutrient loadings. Nutrient management, a popular type of agricultural BMP, is the management of nutrient applications for crop production that maximizes nutrient use efficiencies and minimizes nutrient losses. However, an integrated tool is needed for cost-effectively applying nutrient management practices for corn, soybeans, and wheat considering the 4Rs (Right nutrient source, Right rate, Right time, and Right place of nutrient applications) at the watershed scale. In this study, by combining an improved Soil and Water Assessment Tool (SWAT) model for nutrient management (SWAT-NM) and an improved BMP Cost Evaluation Tool (BMP-COST) for economic evaluations (BMP-COST-NM) considering the 4Rs for corn, soybeans, and wheat production, an integrated tool SWAT-COST-NM was created. SWAT-COST-NM was demonstrated in the AXL watershed in DeKalb County, Indiana, which is a typical agricultural area in the Maumee River watershed. The impacts of single nutrient management practices (single-NM, which separately changed the rate, place, time, or nutrient source of fertilizer applications) and combined-NM practices (a number of single-NM practices combined as one nutrient management practice) for corn, soybeans, and wheat on crop yields, March-July/yearly nutrient losses (Total Phosphorus-TP, Dissolved Reactive Phosphorus-DRP, and Total Nitrogen-TN), yearly gross costs, yearly crop revenues, yearly net costs, and cost-effectiveness in reducing March-July/yearly nutrient loadings were evaluated. Tradeoffs in yearly net costs, crop yields, and March-July/yearly nutrient losses existed when determining the impacts of nutrient management practices. A combined-NM practice (Scenario 7d) could simultaneously reduce March-July TP, DRP, and TN losses by 5.89%, 8.19%, and 8.23%, respectively, while increasing crop yields with additional income (0.50 $/ha/yr of cropped area). The SWAT-COST-NM tool, which can quantify various factors and tradeoffs when evaluating the impacts of nutrient management practices for corn, soybeans, and wheat, can assist decision-makers in cost-effectively applying nutrient management practices considering the 4Rs.