Effects of nutrient management on soil health and leachate water quality in a corn agroecosystem

Fertilizer applications are popular for enhancing crop productivity, yet they pose significant environmental risks, particularly nutrient runoff and water contamination. However, the relevant field data for Kentucky is limited. This 2024-2025 study at Kentucky State University’s Harold R. Benson Research Demonstration Farm assessed short-term impacts of three treatments: dairy manure, composted dairy manure, and synthetic fertilizers on soil health and leachate water quality under corn. Three treatments were randomly applied to a 4047 m 2 (1.77-acre) field with four replications, and soil and leachate water samples were collected over the growing season from 10 and 20 cm depths of each plot using bulk density core samplers and suction cup lysimeters, respectively. Soil samples were analyzed for a suite of soil physicochemical parameters and leachate water samples were analyzed for nutrients, pH and electrical conductivity (EC). A few soil health parameters were significantly affected by management, however, some of the observed initial changes were not significant over time. Manure significantly increased soil aggregation, and organic matter compared to fertilizer treatment by 7.5 and 40%, respectively. Compost significantly improved specific surface area of soil compared to manure and fertilizer by 22.8% and 10.9%, respectively. Soil pH was significantly increased by manure and compost than that of the fertilizer and fertilizer significantly increased EC than manure and compost by 7.6% and 15.7%, respectively. Fertilizer-amended soils significantly reduced initial soil compaction, compared to other treatments, but no significant differences in compaction were observed in post-harvest soils either. Leachate water samples showed significantly higher concentrations of nitrate (NO 3 -N) at both soil depths and phosphate (PO 4 -P) at 20 cm under fertilizer compared to manure and compost amendments over time. These findings suggest that most of the measured soil properties were varied by management but temporal variation was absent as they did not respond to various treatments in short-term period during first growing season and longer time is needed to understand the full effects of management over time. Yet, these data indicate that fertilizer treatment may pose significant water quality impairment over time under corn cropping system in Kentucky.