Graduation Term

Spring 2026

Degree Name

Master of Science (MS)

Department

Department of Agriculture

Committee Chair

Rob Rhykerd

Committee Member

Bill William Perry

Committee Member

Nicholas Heller

Committee Member

Liangcheng Yang

Abstract

Adoption of winter cover crops in the U.S. Midwest may reduce nitrogen (N) and phosphorus (P) leaching from soils, potentially shrinking the hypoxic zone by limiting nutrient runoff into the Gulf of Mexico. To evaluate the impact of selected winter cover crops on soil porewater N and P concentration, a field study was conducted at the Illinois State University Research Farm (ISURF) and the Western Illinois University Research Farm (WIURF). The experimental design was a block experiment with four replications.  Cover crop treatments included a winter fallow, wild pennycress (WPC), golden pennycress (GPC), cereal rye (CR), annual ryegrass (AR), and a mix of peas, clover, radish, and oats (PCRO). Soil porewater was collected using lysimeters from the root zone (45cm) and near the depth of tile lines (90 cm), and nitrate-nitrogen (NO3-N), dissolved reactive phosphorus (DRP), and ammonia (NH3) were analyzed. In addition, a soil sensor study was conducted at ISURF in 2025 to measure soil moisture and temperature. Cover crops reduced NO3-N loss in soil porewater by 55-99% compared to the winter fallow treatment. At both sites, CR reduced NO3-N loss by 92-99% from both depths and years, even when N fertilizer was applied to the summer cash crop, corn. Except for PCRO, cover crops, following soybean, reduced NO3-N in soil porewater by up to 99% at the ISURF but were less effective at WIURF, likely due to poor cover crop establishment. The PCRO mix showed inconsistent performance, often increasing porewater NO3-N. At both sites, detection of DRP and ammonia was low, typically below the detection limits, indicating no leaching loss. Additionally, cover crop species influenced early-season soil temperature. Compared with winter fallow, soil temperatures were cooler under the CR treatment and warmer under the WPC treatment. Soil moisture was not affected by any of the cover crop treatments. Overall, winter cover crops show potential to reduce soil porewater NO3-N leaching, which could help reduce fertilizer loss from agricultural fields, but effectiveness depends on the type, time, and management.

Access Type

Thesis-Open Access

Download

Share

COinS