Date of Award


Degree Name

Master of Science


Plant, Soil, and Agricultural Systems

First Advisor

Sadeghpour, Amir


Cover crops are often planted during the fallow periods of cash crop harvests to cover the soil and reduce erosion but also to provide other ecosystem benefits including capturing residual nutrients and thus, reducing environmental losses of nitrogen (N) and phosphorus (P) in agroecosystems. Among these cover crops, winter rye (Secale cereale) is popular due to its winter hardiness and relatively cheap seed costs. However, growers in the Midwest, USA are reluctant to use winter rye prior to corn (Zea mays L.) due to the potential yield penalty in corn. This thesis introduces two strategies that could minimize winter rye’s effect on corn while providing nutrient loss reduction benefits are precision planting and reducing the seeding rate of winter rye ahead of corn. One study evaluates whether precision planting (planting winter rye strategically to avoid intersecting zones with corn) of winter rye at low seeding rate (37.5 kg ha-1) could produce similar cover crop biomass and quality to normal planted winter rye (50 kg ha-1) and if precision planting can improve performance and N requirement of corn (Chapter 1). The study was conducted in central Indiana during 2020-2021 (CIN21), and southern Illinois during 2021-2022 (SIL22), and 2022-2023 (SIL23) growing seasons. The experiment was arranged in a randomized block design with split plot arrangement. Main plots were three cover crops (a no-cover crop control (NoCC), conventional planted winter rye (CR), and precision planted winter rye (PR). Subplots were six rates of N fertilizer that ranged from 0-280 kg ha-1 for the CIN21 and 0-359 kg ha-1 for SIL22 and SIL23. Our results indicated that shifting from normal planting to precision planting resulted in similar cover crop biomass production with limited effect on winter rye quality [N concentration, Carbon (C):N ratio] and N and C accumulation. In CIN21, the no-cover crop control had higher yield and lower N requirements which was consistent with those of SIL22. The economic optimum rate of N (EORN) was below the typical recommended range for central Indiana and was above the recommended range for southern Illinois. Precision planting resulted in a slight increase in corn yield and N requirement, but overall was more profitable than normal planting due to a reduction in the number of seeds required and higher corn to fertilizer prices. Therefore, we recommend that (i) decision support tools for N management in corn should be revised for addition of cover crops in the Midwest, and (ii) precision planting should be implemented instead of normal planting for greater economic benefit. Future research should evaluate ecosystem services of precision vs. normal planting of winter rye over time. The other study evaluates whether planting method of winter rye (precision vs. conventional) at medium and low seeding rates of winter rye influence cover crop biomass production, N and C concentrations and accumulations, and corn performance (Chapter 2). A trial was conducted in 7 site-yrs in Indiana and Illinois during 2020-2021, 2021-2022, and 2022-2023 growing seasons. The trial was arranged in a randomized complete block design with four replicates. Cover crops [conventional planting (CR) and precision planting (PR)] were factorially arranged with two seeding rates (18.75 vs. 37.5 kg ha-1) for PR and (25 vs. 50 kg ha-1) for CR. Two extra treatments were included as control which were no-cover crop with zero-N and a 224 kg N ha-1 addition to corn. Cover crop biomass, C, N, their uptake, and C:N ratio were evaluated along with corn plant population, and corn grain yield. Our results indicated that winter rye had similar aboveground biomass, N uptake, and C accumulation regardless of planting method and seeding rate suggesting a precision planting at low seeding rate is most economical for cover crop establishment. Corn plant population was only affected by winter rye in one site-yr (CIL23) in which precision planting did not help with minimizing the negative effect of winter rye on corn population. In this study, lack of N fertilization did not decrease corn population but significantly reduced corn grain yield in all site-yrs. Corn grain yield was similar among cover crop treatments (with exception of no cover crop no N) but in one of the site-yrs, precision planting at 18.75 kg ha-1 resulted in greater corn yield than the no-cover crop with 224 N ha-1. We concluded that growers that plant winter rye prior to corn could use precision planting at a seeding rate of 18.75 kg ha-1 to take up residual soil N with limited interference with corn production at a reduced cost compared to conventional winter rye management.

Available for download on Wednesday, February 25, 2026




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