Quantifying Nitrogen and Sulfur Release from Winter Hardy Legume Cover Crops Using 15N and 34S Stable Isotopes Labeling

Commodities

Practices

While cereal rye is the most common cover crop planted nationwide, concerns surrounding its agronomic impact on corn and soybean production have limited its adoption in the North Central Region. Thus, alternative cover crop species such as winter hardy legumes, which are expected to pose lower risk to corn and soybean production, should be explored as potential alternatives. Our research project aims to quantify the release of sulfur and nitrogen from various winter hardy cover crop varieties including cereal rye (Hazlet), hairy vetch (Winter Warrior), balansa clover (FixatioN), persian clover (eNhance), berseem clover (Frosty), and crimson clover (Kentucky Pride), utilizing ¹⁵N and ³⁴S isotope labeling techniques. We will investigate the fate of these released nutrients across different soil nutrient pools, including the organic, microbial biomass, and bioavailable nutrient pools. To answer these questions, this study will utilize aerobic incubation, with sampling of incubation microcosms at eight intervals over a total incubation period of 248 days. By employing stable isotope labeling and assessing nutrient distribution among soil pools over an extended incubation period, we seek to provide insights into the longer-term (more than one growing season) dynamics of nutrient release and cycling within agroecosystems. Our findings have the potential to enhance understanding of cover crop contributions to soil fertility and ecosystem services, aiding in the optimization of cover crop management practices for sustainable agricultural systems in the North Central Region.

Over the past decade, Cover Crop (CC) adoption in the North Central Region has risen steadily, yet remains a small portion of total cultivatable acres. Despite well-known environmental benefits such as nutrient scavenging, reduced nitrate leaching, erosion control and building soil health, there remains a lack of adoption likely due to the uncertainty surrounding their impacts on row crop production, specifically the release and bioavailability of nutrients (nitrogen (N) and sulfur (S)) scavenged during CC growth. Cereal rye, the most common CC nationwide, is central to these concerns, prompting exploration of winter-hardy legume CC species as alternatives. These legumes are expected to pose lower risk to crop production as they should more readily decompose and release nutrients, though understanding of their decomposition and nutrient release dynamics is limited. Therefore, the anticipated learning outcomes of this study are to 1.) quantify the release and fate of N and S from six winter hardy cover crops (cereal rye, hairy vetch, balansa clover, persian clover, berseem clover, and crimson clover) amongst the organic, microbial and bioavailable soil nutrient pools, 2.) Measure long-term (equivalent to two corn/soybean growing seasons post-termination) bioavailability of N and S released from these CC species. Accomplishing our learning outcomes could lead to the education of producers, trainers, and researchers on the bioavailability of CC N and S to subsequent cash crops. Findings could allow for adjustment of fertilizer management plans to account for bioavailable N and S released during CC decomposition.