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Cover Crop Nitrogen Release During Corn Growing Season
According to researchers at the University of Nebraska, well managed cover crops offer nutrient cycling benefits. They say grass cover crop species such as cereal rye can scavenge nutrients such as nitrogen (N) from deeper soil layers, avoiding losses by leaching and releasing them as residues decompose. They add that legume cover crops, such as hairy vetch biologically fix atmospheric N in addition to releasing N during decomposition, which can help supply the N to the subsequent cash crop and cover crop mixtures can diversify agroecosystems and optimize the characteristics and functions of different species.

To help understand cover crop decomposition and N release throughout the growing season, in 2021 the University designed a study as part of the Precision Sustainable Agriculture (PSA), a collaborative project supported by the Agriculture and Food Research Initiative’s Sustainable Agricultural System Coordinated Agricultural Projects from the United States Department of Agriculture (USDA). This experiment will be repeated over three years.

In an article discussing the research, published in Soil Health in May of 2022, it says the biomass amount produced by cereal rye, hairy vetch and mixture (cereal rye and hairy vetch), achieved an average of 5,500, 1,600 and 4,900 lbs per acre, respectively. No differences of nitrogen released by the cover crops were observed throughout the season. During the 16 weeks after sampling, a total of 70, 66 and 62 lb/acre of N were released by cereal rye, hairy vetch and mixture, respectively.

Corn grain yields following cover crop and no cover treatments were not significantly different. The corn yield in the 160 lb/acre N treatment had an average of 205, 235, 222 and 190 bushels per acre for cereal rye, hairy vetch, mixture and no cover, respectively.

Considering strategies to supplement or offset nutrient input needs is increasingly important due to increases in N fertilizer costs. For example, the cost of anhydrous ammonia reached nearly $1,500 per ton in January 2022, representing an increase of approximately $750 per ton (ESMIS-USDA, 2022). The results from the first year of this study demonstrate the potential of grass, legume and mixed cover crop species to recycle nutrients without negatively impacting corn yields.