Winter Wheat Cover Crops Increase Corn Potential

By Scout Nelson

A study by researchers at the University of Nebraska-Lincoln (UNL) found that planting legume cover crops after winter wheat can increase soil nitrogen levels and improve corn yields. The findings suggest growers can use the period after wheat harvest to generate part of the nitrogen needed for the next corn crop.

Because winter wheat is harvested early, growers have a longer window to establish cover crops before winter. This extra growing time allows legumes to produce biomass and capture or fix nitrogen that can benefit the following crop.

Researchers evaluated several cover crops, including hairy vetch, soybean, cowpea, sunn hemp, forage pea, and a legume mixture, at UNL's Rogers Memorial Farm in Nebraska. These were compared with cereal rye and fields that received either standard fertilizer or no fertilizer.

The study found that sunn hemp and the legume mixture produced the most biomass, while hairy vetch and soybean accumulated the highest amounts of nitrogen. Hairy vetch and soybean stored more than 150 pounds of nitrogen per acre, significantly exceeding the levels recorded for cereal rye.

Legume cover crops increased nitrogen availability in the soil and improved corn performance. Corn planted after legumes yielded about 40 bushels per acre more in 2021 and 36 bushels per acre more in 2024 compared with fertilized fields without cover crops.

Researchers also found that legumes could replace a portion of fertilizer needs. Apparent nitrogen credits ranged from 29 to 88 pounds per acre, with hairy vetch providing the highest credit and an average of about 49 pounds per acre across legume treatments.

Cereal rye produced different results, contributing less nitrogen and reducing nitrogen availability to the subsequent corn crop under the study conditions. As a result, additional fertilizer may be needed when rye is used.

Overall, the findings indicate that summer legumes such as hairy vetch, sunn hemp, cowpea, and forage pea can improve soil fertility, support higher corn yields, and help reduce fertilizer requirements in wheat-corn production systems.

Photo Credit: gettyimages-dleonis