Document Type

Article

Publication Date

5-15-2026

Publication Title

Field Crops Research

Abstract

Context: Warm-season legume cover crops in subtropical environments provide many agroecosystem services but have not been widely adopted because their use usually entails replacing cash crops. Planting short-term legume cover crops following maize (Zea mays L.) to replenish soil nitrogen (N) pools for cool-season cash crops, such as wheat (Triticum aestivum L.), is an innovative approach for integrating legumes into subtropical cereal cropping systems that has not been widely investigated.

Objectives: A maize – legume cover crop – wheat cropping sequence under conservation tillage management was investigated with the following objectives: 1. Evaluate the performance of short-term cowpea [Vigna unguiculata (L.) Walp)] and sunn hemp (Crotalaria juncea L.) cover crops in terms of N accumulation, 2. Track soil N availability and wheat N recovery following cover crops, and 3. Assess wheat productivity in response to cover crops terminated and left on the soil surface.

Methods: A five site-year study was conducted in Citra and Jay, Florida, USA beginning in 2016. The experiment was arranged as a split-plot in which cover crop (cowpea, sunn hemp, and weed-free fallow) was the main plot factor, while N rate (0, 34, 67, and 101 kg N ha -1) to wheat was the split plot factor. Corn was planted under strip-tillage, while cover crops and wheat were planted into residues using a no-till grain drill.

Results: Cover crops accumulated 58–126 kg N ha -1 in eight to 11 weeks, with cowpea and sunn hemp deriving up to 67 and 90% of N from biological N fixation, respectively. Plant Root Simulator probes and Normalized Difference Vegetation Index data provided evidence for higher N uptake by wheat following cover crops compared to weed-free fallow during early stages of wheat growth. However, N availability following cover crops was either short-lived or insufficient as wheat stover production, grain yields, and grain N recovery were not affected by cover crops in most cases. On the few occasions when positive cover crop effects were detected, results were both marginal and inconsistent.

Conclusions: Maintaining cowpea and sunn hemp residues on the soil surface may be beneficial from a soil conservation perspective, but this strategy does not result in consistent improvements in the productivity of cool-season cereals. Additional research that elucidates the environmental pathways by which legume cover crop-derived N is lost from soil is warranted to facilitate the development of management practices that increase the likelihood and size of N benefits from short-term legumes.

Comments

Published in Field Crops Research by Elsevier B.V. Available via doi 10.1016/j.fcr.2026.110471.

This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).

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