Legume-cover crops like clovers, vetch, and peas form a symbiotic relationship with Rhizobium bacteria in soils, allowing them to fix nitrogen from the air into soils or plants. This additional nitrogen can provide cost savings for farmers who use nitrogen fertilizers.
Influential Factors
Several factors will influence the exact amount of nitrogen a legume cover crop can add to a farmer’s field.- Species
- Growing Conditions
- Biomass Achieved
- Location
Timing Challenges
North Carolina's warmer and humid climate increases the decomposition rate for legume residues after termination. This rapid decomposition may release some nitrogen before it is needed by the following cash crop.Due to the planting date of cash crops, some cover crops need to be terminated before they express their full potential of fixing nitrogen, limiting their contribution of nitrogen to the next crop.Management Approach
Farmers must take a systems approach for the best results when utilizing cover crops for nitrogen fixation. Growers need to consider…- Nitrogen Source
- Nitrogen Rate
- Nitrogen Timing
- Nitrogen Placement
Nitrogen Calculator Decision Support Tool
An online tool developed by Precision Sustainable Agriculture can help farmers better understand how much nitrogen will be released and when.
The Nitrogen Calculator will chart nitrogen release for 18 weeks past cover crop termination and compare this nitrogen release to the nitrogen demand for the following cash crop.
References
- Creamer, N., & Baldwin, K. (2019). Summer Cover Crops. NC State Extension
- Gatiboni, L., & Reberg-Horton, C. (2021). Winter Annual Cover Crops. NC State Extension
