Winter pea, crimson clover, and hairy vetch planted in mixture with small grains in the Southeast USA

Authors: VANN, RACHEL - North Carolina State University; REBERG-HORTON, CHRIS - North Carolina State University; CASTILLO, MIGUEL - North Carolina State University; Mirsky, Steven; McGee, Rebecca

Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/16/2018
Publication Date: 1/24/2019
Citation: Vann, R., Reberg-Horton, C., Castillo, M., Mirsky, S.B., Mcgee, R.J. 2019. Winter pea, crimson clover, and hairy vetch planted in mixture with small grains in the Southeast USA. Agronomy Journal. 111:805-815.

Interpretive Summary: Combining species into a cover crop mixture is a useful approach to meeting multiple crop production needs. Grass and legume cover crops are routinely combined as legumes are useful in providing nitrogen to the subsequent cash crop while grasses provide good weed control as a mulch and scavenge soil nitrogen. The extent to which grasses and legumes provide these functions depends on their proportion of the total cover crop biomass. Both species and cultivar can impact the performance of grasses and legumes grown in mixture. There is particular interest in using winter peas as a cover crop. Therefore, field experiments were conducted from 2015 to 2017 in Maryland and North Carolina to compare winter pea to crimson clover and hairy vetch for production in mixture with small grains for cover crop use. Five winter pea genotypes, one crimson clover cultivar, and one hairy vetch cultivar were screened in mixture with barley, oats, and wheat. Cold injury to the pea genotypes in Maryland severely impacted pea biomass. Peas were able to recover from cold injury in North Carolina. A robustly growing small grain aided in legume cold tolerance in some environments. In the Coastal Plain environments where soil residual N is generally low, all legume genotypes generally contributed to at least 50% of mixture biomass production. At the Maryland and Piedmont environments where soil residual N is generally higher than in the Coastal Plain, the small grain dominated the cover crop mixture. In the Coastal Plain and Piedmont environments in North Carolina, several winter pea genotypes produced as much biomass in mixture as crimson clover and hairy vetch. Hairy vetch was the most competitive legume with the small grains across environments. This work provides additional understanding on how soil and climate interact with cover crops, specifically, grass/legume cover crop mixture performance. Furthermore, this data will be used as part of a broader effort to develop cover crop focused decision support tools.

Technical Abstract: Legume and small grain cover crops are combined in mixture to provide N fertility and weed suppression for the following cash crop. Studies were conducted from 2015 to 2017 in Maryland and North Carolina to compare winter pea (Pisum sativum L.) to crimson clover (Trifolium incarnatum) and hairy vetch (Vicia villosa Roth) for production in mixture with small grains for cover crop use. Five winter pea genotypes, one crimson clover cultivar, and one hairy vetch cultivar were screened in mixture with barley (Hordeum vulgare), oats (Avena sativa), and wheat (Triticum aestivum). Cold injury of the pea genotypes in Maryland severely impacted pea biomass. Peas were able to recover from cold injury in North Carolina. A robustly growing small grain aided in legume cold tolerance in some environments. In the Coastal Plain environments where soil residual N is generally low, all legume genotypes generally contributed to at least 50% of mixture biomass production. At the Maryland and Piedmont environments where soil residual N is generally higher than in the Coastal Plain, the small grain dominated the cover crop mixture. In the Coastal Plain and Piedmont environments in North Carolina, several winter pea genotypes produced as much biomass in mixture as crimson clover and hairy vetch. Hairy vetch was the most competitive legume with the small grains across environments. The variability in total biomass composition across environments in this study demonstrates the importance of site specific cover crop mixture seeding rate recommendations.