Cover crops can help slow erosion, improve soil, smother weeds, enhance nutrient and moisture availability, help control many pests, and bring a host of other benefits to farms across the country.
Cereal-legume cover crop mixtures are of particular interest to growers because they can effectively suppress weeds, control erosion, and scavenge leachable nitrate while also fixing atmospheric nitrogen.
Michigan State University graduate student, Zachary Hayden, knows that few legumes match hairy vetch for spring residue production or nitrogen contribution. He also recognizes that the hardiest of cereals, rye, can be seeded later in fall than other cover crops and still provide considerable dry matter, an extensive soilholding root system, significant reduction of nitrate leaching, and exceptional weed suppression.
Hayden wanted to optimize seeding rates for mixtures of cereal rye (Secale cereale L.) and hairy vetch (Vicia villosa Roth) based on growers’ principal goals and crop management practices. Hayden applied for an NCR-SARE Graduate Student Grant in 2009 and received $9,983 to explore how species proportions (based on seeding rates) of a mixture of cereal rye and hairy vetch could influence cover crop performance in a vegetable production system with respect to crop grown and plastic mulch use.
Hayden used an experimental design where treatments consisted of a bare ground control and a gradient of seven rye:vetch mixture proportions, from 100% rye to100% vetch. Following cover crop kill and incorporation, each mixture plot was planted with both cucumber and bell pepper, and each crop was grown with and without black plastic mulch.
According to Hayden, changing the proportion of rye and vetch in the mixture produced tradeoffs in services such as fixed nitrogen accumulation and winter annual weed suppression. In both years of the project, all cover crop treatments significantly suppressed winter annual weed populations; however, suppression increased with increased rye in the mixtures. Rye monocultures generally provided the greatest level of suppression, reducing weed biomass by over 95% compared to the control in 2010 and 2011.
Hayden said plastic mulch could go a long way toward preserving N fertility benefits from legume and grass-legume cover crop residues, particularly in the face of leaching precipitation during wet springs. He noted that higher N levels and higher vegetable yields were associated with using cover crop mixtures that contained higher proportions of vetch and using plastic mulch.
Through the project, Hayden reached about 150 farmers and community members directly through extension presentations and field tours.
“Farmers recognize first-hand the complexity involved with cover crop management, and many have expressed appreciation for the systems-approach we took in this study,” said Hayden. “Understanding how management interacts with weather and environment to impact nutrient dynamics, weeds, and soil biology, in addition to vegetable yields, helps them make more informed decisions on the farm.”
Hayden hopes that this systems-level information can support more informed decision-making in the future regarding cover crop selection, mixture seeding rates, and plastic mulch use—resulting in input savings and crop production benefits. In addition, the approach used for evaluating rye-vetch mixture proportions could be applied to better understand and optimize the management of other cover crop mixtures as well.
Want more information? See the related SARE grant:
- A novel approach for optimizing the benefits of cereal-legume cover crop mixtures in vegetable cropping systems (GNC09-108)