Hairy vetch (Vicia villosa) is a winter annual with a history of use as a soil cover and green manure crop. Its use in the United States, however, has predominantly been in the southern states which have milder winter temperatures than Ohio. Hairy vetch will usually survive Ohio winter temperatures, but diseases often severely damage or kill stands.
Hairy vetch requires use of a specific vetch inoculum different from the kind used with alfalfa and clovers. This legume recently has received renewed interest as a soil cover and source of nitrogen, especially in no-tillage corn production.
Several climatic factors and agronomic principles determine the amount of soil cover and nitrogen fixation that can be obtained from hairy vetch in Ohio. Plant growth is influenced by several factors, soil and air temperatures being of utmost importance. Very little nitrogen is mobilized by the soil rhizobium bacteria at soil temperatures below 50 degrees F., and essentially none occurs below 40 degrees F. It takes three weeks for nodules to form on a germinated and growing legume seedling. This leaves a short period for nitrogen to be "fixed" in Ohio during the fall. Thus, the final result is primarily dependent upon the spring season and the date of herbicide application and corn planting. In Ohio, hairy vetch "fixes" little nitrogen unless permitted to make considerable spring growth.
The roots of hairy vetch, typically of annuals, are not as extensive compared to roots of the biennial and perennial legumes. Most of the nitrogen is contained in the top growth; therefore, if hairy vetch is to be used as a nitrogen source, this top growth must not be removed.
The following rules should be observed when hairy vetch is utilized for a soil cover crop in Ohio:
WORDS OF CAUTION: Hairy vetch contains many hard seeds with 15 to 30 percent common. These hard seeds can remain in the soil for several years, then germinate to develop into unwanted plants. Vetch is an especially serious weed plant in wheat. Thus it should never be permitted to mature and set seed.
Seed cost-economics. Under Ohio conditions and with current prices vetch seed cost essentially equals the value of nitrogen produced.
Donald K. Myers
Extension Agronomist Emeritus
District Agronomy Specialist
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