The Utility of Crotalaria juncea as a Cover Crop in a Temperate Climate

View the project final report

• 2009 annual report
• 2010 annual report

Commodities

• Agronomic: buckwheat, vetches

Practices

• Education and Training: extension, on-farm/ranch research
• Pest Management: allelopathy, mulches - living, smother crops, weed ecology

Weed control is the biggest cost to certified organic farmers and gardeners. This cost for weed control is also a factor for others who wish to reduce the use of herbicides, especially in fruit and vegetable production for local markets. Crop rotation, mechanical cultivation, plastic mulching, and hand weeding are the most effective, but expensive methods for weed suppression now used by these producers. Chemical formulations approved for weed control in organic cropping are mostly “burn down-non selective” products that affect only the leaves and growing stems of the sprayed plant. More effective, less expensive methods of weed control are required to increase production and profitability of organic and sustainable farms and gardens.

Although cover crops are extensively used in sustainable agriculture, mostly as green manure and for over-winter soil protection, their effects on weed populations are limited.
In large tree fruit production, the additional problems are nematode populations that lead to stunted growth or death of fruit trees, and meadow vole (Microtus sp.) girdling of trees if the orchard floor provides winter shelter. Common nematode pests in apple production include dagger nematode (Xiphinema) and lesion nematode (Pratylenchus), and the site chosen is infested with both genera. Other common nematode genera in the area include root knot (Meloidogyne) and lance (Hoplolaimus). All four of these can be pest problems in vegetable production.

We propose to evaluate the weed-suppressive benefits of hairy vetch (Vicia villosa), buckwheat (Fagopyrum sagittatum), and a tropical plant, Crotalaria juncea (sunn hemp), as cover crops in the temperate climate of West Virginia. Sunn hemp has been shown to grow well as far north as Pennsylvania but does not produce seed. Cover crops in common use within the temperate area of the northeastern United States such as rye (Secale cereale) and hairy vetch are allelopathic to some weeds. Hairy vetch is an important cover crop because it produces nitrogen that is available to succeeding crops. Buckwheat has been used in the northeastern states as a “smother” crop for control of quackgrass (Agropyon repens) and other weeds. Both buckwheat and vetch are good hosts for common genera of plant-parasitic nematodes.

In tropical and subtropical climates, sunn hemp fixes high levels of nitrogen and reduces nematode and weed populations. This plant produces an allelochemical that is highly concentrated in its seeds and is readily leached into the soil by water and thus, may provide early weed control until germination and seedling establishment. Few studies have evaluated the nematode suppressive effect of sunn hemp in Northeastern States. Our experiments will form a basis for comparison of the effectiveness of sunn hemp to control weeds and nematodes and to increase soil nitrogen with hairy vetch, buckwheat and rye in Northeastern US.