Cover Crops in Integrated Vegetable Production Systems
Lexington County, South Carolina is a major vegetable producing area. Around 4,000 acres of collard greens, green onions, squash, tomatoes and beans are produced annually. Cover crops are needed to reduce soil losses and improve soil conditions. The current vegetable cropping systems used on much of the land in the county contribute to the loss of seven to eight tons of soil per acre annually. The soils are deep and sandy, requiring high irrigation rates. Because of this, high rates of nitrogen are applied and lost.
Winter cover crops could be used to reduce erosion. Cover crops would also reduce nitrogen losses (by using a nitrogen-fixing species less nitrogen fertilizer would have to be applied), improve organic matter levels, soil texture, soil structure and water-holding capacity. Cover crops can potentially control certain diseases through their place in a rotation, but some studies have indicated that the incidence of root-knot nematodes and diseases caused by Pythium and Rhizoctonia can increase following certain cover crops.
The producer will test treatments of the cover crops: rye, oats, rye + crimson clover, rye + cahaba vetch, crimson clover, cahaba vetch, hairy vetch, Austrian winter pea, arrowleaf clover and a fallow to control erosion and improve soil fertility. He will determine if any of these cover crops encourage the growth of plant diseases caused by Rhizoctonia and Pythium.
He will plant the cover crop treatments in a randomized complete block design replicated four times. He will test the soil for pH, nitrogen, physical properties, nematodes and Rhizoctonia and Pythium. Crop dry weight, N content and disease incidence will be observed and recorded.
Preliminary trials have shown that cover crops can potentially control certain diseases through their placement in a rotation. The incidence of root-knot nematodes have been very low in all the cover crops. Preliminary observations also indicate that Rhizoctonia solani counts in all cover crop treatments have decreased. However, Fusarium counts have increased slightly over the life of the project, but the analyses to separate the counts of pathogenic from non-pathogenic Fusarium species have not yet been performed.