A Sustainable Way to Protect Vegetables: Cover Crops

by Chris Gonzales, Northeastern IPM Center

If you’re a vegetable grower, you spend a lot of time thinking about production yield. In studies conducted at Cornell University, researchers are finding that sustainable protection is equally important. Cover crops play an important role in both raising production yield and sustainably protecting cash crops.

Growers mow then disc rapeseed to incorporate it into the soil. Growers who use cover crops not only can improve soil health, but also protect vegetables from soilborne pathogens. These findings come from a study funded by the Northeastern IPM Center and the USDA National Institute of Food and Agriculture, and led by George Abawi of Cornell.

Abawi and his team began work on the project in 2008 when they planted eight acres of snap beans in Geneva, New York. They studied eight types of cover crops—plants grown to enrich and protect the soil: winter rye grain and hairy vetch, oat, sudex, forage radish, red clover, rapeseed, buckwheat, and Jensen wheat. They also tested a fallow control. They compared four cropping systems: future IPM, present IPM, organic, and conventional. The researchers followed commercial production guidelines for IPM, organic, and conventional systems. According to Abawi’s research team, “future IPM” is a cropping system based on present IPM and the use of rotational and cover crops.

Cover crop story

"Through our project, growers and industry personnel are learning more about the general benefits of cover crops on root diseases, weeds, soil fertility, and the factors that contribute to overall soil health,” Abawi said.

Rye/vetch, wheat, and rapeseed provided the highest biomass in all production systems and during all seasons. Clover, oats, and buckwheat also provided considerable biomass gains. The highest marketable yield of snap bean was grown in the field managed as the future IPM production system. This field also had the highest soil quality level and the lowest ratings for root rot severity. The conventionally managed field had the lowest soil quality and the highest root rot ratings. The lowest bean yields were generally in the buckwheat and fallow fields.

Preventing weeds and diseases

Researchers documented the prevalent root disease pathogens Fusarium solani f. sp. phaseoli, Pythium ultimum, Thielaviopsis basicola, and Rhizoctonia solani in study plots. Surprisingly, a cover crop of buckwheat or clover increased root rot severity in snap beans, similar to the fallow check. The lowest accumulated increases of root rot occurred in the cover crop plots of wheat, sudex, oat, and radish. Wheat appeared to be most effective against root rot in the organic production field.

Weed pressure was least in the rye/vetch, wheat, and rapeseed plots, and most severe in the fallow/check, buckwheat, and sudex plots.

In terms of soil health, the highest active carbon values were found in the organic and future IPM system fields. Specifically, rye/vetch, radish, and oats yielded the highest active carbon values in the organic system. Not surprisingly, the lowest values were in the fallow/check plots. Organic matter was highest in the organic and future IPM systems fields.

Show on the road

The researchers presented at nine farm expositions with hundreds of participants, and a meeting of the American Phytopathological Society with attendance of over 1,500. They also published six research papers.

“We were especially pleased with the enthusiasm shown by the participants in our workshops, field days, and presentations,” said Abawi. “Cover crops have indeed become a major tool for the sustainable and long-term management of soil health."

Although cover crop ratings may change as more data is collected in the future, it is clear that a pattern is emerging. Abawi hopes to soon make specific recommendations for cover crops that could be adopted by growers in the northeast for the management of certain soil health conditions and root disease pathogens.

Sidebar: Root effects

In Connecticut, scientists grew snap beans in plots infested with nematodes and soilborne fungal pathogens. They then tested how various cover crops protected the cash crop.

The highest shoot and root weights resulted after a cover crop of forage radish and rapeseed. Also, beans grown after radish, rapeseed, sorghosudangrass and millet had the lowest root rot ratings. Highest shoot, root and bean yield were again obtained after forage radish and rapeseed. Pearl millet also resulted in increased bean growth and yield.

In Pennsylvania, researchers located four fields with a history of significant root disease pressure. They set up plots, half with and half without a cover crop. Scientists found a reduction in soilborne pathogens in rye and rapeseed cover crop fields. Root health ratings also improved.

Caption for photo: Growers mow then disc rapeseed to incorporate it into the soil. Source: G. Abawi, Cornell University