Growers know that after years of driving heavy farm equipment over wet soil during the planting or harvest seasons, the soil gets compacted. In compacted soil, crops have difficulty growing. Deep tillage to break up compacted "hardpan" layers requires powerful tractors that are not available to some growers and often is not an effective long-term solution. Cornell University scientists are developing a kinder, gentler way to rejuvenate the soil: through biological means.

On Friday, Aug. 1, officials from the U.S. Department of Agriculture and growers from around the Northeast will tour Cornell's Homer C. Thompson Vegetable Research Farm in Freeville, N.Y. -- one of the fields used in testing the biological remediation of compacted soil.

"Soils vary in the susceptibility to compaction," said David Wolfe, project coordinator and Cornell associate professor of fruit and vegetable science. "Clay soils are very susceptible, particularly when they have low organic matter content. Some medium-textured soils are also quite susceptible to compaction because of interlocking among soil particles of various sizes.

"There is nothing good about compact soils," Wolfe said. "They hamper crop growth as they restrict roots, and the plants show an increased tendency for root disease, nutrient deficiency, pest damage and weed competition. Compacted soils also are more prone to both flooding and drought."

The biological solutions being crafted at Cornell involve the use of particular rotation crops that have the ability to grow deep roots into compacted soils and produce abundant organic matter above and below ground. "We've known that taking land out of vegetable production for several years to grow alfalfa is pretty effective," Wolfe said, "but this is not an option many growers can afford." Instead, the researchers have sought alternatives that do not require taking land out of production for more than one summer.

During the past three years of the study, the researchers have evaluated more than a dozen different summer and winter cover crops at the Cornell research farm and on commercial farms with grower cooperation throughout New York. One crop that has begun to stand out from the rest of the pack is Sudangrass. It is particularly effective at sending down deep roots to loosen the soil when it is mowed once during the season. It also produces an abundant amount of organic matter that fortifies the soil's microbial community and appears to protect plant roots from parasitic soil nematodes.

The researchers also have identified some other cover crops, such as yellow mustard, that show promise, but they have been difficult to establish in some locations. "We still have a lot to learn about how best to grow these crops and how best to fit them into rotations with vegetables," Wolfe said. A follow-up research initiative currently is being developed, and will include examining in more detail the effects of compaction on pathogenic and beneficial microorganisms in the soil.

Wolfe is collaborating with Harold M. Van Es, Cornell associate professor of soil, crop and atmospheric sciences; George S. Abawi, Cornell professor of plant pathology at the Agricultural Experiment Station, Geneva, N.Y.; Michael Glos, Cornell research technician; and Cornell Cooperative Extension vegetable specialists Lee Stivers, Dale Riggs and Laura Pedersen. The project is funded by USDA Hatch grants and a grant from the USDA Sustainable Agriculture Research and Education (SARE) program.

A paper, "Growth and Yield Sensitivity of Four Vegetable Crops to Soil Compaction," was published in the Journal of the American Society of Horticultural Sciences (1995) by Wolfe, Daniel T. Topoleski, Cornell graduate student; and Cornell research technicians Norman A. Gundersheim and Betsy A. Ingall. Wolfe also prepared a brief for growers, "Soil Compaction: Crop Response and Remediation," published through the Cornell Department of Fruit and Vegetable Science, Report No. 63, January 1997.