Does Grazing Impact Organic Crops Negatively?

By Gail Stephens

A University of Maryland Eastern Shore research team will share $1 million in federal funding with three partner institutions to gauge how cover-crop grazing by livestock affects soil quality in fields alternately used to grow organic consumer crops.

The money is part of a $9.5 million package of grants the U.S. Department of Agriculture recently awarded to 11 collaborative, multi-state projects to “enhance the competitiveness of (domestic) specialty crops.”

UMES, in partnership with the University of California at Davis, the University of Minnesota, The Organic Center in Washington, D.C. and the USDA's Agriculture Research Station in Beltsville, Md. will “investigate the benefits of livestock integration through cover-crop grazing on bacterial population dynamics, food safety, and soil and environmental health,” said Dr. Fawzy Hashem, a research associate professor in the university's Department of Agriculture, Food and Resource Sciences.

“Many growers and scientists consider livestock grazing with winter cover crop management in fresh produce or other agronomically important crop operations as a good approach to enhance soil health and benefit the environment by increasing carbon inputs,” Hashem said.

“It also can be helpful,” Hashem said, “in improving nutrient cycling, reducing dependence on external inputs, improving soil health and diversifying profit streams.”

The practice, however, raises questions about food safety risks involved.  This, Hashem said, is where the study steps in to address the need for “research examining food pathogen persistence, survival in soil and (whether harmful bacteria can) transfer to vegetable crops.”

Hashem and fellow researchers will graze sheep in fields with cover crops prior to planting spinach and cucumber.  They will measure changes in soil health indicators over two years of grazed cover-crop / vegetable production in Maryland, California and Minnesota and assess benefits and potential trade-offs of vegetable cash crop productivity.  Results will be compared to fields planted in tilled cover crops and a fallow field.

Joining Hashem, the joing project's co-principal director and the mid-Atlantic region's principal director, are colleagues Drs. Salina Parveen, professor of UMES' Food Science and Technology program; E. Nelson Escobar, small ruminant Extension specialist and UMES' interim associate administrator for Extension; and Patricia Millner of USDA's Agriculture Research Station in Beltsville.

“Evaluating the Food Safety Impacts of Cover-Crop Grazing in Fresh Produce Systems to Improve Cover Crop Adoption, Crop-Livestock Integration, and Soil Health” was the grant application's formal title.  UMES' share of the award is $310,000.