ATTRA's Organic Matters publication series was created to speed the flow of technical information on current topics to organic farmers, researchers, and others involved in organic production. Support in initiating this series has been provided by the Organic Farming Research Foundation, the USDA's Agricultural Marketing Service, and the Kerr Center for Sustainable Agriculture.

Protecting Water Quality on Organic Farms
Executive Summary

by Barbara Bellows
NCAT Agriculture Specialist
October 2002

For the complete publication, please call our
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Organic farms protect the environment by building soil organic matter and by mimicking natural systems rather than relying on synthetic fertilizers and pesticides. Research studies have demonstrated that compared to soils on conventional farms, organically farmed soils tend to have:

		Less nitrogen leaching
		Better nutrient holding ability
		More efficient biological nutrient cycling
		Less runoff and erosion

However, without proper management, organic farming practices can create the same environmental problems as conventional farming practices. Potential environmental concerns associated with organic production practices are primarily related to:

		The transition period from conventional to organic farming practices
		Improper or incomplete nutrient management planning practices
		Improper storage of manure or compost materials

The transition period from conventional to organic farming practices

During the transition from conventional to organic farming practices nutrients from organic fertilizers often are mineralized before or after the time when plants can best use them for their growth. When this happens, farmers obtain poor yields from their crops, while nutrients intended for plant growth may be leached into the groundwater or carried into rivers by runoff. This lack of synchrony between nutrient release and nutrient uptake occurs primarily because the soil undergoes chemical and biological changes during the transition from synthetic to organic inputs. Synthetic inputs kill or inhibit the growth of many soil organisms while organic inputs stimulate their growth. As organic matter is added to the soil and populations of soil organisms increase, these organisms become more effective in breaking down added organic matter and making its nutrients available to plants. They also hold within their own bodies many nutrients not used by plants. This process allows for greater nutrient availability during times of plant growth, while conserving excess nutrients against environmental loss. Unfortunately, this balance does not exist in the soils of many transitional organic farms. To mineralize sufficient nutrients for plant growth, the relatively small populations of soil organisms in transitional farms need to have access to high amounts of organic matter. However, these soil organisms will continue to decompose the added organic matter even after plants are done growing. These excess mineralized nutrients may then contaminate groundwater or streams. The potential for runoff and erosion is higher if synthetic inputs used previously created a surface crust, poor soil aggregation, or other conditions that hinder water infiltration.

Improper or incomplete nutrient management planning practices

Good nutrient management planning is critical for any farming operation in order to optimize plant growth and decrease risks of nutrient leaching and runoff. In organic production, good nutrient management is particularly important because nutrient release from organic matter is on-going while most plant uptake of nutrients occurs during the growth stage. This is especially true when "high yielding" or hybrid crop varieties are being raised. Organic farmers can use a variety of management practices to simultaneously conserve nutrients and enhance soil quality. These practices include:

Using annual soil tests to help calculate appropriate amounts of organic fertilizers to add

Composting animal manure and other organic residues to form a more uniform and chemically stable fertilizer material

Using crop rotations to trap and recycle nutrients in the soil profile, increase soil tilth, and provide a diversity of crop residues

Applying manure and incorporating cover crops in the spring prior to plant production and nutrient uptake and avoiding applications of manure or incorporation of cover crops in the fall unless a catch crop is planted to conserve mineralized nutrients

Avoiding surface application of manure prior to rainstorms, irrigating, or when the ground is frozen or saturated

Using practices that enhance soil quality and reduce the potential for water runoff and wind and water erosion

Providing buffers or filter areas between cropping areas and water bodies to protect against nutrient and sediment movement into lakes and streams

Improper storage of manure or compost materials

Many organic farmers make their own compost or store manure to be used in crop production. These materials are a concentrated source of nutrients that can easily leach through the soil into the groundwater or be washed into streams through runoff. To minimize the potential for these environmental losses, manure or compost piles should be set up on soils that have been cemented or compacted to minimize leaching under the piles. Diversions should be established upslope from the manure or compost pile to prevent contamination of clean rainwater and filter areas should be constructed and maintained downslope to treat any contaminated water running off the pile. Setting up manure or compost piles in a roofed enclosure will decrease the potential for runoff while protecting the quality of these valuable nutrient sources.

Other Environmental Issues

Pathogens. E. coli, Cryptosporidium, and Giardia are disease-causing microorganisms often found in manure. Crops can be contaminated with pathogens if fresh manure is applied to growing crops or shortly before planting or if contaminated water is used to irrigate crops. Poor sanitary practices by farm workers during crop production and harvesting can also cause produce to become contaminated with pathogens. People who consume contaminated food or water can suffer gastrointestinal problems. These problems pose the greatest threat to young children, elderly people, and persons who are immuno-compromised. Heavy metals. The term heavy metals refers to lead, cadmium, arsenic, copper, zinc, and iron. While the last three elements are required for plant growth in small amounts, build-up of these elements in the soil environment can be phytotoxic as well as damaging to the growth of soil organisms. While the National Organic Standards prohibit the use of sewage sludge or biosolids because these products tend to have high concentrations of heavy metals, they do not regulate the source of animal manures used as fertilizers. However, animal manure may be contaminated with heavy metals if these materials were used as feed supplements. To avoid a build-up of heavy metals in your soil, analyze manure used as fertilizer and check your soil regularly for changes in the accumulation of these contaminates. Plastics. Plastics have revolutionized horticulture production by serving as mulches and row covers. Unfortunately, the advantages of plastic use come with an environmental price. While plastics reduce leaching and water logging of covered soils, they also concentrate water that cannot soak through the plastic into the soil. Concentrated water flowing off from plastics forms erosive streams, which has been shown to cause up to four times more water runoff and 15 time more soil erosion as compared to fields mulched with organic materials. Disposal of plastic mulches poses an additional environmental problem. The National Organic Standards require removal of plastic mulches from beds at the end of the production season, and once removed, good methods for plastic disposal or recycling are lacking. Since soiled plastics cannot be recycled economically, plastic users are forced to dispose of this material through incineration, burying on the farm, or landfilling. All of these methods are damaging to the environment and ultimately unsustainable.

by Barbara Bellows
NCAT Agriculture Specialist
October 2002

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ATTRA is the national sustainable agriculture information service operated by the National Center for Appropriate Technology under a grant from the Rural Business-Cooperative Service, U.S. Department of Agriculture. These organizations do not recommend or endorse products, companies, or individuals. NCAT has offices in Fayetteville, Arkansas (P.O. Box 3657, Fayetteville, AR 72702), Butte, Montana, and Davis, California.