Chapter 9

Manure Management on Organic Farms

Benefits and Limitations of Manure

Raw livestock manure is an excellent resource for organic crop production. It supplies nutrients and organic matter, improves soil structure, stimulating the biological processes in the soil that help to build fertility. Still, a number of cautions and restrictions are in order, based on concerns about produce quality, food contamination, soil fertility imbalances, weed problems, and pollution hazards.

Benefits in Using Livestock Manure

Ogranic Nitrogen

In addition, organic nitrogen (manure N tied to organic compounds) is more stable than nitrogen applied as commercial fertilizer. A significant fraction of manure nitrogen is stored in an organic form that is slowly released as soils warm and as crops require nitrogen.

Organic Matter Content

Manure not only supplies many nutrients for crop production, including micronutrients, but it is also valuable sources of organic matter.

Soil Biological Activity

Organic matter additions, as manure or compost, are a source of energy (carbon) for the soil organisms (e.g., bacteria, fungi, and protozoa), helping to sustain their populations and their activity.

Manure Effects on Soil Erosion

Surface manure applications have the ability to decrease soil erosion leading to a positive impact on environmental protection.

Limitations in Using Livestock Manure


Some manure may contain contaminants such as residual hormones, antibiotics, pesticides, disease organisms (e.g., E. Coli, Salmonella, etc.), and other undesirable substances. Since many of these can be eliminated through high-temperature aerobic composting, this practice is recommended where low levels of organic contaminants may be present.

Nutrient Availability

Manure contains nutrients in organic and inorganic (crop available) forms. The organic form functions as a slow release fertilizer, gradually releasing nutrients to the crop.

Fertility Imbalances

Raw manure use has often been associated with imbalances in soil fertility. There are several causal factors:

Fertility Imbalances

Raw manure use has often been associated with imbalances in soil fertility. There are several causal factors:

Transportation Cost

The proximity of the site where manure is produced and crops are grown is key to managing manure for its agronomic benefits. During the early to mid part of the last century, crops and livestock were operationally and functionally linked enterprises. Most feed was homegrown and nitrogen provided by legumes and manure sustained crop yields. The introduction of inexpensive fertilizers and inexpensive transport costs allowed crops to be grown in one location and livestock produced in another.

Weed Problems

Use of raw manures has often been associated with increased weed problems. Some manure contains weed seed, often from bedding materials like small-grain straw and old hay. Hightemperature aerobic composting can greatly reduce the number of viable weed seeds.

Risks to Water Quality

Runoff or leached water from farm fields or holding areas presents a potential pollution problem to surface water and groundwater.

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