Chapter 9

Manure Management on Organic Farms

Benefits and Limitations in Using Animal 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

When correctly applied, livestock has the following beneficial effects on soil properties, thus creating suitable conditions for root development and consequently promoting higher yield and higher quality of crops:

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

There are also limitations to livestock manure:

Contaminants

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

It has long been acknowledged that improper use of raw manure can adversely affect the quality of raw vegetable crops such as potatoes, cucumbers, squash, turnips, cauliflower, cabbage, broccoli, and kale.

Fertility Imbalances

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

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.

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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