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:
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:
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.
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.
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.
Raw manure use has often been associated with imbalances in soil fertility. There are several causal factors:
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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Topics Within This Chapter:
- Introduction to Manure Management on Organic Farms
- National Organic Program Standards for Manure
- Benefits and Limitations in Using Livestock Manure
- Managing Nutrients in Livestock Manure
- Timing of Manure Application
- Manure Application Rates
- Manure Application Methods
- Manure Storage Systems