How to Use Manure in Organic Growing


| 9/19/2014 3:45:00 PM


Tags: organic farming, manure, livestock, OMRI, Lindsay Fernandez-Salvador,

Farmer Uses Manure The use of animal manure in organic farming has been significant in the sustainable agriculture movement. Manure is a great source of many crop nutrients, including both micronutrients and macronutrients. Nitrogen is typically the nutrient with the most value, as well as the greatest potential for soil and water pollution. Quality and potential for contamination are both factors when learning how to use manure and selecting a manure source. Similarly, there are concerns with food safety when applying manure, and specific application guidelines have been designed to reduce the risk of pathogen contamination.

Nutrients are essential to proper growth of all plants, and farmers carefully plan to provide them, including finding the best source of manure for their nitrogen needs. Different animals produce manure with variable nutrient content, and some manure sources are more readily available and cost effective than others.

Manure from layer poultry, for example, provides nearly four times the nitrogen per ton as that from lactating cows. It also contains upwards of 12 times the potassium and phosphorus content of dairy manure. However, poultry manure is more costly than dairy manure — sometimes running twice the price. Poultry manure can also burn plants because of the large quantity of nitrogen it contains, so it’s generally composted or aged before being applied to a garden or farm. Another option is to apply it to a fallow field months before planting, so the soil microorganisms can break down the nutrients and make them more available to the plant. Whatever method is used, it’s important to note that under the best conditions only about half to three-quarters of the nitrogen in the manure is available to the crop in the year it’s applied. The remaining nitrogen will become available over a period of years. That’s why it’s important to regularly sample the soil to determine nutrient needs for the year. It’s also key to monitor crop nitrogen needs so that manure isn’t over-applied, contributing to contamination of water by ammonia, organic matter, nutrients and bacteria.

Another factor to consider when selecting a manure source is potential contaminants. Some contaminants, such as heavy metals, can be avoided by requesting a laboratory analysis. Heavy metals are a concern in manure, since there can be high potential content and farmers may also use high application rates. Heavy metals present in manure may include cadmium, lead, zinc and arsenic. Poultry manure is particularly at high risk for arsenic contamination, because nonorganic chickens are often fed arsenic to promote growth and weight gain. For this reason, poultry manure from organic sources is popular.

Another way to avoid heavy metals in manure is to select an Organic Materials Review Institute (OMRI) Listed manure product. OMRI requires heavy metals to be below a certain threshold before listing the product for use in organic production. Although other contaminants are present in manure, heavy metals are the easiest to avoid. Contaminants such as hormones and antimicrobials are difficult to even identify because they are so pervasive in the conventional manure supply, and there are no guidelines in place to control this contamination. Finding an organic source of manure is therefore the best way to avoid many potential hazards.

The application of manure also has implications for food safety. Pathogens such as Salmonella and fecal coliform are the main concerns when applying manure to edible crops. The USDA organic regulations require that a harvest interval be followed after applying manure, where crops in contact with soil (carrots, potatoes, lettuce) may be harvested only after 120 days, and crops not in contact with soil (blueberries, apples, peppers) may be harvested after 90 days. The logic behind this harvest interval is that pathogens will likely be rendered unviable by soil microorganisms after a certain time period, and will no longer pose a threat to food safety.

mjr
5/29/2015 8:38:03 AM

Two comments... one the temperature to achieve is only a convenience to match their rule for delayed harvest... composting research shows that the length of time at various temperatures to eliminate pathogens is a nice graph... lower temperatures take longer.. find the graphs Second, and crucially.... why would you need to go looking for manure from sources you know nothing about when you could use composting toilets... the National Sanitation Foundation tests such toilets and has determined that certain ones have well described processes and designs that produce reliable compost... look for NSF-41 Standard models... then the heavy metal risk and pharmaceuticals/etc are under your control (and you know your health standards improve, from a multiplication of benefits) If you have European rural and gardening ancestry that remembers how to deal with proper composting of family human waste then you can consider European standard composting toilets, but getting the plagued local health department to properly qualify them is the reality for some regulated areas.... ttyl


mjr
5/29/2015 8:28:04 AM

Two comments... one the temperature to achieve is only a convenience to match their rule for delayed harvest... composting research shows that the length of time at various temperatures to eliminate pathogens is a nice graph... lower temperatures take longer.. find the graphs Second, and crucially.... why would you need to go looking for manure from sources you know nothing about when you could use composting toilets... the National Sanitation Foundation tests such toilets and has determined that certain ones have well described processes and designs that produce reliable compost... look for NSF-41 Standard models... then the heavy metal risk and pharmaceuticals/etc are under your control (and you know your health standards improve, from a multiplication of benefits) If you have European rural and gardening ancestry that remembers how to deal with proper composting of family human waste then you can consider European standard composting toilets, but getting the plagued local health department to properly qualify them is the reality for some regulated areas.... ttyl





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