Manure, in its basic form, is an organic material generally composed of animal feces. While simple in concept, manure has become a complicated and sometimes emotional issue for both farmers and non-farmers.
Animal manure is most likely the first fertilizer used on crops produced by humans. A University of Oxford researcher analyzed early cropping sites across Europe and determined that manure was in fact used by farmers over 8,000 years ago. Also, records kept by the Babylonians, Egyptians, Romans and early Germans show manure was used to increase yields on their farms.
The practice of applying a purchased fertilizer is considered recent in relation to the use of animal manure as a fertilizer. Most commercial fertilizers contain the three basic plant nutrients: nitrogen (N), phosphorus (P) and potassium (K), which are mined, manufactured and sold to supplement the crop’s needs.
Manure also contains nitrogen, phosphorus and potassium, and the agriculture community values animal manure as a source of these nutrients for crop and hay production, and on pastures.
In addition to providing plant nutrients for optimum plant growth and production, manure also has environmental benefits when properly applied to the soil. Manure contains organic carbon, which is a source of energy for the microbes that live in a healthy soil environment. These microbes help stabilize nutrients, as well as provide nutrients to plants.
Some of the organic carbon is not immediately available for use by the soil microbes. This portion of the organic carbon is called soil organic matter, and consists of plant or animal tissue in various stages of decomposition.
In addition to providing nutrients, organic matter from manure aids in improving soil structure. Improved soil structure helps increase water infiltration during rain events and can increase the water-holding capacity of the soil. These important benefits can reduce plant stress during periods of drought, and aid in reducing soil erosion.
Fully utilizing nutrients contained in manure within a cropping system also has energy benefits when one considers how much energy is used to actually mine and manufacture commercial fertilizer. When commercial nitrogen fertilizer is made, significant amounts of energy are used, resulting in greenhouse emissions. Anhydrous ammonia, frequently used to side-dress our corn crops, uses an estimated 3,300 cubic feet of natural gas to produce enough for an acre of corn, assuming at 200-pound application. Meanwhile, phosphorus and potassium fertilizers also have significant energy requirements related to the actual mining and processing of these elements from the ground.
Land application of manure is the most cost-effective and accepted method for handling animal manure. As more people move into traditional agriculture areas and dairy farms continue to increase cow numbers to remain economically sustainable, neighbors become concerned about the potential impact on the local environment and water quality. Farmers strive to manage manure in ways that maximize its benefits and protect water quality.
With the introduction of manure storages, the need for daily hauling and spreading is eliminated and allows manure to be stored until conditions are both environmentally safe and agronomically correct for field application. Whether manure is hauled and spread daily or stored and spread seasonally, it should always be utilized according to a nutrient management plan.
In addition to the advantages, there are some disadvantages to manure storage systems. For the farmer, often the costs are not offset by the fertilizer savings; the unloading seems to occur during busy spring and fall seasons; and they can pose water quality and safety hazards if not designed and maintained properly.
Fortunately in New York, the state Department of Environmental Conservation is responsible for protecting streams, rivers and other waterways by comprehensively regulating activities that could impact water quality. This includes the requirement for all livestock farms over a certain size that confine animals for 45 days or more during any 12-month period to obtain a permit from the DEC, known as a Concentrated Animal Feeding Operation general permit. More information about the CAFO permit can be found at agriculture.ny.gov/faq_manure_storage.pdf.
This past fall was unusually wet, which created challenges for farmers to harvest crops and apply manure. New York does allow for winter spreading of manure, with more information found at Cornell University’s Nutrient Management Spear Program.
Farmers have long understood the importance of manure for the nutrients and soil health benefits it provides. As stewards of the land, farmers strive to protect the environment and water quality as well as commit to keeping manure and its associated nutrients on their fields.