By Mary Wicks
You can’t get more basic than manure — all animals create it although only humans manage it. We have created litter boxes, toilets, wastewater treatment plants, and a variety of systems for handling livestock manure. Let’s look at the latter.
Not all manure is the same. Fresh manure is a mixture of feces and urine and can include livestock bedding materials or poultry feathers. All manure is valuable. It contains nutrients, including nitrogen (N,) phosphorus (P), potassium (K), organic matter, and micronutrients, so it’s often applied to cropland as a fertilizer. However, manure properties vary depending on the species, handling practices, and application methods.
Animals are different and so is their manure. For example, fresh manure from a broiler chicken is 4.91% N and 2.99% P on a dry basis, while a milk cow is 5.44% N and 0.80% P, and a hog is 7.66% N and 4.78% P. Manure nutrient content also varies within a species. To further complicate matters, differences in feeding programs can affect nutrient content. Modern feed rations match animal nutrient needs much more closely than years ago and this reduces nutrients lost in the manure.
Manure properties are affected by bedding, added water, and storage. Organic bedding such as straw or sawdust can absorb water in manure – up to 2.2 pounds per pound of bedding. While there are nutrients in bedding, the amount is less than in the fresh manure, so the nutrient content of the mixture will be diluted. Sand, which can be used for bedding at dairies, does not absorb water or contain nutrients but does increase volume, diluting the nutrient concentration.
Manure is handled as a dry or wet material depending on its water content. Dry manure, with less than 88% water, is removed from the barn and stockpiled or placed in a storage area. Fresh poultry manure is handled as a dry material, while dairy and hog manure needs bedding added to reduce the water content. Wet systems, in which the manure is pumpable, include dairies that use minimal or sand bedding where manure may be scraped or flushed with water to a storage pond. The ponds are often outdoors and open, where more water is added from precipitation. Hog barns that do not use bedding typically have a storage pit beneath a slatted floor.
Small operations may remove and land apply manure daily, but most farms store the manure so that it can be land applied based on weather conditions and crop needs. However, during storage, nitrogen may be lost to the atmosphere through volatilization, precipitation can dilute nutrients, and methane and odors may be released.
Applying manure to cropland at the right time and agronomic rate optimizes nutrients for crop production and improves soil quality. Because nutrient content can vary due to many factors, a lab analysis prior to application is recommended. While solid manure can be dispersed with a spreader and liquid manure is applied via a hose or tanker, both can be applied on the surface or incorporated into the top layer of soil. Incorporation may require specialized equipment, but it reduces the risk of runoff, odor emissions, and nitrogen loss. Applying manure nutrients closer to when a growing crop can use them has been a focus of university research in Ohio.
Beyond the basics
Getting the most value from manure requires understanding the details. Fortunately, help is available. The OCAMM website (ocamm.osu.edu) has links to resources. Or, contact your OSU Extension county educator or Glen Arnold, the OSU manure management field specialist (extension.osu.edu). Finally, watch for the Manure 1st initiative later this summer. Manure 1st, an outreach and education program being developed by the American Dairy Association Mideast in collaboration with Ohio livestock and poultry commodity groups, is designed to promote the use of livestock manure as the first choice for crop nutrient needs.
Mary H. Wicks is a Program Coordinator in the Department of Food, Agricultural and Biological Engineering of The Ohio State University. E-mail: firstname.lastname@example.org. Phone: (330)202-3533. This column is provided by the OSU Department of Food, Agricultural and Biological Engineering, OSU Extension, Ohio Agricultural Research & Development Center, and the College of Food, Agricultural and Environmental Sciences.