Most manure applied to corn fields is not incorporated into the soil

Corn farmers most frequently apply manure to the soil surface without incorporating it, rather than using other methods. Manure types vary based on water content, such as lagoon liquid, slurry liquid, and dry or semi-dry. USDA, Economic Research Service (ERS) researchers found that irrespective of manure type, corn farmers used surface application most often, tending not to incorporate the manure with tillage afterward. With incorporation, manure is first spread on the soil surface and then mixed into the first few inches with a tillage implement, thus increasing its contact with the soil. Less than 30 percent of all surface-applied manure on corn fields is incorporated. Surface application without incorporating into the soil or applying manure through an irrigation system results in less nutrient retention and lower fertilizer value. Farmers gauge manure moisture content to determine which application method to use when addressing crop nutrient needs. On operations such as swine or dairy farms, it is common to use water to wash manure out of barns, creating lagoon and slurry liquid manure with a high water content. Liquid manure is usually applied to the land’s surface, but roughly 20 percent is injected into the soil using specialized equipment like a manure injector. Only a small portion of liquid manure stored in lagoons is sprayed through irrigation systems. Poultry and beef feedlot manures are typically dry or semisolid. Almost all dry or semisolid manures are surface applied. In 2020, more acres were planted to corn (90.8 million acres) in the United States than any other crop, and a larger percentage of corn acres (16.3 percent) received manure than any other crop. This chart appears in the ERS report Increasing the Value of Animal Manure for Farmers, published in March 2023.

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