Application rates of manure as a nutrient source vary by crop
Manure has long been used as a source of primary plant nutrients, including nitrogen, phosphorus, and potassium. However, the proportions available in manure are unlikely to match a crop’s nutrient needs perfectly. For instance, while manure could be used to satisfy many crops’ nitrogen requirements, this would result in more phosphorus being applied than what most crops need. Excessive application of manure on cropland can cause nutrients to accumulate in soil, leach, or to run off into nearby bodies of water. To help avoid over-application of nutrients, farmers can test the nutrient content of manure, restrict manure applications, and/or apply just enough supplemental commercial fertilizer nutrients to meet their crop’s needs. Between 2013 and 2019, producers of seven major crops in the United States who used manure were asked how much manure they applied per acre on these croplands. Using this information, ERS estimated crop nutrient application rates. Corn received the highest application rate of nitrogen from a manure source—92 pounds per acre—followed by cotton, wheat, barley, oats, soybeans, and peanuts. Cotton led phosphorus application at 37 pounds per acre, and corn led potassium application at 59 pounds per acre. Soybeans and peanuts require less nitrogen fertilization; therefore, they were applied with the lowest manure nitrogen application rates. Manure applied to soybeans and peanuts is valued primarily for its phosphorus and potassium. In 2020, manure was applied to about 8 percent of the 240.9 million acres planted to 7 major U.S. field crops. This chart appears in the USDA, Economic Research Service report Increasing the Value of Animal Manure for Farmers, published March 2023.
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