|MOLINA, J A|
Submitted to: Lesislative Commission on Minnesota Resources
Publication Type: Other
Publication Acceptance Date: 7/1/1995
Publication Date: N/A
Interpretive Summary: Livestock manures are a source of nutrients and their use on fields improves crop yields. Little is known regarding the amounts of manure that should be used on a given area. Nitrogen (N) is the crop nutrient that most often improves crop growth and grain yield. The amount of N needed by a soil depends on the amount of nitrate-N that the soil will naturally produce. The amount of nitrate-N that a soil produces depends on soil water and soil clay content. The amount of manure needed for best grain yield differs for each soil type. Use of the same amount of manure on three soil types, a sandy soil, a clay loam and a silt loam, showed that the largest yields were obtained from the silt loam in a wet year. A water content in the soil of about 26 to 28% by weight seemed to be best for the formation of nitrate-N from manure. Manure should be applied to the soils to provide about 140 to 160 pounds of available N per acre. Some value is obtained in the second year after manure is applied. Amounts of manure applied in the second year should be smaller than the amounts applied the first year. Corn flowers earlier when livestock manure is applied before planting.
Technical Abstract: Nitrate-nitrogen produced by the mineralization of manure is expected to be affected by the same environmental factors affecting mineralization of indigenous organic matter. One of these factors, aeration, is affected by soil water content which in turn is largely controlled by soil clay content. To examine this affect in more detail, plots were established on an Aastad clay loam, a Kranzburg silt loam, and a Sioux sandy loam by applying 7,700 L of liquid dairy manure/acre (equivalent to application of about 160 lbs of available N/acre). Plots were then irrigated with different amounts of water to establish different soil water contents. Soil samples were collected and analyzed for nitrate-N and water content. Rather large amounts of nitrate-N developed in the surface depth increments at all three sites and some tendency of texture and water content developed but was inconclusive in establishing the effect of aeration on development of nitrate-N. Corn grain yields averaged 115.3 bu/a, 91.0 bu/a, and 62.9 bu/a on the silt loam, clay loam, and sandy loam sites, respectively in 1993; these yields were competitive with applications of conventional inorganic N-fertilizer at recommended rates of application. Manure applications showed clear effects of advancing the rate of corn development; flowering was advanced by as much as 2 to 4 days on sites receiving liquid dairy manure in the previous fall.