Effect of Composted Manure on Soil Chemical Properties and Nitrogen Use by Grain Sorghum

Compared to fresh manure, composting reduces material quantity, hauling and spreading costs, odor, and weed seed viability, while improving physical properties. The availability of nutrients for plant growth, however, may be less from manure compost. Objectives of this field study were to evaluate beef cattle manure compost as a nutrient source for irrigated grain sorghum [Sorghum bicolor (L.) Moench] and to determine the effects of annual compost and N fertilizer applications on soil chemical properties. Five rates of manure compost (0, 0.9, 1.8, 3.6, and 7.2 ton dry matter/acre) and four rates of N fertilizer (0, 55, 110, and 165 lb/acre) in a factorial arrangement were applied annually from 1987 to 1990 on a Ulysses silt loam (fine silty, mixed, mesic, Aridic Haplustoll) at Tribune, KS. Grain yields were greater from combinations of compost and N fertilizer than from either applied alone. The apparent fertilizer efficiency was 13% for compost compared with 36% for N fertilizer. Soil P, K, and organic matter increased linearly with increased rates of compost. Conversely, increased rates of N fertilizer decreased soil P and K, while having no effect on organic matter. Soil Na levels were increased by compost additions but not to excessive levels. Soil NO3−‐N levels were not affected by compost applications but were increased by N fertilizer. Manure compost is effective for maintaining or increasing soil chemical levels, especially P, without excessive accumulation of NO3−; but should be applied with N fertilizer for optimum grain production.