Agronomic Evaluation of Poultry Manure as a Nitrogen Source for Conventional and No-Tillage Corn

Poultry manure is useful as a source of N for corn (Zea mays L.) production. An approach to predict available N in poultry manure (PM) was evaluated in a 3-year (1983–1985) field study with conventional (CT) and no-tillage (NT) corn. Poultry manure and ammonium nitrate (AN) were applied to an Evesboro loamy sand soil (mesic, coated Typic Quartzipsamments) at rates designed to supply 0, 84,168, and 252 kg potentially available N/ha. Potentially available N (PAN) in the PM was defined as PAN = 80% Nᵢ + 60% Nₒ, where N₁ = NH⁺₄-N + NO⁻₃ and Nₒ = total N - Nᵢ. Soil N₁ (0–0.6 m), plant N, corn N uptake, and grain yields were measured. Cover crop N concentrations and N uptake, as well as soil N₁ prior to planting and post-harvest were also determined to estimate residual N from PM and AN. Soil N₁ levels and N leaching (to 0.4–0.6 m) were generally higher with AN than PM. Plant N concentrations, N uptake, and corn grain yields were seldom significantly different with PM, compared to AN in 1983 and 1985, but were consistently lower with PM in 1984. Conventional tillage significantly increased grain yields, relative to NT, in 1984 (7.6 and 7.2 Mg/ha, respectively) and 1985 (7.7 and 5.5 Mg/ha, respectively). Little residual N was detected in 1984 or 1985 from prior applications of PM. Based on N budget calculations, the potential existed for considerable leaching losses of N. The efficiency of recovery of added N (ef) averaged 0.56 kg/kg for AN and 0.36 kg/kg for PM. Excess N (NEX) remaining in the soil, based on these ef values, was as high as 265 kg N/ha for PM and 166 kg N/ha for AN. Therefore, despite the selection of PM rates that resulted in soil N, plant N, and corn grain and dry matter yields comparable to those obtained with recommended rates of AN, N leaching may still occur when PM is used on coarse-textured soils