Nitrogen, Phosphorus, and Liming Effects of Poultry Layer Manures in Coastal Plain and Piedmont Soils

Since soil type and manure processing can affect nutrient release, laboratory and greenhouse experiments determined N and P availability, and liming value under representative layer manure application scenarios. Fresh, composted, and pelleted manures were applied to surface samples of three North Carolina soils (Belhaven, loamy, mixed, dysic, thermic Terric Haplosaprists; Cecil, fine, kaolinitic, thermic Typic Kanhapludults; and Lynchburg, fine-loamy, siliceous, semiactive, thermic Acne Paleaquults). A 90 d N mineralization incubation found greater N mineralization (83, 73, and 61% of total N applied in fresh, composted, and pelleted manures, respectively), in the Lynchburg than in the Cecil soil (41, 33, and 25% for the same manures); while mean N availability of urea was 80% for all soils. All manures exhibited effects on soil pH and Mehlich-3 extractable soil P during separate 21 d incubations that were consistent with their calcium carbonate equivalence and total P content. In a 30 d greenhouse experiment with millet [Urochloa ramosa (L.) T. Q. Nguyen] in the same soils, plant available N from the manures followed the decreasing order of fresh > composted > pelleted, similar to the rank order obtained in the N incubation study. Application of either inorganic or manure P sources to the Belhaven muck resulted in more water soluble soil P and greater plant P uptake than when P was applied to the mineral soils. Both soil and manure source influenced manure nutrient availability, but the availability coefficients from these laboratory and greenhouse experiments should be verified under field conditions.