Nitrogen Transformations in Broiler Litter-Amended Soils

Abstract

Nitrogen mineralization rates in ten surface soils amended with (200 μg N g−1 soil) or without broiler litter were investigated. The soil-broiler litter mixture was incubated at 25±1∘C for 28 weeks. A nonlinear regression approach for N mineralization was used to estimate the readily mineralizable organic N pools (N0) and the first-order rate constant (k). The cumulative N mineralized in the nonamended soils did not exceed 80 mg N kg−1 soil. However, in Decatur soil amended with broiler litter 2, it exceeded 320 mg N kg−1 soil. The greatest calculated N0 of the native soils was observed in Sucarnoochee soil alone (123 mg NO3− kg−1 soil) which when amended with broiler litter 1 reached 596 mg N kg−1 soil. The added broiler litter mineralized initially at a fast rate (k1) followed by a slow rate (k2) of the most resistant fraction. Half-life of organic N remaining in the soils alone varied from 33 to 75 weeks and from 43 to 15 weeks in the amended soils. When N0 was regressed against soil organic N (𝑟=0.782∗∗) and C (𝑟=0.884∗∗∗), positive linear relationships were obtained. The N0 pools increased with sand but decreased with silt and clay contents.