Effect of Five-Year Continuous Poultry Litter Use in Cotton Production on Major Soil Nutrients

Repeated application of poultry (Gallus gallus) litter to crop lands may lead to nitrates leaching and build up of P and other elements in the soil profile, which are prone to loss from runoffand erosion. A study was conducted for 5 yr at Belle Mina, AL on a Decatur silt loam (fine, kaolinitic thermic Rhodic Paleudult) during 1994 to 1998 to determine the nitrate movement and quantify the build up of P, K, Ca, and Mg due to the application of nitrification inhibitor, carboxymethyl pyrazole (CP), treated fresh and composted poultry litter and urea in conventionally tilled cotton (Gossypium hirsutum L.). Poultry litter maintained soil pH (0-30 cm depth) where as application of urea resulted in a pH decline. The inhibitor, CP, significantly reduced the NO 3 - -N formation in all N sources for 41 d following application. However, over the longer period of time, very minimal changes in nitrate concentrations were observed due to change in rates or sources of N. Over the experimental period, P concentration increased significantly (by 74%) in composted litter applied plots (17.7 mg kg -1 ) but not in fresh litter plots (1.5 mg kg -1 ). Linear increase in P accumulation was observed with increase in rate of composted litter. Concentrations ofK and Mg increased significantly both in fresh (93 and 25 mg kg -1 , respectively) and composted litter (127 and 36 mg kg -1 , respectively) applied plots by the end of 5 yr period. These results indicate that a well-planned application of fresh poultry litter in soils that are not already overloaded with P is safe and treating litter with CP is advantageous from an environmental perspective.