Phosphorus availability and fractions in a humic soil amended with poultry manure and lime

Abstract

Phosphorus (P) availability in highly weathered soils is limited. The objective of this study was to determine the effects of poultry manure (PM) and lime on P availability in humic soils. The soils were amended with lime and PM, separately and in combination, and incubated at field capacity moisture in a dark room at 25 °C. Destructive sampling was done after 0, 7, 14, 21, 28, 42, 56 and 84 days and analyzed for extractable P. Soil microbial biomass phosphorus (SMB-P) was analyzed at days 14, 28 and 84 while other soil P fractions were determined after day 84 only. The PM alone had significantly higher extractable P than lime alone and co-application, and some mineralized P from PM was fixed with no contribution of resident soil organic matter (SOM). Higher P availability was observed at 0–10 cm than at 10–20 cm depth. Application of PM and lime increased P availability and SMB-P and decreased Al-P and Fe-P. The SMB-P decreased with increased incubation time in all treatments. These findings imply that the addition of PM and lime increase P availability and SMB-P, reduce fixation of P in humic soils, and that PM addition reduces contribution of resident SOM to available P.