Influence of Poultry Manure on Sorption Characteristics and Standard Phosphorus Requirement in Some Calcareous Soils of Hamadan Province

Mobility and availability of phosphorus (P) in soils is affected by Phosphorus Sorption Characteristics (PSC). The objective of this research was to study the effect of Poultry Manure (PM) PSC and Standard Phosphorus Requirement (SPR). Ten calcareous soil samples were incubated without and with 1.5% (w/w) PM for 5 months at field capacity at 25±1° C. The PSC of these samples were determined by using traditional isotherms and single point (1500 mg P kg-1). The results showed that available P increased with an application of PM. Mean available P increased by 58.5%. Sorption data in all the samples were described by Freundlich and linear models. Adsorption isotherm constants decreased with an application of PM. The mean distribution coefficient and Freundlich values of n decreased by 72.4 and 63.6 %, respectively. The mean equilibrium buffering capacity (slope of linear model) in treated soils decreased by 12.9%. The mean available P (Y intercept of linear model) and equilibrium P concentration (X intercept of linear model) increased by 34.4 and 132% respectively. The Standard Phosphorus Requirement (SPR) was lower in treated than in untreated soils. The mean P Sorption Index (PSI) decreased in treated soils by 11 %. The results in this research revealed that an application of PM may increase the risk of P release into surface water.