buffering capacity in the soils with different soil management systems in dryland condition of Maragheh

Changes of soil physico-chemical properties for different management systems leading to change phosphorusrequirement، adsorption and buffering capacity in soils were studied. Soil samples of different soil management systems were analyzed for soil properties changes. Then، phosphate adsorption isotherms for the soils of different managements ((Langmuir adsorption isotherm) were examined. For all samples، adsorption of P was determined at standard equilibrium concentration (C). Adsorption capacity (Xm)، requirement and buffering capacity were determined from plot of C/X as function of C with linearly equation (C/X= C/Xm+1/K*Xm). The results indicated that different soil management systems changed soil physico-chemical properties. P sorption curve showed that with an increase in equilibrium concentration of P، the amount of adsorbed P increased linearly at different soil management systems. Accordingly، by using Langmuir adsorption isotherm، results indicated that phosphorus adsorption capacity differed from 800 to 1500 mg/kg at different soil managements. P adsorption capacity in natural pasture and forage-wheat system compared to others systems were highest. The lowest P adsorption capacity was at fallow-wheat system. It can be concluded that soil management systems change soil physico-chemical properties. P requirement، adsorption and buffering capacity were varied for different soil management systems. Phosphorus availability depend on P adsorption and buffering capacity.