Phosphorus Sorption and Desorption Characteristics of Some Surface and Subsurface Vineyard Soils of Malayer Area in Hamedan Province

Phosphorus (P) sorption characteristics of soils influence P availability. This study was conducted to investigate P sorption isotherm, standard P requirement (SPR), P buffering capacity (PBC), desorption, and P hysteresis index (PHI) by 10 surface (0-30 cm) and 10 subsurface (30-60 cm) soils in vineyard soils of Malayer area in Hamadan province. Isotherm experiment was carried out by concentrations of P ranging from 0 to 200 mg l-1 of KH2PO4 salt in the presence of 0.01 M CaCl2. Desorption experiments were conducted with 0.01 M CaCl2. Phosphorus sorption characteristics in soil were calculated from isotherm equations. The average values of Olsen’s extractable P (Olsen P) in surface and subsurface soils were 24.3 and 19.4 mg kg–1, respectively. In surface and subsurface soils, Olsen P was higher than the optimum concentration of P for most crops (7-10 mg P kg–1). Phosphorus sorption curves were well fitted to the Freundlich, Van-Hay and Temkin equations. The SPR average of surface and subsurface soils, defined as the amount of P sorbed at an equilibrium concentration of 0.3 mgP l–1 was 18.7 mg kg-1 and 19.7 mg kg-1, respectively. The PBC average of surface and subsurface soils, account from Van-Hay equation was 89.2 l kg-1 and 103.5 l kg-1, respectively. The average value of PHI in surface soils (1.7) was greater than subsurface soils (1.6). There was significant negative correlation between SPR with Olsen-P in surface (p 15≤"> 0.01) and subsurface (p 15≤"> 0.05) soils. We found significant positive correlation between PBC with clay (p 15≤"> 0.01) and ECC (p 15≤"> 0.05) of soils. Our finding showed that high level of Olsen P concentration in surface and subsurface soils may decrease the availability of other nutrients.Appropriate P fertilizer management according to isotherm finding is needed.