The Influence of Bean Rhizosphere on Phosphorus Release Kinetics in Calcareous Soils of Shahrekord Plain

Rhizosphere region soils have different chemical and biological properties from bulk soils. Information about phosphorus (P) release in the rhizosphere region soil of bean is limited. Therefore, the objective of this research was to evaluate the effects of bean (Phaseolus vulgaris L.) rhizosphere on P release kinetics in 9 types of calcareous soils from Chaharmahal-Va-Bakhtiari province under greenhouse conditions in a rhizobox. The kinetics of P release in the bulk and the rhizosphere region soils were determined by successive extractions with 0.5 M NaHCO3 in a period of 2 to 1008 h at 25 ± 1°C. The results of kinetics study showed that the mean amount of the extracted P after 1008 h in the extraction period in the rhizosphere region soils (215 mg kg-1) was significantly lower than that in the bulk soils (226 mg kg-1). The release kinetics of P from the rhizosphere region and bulk soils could be defined well by use of the first order, power functions and also, the simplified Elovich equation. The results showed that the amount of the P released after 1008 h and the constant P release rate in power function of the rhizosphere region and the bulk soils had a significant correlation with bean plant growth indices. This research indicated that bean rhizosphere could modify the P release characteristics. In addition, the released P amount and rate are important factors in supplying available P to plants.