Phosphorus release rate and plant response in some calcareous soils

Abstract

Phosphorus release studies are of considerable interests in soil and environmental science. The objective of this research was to study on the P release in 10 Iranian calcareous soils by successive extraction with 0.5 M NaHCO3 over a period of 1752 hours and the correlation of P release characteristics with soil properties and growth indices of corn. The results showed soil phosphorus desorption from soils began with a fast initial reaction followed by a slow secondary reaction and the rate of P desorption did not reach a plateau until 1752 h. This indicated that desorption would continue, at considerable rates, for much longer periods than 1752 h. The cumulative amount of soil P released ranged from 309–586 mg kg−1. The cumulative amount of P release was evaluated by six kinetics equations. Statistical analysis showed that phosphorus desorption kinetics were described by parabolic diffusion, first order and power function equations. The values of pH, calcium carbonate equivalent and initial Olsen-P influenced value and rate of P desorption from soils. Growth indices of corn have showed relationships with some P release parameters such as a, a.Kd, and also cumulative P desorbed at the end of extraction period, indicating that release kinetic parameters of P release might control the plant available P in soils studied.