Effect of salicylic acid on phosphorus sorption characteristics in a calcareous soil

Document Type : Research Paper


1 Assistance Prof., Faculty of Agriculture, University of Urmia, Urmia, Iran

2 MSc. Student, Department of soil science, Faculty of Agriculture, University of Urmia, Urmia, Iran


Salicylic acid is an important organic acid in plants rhizosphere soil exuded in the phosphorus (P) deficiency condition. To study the sorption behavior of P in the presence of salicylic acid, a batch experiment was conducted with different concentrations of salicylic acid (0, 2, 5 and 10mM) and P (0- 45 mg P/L) in a calcareous soil. The results showed that application salicylic acid decreased the sorption of phosphate due to competition with organic acid for the sorption sites. The maximum phosphorus sorption (qmax) decreased by increasing salicylic acid concentration from 326 to 246 mg/kg. The application salicylic acid decreased all sorption parameters such as Langmuir binding strength (KL) (from 0.20 to 0.14 ml/g), sorption capacity of Freundlich (Kf) (from 59 to 46 mg/kg), the slope of Temkin equation (KT) (from 62 to 46) and the intercept of Temkin equation (A) (from 59 to 52 mg/kg). The standard phosphorus requirement (SPR) in equilibrium concentration 0.3 mg P/L calculated by Langmuir (SPRL), Freundlich (SPRF) and Temkin (SPRT) equations significantly decreased, for example SPRF decreased from 31.5 to 24.7 mg P/kg. Eventually it can be said, application salicylic acid and /or plants genetic improvement for more exudation this acid cause to increase P availability and reduce fertilizer requirement.


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