Relationships between labile phosphorus and olsen phosphorus test values of alkaline soils
2001
Rashid, A. (University of Agriculture, Faisalabad (Pakistan). Plant Protection Inst.) | Hussain, T. | Razzaq, A.
For the development of soil and plant phosphate (P) model, the soil labile-P values Ira required in addition to fertilizer P availability indices. This study was conducted to determine the relationship of labile-P (IRA-400 anion exchange resin, NaHCO3 form) with a routine Olsen-P (NaHC03 extractant) method in order to develop predictive equations for labile-P. Nineteen alkaline surface soils representing a wide range of properties with initial P treatment at the rate of 0, 30, 60, and 90 mg P kg-1 soil were used in laboratory experiment for a 7- day and a 6-month incubation period. Labile-P (Pil) and Olsen-P (OP) increased with increased P rates. Pil related linearly to OP values at all P rates, showing a decreasing trend in correlation coefficient (r = 0.877** - 0.751** with a 7-day incubation; r = 0.856** -0.643** with a 6-month incubation) with increased P rates. After a 7- day incubation, about 77% of variation in Pil were explained by the regression equation and it decreased to 50% at higher P rate. Both incubation periods showed similar relationships, indicating the feasibility of a 7- day incubation period for such studies. Using mean values of all P treatments of a 7-day incubation (76 soil P test values), the relationship was further improved (r = 0.92**, P = 0.01) by a workable predictive equation of labile-P (Pil) from Olsen-P (OP): Pil = 7.936 + 1.385 OP.
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