Assessment of phosphorus fixing capacity in contrasting soil orders in central India

Abstract

Phosphate adsorption by soils is important because adsorbed P equilibrates with soil solution P, which in turn is immediate source of P. While P fixation continues to receive much attention it is more important to know the effect of soil characteristics on P fixation. Phosphorus sorption characteristics of JNKVV, Farm, Jabalpur representative agricultural soils belonging to three soil orders namely Vertisol, Inceptisol and Alfisol were investigated for adsorption behaviour of P and sorption data were fitted to Langmuir equation. The Langmuir constant i.e. adsorption maxima was highest for Vertisol (504.26 μg g-1), followed by Alfisol (480.89μg g-1) and Inceptisol (452.98μg g-1) respectively. The phosphate adsorption isotherm gave good fit adopting Langmuir (r2 = 0.98 to 0.99) for the three soils. The value of equilibrium solution P concentrations were found significantly variation under different soil orders but the adsorb P value was also found significant varied. The equilibrium solution P concentrations minimum in Alfisols 0.03 to 8.95 mgµg mL-1 and maximum in Inceptisols 0.09 to 10.95µg mL-1, but the adsorb P value was minimum in Inceptisols 19.01 to 290.41µg mL-1 and maximum were recorded in Alfisols 19.64 to 310.47µg mL-1. In Vertisols the value of equilibrium solution P concentrations were found in the range of 0.13 to 10.08µg mL-1 and adsorb P values were 18.65 to 299.13µg mL-1. The range of P buffering capacity was 60.07 to 70.89 L kg-1. The highest value of MPBC was found in Alfisols with the mean value 68.89L kg-1and the lowest of MPBC value was found in the Inceptisols with the mean value was 63.72L kg-1. Correlation of Adsorption parameters of Langmuir and were worked out taking all soil types together with pH, EC, organic carbon, clay, CEC and CaCO3. For the Lamgmuir equation, value of ‘r’ indicated that P adsorption maxima (b) was significantly and positively correlated with pH (r=0.993**), clay (0.916**) EC (r= 0.734*).