Effect of citric acid treatment on release of phosphorus, aluminium and iron from three dissimilar soils of India

To evaluate different mathematical models for describing cumulative release of phosphorus (P), aluminium (Al) and iron (Fe) by citric acid (CA) from soil, an experiment was conducted in packed soil columns with three contrasting soils viz. Alfisol, Vertisol and Inceptisol. The soils were saturated with CA at 0, 5, 10, 20, 40 and 100 mg L-1, the leachate were collected by liquid displacement at 15, 30, 45, 60 day intervals, and P, Al and Fe releases were analyzed. The release data were fitted to linear, quadratic, exponential, logarithmic, and power form of equations. The results revealed that the highest cumulative release of P, Al and Fe was observed in the 40 mg L-1 CA treatment. In the majority of cases, the relationship between CA concentration and cumulative release of ions fitted well in quadratic equation (y = ax(2) + bx + c). The Fe and Al releases with time were fitted well in power-form (y = at(b)), while the cumulative P release in linear equation (y = mx + c). The study also revealed that a substantial amount of released P could serve as potential source of plant nutrient in fixation prone soils. The study demonstrated that CA can be used as a 'solubilizer' of soil P, 40 mg L-1 dose released the highest P, 0-20 mg L-1 dose was observed to be economical and 5 mg L-1 was the most promising dose in Alfisol.