Enhancement of the fertilizer value of rock phosphate engineered through phosphate-solubilizing bacteria

Abstract

Increasingly high costs of chemical fertilizers are major problems to the fish farmers of India. This was the main stimulus for searching for an alternative, naturally-occurring, dependable, biodegradable, phosphatic fertilizer. Phosphate-solubilizing bacteria (PSB) and solubilization of Mussoorie phosphate rock (MPR) were examined in simulated fish ponds using four treatments: (a) addition of compost of straw, waterhyacinth and cattle manure; (b) exogenous introduction of PSB, compost and MPR; (c) compost and MPR; and (d) bacteria-free compost, PSB and MPR. Exogenous introduction of PSB with the compost resulted in the highest concentrations of different species of phosphate in water or sediments among all treatments. This was attributable to the combined effects of the PSB population of both exogenous and compost origin with short generation time. The relationship between the phosphorus level of water and PSB population was expressed in exponential equations in all but compost treatment without MPR. The results of stepwise multiple regression analysis indicated that the MPR-leached phosphate was strongly influenced by PSB, followed by alkaline phosphatase in all treatments, except that treated only with compost.