Fertilizer Value of Indigenous Rock Phosphates Compared with Single Superphosphate: Laboratory Incubation Studies with Farmyard Manure

Fertilizer value of indigenous rock phosphates in a slightly alkaline soil (pH 7.5) was evaluated in laboratory incubation studies. The efficiency order of the rock phosphate from different deposits was found to be Laccadive > Mussoorie > Udaipur, which was related to their citrate solubility. Superphosphate par excelled as P source to all indigenous rock phosphates. Phosphorus availability from these sources increased with (i) the P application levels from 60 to 180 kg P₂O₂/ha, and (ii) with the incubation period upto 75 days only. Application of FYM at the rate of 60 tonnes/ha showed little effect on the availability of P from the rock phosphates.