Phosphorus Availability in Soils as Affected by Fertilizer Phosphorus, Sodium Silicate and Farmyard Manure

A green house experiment was conducted to study the effect of applied superphosphate, sodium silicate and farmyard manure on the P absorption by rice in three different soils ranging from calcareous, alkaline to acid. The drymatter, yield and total P removal by rice increased significantly with the increase in applied fertilizer P. Increased P uptake waS also observed with the farmyard manure application in acid and calcareous soils, though the increase was of lower magnitude compared to the applied fertilizer P. Sodium silicate application increased P uptake only in the absence of applied fertilizer phosphorus. Soil phosphorus availability registered a marked increase with increase in the rate of applied fertilizer P. The application either of sodium silicate or farmyard manure resulted in smaller increases in soil available P as compared with fertilizer phosphorus. The estimates of P availability were of similar nature as measured by supply parameter, cumulative desorbed P and each of NH₄Cl. NH₄F, NaHCO₃ and CaCl₂ extractable P.