How much of phosphorus to be applied for rice crop?
The texture of the soil is important while considering phosphorus application. Recovery of phosphorus from added fertilizer is much less in heavy soils than in light soils. For example: in black clay soils the recovery is 20 to 40% compared 60 to 80% recovery in red sandy soils. It is now known that the phosphorus status of soil should be built up to a particular level to achieve higher yields. At least 35 kg P2O5 per ha should be available in soil to get profitable returns to fertilizer application in rice. If soil analyses shows below this level, the phosphorus fertilizer requirement is calculated as given below: Example: Optimal requirement is 35 kg P2O5 Soil test value is 20 kg P2O5 Say, the recovery of added phosphate is 25% The amount of fertilizer needed to bring up the soil to 35 kg P2O5 per ha level is: ((35-20) x 100) / 25 = 60 kg P2O5 per ha This amount of 60 kg P2O5 per ha in terms of super phosphate (16% P2O5) is: ((60×100) / 16) = 375 kg of super phosphate Thus knowing th
