🚶 Phosphatic Fertilizers

Classification

a. Water soluble: Ca(H2PO4)2

👉🏻 Such water soluble phosphatic fertilizers are used for quick start and short duration like wheat, for neutral and alkaline soils.

SSP

  • 12 % S, 16% P2O5, 19% Ca
  • SSP is the first manufactured fertilizer in India.
  • Among phosphatic fertilizers, SSP is widely used in India. It is prepared by treating Rock Phosphate with equal amount of Sulphuric acid. After treatment dusty coloured mixture of calcium phosphate and calcium sulphate in equal amount is obtained. But SSP is generally formed by the mixing of Mono calcium Phosphate and Calcium Sulphate (Gypsum) in both forms i.e. powder and granular.
  • In alkaline or acidic soils SSP forms Calcium Phosphate, Iron phosphate or Aluminium phosphate, thereby preventing the fertilizer loss with water and thus is solubilized slowly in soil. That’s why total amount of this fertilizer is applied as a single dose either at sowing/ planting time or before the time of sowing/planting.
  • In general, SSP is suitable for all the crops and different soils.
  • According to standard: SSP must contain → Moisture content by wt.: 12% (maximum) Free Phosphoric acid by wt.: 4% (maximum) (H3PO4) Water soluble Phosphate by wt.: 16% (minimum)

DSP

  • 32 % P2O5

TSP

  • 46-48 % P2O5

DAP (complex)

  • 18 % N, 46 % P2O5
  • Diammonium Phosphate

MAP

  • 12 % N, 48 % P2O5
  • Mono ammonium phosphate is new grade P fertilizer

b. Citrate soluble P fertilizer: Ca2H2(PO4)2 or Ca2(HPO4)2 RRB-SO-2020

  • Used in acid soils, for long duration crops like sugar cane, low land rice, tapioca & tea. e.g.
  • Di Calcium Phosphate (DCP): 34-40 % P2O5
  • By neutralising the phosphoric acid by lime, Dicalcium phosphate is prepared and phosphoric acid is obtained by reacting HCL, H2SO4 or HNO3 with rock phosphate.
  • This fertiliser is equally suitable for acidic, neutral and alkaline soils but it is especially useful for acidic soils because it does not form compounds in such soil.
  • Basic slag: 14-18 % P2O5
  • Rhemania Phosphate: 23-26% P2O5

c. Citrate & Water insoluble P fertilizer: Ca3(PO4)

  • Tricalcium phosphate: used in strongly acid soils and suitable for plantation crops e.g.
  • Rock phosphate: 20-30 % P2O5 (It is used for acidic soil reclamation)
  • Raw bone meal: 20-25% P2O5
  • Steamed bone meal: 25-30% P2O5

Bio-super

  • It is form of organic fertilizer mostly in Australia.
  • Biosuper = Rock phosphate + Sulphur + S oxidizing bacteria (Thiobacillus)

Conversion factor for P

  • % P2O5 = % P x 2.29
  • % P = % P2O5 x 0.43

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