Phosphatic fertilisers:

The nutrient phosphorus present in phosphate fertilizers are usually expressed in terms of phosphoric anhydride or simply as phosphorus pentaoxide, P2O5. The availability of phosphorus in which it is present. The amount of phosphorus available to the plants depends upon the extent to which the fertilizer supplies HPO4----or H2PO4 –ions. According to the solubilities, the phosphatic fertilizers are divided in following groups.

  1. Water soluble phosphatic fertilizers: These fertilizers contain phosphorus in available form in neutral soils, which can be readily absorbed by young plants. In acid, soils and free iron, aluminium hydroxy phosphates but in alkaline and calcareous soils, water soluble phosphorous is converted into insoluble calcium phosphate. The common examples of these fertilizers are:

  2. S.N. Fertiliser % P2O5

    i

    Single Superphosphate (CaH2PO4)16

    18% P2O5

    ii

    Double superphosphate CaH4(PO4) 2

    32% P2O5

    iii

    Triple superphosphate Ca(H2 PO4) 2

    46 to 48% P2O5

    iv

    Ammonium phosphate

    20% P2O5

     

  3. Citric acid soluble Phosphatic Fertilizers: The citric soluble fertilizers are suitable for acidic soils because at low pH citrate soluble phosphorus is converted to monocalcium phosphate not as water soluble phosphate and therefore, phosphorus is not fixed as iron and aluminium phosphate.

    S.
    No.

    Fertiliser

    % P2O5

    i

    Dicalcium phosphate, CaHPO4

    14% P2O5 extract soluble

    ii

    Basic slag (CaO) 5P2 O5. SiO2 17

    20% P2 O5 extract soluble

    iii

    Calcium metaphosphate Ca (PO3) 2

    60 to 64%P2 O5 extract soluble

     

  1. Water and citrate insoluble phosphatic fertilizers: These mineral fertilizers contain phosphorus, which is insoluble in water as well as in citric acid. They are suitable in strongly acid soils or organic soils. These fertilizers are given in green manured fields. The phosphorus is very slowly released by microbes at action and remains in soil for long time.

S.
No.

Fertiliser

% P2O5

i

Rock Phosphate Ca3 (PO4)2CaF2

20 to 30% P2O5extract soluble

ii

Bone meal (Ca(PO4) 2) 3 CaF2

21 to 25% P2O5 extract soluble


(d) Other phosphatic fertilizers: Following are the other phosphatic fertilisers.

S.
No.

Fertiliser

% P2O5

i

Kotka phosphate

26% P2O5

ii

Rhenmia phosphate

26 to 28% P2O5

iii

Thermophos

18.3% P2O5

iv

Pelophos

18% P2O5

v

Coronat phosphate

21% P2O5


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