In this article we will discuss about:- 1. Meaning of Fertilizers 2. Classification of Fertilizers 3. Materials Used in Manufacturing of Fertilizers (Mixed) 4. Acidity and Basicity of Fertilizer.
Meaning of Fertilizers:
Liebig in Germany and Lawes in England developed independently the idea of treating phosphate with H2SO4 and producing a water soluble phosphate by about 1840. It is known as superphosphate or simply super. Lawes set up a factory at Deptford in 1843 for the production of superphosphate. Possibly this was the first factory to be set up for the production of artificial fertilizers on a commercial scale.
Fertilizers are the organic or inorganic materials of natural or synthetic origin which are added to the soil to supply certain elements essential to the growth of plants. The term ‘Fertilizer’ is now commonly restricted to commercial products.
Amendments are the substances other than manures and fertilizers which are added to soils for the improvement of their condition.
Amendments are also termed as ameliorants, improvers or soil conditioners e.g. gypsum and lime though they supply nutrients but the main objective of applying them is for correcting the soil condition.
Classification of Fertilizers:
(a) Straight Fertilizers:
Such fertilizers has declarable content of only one major nutrient e.g. urea, ammonium sulphate.
(b) Binary Fertilizer:
It contains two major nutrients e.g. – Potassium Nitrate.
(c) Ternary Fertilizer:
It contains three major nutrients e.g. Ammonium potassium phosphate.
(d) Compound/Complex Fertilizer:
Such fertilizer has a declarable content of at least two of the major nutrients obtained chemically and generally granular in form. e.g. Nitro- phosphate, Amm- phosphate and Diammonium phosphate (DAP).
(e) Mixed Fertilizer:
Individual or straight fertilizer materials are blended together physically to permit application in the field in one operation. Such fertilizers supply two or three major nutrients in a definite proportion or grade e.g. – nitrophosphate with potash 15: 15: 15 of NPK.
(f) Complete Fertilizer:
They have all the three primary major nutrients viz. N, P, & K.
(g) Incomplete Fertilizer:
It contains any two primary nutrients.
(h) Low- Analysis Fertilizers:
They have less than 25% of the primary nutrients e.g. SSP (16% P2O5), sodium nitrate (16%N).
(i) High- Analysis Fertilizer:
They have more than 25% of the total primary nutrient content e.g. urea, anhydrous ammonia (82.2%N), Ammonium phosphate (20% N + 20% P2O5), DAP (18% N + 46% P2O5).
It refers to the guaranteed analysis of its plant nutrients. It is the minimum guarantee of the plant nutrient contents in the terms of N, available P2O5 and K2O e.g. 6:24:24.
It refers to the relative percentage of N, P2O5 and K2O i.e. 1:4:4 if fertilizer grade is 6:24:24.
Materials Used in Manufacturing of Fertilizers (Mixed):
1. Suppliers of Plant Nutrient:
Straight fertilizers are used for this purpose.
To check absorbing moisture and making one, conditioners like straw, groundnut husk, paddy husk, peat soil etc. are used they just reduce caking and applied in drilling conditions and these conditioners are of low organic materials.
3. Neutraliser of Acidity or Basicity:
Dolomitic limestone is used to reduce residual acidity. Most fertilizers leave residual acidity or basicity.
4. Filler Material or Make Weight Material:
Sand, soil, earth, coal ash, charcoal such waste materials are added to make up the difference between the weight of the added fertilizers required to supply the plant nutrients and the desired quantity of the fertilizer mixture.
Precautions in Mixing Fertilizers:
1. Hygroscopic fertilizers should not be mixed because they form cakes after mixing.
Hygroscopic fertilizers are in descending order:
(a) NH4NO3 (Amm. Nitrate)
(b) Urea – CO(NH2)2
(c) Ammonium sulphate – (NH4)2SO4
(d) Amm.sulphate nitrate – (NH4)2SO4NH4 NO3
(e) Calcium ammonium nitrate (CAN)
The most hygroscopic fertilizers ammonium nitrate and urea stands second. All these fertilizers have NH+4.
2. Fertilizers containing NH4+ should not be mixed with basically reactive materials like lime, basic slag and rock phosphate because mixing results in the loss of N through escape of NH3 gas.
3. All water soluble phosphatic fertilizers like super phosphate should not be mixed with those fertilizer that contain free lime because it will convert the soluble phosphate into insoluble form.
4. Slightly acidic fertilizer containing chloride may damage the gunny bags and drilling equipments.
Acidity and Basicity of Fertilizer:
The amount of CaCO3 required to neutralise the acid residue caused by application of acidic fertilizers in the soil e.g. 100kg (NH4)2SO4 produces acidity which needs 110 kg of CaCO3 to neutralise it. Therefore equivalent acidity of (NH4)2SO4 is 110, Anhydrous NH3 has more equivalent acidity than other fertilizer.
Residual basicity caused by application of basic fertilizers, expressed in terms of CaCO3 equivalent of basic residue left by a fertilizer material (in kg/100kg of fertilizer salt).
Commercial Nitrogenous Fertilizers:
Except paddy and potato, the ammoniacal form is not directly absorbed by crops. Ammonia always produces acidity. Except NO–3, CaCN and CAN; all other nitrogenous fertilizers are acidic in nature. NO–3 and CaCN are basic in reaction, whereas CAN is neutral.