FERTILIZER

Sixteen elements are required for plant growth, these are carbon (C), hydrogen (H), oxygen (O), nitrogen (N), potassium (K), magnesium (Mg), calcium (Ca), phosphorus (P), sulphur (S), iron (Fe), manganese (Mn), copper (Cu), zinc (Zn), molybdenum (Mo) boron (B) and chlorine (Cl). Due to repeated cultivation soils get exhausted from these elements. So, for further cultivation and to make the land fertile, artificially prepared chemicals are used. So, fertilizers are the artificially prepared chemicals, which are mixed with the soil to make the land fertile for further cultivation. In other words, fertilizers are those substance which are mixed with the soil in order to remove the deficiency of essential elements required for plant growth.

Type of Fertilizer

(1) Complete fertilizer---

Fertilizers which supply all the essential elements, such as nitrogen (N), phosphorus (P) and potassium (K) [which are essential for plant growth] in varying proportion are known as complete fertilizer. Complete fertilizers are expressed as 6-12-12. This 6-12-12 signifying that, in this fertilizer, nitrogen (N) content by weight is 6%, phosphorus as P₂O₅ is 12% and potassium as K₂O is 12%. Examples of complete fertilizers are guano, nitro phosphate with added KCl etc.

(2) Incomplete fertilizer---

Fertilizers which supply one or two of the essential elements to the soil for plant growth are called incomplete fertilizer. Examples are super phosphate, nitro phosphate, calcium phosphate.

(3) Direct fertilizer---

Direct fertilizers are those, which can supply plants nutrients directly. Examples of direct fertilizers are super phosphates, nitrates and potassium salts.

(4) Indirect fertilizer---

Indirect fertilizers are those, which are used for improving physical and chemical properties of soil for better cultivation. Examples of indirect fertilizers are dolomite, lime, gypsum.

(5) Micro fertilizer---

Micro fertilizers are those, which can supply micronutrients such as calcium (Ca), magnesium (Mg), iron (Fe), zinc (Zn), boron (B), copper (Cu) etc. Plants required these elements in very small quantities, but these elements are very essential for plant growth.

(6) Mixed fertilizer---

Fertilizers which can supply more than one essential element to the soil for plant growth are called mixed fertilizer. Examples are nitro phosphate, KNO₃, mixture of triple super phosphate and potassium sulphate.

Essential Requirement of a Fertilizer

Nitrogen (N), phosphorus (P) and potassium (K) are the essential nutrients for a plant growth, but every compound containing nitrogen (N), phosphorus (P) and potassium (K) cannot be used as a fertilizer. The essential requirement of a fertilizer is---

(i) The nutrient elements such as nitrogen, phosphorus and potassium etc present in the fertilizer compound in such a form that, they must be easily available to the plant.

(ii) The compound used as fertilizer, should be soluble in water.

(iii) The compound used as fertilizer should be stable, so that after a long time this made available to the plant.

(iv) The fertilizer compound should be non toxic for plant as well as human life.

(v) The compound used as a fertilizer should be cheaper.

(vi) The P^H of the fertilizer compound, is such that it can adjust the P^H of the soil.

(vii) Due to rain water, the fertilizer compound should be converted in such a form that, they must be easily available to the plant.

Nitrogenous Fertilizer

Nitrogenous fertilizers supply nitrogen (N) element to the soil. So, this type of fertilizers is called N-type fertilizers. Nitrogenous fertilizers are added to the soil in order to remove the deficiency of nitrogen in the soil. The fertilizing value of N-type fertilizers is expressed as available quantity of nitrogen present in them. Some examples of nitrogenous fertilizers are---

(i) Ammonium sulphate [(NH₄)₂SO₄]

(ii) Calcium cyanamide or Nitrolim [CaNCN]

(iii) Urea [CO(NH₂)₂]

(iv) Sodium nitrate [NaNO₃]

(v) Calcium ammonium nitrate [Ca(NO₃)₂.NH₄NO₃]

(vi) Ammonium sulphate nitrate [(NH₄)₂SO₄.2NH₄NO₃]

Phosphatic or Phosphorus Fertilizers

Phosphatic or phosphorus fertilizers supply phosphorus (P) element to the soil. So, this type of fertilizers is called P-type fertilizers. Phosphatic or phosphorus fertilizers are added to the soil in order to remove the deficiency of phosphorus in the soil. Some examples of P-type fertilizers are---

(i) Phosphate slag [Ca₃(PO₄)₂.CaSiO₃]

(ii) Super phosphate of lime [Ca(H₂PO₄)₂ + 2CaSO₄.2H₂O]

(iii) Triple super phosphate [Ca(H₂PO₄)₂]

Potassium Fertilizer

Potassium fertilizers supply potassium (K) element to the soil. So, this type of fertilizers is called K-type fertilizers. Potassium fertilizers are added to the soil in order to remove the deficiency of potassium in the soil. Some examples of K-type fertilizers are---

(i) Potassium sulphate [K₂SO₄]

(ii) Potassium chloride [KCl]