Classification Of fertilizers

Classification of fertilizers

Depending on the nature of the essential element/elements that a fertilizer can supply to the soil,the fertilizer have been classified into the following types.

i)Nitrogenous fertilizers(N-type fertilizers)

These fertilizers supply only nitrogen to the plants or soil.(NH₄)₂SO₄,calcium ammonium nitrate(CAN),basic calcium nitrate,calcium cyanamide,urea,etc. are the examples of nitrogenous fertiliers.They are essential to the plant for their growth,particularly of leaves.Nitrogen fertilizers are necessary for the plant for the early growth to promote stem and leaves.Nitrogen is abundant amount in air which can be fixed commercially with the low cost by hydrogen to give ammonia produced in low cost can be used for the production of nitrogen fertilizer in the form of liquid ammonia and aqueous solution of ammonium, ammonia sulphate,ammonium nitrate and urea most of the nitrogen containing chemical compounds.Almost majority of ammonia is used to make fertilizers.In Nepal,most of the people are agricultural dependent so,the production of ammonia is essential in Nepal which in turn can produce nitrogen fertilizer in commercial scale.The nitrogen fertilizer production should be given emphasis and priority.

ii)Phosphatic or phosphorus fertilizers(P-type fertilizers)

These fertilizers provide phosphorus to the soil.Superphosphate,triple superphosphate,phosphate slag,natural organic phosphate fertilizers,phosphate rocks,nitrophosphate,diammonium phosphate,monoammonium phosphate,etc are the examples of phosphorus fertilizers.Phosphorus fertilizers stimulate early growth and accelerate seeding or fruit formation in the later stages or growth.They stimulate root formation and rapid growth of root.They also help in the formation of high-yielding seeds.They are easily soluble in water.Like nitrogen phosphorus,phosphorus fertilizers are also important for the plants as phosphorus is one of the major primary nutrient for the plant.Phosphorus fertilizers are produced bt the phosphorus industries.The rock phosphates are used for the manufacture of superphosphate fertilizer,elemental phosphorus production in fertilizer mixtures,some phosphate rocks are directly applied to the soil as fertilizers.

iii)Potash fertilizers(K-type fertilizers)

These fertilizers supply potassium to the plant.All the potash fertilizers occur in nature.Potassium chloride(KCl),potassium sulphate(K₂SO₄),salt petre(KNO₃),Sylvinite(mixture of KCl and NaCl),potassium magnesium minerals,kainite,lomgnite,carnalite,etc are some of the common potash fertilizers.Potassium ions for flowering.It retain water in the plant cell by osmotic pressure.They provide healthy root system to the plants.With the help of these fertilizers,plants become able of getting a regular supply of nutrients from the soil.They are essential for the development of starch in potatoes and grains,the sugar of fruits and vegetables,fibrous material for plants,help to prevent disease and minimize the effect of excessive nitrogen application.

iv)Mixed Fertilizers

Mixed fertilizers are those fertilizers which can supply more than one essential element to the plant or soil.Depending on the nature of the essential elements supplied by the fertilizers,mixed fertilizers can be supplied into the following types:

a)Nitrogen-phosphorus fertilizers(NP type fertilizers)

Examples are ammoniumdihydrogen phosphate(NH₄H₂PO₄),diammonium monohydrogen phosphate NH₄HPO₄,calcium superphosphate nitrate Ca(H₂PO₄)₂.2Ca(NO₃)₂,ammoniumdihydrogen phosphate sulphate NH₄(H₂PO₄)(NH₄)₂SO₄.

b)Phosphorus-Potassium fertilizers(PK type fertilizers)

Examples are mixture of triple superphosphate and potassium sulphate.

c)Potassium-nitrogen fertilizers(KN-type fertilizers)

Example:KNO₃

d)Nitrogen-Phosphorus-Potassium type fertilizers or NPK type or complete fertilizers

Examples:mixture of (NH₄)₂SO₄(N-type),triple superphosphate(P-type) and K₂SO₄(K-type) gives a NPK type fertilizer.

Environmental impacts caused by the excessive use of chemical fertilizers

The excessive use of the chemical fertilizers greatly increases the crop yields.Since chemical fertilizers(nitrate phosphate) are soluble in water,the run off water into the lakes,river and sea also contain NO₃^-,NH₄^-,SO₄^-,Na+,K⁺,etc.The environmental impacts caused by the excessive use of nitrates are as follows:

i)Eutrophication:

The term 'eutrophication' has been derived from Greek word which means "well nourished".It decribes a condition of lakes or reservoirs involving excessalgal growth,which eventually cause the destruction.The first step in eutrophication of a body of water has been an input of nutrients from sewerage or agricultural runoff.The nutrient rich body of water gives rise to a great deal of plant biomass by photosynthesis,and a smaller amount of secondary animal biomass.Dead biomass gets accumulated in the bottom of the lake,where it partially decays,recycling nutrient,carbondioxide,phosphorus,nitrogen and potassium.If the lake has been not too deep,bottomrotted plants begin to grow accelerating the accumulation of solid material in the basin.Eventually,a marsh is formed which finally fills to produce a dry land or forest.

The eutrophication process has been not a new phenomenon.It has been basically responsible for the formation of huge deposits of coal and other fossil fuels.However,man's activities are able to accelerate eutrophication.The excessive use of chemical fertilizers produces increased growth of algae and other aquatic plants which may clog off river and lakes.

ii)Change in soil acidity:

Excess use of some fertilizers may pollute the soil.If excess (NH₄)₂SO₄ is used in the same field,then NH₄⁺ ions are used by the crops but the SO₄^2- ions get accumulated into the soil and it causes soil haighly acidic.Similarly,accumulation of Na⁺,K⁺ ions into the soil make the soil alkaline.

iii)Soil Texture:

Excess use of fertilizers change the soil texture.

iv)Higher level of nitrates in the drinking water would result many diseases.

v)Denetrification of nitrates into the oxides of nitrogen particularly N₂O may harm the ozone layer.

References

Poudel, Bhoj Raj Poudel and Dr.Megh Raj. A Text Book Of Inorganic Chemistry. Kathmandu: National Book Centre, 2012.

Sons, John Wiley and. J.D Lee Concise Inorganic Chemistry. 2007.