Fertilizers

FERTILIZERS

3 . Complete fertilizers

         These fertilizers supply all the essential elements namely N,P and K to the soil, in combine form. These are also known as mixed fertilizers or NPK fertilizers. For example guano, it is prepared artificially.

4. Incomplete fertilizers

         These fertilizers contain only one or two elements needed for the growth of plants. For examples Ammonium Phosphate, Potassium Nitrate etc.

5. Natural fertilizers

These fertilizers are classified as:-

(a) Natural organic fertilizer

such as plant matter, farmyard manures, animal matter etc.

(b) Artificial organic fertilizer

Examples are waste materials from animals excretion, Meat obtained from slaughterhouses, urea etc.

(c) Natural Inorganic fertilizers

         Example being Chile saltpeter, rock phosphates, potassium salts etc.

(d) Artificial inorganic fertilizers

         Examples are Ca(NO3)2, (NH4)2SO4, NHNO3, NH4Cl, Calcium Cyanamid, Super phosphates etc.

6.  Micro fertilizers

         These contain the elements, Boron, Manganese, Zinc and Copper needed in very small amounts to stimulate the plant growth.

Fertilizers are the sources of plant nutrients, manufactured commercially from chemicals.         They contain much higher amount of nutrients in comparison to the manures and are, therefore, used in very small quantities. These fertilizers may supply one or more nutrients. Chemically they may be inorganic compounds (e.g., ammonium sulphate) or organic compounds (e.g. urea). On the basis of the availability of nutrients from them, fertilizers are divided into following four groups :

1. Nitrogenous Fertilizers :

These fertilizers supply the macronutrient nitrogen. Examples of nitrogenous fertilizers are the following :

(i) Urea, CO (NH2)2 ;

(ii) Ammonium Sulphate, (NH4)2 SO4 ;

(iii) Calcium ammonium nitrate ;

(iv) Sodium nitrate, Na NO3 ;

(v) Ammonium Nitrate, NH4NO3 ;

2. Phosphatic Fertilizers :

They are the source of the macronutrient phosphorus. Examples of phosphatic fertilizers are the following :

(i) Single Superphosphate ;

(ii) Triple Superphosphate ;

(iii) Dicalcium phosphate.

3. Potassic Fertilizers :

         These fertilizers supply the potassium which is one of the essential macronutrient to the plants. Examples of potassic fertilizers are the following :

(i) Muriate of potash or potassium chloride, KCl ;

(ii) Potassium Sulphate, K2SO4 ;

(iii) Potassium nitrate, KNO3 ;

4. Complex Fertilizers :

When a fertilizer contains at least two or more nutrients (N, P2O5 and K2O), it is called Complex Fertilizers. Examples of complex fertilizers are the following :

(i) Nitrophosphate ;

(ii) Ammonium phosphate ;

(iii) Urea ammonium phosphate.

         Modern agriculture depends greatly on the chemical fertilizers. Indeed high doses of these chemicals greatly increase crop yield but then chemicals get washed off through irrigation, rainfalt as drainage and reach rivers, lakes, streams and pollute them (by causing toxicity, algal bloom and eutrophication) disturbing the ecosystem. The water of these water bodies become unfit for human consumption and even kills the aquatic animals such as fishes. So chemical fertilizers must be used carefully and judiciously.

Biofertilizers :

         The biofertilizers containing biological nitrogen fixing organisms are of utmost importance in agriculture Advantages Of Biofertilizer i) They help in the establishment and growth of crop plants and trees. ii) They enhance biomass production and grain yields by 10-20 percent. iii) They are useful in sustainable agriculture. iv) They are suitable in organic farming. v) They play an important role in Agrotorestry/ Silvi- pastaural system.

Types of Biofertilizers :

Rhizobium

         Most widely used biofertilizer is Rhizobium which colonizes the roots of specific legumes to form tumor like growths called root nodules. These nodules act as factories of ammonia production. The Rhizobium – legume association can fix up to 100-300 KG/N. in one crop season.

Azotobacter :

         Application of azotobacter has been found to increase yield of wheat, rice, maize, pearl-millet and sorghum by 0-30 p.c. over control. Apart from nitrogen this organism is also capable of producing antifungal and antibacterial compounds, hormones.

Azospirillum :

         Certain micro-organisms like bacteria and blue green algae have the ability to use atmospheric nitrogen and transport this nutrient to the crop plants. Azospirillum is inoculated to maize, barley, oats, sorghum, pearlmillet and forage crops. It increases grain productivity of cereals by 5-20%, of millets by 30% and fodder by over 50%.

Blue-green algae :

         The utilization of blue green algae as a biofertilizer for rice is very promising. A judicious use of these algae could provide to the country’s entire rice acreage as much nitrogen as obtained from 15-17 lakh tones of urea. Algae also helps to reduce soil alkalinity.

Azolla :

         A small floating water form Azolla is commonly seen in low land fields and in shallow fresh water bodies. These fern harbors a blue-green algae. Anabaena azollae. The Azolla – Anabaena association is a live floating nitrogen factory using energy from photosynthesis to fix atmospheric nitrogen accounting to 100-150 kg N/ ha / year from about 40 – 60 tones of biomass.

Mycorrhizae:

         It is the symbiotic association of fungi with roots of vascular plants. It is useful in increasing phosphorus uptake e.g. in fruit crops like citrus, papaya.

The first manufacturing unit was started by the Indian Fertilizer Industry which was of Single Super Phosphate (SSP) in Ranipet near Chennai with a capacity of 6000 MT a year. India's green revolution in 60's gave a positive boost to this particular sector. The industry of Fertilizer experienced a faster growth rate and presently India is the third largest fertilizer producer in the world. According to Statistics, total capacity of the industry as in .2003 has reached a level of 121.10 lakh MT of nitrogen (inclusive of an installed capacity of 208.42 lakh MT of urea after reassessment of capacity) and 53.60 lakh MT of phosphatic nutrient.

         In India, presently there are 57 large fertilizers plants producing urea, DAP, Complex fertilizer, Ammonium Sulphate (AS) and Calcium Ammonium Nitrate (CAN). There are others also boosting the Industry like the Tranvancore of India Ltd. (FACT) in Cochin, Kerala, and the another one Fertilizers Corporation of India (FCI) in Sindri, Bihar.Both of these were established as pedestal fertilizer units to have self sufficiency in the production of foodgrains. Later the industry gained impetus in its growth due to green revolution. Then followed by seventies and eighties when fertilizer industry witnessed an incredible boom in the fertilizer production.

Classification

         Fertilizers are classified in several ways. They are classified according to whether they provide a single nutrient (say, N, P, or K), in which case they are classified as "straight fertilizers." "Multinutrient fertilizers" (or "complex fertilizers") provide two or more nutrients, for example N and P. Fertilizers are also sometimes classified as inorganic (the topic of most of this article) versus organic. Inorganic fertilizers exclude carbon-containing materials except urea. Organic fertilizers are usually (recycled) plant- or animal-derived matter. Inorganic are sometimes called synthetic fertilizers since various chemical treatments are required for their manufacture.

Single nutrient ("straight") fertilizers

         The main nitrogen-based straight fertilizer is ammonia or its solutions. Ammonium nitrate (NH4NO3) is also widely used. About 15M tons were produced in 1981. Urea is another popular source of nitrogen, having the advantage that it is a solid and non-explosive, unlike ammonia and ammonium nitrate, respectively. A few percent of the nitrogen fertilizer market (4% in 2007) has been met by calcium ammonium nitrate (Ca(NO3)2•NH4NO3•10H2O).

         The main straight phosphate fertilizers are the superphosphates. "Single superphosphate" (SSP) consists of 14–18% P2O5, again in the form of Ca(H2PO4)2, but also phosphogypsum (CaSO4 · 2 H2O). Triple superphosphate (TSP) typically consists of 44-48% of P2O5 and no gypsum. A mixture of single superphosphate and triple superphosphate is called double superphosphate. More than 90% of a typical superphosphate fertilizer is water-soluble.

Multinutrient fertilizers

These fertilizers are the most common. They consist of two or more nutrient components.

Binary (NP, NK, PK) fertilizers

         Major two-component fertilizers provide both nitrogen and phosphorus to the plants. These are called NP fertilizers. The main NP fertilizers are monoammonium phosphate (MAP) and diammonium phosphate (DAP). The active ingredient in MAP is NH4H2PO4. The active ingredient in DAP is (NH4)2HPO4. About 85% of MAP and DAP fertilizers are soluble in water.

NPK fertilizers      

         NPK fertilizers are three-component fertilizers providing nitrogen, phosphorus, and potassium.

NPK rating is a rating system describing the amount of nitrogen, phosphorus, and potassium in a fertilizer. NPK ratings consist of three numbers separated by dashes (e.g., 10-10-10 or 16-4-8) describing the chemical content of fertilizers. The first number represents the percentage of nitrogen in the product; the second number, P2O5; the third, K2O. Fertilizers do not actually contain P2O5 or K2O, but the system is a conventional shorthand for the amount of the phosphorus (P) or potassium (K) in a fertilizer. A 50-pound (23 kg) bag of fertilizer labeled 16-4-8 contains 8 lb (3.6 kg) of nitrogen (16% of the 50 pounds), an amount of phosphorus equivalent to that in 2 pounds of P2O5 (4% of 50 pounds), and 4 pounds of K2O (8% of 50 pounds). Most fertilizers are labeled according to this N-P-K convention, although Australian convention, following an N-P-K-S system, adds a fourth number for sulfur.

Micronutrients

         The main micronutrients are molybdenum, zinc, and copper. These elements are provided as water-soluble salts. Iron presents special problems because it converts to insoluble (bio-unavailable) compounds at moderate soil pH and phosphate concentrations. For this reason, iron is often administered as a chelate complex, e.g., the EDTA derivative. The micronutrient needs depend on the plant. For example, sugar beets appear to require boron, and legumes require cobalt.

CLASSIFICATION OF FERTILIZERS 

1. Straight fertilizers:  Straight fertilizers are those which supply only one primary plant nutrient, namely nitrogen or phosphorus or potassium. 

         eg. Urea, ammonium sulphate, potassium chloride and potassium sulphate.

2. Complex fertilizers:  Complex fertilizers contain two or three primary plant nutrients of which two primary nutrients are in chemical combination. These fertilisers are usually produced in granular form. 

         eg. Diammonium phosphate, nitrophosphates and ammonium phosphate.

3. Mixed fertilizers: are physical mixtures of straight fertilisers. They contain two or three primary plant nutrients. Mixed fertilisers are made by thoroughly mixing the ingredients either mechanically or manually.

Fertilisers can also be classified based on physical form:

1. Solid

2. Liquid fertilizer.

Solid fertilizers are in several forms viz.

1.          Powder (single superphosphate),

2.          Crystals (ammonium sulphate),

3.          Prills (urea, diammonium phosphate, superphosphate),

4.          Granules (Holland granules),

5.          Supergranules (urea supergranules) andBriquettes (urea briquettes) 

Liquid fertilizers:

1.          Liquid form fertilizers are applied with irrigation water or for direct application.

2.          Ease of handling, less labour requirement and possibility of mixing with herbicides have made the liquid fertilisers more acceptable to farmers.