Fertilizers classification



1) Straight Fertilizers

When a fertilizer contains and is used for supplying a single nutrient, it is called a straight fertilizer. This is further classified as nitrogenous, phosphatic and potassic fertilizers depending on the specific macro nutrient present in the fertilizer

Nitrogenous fertilizers

  Nitrogen other
Ammonium sulphate 20.6% S 24%
Ammonium chloride 25-26% Cl 66%
Ammonium nitrate 33-34%
Ammonium sulphate nitrate 26%
Anhydrous ammonia 82%
Calcium ammonium nitrate 25% Ca 8.1%

Mg 4.5%

Calcium nitrate 15% Ca 34%
Sodium nitrate 16%
Urea 46%
Calcium cynamide 21%

Phosphatic fertilizers

Water soluble phosphate (Mono calcium phosphate)
  Phosphorus %
Single super phosphate 16%
Double super phosphate 32%
Triple super phosphate 48%
Citric acid soluble phosphate (Di-calcium phosphate)
Basic slag 14-18%
Di-Calcium Phosphate 34-39%
Insoluble phosphate (Tri-calcium phosphate)
Rock phosphate 20-40%
Raw bone meal 20-25%
Steamed bone meal 22%–30%

Potassic fertilizers (potassium %)

Muriate of potash (KCI) 60%
Sulphate of potash (K2SO4) 48–52%
Potassium nitrate (KNO3) 48%

2) Compound Fertilizers

Compound fertilizers are the commercial fertilizers in which two or more primary nutrients are chemically combined.

Fertilizer N P2O5
Di ammonium phosphate (DAP) 18% 46%
Mono ammonium phosphate 11% 48%
Urea ammonium phosphate 28% 28%
Ammonium phosphate 16% 20%

3) Complex Fertilizers

Complex fertilizers are the commercial fertilizers containing at least two or more of the primary essential nutrients at higher concentration in one compound. The nutrients in complex fertilizers are physically mixed.

Complex Fertilizers

Fertilizer N P2O5 K2O
Complex fertilizers 17 17 17(MF)
14 28 14(MF)
10 26 26(IFFCO)
12 32 16(IFFCO)
14 36 12(IFFCO)
Nitro-phosphate-potash 15 15 15
Gromor 14 35 14

4) Mixed Fertilizers/Fertilizer Mixtures
They are physical mixtures of two or more straight fertilizer. Sometimes a complex fertilizer is also used as one of the ingredients. The mixing is done mechanically. The fertilizer mixtures are usually in powder form but techniques have been developed for granulation of mixtures so that each grain will contain all the nutrients mixed in the mixture.

Bio fertilizer are the living organisms capable of fixing atmospheric nitrogen or making native soil nutrients available to crops. Atmospheric nitrogen is fixed effectively by the microorganisms either in symbiotic association with plant system (Rhizobium, Azolla) or in associative symbiosis (Azospirillum) or in free living system (Azotobactor, phosphobacterium, blue green algae) or in micorhizal symbiosis (VAM fungi).


Rhizobium species Legumes
Rhizobium meliloti Alfalfa (Lucerne)
Rhizobium trifolii Clover
Rhizobium leguminosarum Peas
Rhizobium phaseoli Beans
Rhizobium lupine Lupine
Rhizobium japonicum Soybean
Rhizobium sp. Cowpea

Azolla It is a small water fern of worldwide distribution under natural conditionsThere are six species of Azolla. They are Azolla caroliniana, Azolla filiculoides, Azolla mexicana, Azolla nilotica, Azolla microphylla and Azolla pinnata.
Azolla contains 3.1-4.2% N; 0.16% P2O5 and 0.18% K2O on dry weight basis.

Azospirillum This bacterium is associated with cereals like rice, sorghum, maize, cumbu, ragi,tenai and other minor millets and also for cotton, sugarcane, oilseeds and fodder grasses. These bacteria colonizing in the roots not only

Azatobacter The beneficial effects of Azatobacter on plants was associated (non-symbiotically) not only with the process of nitrogen fixation but also with the synthesis of complex of biologically active compounds such as nicotinic acid, pyridoxine, biotin, gibberellins and probably other compounds which stimulate the germination of seeds and accelerate plant growth.

Azatobacter population in soil or near the root zone of crops (Rhizosphere) is very low when compared to other soil bacteria.
The nitrogen fixation potential of this bacterium is also not very high and appreciable (20 to 30 kg of N per ha per year).

Blue green algae- The blue green algae occur under a wide range of environmental conditions.
They are completely auto tropic and require light, water, free nitrogen (N2), carbon dioxide (CO2) and salts containing the essential mineral elements. They play a major role in the nitrogen economy of paddy soils in tropical countries. Different algal species available are:
• Tolypothric tenuis,
• Nostoc,
• Plectonema,
• Chlorococous,
• Aulosira fertilization,
• Anabaena, and
• Chorococcum

6) Phosphobacterium

Mycorrhizae (VAM) – Vesicular Arbiscular Mycorrhiza is a fungi used as bio-fertilizer.Mycorrhiza increases crop yield, protect against certain root pathogen, helps in uptake of P, Cu, Zn and B and increases tolerance to environmental stress.

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