Crosstradelines

The primary nutrients supplied by fertilizers are nitrogen, phosphorus and potassium. Their concentration in a fertilizer is expressed as percentage of N, P₂O₅ and K₂O.

According to nutrient content of fertilizers, it can be classified as straight and complex fertilizer. Straight fertilizer contain only one plant nutrient where as complex fertilizer contain more than one primary or major nutrient element.

Primary nutrients
Primary nutrients are normally supplied through chemical fertilizers. They are chemical compounds containing one or more of the primary nutrients and are generally produced by chemical reactions. Whatever may be the chemical compounds, its most important ingredient for plant growth is the nutrient content.The primary nutrients are nitrogen, phosphorus and potassium; however, their concentration in a chemical fertiliser is expressed as a percentage of total nitrogen (N), available phosphate (P₂O₅) and soluble (K₂ O).

Straight fertilizer
Nitrogen: Nitrogen is the first fertilizer element of the macronutrients usually applied in commercial fertilizers. Nitrogen is very important nutrient for plants and it seems to have the quickest and most pronounced effect. In the case of nitrogenous fertilizers, nitrogen may be in the ammoniacal, nitrate (or a combination thereof) or amide form.

Nitrogenous fertilizer - Source of Nitrogen

Phosphorus:
Phosphorus is the second fertilizer element and it is an essential constituent of every living cells and for the nutrition of plant and animal. It takes active part in all types of metabolism of plant. Phosphate present in phosphatic fertilizers may be in the water soluble form or citrate soluble form. That portion of phosphate which is soluble in water is called water soluble phosphate and that which is not soluble in water but in 2 per cent neutral ammonium citrate solution is called citrate soluble phosphate. The sum of water soluble and citrate soluble values is termed as available phosphates.

Phosphatic fertilizer – Source of phosphorous

Potassium:
Potassium is the third fertilizer element. Potassium acts as a chemical traffic policeman, root booster, stalk strengthener, food former, sugar and starch transporter, protein builder, breathing regulator, water stretcher and as a disease retarder but it is not effective without its co-nutrients such as nitrogen and phosphorus.

Potassic fertilizer – Source of potassium

Complex fertilizers
Complex NPK fertilizers have the advantage of having each nutrient in each granule. They are more expensive than the equivalent quantity of nutrients achieved by applying the equivalent quantities of straight fertilizers, but the product quality is guaranteed. Sulphur and/or other nutrients can easily be incorporated if required. By using the appropriate complex fertilizer, farmers are applying at least an approximation of each nutrient required. Absolute precision is not necessary in view of soil variability even within the same field.

Complex fertilizers are, therefore, efficient products but trends during the past thirty years in the types of fertilizers used have been determined by their economics, not by considerations of agricultural efficiency or sustainability.

Complex fertilizers

Material	Total Nitrogen (N)	Neutral ammonium citrate soluble phosphate (P₂O₅)	Water soluble phosphate (P₂O₅)	Water soluble potash (K₂O)
Ammonium Phosphate
11-52-0	11.0	52.0	44.2
1846-0	18.0	46.0	41.0
Ammonium Phosphate Sulphate
16-20-0	16.0	20.0	19.5
20-20-0	20.0	20.0	17.0
18-9-0	18.0	9.0	8.5
Ammonium Phosphate Sulphate Nitrate
20-20-0	20.0	20.0	17.0
Nitrophosphate
20-20-0	20.0	23.0	12.0
23-23-0	23.0	23.0

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