Humans, animals and plants all need nutrients to survive. Nutrients can be 'macronutrients' –
because these are needed in greater quantities – such as nitrogen (N),
phosphorus (P), potassium (K), calcium (Ca), sulphur (S) and magnesium
(Mg) or 'micronutrients' such as zinc (Zn), copper (Cu), iron (Fe), boron (B), and molybdenum (Mo) because they are needed in lesser quantities.
Humans
consume crop and animal products for nourishment while crops get most
of their nutrient requirements from the soil. However, many soils do not
provide all the nutrients in quantities needed by the crops. Soil
nutrients removed by continuous cropping must be replaced through the
addition of nutrient sources, such as fertilizers.
Fertilizers are any solid, liquid or gaseous substances containing one
or more plant nutrients in known amount, that is applied to the soil,
directly on the plant (foliage) or added to aqueous solutions (as in
fertigation) to maintain soil fertility, improve crop development, yield
and/or crop quality.
The purpose of fertilizer use, especially for higher yields, is identical in temperate and tropical climates:
- to supplement the natural
soil nutrient supply and build up soil fertility in order to satisfy the
demand of crops with a high yield potential;
- to compensate for the
nutrients exported by the harvested products or lost by unavoidable
leakages to the environment in order to maintain good soil conditions
for cropping.
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to
supplement the natural soil nutrient supply and build up soil fertility
in order to satisfy the demand of crops with a high yield potential;
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to
compensate for the nutrients exported by the harvested products or lost
by unavoidable leakages to the environment in order to maintain good
soil conditions for cropping.
Fertilizers are classified into two major forms:
- organic,
- mineral/manufactured.
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organic,
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mineral/manufactured.
Manufactured fertilizers are classified according to different criteria as follows:
- Number of nutrients
- single-nutrient or straight fertilizers (whether for macro or micronutrients)
examples: urea (46-0-0), triple superphosphate (0-46-0),muriate of potash (0-0-60), zinc/iron chelates, boric acid, etc.
- multi-nutrient/compound (multiple nutrients) fertilizers, with 2, 3 or more nutrients
examples: compound fertilizers (15-15-15), diammonium phosphate (18-46-0), monopotassium phosphate (0-47-31), etc.
- Type of combination
- mixed fertilizers or ‘bulk-blends’ are physical mixtures of two or more single-nutrient or multi-nutrient fertilizers;
- complex fertilizers are products in which two or more of the nutrients are chemically combined (e.g. nitrophosphates, ammonium phosphates).
- Physical condition
- solid (crystalline, powdered, prilled or granular) of various size ranges;
- liquid (solutions and suspensions);
- gaseous (liquid under pressure, e.g. ammonia).
- Nutrient release
- quick-acting (water-soluble and immediately available);
- slow-acting (transformation into soluble form required, e.g. direct application of phosphate rock);
- controlled-release by coating;
- stabilized by inhibitors.
The principles of the right use of nutrient source, rate, time and place
form the minimum basis of any local nutrient stewardship system. Best
management practices must be applied to all of these areas to achieve
local economic, social and environmental goals.
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Number of nutrients
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single-nutrient or straight fertilizers (whether for macro or
micronutrients)
examples:
urea (46-0-0),
triple superphosphate (0-46-0),
muriate of potash (0-0-60), zinc/iron chelates, boric acid, etc.
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multi-nutrient/compound (multiple nutrients) fertilizers, with 2, 3 or more nutrients
examples: compound fertilizers (15-15-15),
diammonium phosphate (18-46-0),
monopotassium phosphate (0-47-31), etc.
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Type of combination
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mixed fertilizers or ‘bulk-blends’ are physical mixtures of two or more single-nutrient or multi-nutrient fertilizers;
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complex
fertilizers are products in which two or more of the nutrients are
chemically combined (e.g. nitrophosphates, ammonium phosphates).
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