(IPPM) in Vegetables - Vegetableipmasia.org

Resource Manual on IPPM in Rice
World Education Philippines, Inc.
K. Fertilizer and Fertilizer Computation
A fertilizer is any organic or inorganic material of natural or synthetic origin
which is added to the soil to supply certain elements essential to plant growth.
Fertilizer materials are used to increase the growth rate, yield and quality or
nutritive value of plants. For many decades in the past, the term fertilizers
practically meant commercial fertilizers of nonliving origin. In recent years,
however, increasing attention has been focused on organic and biofertilizers
which are biological sources of plant nutrients.
Organic fertilizers or farm manures refer to composts, crop residues, animal
manures, green manures, and other municipal or farm waste which supply
nutrients and improve soil physical conditions. Organic fertilizers are added to the
soil in large quantities to meet nutrient demands of crops. The use of organic
fertilizers is a vital component of integrated nutrient cycling systems.
Biofertilizers are microbial inoculants or groups of microorganisms which in one
way or another make nutrients available to plants from sources which those plants
cannot tap themselves. The nitrogen biofertilizers include Rhizobium (for
legumes), the blue-green algae (BGA), Azospirillium, Azotobacter, and Frankia
(for non-leguminous trees). The P biofertilizers are made up of bacteria and fungi
that solubilize unavailable forms of phosphorus, thus converting them into
available forms. Efficient phospho-bacterial isolates have been identified as
Psuedomonas striata, P. rattonis and Bacillus polymyra. Among the fungi, the
efficient P solubilizers have been observed among the Aspergillus and
Penecillium groups. The mycorrhizae constitute another group of biofertilizers in
that they increase the absorption of P from the soil and P-fertilizers.
1. Fertilizer Nutrients
Of the known essential nutrient elements that plants obtain from the soil like
N,P,K, calcium (Ca), magnesium (Mg), sulfur (S), iron (Fe), manganese (Mn),
Zinc (Zn), copper (Cu), the first three are usually limiting to a greater extent than
the rest. These nutrients are removed by plants in relatively large quantities so that
their depletion proceeds at a faster rate. Besides removal by crop, the supply of
these nutrients may also decrease due to leaching, volatization and soil erosion.
Thus it is inevitable that fertilizers containing such elements will be needed.
At present most of the soils in the Philippines require one of the three nutrient
elements N, P and K. Since they are the nutrients commonly found in fertilizers,
these elements are often referred to as the fertilizer nutrients. Most of the fertilizer
materials contain other elements in considerable amounts. For example, ordinary
superphosphate contains 11.5% S and 19% Ca. There is also evidence showing
that micronutrients are limiting the growth of plants on some soils in the
Philippines.
The proper usage of fertilizers requires knowledge not only of their properties but
also of their effects on soil. The amount of fertilizers to be applied depends on
many factors which include the ability of the soil to supply nutrients, the nutrient
requirement of the plant, yield potential, other management practices, the
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