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3.
SOIL
• Prevention of erosion and washing of organic and inorganic (chemical) fertilizers.
• Prevention of weed growth thus reducing competition between main crops and
weeds.
• Reduction of production costs because no weeding is required on fields using
mulch, and inorganic fertilizer dose can be reduced.
Its disadvantages are with soil infected by bacterial wilt, as applying mulch increases
temperature and moisture levels accelerating growth of wilt causing bacteria. Also if
plastic is left lying around after several seasons’ use, it becomes a source of
pollution.
D. Manure
Manure has the same function as other organic fertilizers, but is richer in nitrogen,
because of its urine content. Different types of manure have different water and
nutrient composition depending on the type of animal providing the manure and the
food it got (see Table 2).
Table 2: Water and nutrient content of several types of manure
Source of manure
Nutrient content (kg/ton)
Water content
Nitrogen Phosphorus Potassium
(%)
Beef cattle 85 26.2 4.5 13.0
Dairy cattle 85 22.0 2.6 13.7
Poultry (chicken, duck etc.) 62 65.3 13.7 12.8
Pig 85 28.4 6.8 19.9
Sheep 66 50.6 6.7 39.7
Horse 66 32.8 4.3 24.2
Manure can be applied before or after it is decomposed. Direct application of nondecomposed
manure is not recommended for the following reasons:
• It may contain pests and diseases that can negatively affect plant health.
• It is difficult to apply because it smells bad and is too wet.
• Applying fresh manure at planting time can actually temporarily reduce quantities
of available nutrients in the soil, because of decomposers using nutrients for
decomposition processes.
• Fresh manure needs the oxygen in the soil in order to decompose, so direct
application can starve plants of oxygen.
• It contains toxic gases that can kill plants.
• It reduces soil pH.
3.2.5 Chemical fertilizers
Chemical fertilizers are fertilizers that contain one or a few nutrients (see Table 3)
and are mined or produced in factories. The most common nutrients contained in
chemical fertilizers are nitrogen (N), phosphorus (P) and potassium (K). Chemical
fertilizers are generally applied directly to the soil. They contain nutrients in a form
that plants can readily absorb, so they must be applied when plants require them.
Chemical fertilizers are categorized according to their composition into single nutrient
and compound fertilizers. Single nutrient fertilizers are chemical fertilizers that
contain one type of nutrient. For example, KCI contains potassium, Urea contains
nitrogen and SP- 36 contains phosphorus. The benefits of using single nutrient
fertilizers are their cheaper prices and they can be applied to suit plants’
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ALL ABOUT POTATOES