Nutrient Management
Nutrient Management
Nutrient Management
Grain yield is enhanced with better nourishment throughout the growing period,
especially during the critical development stages of the corn plant.
To attain yield potential of most corn varieties, they should get the optimum
amount of nutrients they need.
Nutrient requirements may be adjusted depending on the desired yield level for a
particular variety.
The quantities removed by the corn plants set the minimum amounts of nutrients
to be provided.
Conduct soil sampling and analysis of your cornfield every 3-5 years.
Step 3. Before digging, brush away stones, rubbish and vegetation from the surface
area.
With a spade or shovel, dig at a depth of about 30 cm and take a slice of soil about 2
cm thick and 5 cm wide (see illustration at right). This represents one spot soil
sample. Put the sample in a clean pail.
Follow Step 3 until the total number of spots per sampling area is completed.
Step 4. After completing the spot sampling of a particular sampling area, pulverize the
soil, remove the stones and fresh plant parts and mix the samples thoroughly in the pail.
Step 5. Airdry the soil with care and keep it away from foreign materials.
Step 6. Take a composite sample of one kilo and place it in a clean plastic bag with a
proper label that includes the name of the farm owner, farm location and sample
number.
Step 7. The soil is now ready for analysis. You can use a soil test kit (STK) or send the
samples to the nearest soil testing laboratory in your area.
Types of Fertilizers
Fertilizers are materials that supply nutrients to plants. They may be inorganic or
organic fertilizers.
Inorganic fertilizers. Inorganic fertilizers are synthesized fertilizers, like urea (46-0-0)
and ammonium sulfate (21-0-0) that supply nitrogen (N), complete fertilizers (14-14-14)
that supplies N, phosphorus (P) and potassium (K) and ammonium phosphate (16-20-0)
that supplies N and P.
Inorganic fertilizers release great quantities of nutrient elements that can be easily
absorbed by the corn plants. You can see the result of application within a few days.
Organic fertilizers. Organic fertilizers, on the other hand, are those derived from
decomposed plant parts or residues, animal manures, green manures (legumes like
mongo or sitao) and domestic refuse. They may also come from natural deposits
(guano, phosphate rocks) and biological nitrogen fixers.
There is slow availability of nutrients with this type of fertilizers. The organic materials
require microbial action to transform the nutrients in their available form for plants to
absorb them.
However, when organic materials are fully decomposed and applied in large quantities,
they improve soil fertility and soil aeration and promote good physical conditioning of the
soil.
If concentration of a given element in the plant root zone is low, a deficiency of that
element occurs and plant growth is restricted.
Likewise, if the root zone concentration of a given element is too high, toxicity occurs
and plant growth is similarly limited.
Only in a specific middle range concentration is optimum plant growth attained. One
principal concern, therefore, of corn farmers is how to maintain concentrations of each
essential element in this middle range.
Six of the 14 are used in relatively large amounts and are called macronutrients. while
the other eight, needed in only very small amounts, are called micronutrients.
Three of the six macronutrients: nitrogen (N), phosphorus (P) and potassium (K) are
absorbed by plants in sufficiently large quantities, taxing the abililty of most soils to
supply the plant's need and are normally supplemented by fertilizer application.
This means that a 5-ton grain yield target will need about 135 kg of N, 37.5 kg of P and
100 kg of K per hectare.
Nitrogen
Nitrogen (N) is needed to assure adequate growth of the plant, ensuring its leaves dark
green and promoting full development of the ear and grains.
Nitrogen-deficient leaves turn pale green or yellowish in color with thin or spindly stems
and small ears with unfilled tips.
Phosphorus
Phosphorus (P) is vital in growth processes like the use of sugar and starches. It
stimulates good root systems and flowering and helps in seed formation. It
counterbalances the effect of nitrogen by strengthening the stem and hastening plant
maturity or the ripening of grains.
When phosphorus is deficient in the plant, the tips and margins of the young leaves turn
purple. The plant grows slowly and the stem remains thin. This leads to poor grain
formation on one side of the ear, causing uneven rows and curving of the cob.
Potassium
Potassium (K) is essential in the production of carbohydrates, formation of proteins and
translocation of sugar. It promotes appropriate cell processes to strengthen the stem,
improves the quality of ears and minimizes the susceptability of the plant to certain
diseases like stalk rots and pests.
When potassium is lacking, the plant appears squat due to shortened internodes. The
leaf margins of the older leaves turn yellow, then brown and finally die. The tip of the
ear (or cob) has a sharpened look due to the poor grain filling. The grains are light and
fluffy.
Fertilizer Calculation
The rate of fertilizer to be applied should be based on the results of soil
analysis. Basing on the results of soil analysis, you can now compute the correct
amounts of fertilizer to be applied.
For example, the recommended rate 80-40-20 means that 80 kg N, 40 kg P and 20 kg K are needed
per hectare
Fertilizer grade. This refers to the minimum guarantee of the nutrient content in terms of percent N,
P and K available.
For example, if ammonium sulfate is 21% N, it means that 21 kg of every 100 kg of the material is
available N.
Fertilizer Calculation
You can use the following formulas to calculate the amount of fertilizer needed to satisfy
a given recommended rate (RR):
Formula 1:
Formula 2:
You will need 429 kg N, 300 kg P and 50 kg K to satisfy the recommended rate of 90-
60-30 kg NPK per hectare.
However, in the absence of soil analysis, use the following general recommendation:
Use four bags of complete fertilizer (14-14-14) per hectare as basal application in
the furrows and cover the fertilizer with a thin layer of soil, about 2 cm thick.
After 25-30 days of planting, side dress with four bags of ammonium sulfate or
two bags of urea. Cover the fertilizer immediately by shallow hilling-up.
Apply all the needed phosphorus and potassium and half of the recommended
amount of N in the furrows before planting.
Side dress the other half of N at least 4-5 cm away from the base of the plant 20-
24 days after emergence or immediately before hilling-up when there is right soil
moisture.
To attain higher yields, apply animal manures and crop residues just before land
preparation.
Liming
Soil acidity is a common problem in areas where precipitation is high enough
to leach appreciable amount of calcium and magnesium from the surface of the
soil.
It also arises from a variety of factors, such as the type of clay, presence of iron
and aluminumo oxides and free acids from continuous application of large
amounts of acid-forming fertilizers like ammonium sulfate, ammonium phosphate
and ammonium nitrate.
Soil acidity reduces corn yields because less nutrients are available in acidic
soils. Corn yields are greatly reduced in soils having a pH (degree of soil acidity
or sourness) much lower than 5.3. For better yields, liming is normally practiced
for acidic soils.
Benefits of Liming
As soil pH approaches neutrality, most soil nutrients become available for plant
use.
Lime Application
The agricultural lime commonly available in the Philippines is calcitic limestone or
calcium carbonate.
A usual rate of 3 tons per hectare is recommended but this varies depending on the
magnitude and nature of soil acidity.
Pulverize the limestone before applying to the soil. Finer lime materials act at a
faster rate in neutralizing soil acidity.
Plow in the lime a week before planting for better incorporation in the soil.
Solution:
You need 8.57 bags of ammonium sulfate, 6 bags of solophos and 1 bag of muriate of potash per
hectare to satisfy the recommended rate of 90-60-30 kg NPK.
Self-Assessment Questions
Why is nutrient management important in corn production?
Guide Questions: