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EFFECT
OF WATER SOLUBLE FERTILIZERS ON IMPROVEMENT OF CALCAREOUS AND
ALKALINE SOILS
MR.R.R.SHAH AND MR. J.K.SHARMA VARDHAMAN HI-TECH AGRO PRODUCTS,
PUNE |
About
11 Million Hectares of cultivable soils in India are alkaline
or saline (including coastal saline) in nature. The productivity
of crops grown in alkaline soils is low, basically because the
pH of these soils ranges above 8.0 to 10.0. The suitable pH
for most crops to yield high produce is between 6.5 to 7.5.
Very few crops can grow in Acidic (Coastal Sandy Acidic) or
Alkaline soil (pH more than 8.5), while most acidic soils can
be improved by comparatively easily process of liming, improving
the alkaline or calcareous soils is difficult and long duration
process. Tlie nature of the soil vis-a-vis alkalinity or acidity
is important because the uptake of nutrients by the plant roots
is strongly influenced by soil pH. This is especially true for
vital micronutrients. As the pH increases in alkaline soils,
the availability of Nitrogen, Phosphates, Iron, Manganese, Copper,
Zinc and Boron decreases. Absorption eventually is blocked completely,
even when there is generous supply in soil. If the acidity increases
beyond pH 5.0, very less of the nutrients except Iron and Manganese
can be absorbed by the plant roots. The phenomenon is due to
leaching of Nitrates and fixation of nutrient Ions in the soil
matrix. All nutrients are taken up by roots and plants in Ionic
form as water solution, In the conventional method of agriculture
and fertilization the plants depend for their nutrition and
growth on nutrients present in the soil and applied through
fertilizers.
Due to alkaline and saline nature of the soil many nutrient
elements are lost due to leaching and fixation and are not absorbed
by the plants. Annexure -1, below gives suitable pH for good
take up of nutrients by the plants.
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| ANNEXURE
NO.1, SUITABLE pH FOR PLANT NUTRIENT TAKE UP :-
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| Nutrient |
Best
pH Range |
| Nitrates |
6.0-7.0 |
| Potassium |
6.0-7.0 |
| Calcium |
7.5-8.0
, |
| Phosphates |
6.0-7.0 |
| Magnesium |
5.5-7.5 |
| Sulphur |
5.5-7.5 |
| Iron |
4.0-6.5 |
| Manganese |
5.0-6.5 |
| Zinc |
5.0-6.5 |
| Copper |
5.0-6.5 |
| Boron |
5.0
- 7.5 |
| Molybdenum |
6.5-9.0 |
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Annexure
No. 2 gives an indication of suitable pH for uptake of nutrient
by plants.
In areas with considerable rains, land under crop production
gradually acidifies. In arid areas, regular irrigation combined
with improper drainage results in salt accumulation and raises
pH. In both cases availability of nutrients to plants worsens.
In alkaline and saline soil problem of fixation of nutrient
ions with the clay particles is common. Application of Gypsum
(Phospho) replaced Sodium levels with Calcium. Thus releasing
sulphate ion which in contact with moisture generates acid and
reduced pH of the soil. However,this may increase salinity of
subsoil, water due to leaching of sodium salts, or may increase
E.C. of soils. The process has also long term effectivity.
The effective solution to the problem is drip irrigation, Mini
Sprinkler Irrigation and Foliar Spray of dilute water solution
of water soluble acidic fertilizers. In this system of Fertigation
(Irrigation + Fertilization), the nature of soil plays a minor
role where it acts only as growing base for plants. Complex
water soluble fertilizers consist of all required nutrients
(except Calcium) and are acidic in nature, yielding acidic water
solution (pH 5.5 - 6.5). e.g. Grade NPK 19;19;19, Fully water
soluble complex fertilizer consists of:-
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| Nitrogen |
19% |
| Phosphate
(P2O5) |
19% |
| Potash
(K2O) |
19% |
| Magnesium
(MgO) |
1% |
| Sulphur
(S) |
3% |
| Iron
(EDTA) |
0.1% |
| Maganese
(EDTA) |
0.05% |
| Copper
(EDTA) |
0.01% |
| Zinc
(EDTA) |
0.05% |
| Boron |
0.02% |
| Molubdenum |
0.001% |
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It
is acidic due to raw material used in their manufacture like
Phosphoric Acid, Nitric Acid,, Sulphuric Acid and Sulphate of
Micronutrients. When dissolved in water, nutrients become their
Ions like NO3, K+, P+ etc.
and become chemically active. One single fertilizer contains
all nutrients (except Calcium) in balanced ratio, thus providing
full nourishment for healthy growth and high yield. For using
these fertilizer via drip, mini sprinlder or foliar spray system,
a dilute water solution is prepared and this solution is applied
to root zone, plants and their leaves.
The residual solution in root zone reacts with calcareous or
alkaline soil elements and reduces the pH of the soil towards
neutral over the period of time. Thus using water soluble complex
acidic fertilizers through drip, mini sprinkler or foliar spray
systems, over a long period of cultivation, shall improve the
nature of soil toward suitable pH and higher fertility.
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