Fertilizer recommendations may be modified on the
basis of soil test results.
Apply gypsum before sowing or one month after sowing.
Do not give excess irrigation upto 4 weeks after
sowing and give minimum 2 irrigations after fourth week.
Nitrogen
It is recognised that small supplementary
application of nitrogen can be of value in meeting the gap of nitrogen
supply before the efficient operation of the root nodule symbiosis.
The fixation of nitrogen by the rhizobia in the
root nodules commences one month after sowing.
Nitrogen has generally proved to be economic at
a relatively low level of application.
The uptake of nitrogen closely follows the dry
matter production and the peak period of uptake is between 48 and 78
days.
Basal application of a small dose of N
is, therefore, necessary.
If an examination of the groundnut plant at 30
days after sowing shows that nodulation is not adequate and the nodules
are not active, it is necessary to add nitrogen when the last weeding
is done.
The quantity of nitrogen to be applied
depends upon the fertility of the soil, plant population, rainfall distribution
and the yield aimed at.
The dose of nitrogen recommended varies from 25
kg/ha for both rainfed and irrigated crop.
The basal dose of nitrogen is applied at the time
of sowing or three to four days prior to sowing and incorporated into
the soil.
The fertilizer should not come in direct contact
with the seed.
If nitrogen is applied as top dressing, it should
be broadcast on the soil and incorporated by stirring at the time of
weeding.
Response to phosphorus can be obtained when the available phosphorus
in the soil is less than 35 kg P2O5/ha.
The quantity of P2O5 to be applied depends upon
the phosphorus status of the soil besides plant population, rainfall
distribution, etc.
The quantity of P2O5 recommended is 50 kg P2O5/ha
for rainfed and 75 kg P2O5/ha for irrigated crop.
Single superphosphate is the best source of supplying P2O5
as it contains besides phosphorus (16%), calcium (19.5%) and sulphur
(12.5%) which are needed for the groundnut plant.
Phosphorus is required from the early stage of the crop growth to
maturity. It is applied before sowing.
Phosphorus fertilizer should not come in contact with the seed as
it affects germination.
Placement of phosphatic fertilizer is important since conversion
of phosphorus into unavailable form is high and movement of phosphorus
in the soil is limited.
Phosphorus fertilizer should not be broadcast. Localised application
of phosphorus fertilizer in a band in seed rows and about 5 cm below
seed placement is desirable.
A good crop of groundnut removes considerable
amount of potassium from the soil, but most of the soils are rich in
potassium.
Response to potash can be obtained when the available
K20 in the soil is less than 150 kg/ha.
Excessive potassium in the pod zone is deleterious.
A dose of 25 kg K20/ha under rainfed condition and 50 kg
K20/ha under irrigated conditions is recommended depending
upon the available K20 status of the soil.
Potassium is needed by the groundnut crop
from early stage of its growth to maturity.
Potash fertilizer is applied before sowing as
a band placement in the seed row 5 cm below the depth of seed placement.
These two nutrients are considered together
as both are taken up from the pod (fruiting) zone by the pegs and developing
pods.
Sulphur
About 10 ppm of sulphur is required in
the pod zone (0-5 cm depth of soil layer).
The common sources of sulphur are given below
Sulphur content of common sources
Source
Sulphru content
Gypsum
Ammonium sulphate
Single superphosphate
Potassium sulphate
18.60
24.26
12.50
17.50
Ten ppm of sulphur amounts to about 10
kg sulphur/ha in 0-5 cm depth of pod zone. Gypsum contains about 18.60
per cent of sulphur. So, even 100 kg of gypsum can meet the requirement
of sulphur.
The quantity of gypsum applied for supplying calcium
is more than adequate to meet the needs of sulphur.
Zinc
Zinc deficiency is most common in sandy
and sandy loam soils. The critical limit of zinc in the soil is 0.6
ppm.
Application of zinc sulphate at 25-50 kg/ha to
the soil once in three years will correct the deficiency and increase
yield.
When zinc deficiency is noticed in the standing
crop, foliar application of zinc sulphate at 0.2 per cent is suggested.
Iron
Iron chlorosis is a problem in most of
the black soils, which have a high content of calcium.
On calcareous black soils, sandy soils, on soils
with high pH (7.5) and high CaCO3 content the deficiency
of iron can be corrected by spraying 1 per cent ferrous sulphate, 1
per cent ammonium citrate at 40 to 60 days after sowing of the crop.
Boron
The threshold value for boron is 0.25 ppm.
The deficiency is corrected by the application of 5-10 kg/ha Borax depending
upon the extent of deficiency.
Slight excess of boron leads to toxicity as iron
uptake is inhibited resulting in typical burning of the leaf margin.
When the deficiency is noticed in a crop, spraying
with 0.1 per cent borax will correct the deficiency.
Application of farm yard manure at 7.5-10
t/ha is desirable. Little organic matter is returned to the soil from
a crop of groundnut.
Addition of farm yard manure will add organic
matter to the soil. Working of the soil repeatedly tends to compact
it and pore space for both penetration of air and moisture is reduced.
When soils dry out, pore space tends to be occupied
by air and in this condition soils may be water repellant and surface
movement of water is favoured rather than penetration, tending to result
in rain water being runoff.
Surface crusting and compaction of the surface
soil are prevented and ready acceptance of moisture by the soil takes
place with the application of organic matter by way of farm yard manure.
The organic matter in the farm yard manure will
help to retain moisture and reduce losses of plant nutrients.
Since hardening of the surface soil does not take
place when farm yard manure is applied, peg penetration is not hindered
even during prolonged dry spells between two rains during the crop period.
Application of farm manure has been observed to
increase nodulation in groundnut. Farm yard manure is broadcast over
the soil and incorporated by ploughing.
Where the soils are sandy and do not retain moisture,
farmers apply 15 to 25 t/ha of tank silt once in three years.
Nutrient Management
