Generally groundnut is grown as a rainfed
crop during kharif season, but if the crop is caught in a long
shell of drought, especially at the pod formation stage, supplemental
irrigation is given.
In case of irrigated crop the frequency of irrigation
depends upon soil texture and the interval between the irrigations ranges
between 8-12 days.
The critical stage for irrigation is branching,
flowering and pod formation. There should be sufficient moisture at
the sowing time in the field; thus if the crop is to be sown before
onset of monsoon the field should be given one light pre-sowing irrigation
for better germination of the seeds.
The water requirement of crop on black soils at
Navalgund (Dist Dharwad) was found to be 55 cm.
The optimum quantity of irrigation required at
each irrigation on black soils was found to be 6 cm.
Kharif
season
Kharifgroundnut
is often subjected to various weather viz.,
(i) early-season drought associated with late
sowing
(ii) mid-season drought due to failure of rain
during peak, growing period and
(iii) late-season drought due to early assertion
of monsoon. If groundnut receives total rainfall of 400-600 mm, well
distributed over the entire growth period it is sufficient to harvest
a good crop. But very often non-availability of sufficient moisture
at pod development stage (in September) is common in many places.
Providing life saving irrigation at this stage
may result in increased yield to the tune of 33-63 per cent.
Following methods of irrigation are used
for groundnut
Border strip method
Strips should be of 3-5 m width and water from main channel is diverted
into border strips. This is one of the most suitable surface irrigation
method and labour cost for forming fund is less than check basin method.
Check basin method
When fields are undulated this method is followed. Water is diverted
into the sub-channels and then finally to sub-plots.
Furrow method
This method is the most effective with maximum water use efficiency
of 3.71 kg/ha-mm and also saves 2-3 irrigations compared to border strip
and check basin methods.
Sprinkler and drip method
Use of sprinkler and drip irrigation methods are becoming popular
since water requirement in these methods is about half and the water
use efficiency is also quite high but the only drawback is the high
initial cost involved. An yield advantage of 32 per cent over the check
basin method was realised with the sprinkler irrigation system .
Maintenance of optimum soil moisture at critical growth
stages is the key factor for releasing higher yields.
Early vegetative growth, flowering, pegging and
pod formation are considered as critical stages, of which peak flowering
and pod formation stages are the most crucial.
Imposing drought of 20 days, after 15-20 days of
sowing (with pre-sowing irrigation) followed by releasing water stress
providing two irrigations at five days interval helps in the development
of deeper root system, synchronized flowering, higher biomass production
and higher pod yield.
Irrigation should be stopped one week before harvest
so that the quality of seeds does not deteriorate.
Based on irrigation intervals and calculation
Irrigations are scheduled at fixed intervals according
to the soil and climate conditions.
Total amount of water and number of irrigations
required for groundnut very with locations and soil types .
In general rabi summer groundnut requires
8-18 irrigations.
First irrigation should be given at 15-20 days
after sowing and second at 20-25 days after first irrigation.
Subsequent irrigations should be given at 7-10
days interval.
Based on depletion of soil moisture
Irrigation should be given when 25 per cent depletion
of available soil moisture (DASM) occurs but when water supply is crucial,
irrigation should be scheduled at 50 per cent DASM in 0-15 cm of soil
surface through sprinkler system.
Based on IW/CPE
Irrigation water/cumulative pan evaporation (IW/CPE)
ratio for groundnut ranges from 0.6 to 1.0. Irrigation should be scheduled
at 0.5 IW/CPE during 10-40 DAS and later on at 0.75 IW/CPE ratio to
realise higher pod yield but further increase in irrigation efficiency
upto a ratio of 1.0 did not show significant yield advantage.
Water Management
