IRRIGATION SCHEDULING AND TECHNIQUES IN GRAPES

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IRRIGATION SCHEDULING AND TECHNIQUES IN GRAPES
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INTRODUCTION
Irrigation

• Water supply should be ensured in vineyards
  during period of active growth and berry
  development stages. Irrigation should be given to
  field capacity.
• During establishment period of vines after
  planting, frequent irrigation during dry months
  may be required. Watering immediately after
  pruning and fertilizer application should be done
  without fail.

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• Irrigation at an interval of 5-7 days during
  initial berry development stage till they become
  pea size and at 10 days interval till maturity is
  better for good yields.

Watering should be withheld from 25-30 days prior
to harvesting to ensure quality of produce.
Quality of irrigation water is also important.
Excess salt content in irrigation water, with EC
value of more than one causes injury to vines.
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• Phosphoric acid and dry potassic fertilizer
  such as sulphate of potash can be used as sources
  of P20S and K20 for application through
  irrigation systems.
• Numerous formulations containing two or more
  nutrients are available for fertigation. About
  30 saving in quantity of fertilizers can be
  achieved through this technique.

Establishment phase

• Irrigate vines immediately after planting. Vine
  water use is very low in the first 6 to 8 weeks,
  but the vines have a small root system that
  should be kept moist.
• Initially vine growth (including root growth) is
  supported by stored carbohydrates in the
  cutting/rootling.

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FERTIGATION

• Application of fertilizers through irrigation
  system, fertigation, has been tried in grapes
  also.

Drip irrigation system is ideal for fertigation
and only soluble salts are applied through
irrigation system to prevent clogging of
emitters.
Urea is widely used for fertigation since it
readily dissolves in water. Improved yields by
applying 300 kg urea/ha for 60 days after October
pruning at 5 kg/ha/ day.
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• The soil should be kept moist to promote further
  root growth. If the soil becomes too wet, root
  growth will be inhibited. In most soil types this
  means applying small amounts of water daily for
  the first few weeks then less often.

• To ensure the moisture of the soil is at an
  optimum install soil moisture monitoring devices
  (e.g. tensiometers). Maintain the soil moisture
  tension in the vines root zone between 10 and 60
  centibars.

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YOUNG VINES

• The aim is to maximise vine growth in years 1 to
  3. Maintaining moist soil throughout the growing
  season will help to achieve this. Soil moisture
  can be maintained by adjusting irrigation
  according to soil moisture readings (e.g.
  tensiometers or gypsum blocks). Soil moisture
  should be maintained between 10 and 60 centibars.

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ESTABLISHED VINES

• Maintaining soils in the readily available
  moisture range will maximise yield throughout the
  growth cycle of the vines.
• Irrigation techniques such as RDI and PRD can
  also be used to manage vine growth and to
  manipulate fruit quality and yield.

• Grape is a shallow feeder. Light and frequent
  watering is better for grapes.
• Water requirement of grape are very high
  during berry growth.

• This period coinciding with hot and dry weather,
  more water is required at this stage. Least water
  is required during fruit-bud formation. This
  period if coincides with cloudy weather and
  rains, watering are totally to be stopped.

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• Reduced irrigation during ripening, i.e. (one
  month prior to harvesting) improve the quality of
  grapes and hastens ripening. Too much stress
  during ripening can also increase the berry drop
  at and after harvesting.

• Currently due to the shortage of water, grapes
  are irrigated through drips.
• The number of drippers/vine and their placement
  are very crucial in drip irrigation. The active
  feeder root zone is to be wetted by the water
  discharged through the emitters.

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• Since the wetted pattern is more horizontal than
  vertical in clay soils but more vertical than
  horizontal in sandy soils, more emitters with low
  discharge rate for longer duration are advisable
  to get good results with drip irrigation in sandy
  soils.

• Inadequate wetting of root zone reduces shoot
  vigour and weakens the vines. Gradually they
  develop deadwood and go barren 7-8 years after
  planting.

•     The quantity of water to let through drip
  irrigation daily depends not only on the stage of
  growth of the vine but also the
  evapotranspiration in a vineyard. Putting these
  two factors together the water requirement of
  grapes through drips is given in Table3.

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Water requirement of grape through drip irrigation
Stage of growth Water required / ha (litres/day)
1-40 days after summer pruning  48,000-60,000
41-100 days after summer pruning  24,000-32,000
101 days after summer pruning to winter pruning 15,000-20,000
1-45 days after winter pruning   20,000-24,000
46-75 days after winter pruning  16,000-20,000
76-100 days after winter pruning   48,000-60,000
111 days after winter pruning until harvesting 36,000-48,000
After harvesting untill summer pruning  20,000-24,000
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• Grape is sensitive to chlorides and total salts
  content in irrigation water.
• Water with electrical conductivity of less than
  1mmhos/cm, chlorides less than 4m.e/litre, sodium
  adsorption ratio less than 8.0, residual sodium
  carbonate less than 1.25 m.e/litre and boron less
  than 1.0 mg/kg is considered safe for irrigation
  grapes.

            Raising a bund of loose soil to a
height of 1 along the vine rows and mulching the
soil around the drip zone by sugarcane trash or
paddy straw can conserve the soil moisture and
save irrigation water.
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Advantages of drip irrigation system

1. Water saving to the extent of 60 as compared to
   traditional surface irrigation method
2. High water application efficiency
3. Increase in the yield to the extent of 25 - 30
   over traditional irrigation methods.
4. Use of water soluble fertilizer, very high FUE
   with fertilizer saving to the extent of 25 to 30
   Use of saline water is possible
5. Reducing inter-culturing and weeding cost

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• 6. Excellent soil health and maximum soil
  microbiological activities
• 7. Saving in labour cost, due to atomization
• 8. Excellent and cost effective for horticultural
  crops - widely spaced, low cost and long duration
  crop
• Adoptable for undulating topography, variable
  soil types and all crops
• Adoptable for undulating topography, variable
  soil types and all crops.

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However drip irrigation system has also
limitations as below

1. High initial cost due to solid system
2. Skilled man-power is required for design,
   operation and maintenance
3. Availability of electricity as system is to
   operate daily or alternate day deposits
4. The problem of clogging of emitters due to
   physical impurities, chemical and biological
   residues of bacteria and algae
5. Periodical maintenance such as cleaning of
   filters, flushing of piping network and pressure
   regulation in the system

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• 6. Treatment of back water flush system, (Sand
  filter cleaning), acidification (Chemical
  clogging) and chlorination removal of algae and
  bacteria are tedious and time consuming
• 7. Breaking of lateral pipes due to cultural
  operation, rats and other animal troubles

• In spite of the above limitations and some
  problems the micro-irrigation system has proved
  to be the best system amongst all irrigation
  methods.

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• Assessment
• Excess salt content in irrigation water, with EC
  value of more than one causes injury to vines.
  (True/ False)
• Soil moisture should be maintained between
  __________ centibars. (10 and 60)
• Grape is a __________
• a). Heavy feeder b). Shallow feeder
• Low amount of water is required during _________
  stage.
• a). vegetative b). Fruit-bud formation
  c). Flowering stage
• Increased amount of irrigation during ripening,
  i.e. (one month prior to harvesting) improve the
  quality of grapes and hastens ripening (True/
  False).