This document discusses irrigation and water requirements for vegetable crops. It begins by explaining that crop water requirements depend on evapotranspiration and climatic factors, while irrigation requirements also consider the irrigation system and soil characteristics. It then discusses different irrigation methods like surface, drip, sprinkler and central pivot irrigation. It explains that the choice of irrigation method depends on natural conditions, crop type, experience, labor and costs/benefits. The document also provides details on water demands based on crop type, growth stage, soil and season. It outlines critical moisture periods and drought tolerance for various crops.
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Irrigation & Water Requirements of Vegetable Crops
1. Irrigation & Water
Requirements of
Vegetable Crops
Munish Sharma
Dept. of Soil Science
College of Agriculture
C.S.K.H.P.K.V.
Palampur (H.P.)
2. INTRODUCTION
• Crop water requirements refer to the actual water
needs for evapotranspiration (ET) which are related to
soil type and plant growth, and primarily depend on
crop development and climatic factors which are closely
related to climatic demands.
• Irrigation requirements are primarily determined by
crop water requirements, but also depend on the
characteristics of the irrigation system, management
practices, and the soil characteristics in the irrigated
area.
3. • Water is essential for vegetable crops. It is absorbed by
plant roots from the soil through processes of osmosis
and diffusion.
• Besides absorption of water and translocation of
nutrients from soil, water also influences the
photosynthesis, respiration, transpiration, nutrient
utilization and cell division.
4. • Thus the crop plants require water almost
throughout the growing season.
• The water requirement varies with crop species
and growth stage of the crop.
5. IRRIGATION
• The important sources of water to a crop are
mainly rainfall and irrigation.
• The uncertainty of uniformity and level of rainfall
increases the importance of irrigation in vegetable
production.
6. • Irrigation is likely to increase size and weight of
individual fruit and to prevent defects such as
toughness, strong flavor, poor tipfill and podfill,
cracking, blossom-end rot and misshapen fruit.
• On the other hand, it reduces soluble solids in
muskmelons and capsaicin in hot peppers if
applied during fruit development.
8. PROBLEMS IN IRRIGATION
• Scarcity of water: According to Population
Action International (PAI), severe water
scarcity or hydrological poverty is feared in
the world by 2025.
• In India only 34% of the water resources is
available to meet the increasing demands
of agriculture, industry and urban usage.
• The quality and availability of water are two
major factors that affects irrigation in
vegetable crops.
9. Water Demand in relation to Crops
• The water demand and response to
irrigation varies along with crop species.
• Shallow-rooted crops and crops with tap
root system such as potatoes and celery
require frequent, light irrigations.
• Deep-rooted crops and crops with fibrous
roots, can use water from a greater volume
of the soil profile and do not require
irrigation as frequently.
10. • Vegetable crops differ in their water requirements, and
have certain stages of growth when an adequate water
supply is critical.
• Adequate water is essential for good germination of all
crops.
• For flowering crops, such as beans, tomatoes, cucurbits
and maize, another critical period is at flowering, and
then also during the development of fruit and/or seed.
• For heading crops, such as lettuce and cabbage, the
most critical period for water is at heading stage.
• An adequate supply of water is essential for root crops
once the roots start enlarging.
11. Water Demand in relation to Soils
• Soil types differ in their ability to retain
water following rainfall or irrigation.
• Coarse textured soils (e.g. sands and
coarse sandy loams) held less available soil
moisture. So frequent and light irrigation are
required in such soils.
• Fine textured soils retain more available soil
moisture. So heavier and less frequent
irrigations are required in such soils.
12. Water demand in relation to
growing season
• The water requirements of crops also vary
with the growing season.
• Warm season vegetable crops have higher
water requirement in comparison to the cool
season vegetable crops.
• This is mainly due to the high evapo-transpiration
demand in the warm season.
13. Irrigation and water requirement
under various conditions
1. Improving Stands
2. Rooting Depth
3. Critical Moisture Periods
4. Drought tolerance
14. Irrigation for improving stands
• Irrigation is a valuable tool in producing a
good, uniform stand which will help ensure
high yields.
• Good uniform stands mean uniform harvest
dates and greater production efficiency.
• Vegetable transplants also require good soil
moisture. A light irrigation will help in the
establishment of young transplants by
providing a ready supply of water to young,
broken roots.
15. • Most vegetables have small seeds that are
planted 15 cm deep or less. The upper layer of
the soil can dry rapidly, leaving shallowly sown
seeds susceptible to drying out.
• Without enough soil moisture, the seed is left
partially germinated. When this happens, no
stand or, at best, an incomplete stand will result.
• A light irrigation immediately after sowing should
be applied to settle the soil around the seeds
and to begin seed germination.
16. • For larger seeded crops, it is desirable that
irrigation begins a few days prior to sowing.
• If seeds are slow in emerging from the soil due
to cool temperatures or slow germination, then
application of light irrigation is needed to
encourage emergence.
17. Irrigation in relation to rooting depth
• It is important that the soil profile be filled with
water during each irrigation event. Otherwise,
frequent light irrigation events result in the
formation of shallow root systems.
• Shallow root systems result in plants being
stressed even in short periods of water deficit.
In addition, the plants with shallow root
systems are more prone to lodging and nutrient
deficiencies.
• On the other hand, excessive irrigation can
leach nutrients from the soil and encourage the
development of diseases and nutrient
deficiencies.
19. Irrigation in relation to critical moisture
periods
• Critical periods of water needs can best be defined
as that time when soil moisture stress can most
reduce yield in an otherwise healthy crop.
• This is not to say that it is the only time in the life of
the crop that moisture stress reduces yield. It is,
however, the time when moisture stress will exert
its greatest effect.
• Most vegetable crops are sensitive to drought
during two periods: during harvest and two to three
weeks before harvest
20. Crops Critical Period
Beet, carrot, radish, turnip Root enlargement
Cabbage, cauliflower, broccoli,
lettuce
Head development
Tomato, peppers, brinjal,
cucumber, melons
Flowering, fruit set and fruit
development
Beans, peas Flowering and pod development
Onion Bulb development
Potato Tuber initiation and tuber
development
Asparagus Fern development
Sweet corn Tasseling, silking and ear
development
21. Irrigation in relation to drought
tolerance
• Drought tolerance is an indication of a crops
ability to withstand short periods of drought
without significantly reducing yield.
• Vegetable crops vary in their tolerance to
drought depending on their physiology and
water requirements.
• Crops with higher drought tolerance can be
grown where water available for irrigation is
low and the crop can still give economic
yield if supplement irrigation is provided at
critical stages of plant growth.
23. Water requirement for different groups
of vegetable crops
• Leafy vegetables
• Root, tuber, and bulb vegetables
• Fruit and seed vegetables
24. Leafy vegetables
• Cabbage, lettuce, and spinach are generally
planted at or near field capacity.
• Being shallow rooted, these crops benefit from
frequent irrigation throughout the season. Since
leaf expansion relates closely to water availability,
these crops, especially cabbage and lettuce, are
particularly sensitive to drought stress during the
period between head formation and harvest.
Overwatering or irregular watering can result in
burst heads.
• Broccoli and cauliflower are sensitive to drought
stress at all stages of growth, responding with
reduced growth and premature heading.
25. Root, tuber, and bulb vegetables
• In sweet potatoes, potatoes, carrots, and onions,
yield depends on the production and translocation
of carbohydrates from the leaf to the root or bulb.
• The most sensitive stage of growth generally
occurs as these storage organs enlarge.
• Moisture stress causes the formation of small,
woody, and poorly flavored roots. Uneven irrigation
can lead to misshapen or split roots in carrots,
secondary growth in Irish potatoes, and early
bulbing in onions.
26. Fruit and seed vegetables
• Cucumbers, melons, pumpkins and
squashes, lima beans, snap beans, peas,
peppers, sweet corn, and tomatoes are
most sensitive to drought stress at flowering
and during fruit and seed development.
• Fruit set on these crops can be seriously
reduced if water is limiting. An adequate
supply of water during the period of fruit
enlargement can reduce the incidence of
fruit cracking and blossom-end rot in
tomatoes.
27. Methods of irrigation
• Surface irrigation
• Drip or trickle irrigation
• Sprinkler irrigation
• Central Pivot System
34. Choice of Method
Choice of Method
• The choice of method of irrigation depends
on following factors :
– natural conditions
– type of crop
– previous experience with irrigation
– required labor inputs
– costs and benefits.
35. NATURAL CONDITIONS
• Soil type
• Slope
• Climate
• Water availability
• Water quality
36. Type of crop
• Surface irrigation can be used for all types
of crops.
• Sprinkler and drip irrigation, because of
their high capital investment per hectare,
are mostly used for high value crops.
• Drip irrigation is suited to irrigating
individual plants. It is not suitable for close
growing crops.
37. Previous experience with irrigation
• The choice of an irrigation method also
depends on the irrigation tradition within the
region or country.
• Previous irrigation experience reveals the
problems regarding irrigation in the region
and helps in choosing better irrigation
methods based on local conditions.
• The servicing of the equipment may be
problematic and the costs may be high
compared to the benefits.
38. Required labor inputs
• Surface irrigation often requires a much
higher labor input - for construction,
operation and maintenance - than sprinkler
or drip irrigation.
• Surface irrigation requires accurate land
leveling, regular maintenance and a high
level of farmers' organization to operate the
system.
• Sprinkler and drip irrigation require little
land leveling; system operation and
maintenance are less labor-intensive.
39. Costs and benefits
• Before choosing an irrigation method, an
estimate must be made of the costs and
benefits of the available options.
• On the cost side not only the construction
and installation, but also the operation and
maintenance (per hectare) should be taken
into account.
• These costs should then be compared with
the expected benefits (yields).
