PowerPoint Presentation

Irrigation & Water Requirements of Vegetable Crops

Munish SharmaDept. of Soil ScienceCollege of AgricultureC.S.K.H.P.K.V.Palampur (H.P.)

PPT INTRODUCTIONCrop 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.

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.

Thus the crop plants require water almost throughout the growing season.

The water requirement varies with crop species and growth stage of the crop.

IRRIGATIONThe 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.

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.

PERCENTAGE IRRIGATION OF WORLD

AMERICA 17% EUROPE 9% AFRICA 5% OCENIA 1% ASIA 68%

PROBLEMS IN IRRIGATIONScarcity 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.

Water Demand in relation to CropsThe 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.

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.

Water Demand in relation to SoilsSoil 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.

Water demand in relation to growing seasonThe 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.

Irrigation and water requirement under various conditions

Improving Stands

Rooting Depth

Critical Moisture Periods

Drought tolerance

Irrigation for improving standsIrrigation 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.

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.

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.

Irrigation in relation to rooting depthIt 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.

Shallow-Rooted(down to 45-60 cm)Intermediate(90-120 cm depth)Deep-Rooted(deeper than 120 cm)Cabbage, cauliflower, broccoli, Brussels sprout, corn, onion, garlic, lettuce, parsley, onion, radish, spinachBeet, beans, carrot, turnip, cauliflower, cucumbers, muskmelon, summer squash, peppers, brinjal, peaAsparagus, artichoke, tomato, sweet corn, pumpkin, watermelons, winter squash, sweet potato

Irrigation in relation to critical moisture periodsCritical 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

CropsCritical PeriodBeet, carrot, radish, turnipRoot enlargementCabbage, cauliflower, broccoli, lettuceHead developmentTomato, peppers, brinjal, cucumber, melonsFlowering, fruit set and fruit developmentBeans, peasFlowering and pod developmentOnionBulb developmentPotato Tuber initiation and tuber developmentAsparagus Fern developmentSweet cornTasseling, silking and ear development

Irrigation in relation to drought toleranceDrought 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.

Low toleranceMedium toleranceHigh toleranceSummer squash,cucumber, radish, leek, celery, cauliflower,broccoliTurnip, tomato, pumpkin, peppers, eggplant, sweet corn, carrot, watermelonSweet potato, asparagus, parsnip

Water requirement for different groups of vegetable crops

Leafy vegetables

Root, tuber, and bulb vegetables

Fruit and seed vegetables

Leafy vegetablesCabbage, 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.

Root, tuber, and bulb vegetablesIn 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.

Fruit and seed vegetablesCucumbers, 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.

Methods of irrigation

Surface irrigation

Drip or trickle irrigation

Sprinkler irrigation

Central Pivot System

Surface Irrigation

Surface Irrigation

Surface Irrigation

Surface Irrigation

Drip or Trickle Irrigation

Sprinkler Irrigation

Sprinkler Irrigation

Sprinkler Irrigation

Sprinkler Irrigation

Center Pivot

Center Pivot System

Choice of Method

The choice of method of irrigation depends on following factors :

natural conditions type of cropprevious experience with irrigationrequired labor inputscosts and benefits.Choice of Method

NATURAL CONDITIONS

Soil typeSlopeClimateWater availabilityWater quality

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.

Previous experience with irrigationThe 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.

Required labor inputsSurface 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.

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).

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