HOW MUCH WATER DOES MY CROP NEED? Part 8. Tomato

By: Dr.P.Soman, Posted on: October 2020

Tomato, Lycopersicum esculentum, is edible, belongs to the family Solanaceae. It is a herbaceous annual plant with bisexual flowers. The fruit is a true berry. It is a self-pollinated crop but in some cases as high as 30% cross-pollination has been reported. Depending upon the growth habit, tomato plants have been categorized into two-indeterminate and determinate types. The plant of former type terminates in a vegetative bud, whereas that of the determinate type terminates in a flower-bud and is appropriately called 'self topping' or 'self pruning' type. Many varieties of determinate type tomato plants do not have adequate foliage to protect their fruit. Some of them fruit very early. The determinate varieties can be harvested in 2-3 harvests while the fruiting period of indeterminate type is prolonged.

Tomato is a warm season crop, it requires warm and cool climate. The plants cannot withstand frost and high humidity. Also light intensity affects pigmentation, fruit colour, fruit set. The plant is highly affected by adverse climatic conditions. It requires different climatic range for seed germination, seedling growth, flower and fruit set, and fruit quality. Temperature below 100C and above 380C adversely affects plant tissues thereby slow down physiological activities. It thrives well in temperature 100C to 300C with optimum range of temperature is 21-240C. The plant doesn't withstand frost. Avoid water stress and long dry period as it causes cracking of fruits. Bright sunshine at the time of fruit set helps to develop dark red colored fruits.

India produces 20.5 million ton in an area of 0.81 million ha with an average productivity of 25 t/ha. Tomato farming is considered as one of the profitable venture. Tomato cultivation is done in open land and controlled poly houses. In the open field Tomato can be produced throughout the year, Kharif (June-Sept), Rabi (Sept- Jan) and summer (Feb-June) in Central and South India. Example, in Chitoor, Andhra Pradesh it is grown in all three seasons.

While rain supplies part soil moisture, irrigation is required for successful cultivation. Drip irrigation is found to be very suitable for tomato cultivation.

Inline drip line with 4 lph emitters spaced at 40 or 60 cm is found suitable for Tomato. The lateral spacing of 1.3 m would suit for a number of other row crops- Brinjal, Okra, Potato, Cabbage, Cauliflower , Leaf vegetables etc.

Tomato root system is mainly (70 % or more) spread in the top 20 cm soil layer. Irrigate daily as per the schedule through the season.

Water Need of Tomato

Estimate of water use by the Tomato crop is becoming a necessity as the water availability is shrinking. Growers are also looking for opportunities to improve water productivity, by conserving water or reducing its consumption. At this point one start asking "How much water does my crop need?

Where does all the water go after one irrigates a crop field? Water moves out of the field in 7 different ways after an irrigation that floods the field: 1.Direct evaporation from the water surface, 2. Drift of water away from the field due to wind, 3. Transpiration through the body of the crop plant (Mainly thru leaves), 4. Evaporation from the wet ground exposed to the atmosphere, 5. Run off of water from the field, 6. Infiltration to lower soil strata and 7. Deep percolation to far deep soil profile.

Among these, the essential components of crop water use are only two: ,transpiration and soil surface evaporation. Hence water use by crop is referred to as ETP, Evapotranspiration. As the crop grows the surface evaporation gets reduced and when the soil surface is fully covered by the canopy (leaf and leaf bearing branches of the crop) there is only one dominant component of crop water use: Transpiration.

In precision irrigation, the water given should only be equivalent to ETP. The goal of perfect irrigation is to reduce the second component of water loss, surface evaporation. In conventional irrigation major part of water loss are in fact the rest of the 7 listed above.

When a farmer asks the question, HOW MUCH WATER DOES MY CROP NEED? The answer is the ETP (evaporation plus transpiration). Accordingly I have estimated the water required for a good high productive Tomato crop. The difference among the regions is due to difference in evaporation rate during the growing season of the crop.

How Much water I need for Tomato crop?

Table. CROP WATER REQUIREMENT OF TOMATO CROP IN DIFFERENT LOCATIONS IN INDIA.

TOMATO CROP WATER REQUIRMENT UNDER DRIP IRRIGATION WR
mm
WR
m3/ha
Growing Regions kharif
(June-Sept)
Rabi
(Oct-Feb)
Summer
(Feb-June)
kharif
(June-Sept)
Rabi
(Oct-Feb)
Summer
(Feb-June)
Chitoor in Andhra Pradesh (Largest Tomato Hub) 517 538.2 712.5 5170 5382 7125
Siddipet in Telengana (a large vagetable hub near Hyderabad in Medak) 506.6 415.8   5066 4158  
Central West India - Nasik dist. Maharashtra   398.6     3986  
North Central India region - Shivapuri dist of North Madhya Pradesh   375.3     3753  
Southern India - Dindigal dist. TN (Tomato and Veg hub)   399.2     3992  
North Indian Plain (North Haryana and South Panjab) region   380     3800  
Tomato under ridge and furrow fbod irrigation XXX m3/ha for 120 day crop

Precision Irrigation and fertigation in Tomato is maintained by drip method of irrigation.

In the open field, for a growth120 days period, Tomato requires 5000- 5170 m3 water per hectare (Kharif), 3750 m3- 5382 m3 (Rabi) and 7125 m3/ha (Summer) to produce an yield up to 50-60 t/ha yield under drip -fertigation assisted precision farming.

The seasonal difference in water need of the crop is clearly demonstrated by the three seasons in Chitoor, Andhra Pradesh. It is same variety of tomato and similar field conditions; but the ETP is different in Kharif, Rabi and Summer seasons. Hence the crop water requirements are 5170 m3 in Kharif, 5382 m3 in Rabi and 7125 m3 in Summer.

Applying water as per the estimates above is possible only through drip method of irrigation. In conventional irrigation system the whole season (115-120 days) consumes 7000-8000 m3 on an average considering the way farmers apply irrigation water and the productivity is around 25 t/ha in India.

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