Agriculture Reference
In-Depth Information
FIGURE 3
Tomato crop under drip irrigation.
15.3 ESTIMATION OF DAILY CROP WATER REQUIREMENT
The daily crop water requirement was computed by using Eq. (1) [19].
V = E
p
.K
p
.K
c
.S
p
.S
r
.W
p
(1)
where: V = Volume of water required (liter/day/plant); E
p
= Pan evaporation as mea-
sured by Class-A pan evaporimeter (mm/day); K
c
= Crop coefficient which depends
on crop growth stage; K
p
= Pan coefficient, 0.8 [12]; S
p
= plant-to-plant spacing (m);
S
r
= row-to-row spacing (m); and W
p
= Fractional wetted area that varies with crop
growth stage.
Based on the fi eld experiment, the value of
K
c
of tomato was for 0.45 crop es-
tablishment, 0.75 for crop development, 1.10 for mid-season, and 0.65 for maturity
stages, respectively. The values of W
p
was assumed as 0.5 during crop establishment
stage and 0.75 during other stages [2].
Water requirement of tomato was estimated on daily basis for all months of a
particular year by drip method. Daily operating time for drip irrigation system was
worked out taking the application rate per plant. Drip system was scheduled to oper-
ate on alternate days, therefore total quantity of water delivered was cumulative water
requirement of two days. Operating time of the drip irrigation for each treatment was
computed using Eq. (2).
Operating time = [V]/[(Number of emitters per plant) × (emitter discharge rate)]
(2)
where: V is volume of water required (liter/day/plant), and operating time is in hours.
Volume of irrigation water and hence the operating time of each treatment was differ-
ent depending on evaporation rate, crop growth stage as well as treatment irrigation
scheduling. Observations on water requirement and yield of tomato were recorded and
analyzed statistically following the standard procedures [14]. The water use efficiency
(WUE) of the crop was determined by dividing the yield with crop water requirement.
Biometric observations were recorded for plant height, number of branches per plant,
number of leaves and average yield attributing characters such as days taken to first
harvest, number of fruits per plant and the yield of tomato.
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