الفهرس 
Crop coefficient (Kc)Only 14 pages are availabe for public view
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Abstract
The experiments were carried out at theArid Land
Research Laboratory, Faculty of Agriculture, Ain Shams University. Potato, sweet pepper and
spinach crops were grown in volumeteric lysimeters for two successive seasons, i.e., 1994/95 and
1995/96, in order to. study the water consumptive use of the three crops. The trails aimed to
verify the possibility of improving the method of estimating water consumpive use and to detennine
the crop coefficient factors (Kc) for the above-mentioned crops. The required data for some ET
formulae and miming the Pemnan Monteith formula will be collected. All results will be used to
produce the best fonnula (Pemnan monteith) for calculating the potential evapotranspiratin for
three crops under the local condition. Penman Monteith was used to justify the canopy resistant
(rc) The experiments included two treatments which were the two scheduling irrigation methods .
Irrigation scheduling methods were as follows:
1. Pan evaporation method.
2. Modified Pemnan method.
The obtained results can be summarized as follows:1. Sweet pepper
1. Seasonal water consumptive use values were 581.9 and
618.5 mm for Pan evaporation and modified Pemnan methods
treatments in 1995 season. In 1996 season, values w’·re 584.45
and 615 .65mm for the same respective methods. In both
seasons, average seasonal evapotranspiration .values were 582.9 and 516.7mrn for the same
respective methods treatments.
2. Crop coefficient and canopy resistant
2.1 Crop coefficient (Kc) values In 1995 season, for sweet pepper plant were 0.7 at initial
stage, 0.85 at vegetative stage,
1.02 at flowering and 0.9 at harvesting for the Pan evaporation method treatment and 0.8, 0.89,
0.87 and 0.91 at the different stages, respectively, for Penman method treatment. In 1996 season,
values of Kc were 0.7, 0.77, 0.92 and 0.94 for the same respictive stages using Pan evaporation
method wllile they were 0.7, 0.85, 0.87 and 0.96 for the same respective stages using modified
Penman method treatment.
2.2 Crop canopy resistant (rc) values for sweet pepper plant in 1995 were 50.01, 62.82, 77.74 and
8l.n sm-1 for initial, vegetative, flowering and harvesting stages, respectively under Pan method
treatment, wllile values were 48.37, 59.85, 73.47 and 81.59 for the same respective stages tmder
Penman method treatment. Overall average was 66.96 for both methods as seasonal value.
In 1996 season, values of (rc) were 49.53, 58.03, 67.77 and 81.19 sm-1 for initial, vegetaive,
flowering and harvesting stages, respectively, using Pan evaporation method while values were
49.33, 57.39, 67.36 and 81.84 for the same respective
stages using Pemnan method treatment. Overall average was
64.06 for both methods as seasonal value.
3. Values of seasonal calculated reference evapotranspiration (ETo) In 1995 season, of665.50,
561.23 and 599.78 tmn were
obtained by the application of Pan evaporation, modified Penman and Penman monteith methods,
respectively. In 1996 season, values of 660.84, 550.49 and 597.65 mm were found for the same
respective methods.
In both seasons, calculated reference evapotranspirtion values were 663.17, 555.86 and 598.72 mm
for thesame respective methods.
The daily evapotranspiration rate was correlated with the plant growth stage. This consumption
increased till the complete development of the plant. The highest water consmnptive use for sweet
pepper plants was obtained after 78 and 81 days after sowing in the first and second seasons,
respectively. These results were obtained by using both Pan evaporation and modified Penman
methods.
4. In 1995 season, water use efficiency values of 1.69 and 1.55 Kg fresh weight/m 3 water
consumption were obtained by the application of Pan and Penman methods treatments , respectively.
In 1996 season, values of2.12 and 1.58 Kg fresh weight/m 3 water consumed were resulted from the
Pan evaporation and modified Pemnan method treatments, respectively. It is clear that water use
efficiency (WUE)was higher in case of Pan evaporation method treatment compared with modified
Penman method treatment.
5. The ratios beween ET crop and actual ET based on Pan evaporation method treatment and
actual ET values were 1.11,
0.94 and 1.01 for Pan evaporation, modified Pemnan and Penman Monteith methods in 1995, respectively. Values were
1.21, 0.92 and 1.01 for the same respective methods in 1996 season. The overall average values were
1.16, 0.93 and 1.01 for the three respective methods. It is clear that Penman Monteith method was
the most efficient in calculating ET crop compared to the other two methods.