34
growing season, namely 12 months. In addition, the value of ETc of watermelon is
ranked second because its growing season started in February and ended in June
resulted in high values of ETo. The third highest value of ETc is found for sugar beet
as a result of its long growing season, namely 6 months (Table 3.3).
For field crops grown in the summer season, the highest value of ETc is found for
rice, sorghum and cotton. Furthermore, three vegetable crops have the highest value
of ETc, namely eggplant, potato and cucumber (Table 3.4).
To calculate water requirements of a crop, irrigation application efficiency is
considered in the calculation. In Egypt, the common used values of irrigation application efficiency are 60, 75 and 85% for surface, sprinkler and drip, respectively.
0.0
1.0
2.0
3.0
4.0
5.0
6.0
7.0
ETo (mm/day)
30-year
20-year
10-year
Fig. 3.2 Comparison between averaged values of ETo over 10, 20 and 30 years. (Source: Ouda
and Noreldin 2017)
Table 3.3 Crop coefficient (Kc) and crop evapotranspiration (ETc) values for different winter
field and vegetable crops
Crop
Kc ini
Kc mid
Kc end
ETc (mm)
Barley
0.29
1.11
0.19
380
Faba bean
0.27
0.99
0.19
411
Clover
0.25
1.15
1.15
635
Flax
0.29
1.10
0.25
589
Lentil
0.22
0.99
0.19
402
Wheat
0.30
1.08
0.18
455
Sugar beet
0.25
1.15
0.95
604
Fall sugarcane
0.83
1.25
0.75
2982
Potato
0.26
1.09
1.24
232
Strawberry
0.20
0.70
0.70
694
Sweet potato
0.23
1.10
0.69
423
Tomato
0.23
1.10
0.64
395
Peas
0.19
0.98
0.98
340
Onion
0.28
1.19
0.54
581
Watermelon
0.26
1.00
0.75
751
Source: Ouda (2019)
A. E.-H. Zohry and S. Ouda