In this chapter a full calculation example is given. The necessary data are provided below and the aim is to determine:
1. the reference crop evaporation (Data Sheet 3: ETo)
2. the crop water need for the various crops (Data Sheets 4: Kc and 6: ET crop)
3. the Irrigation water needs for the various crops (Data Sheet 6: IN)
GENERAL DATA
|
Location: |
Example (2) |
|
Latitude: |
8° North |
CROP DATA
Three crops are grown: onions (dry) followed on the same fields by potatoes, and cotton.
|
Crop |
Planting date |
Total season growing (days) |
|
Onions (dry) |
1 April |
150 |
|
Potatoes |
1 Oct |
120 |
|
Cotton |
1 July |
190 |
CLIMATIC DATA
|
Relative humidity (year round): |
medium |
|
Windspeed (year round): |
medium |
|
|
J |
F |
M |
A |
M |
J |
J |
A |
S |
O |
N |
D |
|
T min (°C) |
14.4 |
15.5 |
17.4 |
18.5 |
18.9 |
21.0 |
20.1 |
19.3 |
18.7 |
15.6 |
13.8 |
12.3 |
|
T max (°C) |
29.9 |
31.1 |
32.1 |
33.9 |
34.5 |
35.2 |
32.2 |
31.5 |
32.9 |
32.6 |
29.9 |
29.5 |
|
P (mm) |
19 |
21 |
28 |
33 |
37 |
38 |
121 |
134 |
44 |
28 |
19 |
5 |
DATA SHEET 3 Determination ETo: Blaney-Criddle Method
DATA SHEET 4 Determination of crop factors
DATA SHEET 4 - No. 2 - Determination of crop factors
DATA SHEET 6 Determination of Irrigation water needs (see also Data sheet 5)
DATA SHEET 6 Determination of Irrigation water needs No. 2 (see also Data sheet 5)
