1. ESTIMATION OF CROP WATER REQUIRMENT OFDIFFERENT CROPS GROWN IN KUMLUR
By,
NISHIT AMAN
BTE

2. GREEN GRAM Season – Rabi ( Starting Nov) Kharif ( Starting March)
Temperature – degree Celsius
Soil Type - Loamy soil

3. HOW TO CALCULATE CWR? Calculate reference Evapotranspiration
Find out crop coefficient of the green gram during different stages of growth.
Multiply both to get actual evapotranspiration.

4. DATA COLLECTED FOR CALCULATION
Date of sowing – 1st march
Date of harvest – 8th June
Altitude of Kumulur – 78 m
Latitude of Kumulur - 10°8’
Relative humidity – 80%
Mean Max. temperature during March, April May and June are 32.4°C,36.3°C 38.0°C and37°C
Mean Min. temperature during March, April May and June are 22.4°C, 24.7°C, 26.6°C, and 26.1°C

5. ESTIMATION OF ET0 Modified Penman method
Mean max. temperature for four month is 35.57°C.
Mean min. temperature for the four month is 24.95°C.
Mean air temperature will be 30.26
Mean sunshine Hour (n) 3.43
Maximum Possible Sunshine hour 12.3
n/N will be 0.28

6. Cont..
Extra-terrestrial radiation(Ra) in mm/day (from the table).
Wind speed = 6km/hr or 144km/day

7. AERODYNAMICS TERM ea = 42.41 mbr ( From the table) ed = RH/100 × ea
= ×42.41
= mbr
ea – ed = ( ) mbr
= mbr
f(u) = 0.66
( 1- W) = ( from the table)

8. RADIATION TERM Rns = Ra× 0.292 = 12.74 ×0.292 = 3.72
= 3.72
Rnl = f(t) × f(e) × f(n/N)
= ×0.1 ×0.354
= 0.59
Rn = Rns – Rnl =
= 3.13

9. Cont… W = 0.781 ET0 (Unadjusted) = W Rn + (1-W).f(u)(ea - ed )
= (0.781 × 3.13) +
×0.66 ×8.49
= 3.66mm/day
ET0 = c × ET0
= × 3.66
= mm/day

10. DETERMINATION OF CROP COFFICIENT
Initial Stage - 20days
Development stage – 30 days
Middle stage – 30 days
Late stage – 20days

11. Initial Stage From 1st march to 20 march Kc = 0.5 ET0 = 3.99mm/day
ET = Kc × ET0
= 0.5 × 3.99
= 1.995mm/day
= 39.9mm/stage

12. Development stage From21st march to 20th April Kc = 1.05
ET0 = 3.99mm/day
ET = Kc × ET0
= × 3.99
= mm/day
= mm/Stage

13. Middle stage From20st April to 19th May Kc = 1.02 ET0 = 3.99mm/day
ET = Kc × ET0
= × 3.99
= mm/day
= mm/Stage

14. LATE STAGE From20st MAY to 10th May Kc = 0.9 ET0 = 3.99mm/day
ET = Kc × ET0
= 0.9 × 3.99
= mm/day
= mm/Stage

15. Cont…
Total water requirement from day of sowing to day of harvesting will be summation of all.
39.9mm mm mm mm
= mm

16. Result
Total water requirement of the green gram as calculated by Modified penmen method is mm.

17. THANK YOU