Khilesh Kumar Sahu presented on factors determining water needs of crops. Evapotranspiration is the combined water loss from soil and plant surfaces through evaporation and transpiration. It is influenced by climatic factors like temperature, humidity, solar radiation and wind speed. Crop characteristics like crop type, leaf area, and root depth also impact water needs. Properly understanding evapotranspiration allows farmers to effectively schedule irrigation and maximize crop water utilization.

1. PRESENTATION ON
“Soil, Plant and Meteorological Factors Determining Water
Needs of Crops ”
PRESENTED BY
KHILESH KUMAR SAHU
DEPT. OF AGROMETEOROLOGY
Course Title:- WATER MANAGEMENT
Course No:- AGRON- 504

2. CONTENTS
• Introduction
• Evapotranspiration (ET)
• Factor affecting evapotranspiration.
• Estimating method of evapotranspiration
• Factor affecting crop water requirement
• Conclusion

3. INTRODUCTION
• EVAPORATION :-
The process by which any liquid escapes from the surface or free
water surface is diffusive process by which liquid water in the
form of vapour is lost in the atmosphere.
• TRANSPIRATION:-
Transpiration is a process by which water vapour leaves the living plant
body and enters the atmosphere. It involve continuous movement of
water from the soil into the roots, through stem and out through the
leaves to the atmosphere.
Fig-1

4. Evapotranspiration
• The combined loss of water
from the plants and
surrounding soil surface
through transpiration and
evaporation is jointly called
as Evapotranspiration (ET)
Fig-2

5. • Potential evapotranspiration (PET):- The maximum
water lost through evaporation from wet soil and
transpiration from a short cut grass, covering ground
completely, under unlimited water supply.
• Reference crop evapotranspiration (ET0):-Rate of
evapotranspiration from an extended surface of 8-15
cm tall green grass cover of uniform height actively
growing, completely shading the ground and not short
of water (mm/day).
• Actual crop evapotranspiration(Eta crop):- Rate of
evapotranspiration equal to or smaller than predicted
ET crop as effected by a level of available soil
water,salinity,field size or other causes (mm/day)

6. FACTORS INFLUENCING EVAPTRANSPIRATION

7. FIG 4. CLIMATIC FACTORS INFLUENCING CROP
EVAPOTRANSPIRATION

8. Climatic or environmental factors
• Solar radiation
• Ambient temperature
• Relative humidity
• Wind speed
• Soil moisture
Crop characteristics
• Stomata closure and opening
• Stomata number and size
• Leaf area or canopy cover
• Adaptive mechanism

9. • Rooting depth and proliferation
• Length of growing season
Management factors
• Method of irrigation
• Wind break
• Anti- transpirants
• Salinity
Cultural factors
• Tillage operations
• Cover crops
• Weeding
• Mulching

10. Factors Affecting Crop Water Requirements
• Climate
• Type of Crop
• Water table
• Ground Slope
• Conveyance Losses
a. Type of soil
b. Subsoil water
c. Age of canal
• Method of Application of water
• Method of Ploughing

11. Table:- 1. EFFECT OF MAJOR CLIMATIC FACTORS
ON CROP WATER NEEDS
S.NO. Climatic Factor Crop water need
High Low
1. Temperature hot cool
2. Humidity low (dry) high (humid)
3. Wind speed windy little wind
4. Sunshine sunny (no clouds) cloudy (no sun)

12. • Type of Crop:- The influence of the crop type
on the crop water need is important in two
ways.
• Water Table:-If the water table is nearer to the
ground surface, the water requirement will be
less & vice versa
• Ground Slope:-If the slope of the ground is
steep the water requirement will be more due
to less absorption time for the soil.

13. Conclusion:-
• Evapotranspiration are the combine water loss through
evaporation and transpiration.
• For crops of a different type, evapotranspiration will vary
according to their height, colour , leaf area, age and condition.
• Evapotranspiration helpful for irrigation scheduling and batter
utilization by the crops.
• By knowing the rate of water loss from a region farmers will
be better placed to efficiently manage the available water for
their crop.