Page 50 - soil-plant-water relationship and water requirement

SOIL-PLANT-WATER RELATIONSHIP AND WATER REQUIREMENT

The combined loss of evaporation and transpiration from a cropped field is termed as
evapotranspiration which is otherwise known as consumptive use and denoted as ET
and this is a part of water requirement.

CU = E + T + WP

Therefore,

WR = CU + WL + WSP

The crop water requirement can also be defined as water required meeting the
evapotranspiration demand of the crop and special needs in case of wet land crop and
which also includes other application losses both in the case of wet land and garden
land crops. This is also known as crop water demand.

The crop water requirement varies from place to place, from crop to crop and depends
on agro-ecological variation and crop characters. The following features which mainly
influence the crop water requirement are:

1. Crop factors
a. Variety
b. Growth stages
c. Duration
d. Plant population
e. Crop growing season

2. Soil factors
a. Structure
b. Texture
c. Depth
d. Topography
e. Soil chemical composition

3. Climatic factors
a. Temperature
b. Sunshine hours
c. Relative humidity
d. Wind velocity
e. Rainfall

4. Agronomic management factors
a. Irrigation methods used
b. Frequency of irrigation and its efficiency
c. Tillage and other cultural operations like weeding, mulching etc /
intercropping etc

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