**3.1 Climatic factors that affecting ET**

#### *3.1.1 Radiation*

Radiation is the main source of energy for the ET process. It depends on the global solar radiation flux density and vegetation albedo. A darker vegetation

**99**

*Concept and Consequence of Evapotranspiration for Sustainable Crop Production in the Era…*

absorbs more incident solar radiation and evapotranspires more [13, 16]. A thorough understanding of the factors controlling the energy balance of a cropped soil enables making accurate estimates or predictions of ET and irrigation water requirements. It also facilitates more effective irrigation water management [19, 20].

Over the course of a day, an increase of the air temperature causes an increase on the saturation deficit triggering a higher evaporative demand in the air, and leading

Air relative humidity acts in conjunction with temperature. The higher relative humidity, the lesser the evaporative demand and, therefore, the lower ET [13, 16].

Advection represents the horizontal transport of energy from a drier area to another more humid, and such additional energy is utilized in the ET process. Wind

Crop factors such as crop species, radiation reflection coefficient, leaf area index (LAI) in different growth stages of the plant, plant height and root depth (depth of the radicular system) are influenced on the crop ET, which are described details as

This factor is related to the foliar architecture (spatial distribution of the leaves), internal resistance of the plant to water transport, and other morphological aspects (number, size, and distribution of stomata, etc.), which exert a direct influence on

Radiation reflection influences directly net radiation availability for the ET process. The darker the vegetation, the lower the reflection coefficient and the higher

LAI in different growth stages of a plant is directly related to the size of the transpiring foliar surface, for the larger leaf area the larger the transpiring surface,

Plant height also influences the ET. Taller and rougher plants interact more efficiently with the atmosphere in motion, extracting more energy from the air and,

*3.2.3 Leaf area index (LAI) in different growth stages of plant*

and the higher the potential for water use [13, 16].

also helps remove water vapor near the plants to other regions [13, 16].

*DOI: http://dx.doi.org/10.5772/intechopen.83707*

*3.1.2 Temperature*

*3.1.4 Wind*

follows:

*3.2.1 Crop species*

ET [13, 16].

net radiation [13, 16].

*3.2.4 Plant height*

to high ET rates [13, 16].

*3.1.3 Relative humidity (%RH)*

**3.2 Crop factors that affecting ET**

*3.2.2 Radiation reflection coefficient*

therefore, increasing ET [13, 16].

*Concept and Consequence of Evapotranspiration for Sustainable Crop Production in the Era… DOI: http://dx.doi.org/10.5772/intechopen.83707*

absorbs more incident solar radiation and evapotranspires more [13, 16]. A thorough understanding of the factors controlling the energy balance of a cropped soil enables making accurate estimates or predictions of ET and irrigation water requirements. It also facilitates more effective irrigation water management [19, 20].
