**5. Consequences of evapotranspiration for sustainable crop production in the era of climate change**

Water moved from the Earth's surface into the atmosphere by evaporation and T the two distinct mechanisms. Evaporation occurs directly from the water bodies where liquid water is transformed into a gaseous state. Recondition for evaporation to occur is when atmospheric humidity is less than the evaporating surface (at 100% relative humidity there is no more evaporation). The evaporation process requires large amounts of energy, viz*.* 600 calories of heat energy for 1 g of water. Transpiration is the process of water loss from plants through stomata—a small opening found on the underside of leaves that are connected to vascular plant tissues. In most plants, T is a passive process largely controlled by the humidity of the atmosphere and the moisture content of the soil. Around 1% of total transpired water being used in the growth process as it transports nutrients from the soil into the roots and carries them to the various cells of the plant and is used to keep tissues from becoming overheated. Certain plants of dried environment do have the ability to open and close their stomata which is to limit the loss of water from plant tissues; otherwise, they will not survive.

Generally, differentiate between evaporation and T is difficult. Hence a composite term "ET" is used whose rate at any instant from the Earth's surface is controlled by four factors: (1) Vapor pressure gradient. (2) Energy availability as about 600 calories of heat energy to change 1 g of liquid water into a water vapor. (3) The wind speed directly above the surface which moves the vapor from the place of evaporation and in clam days when above ground layer got saturated, ET almost stops. (4) Water availability which is a must parameter as at the global scale, most of the ET of water on the Earth's surface occurs in the subtropical oceans where high quantities of solar radiation convert liquid water into a gas. Further, it is reported that average ET for the northern hemisphere is around 944 mm year<sup>−</sup><sup>1</sup> . Together with the southern hemisphere, with an average ET of 1064 mm year<sup>−</sup><sup>1</sup> , this results in a global ET of 1004 mm year<sup>−</sup><sup>1</sup> . In the Western Pacific and the Indian Ocean values up to 2 m year<sup>−</sup><sup>1</sup> have been observed. Thus it varied a lot depending on the special variations.

Evapotranspiration (ET) is an important soil water balance component and is playing a major role in determining the potential yields in the agricultural sector. Being affected by a number of factors, viz*.* soil temperature, soil moisture and vapor pressure gradients, ET remains almost remains similar for a particular soil textural class and agro-climatic conditions. Regarding estimation of ET, in field conditions, evaporation is generally judged by installing the lysimeters in the field which actually represent the true conditions of the field. Mini-lysimeters were quite effective in understanding the fluctuating behavior of evaporation under different treatments [26, 27]. Mini-lysimeters prepared by using PVC pipes of 8-inch length and with 2.5 inches diameter. Mini-lysimeters were filled from a particular treatment with the help of chain pulley arrangement, an end cap fixed on one side and then finally filled and capped mini-lysimeter was placed inside the outer pipe of the bigger diameter which was already fixed in the sampled plot (**Figure 4**). Daily mini-lysimeters were weighted at field using the digital balance to have an idea of evaporation [29]. After calculating the evaporation T is calculated from the soil water equation where the right-hand side has irrigation and rainfall while left-hand side constituted by seepage, drainage, profile soil moisture and ET.

With this technology, E reduction trends could be very easily monitored because of practiced different resource conservation technologies and thereby for a region the most effective one could also be identified which further be advocated the farmers for improving their livelihoods [30]. Some earlier studies

**103**

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

had shown the promising results of some of the technologies, viz*.* straw mulching caused 70–300 mm of irrigation savings in different crops and benefits of mulching depend upon seasonal rainfall, irrigation regimes and soil texture [31]. These irrigation savings are due to a reduction in soil water evaporation component of ET. However, among the various technologies, zero tillage is emerging as the viable option for planting wheat while retaining surface residues. Earlier there were problems with the direct drilling of wheat seed into combine harvested paddy fields as loose straw accumulates in seed drill furrow openers, seed metering and its placement were non-uniform which is now solved with the Lucky drill directly drilled wheat seeds into anchored and loose rice residues. Major advantages of this technology include about 5–10% increase in yield, 60–70% less weed growth, 30% water saving particularly pre-sowing irrigation and 45 mm reduction in evaporation losses. In spite of these advantages, it solved the problem of straw burning and the leftover paddy straw on the long run improved the soil health and its fertility levels. In the agricultural sector, irrigation efficiency generally is tried to improve by depressing the evaporation share and enhancing the T which further directly linked

*Demonstrating filling of lysimeters (a); pulling out filled lysimeters with specially designed chain-pulley* 

*arrangement (b); and weighting of filled and capped lysimeter (c) [28].*

From the above discussion of the chapter, it may be concluded that climate change will adversely affect the sustainable crop production in future that ultimately lead to decrease the food production of increasing population. Different international organizations already projected that water availability in arid and semi-arid regions across the world will decrease, due to lack of rainfall and increase the temperature which leads to increase in the dry areas. Since climate change will impact on soil water balance that leads to change in evaporation and plant transpiration. While, with the increasing temperature, lack of precipitation and soils water unavailability, crop production will likely to decrease through shortening the crop growth cycle. Therefore, it is important to understand evaporation, transpiration as well as evapotranspiration to mitigate their adverse effect under future changing climate. Researchers already revealed that soils with high water holding capacity and crop cultivars which are tolerant to adverse effect as well as the application of improved management strategies will be better to face the impact of drought. Where, if we could increase the irrigated areas, the total crop production could be

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

with the land as well as water productivity.

increased to the food security of increasing population.

**6. Conclusion**

**Figure 4.**

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

**Figure 4.**

*Advanced Evapotranspiration Methods and Applications*

**production in the era of climate change**

otherwise, they will not survive.

global ET of 1004 mm year<sup>−</sup><sup>1</sup>

up to 2 m year<sup>−</sup><sup>1</sup>

variations.

**5. Consequences of evapotranspiration for sustainable crop** 

Water moved from the Earth's surface into the atmosphere by evaporation and T the two distinct mechanisms. Evaporation occurs directly from the water bodies where liquid water is transformed into a gaseous state. Recondition for evaporation to occur is when atmospheric humidity is less than the evaporating surface (at 100% relative humidity there is no more evaporation). The evaporation process requires large amounts of energy, viz*.* 600 calories of heat energy for 1 g of water. Transpiration is the process of water loss from plants through stomata—a small opening found on the underside of leaves that are connected to vascular plant tissues. In most plants, T is a passive process largely controlled by the humidity of the atmosphere and the moisture content of the soil. Around 1% of total transpired water being used in the growth process as it transports nutrients from the soil into the roots and carries them to the various cells of the plant and is used to keep tissues from becoming overheated. Certain plants of dried environment do have the ability to open and close their stomata which is to limit the loss of water from plant tissues;

Generally, differentiate between evaporation and T is difficult. Hence a composite term "ET" is used whose rate at any instant from the Earth's surface is controlled by four factors: (1) Vapor pressure gradient. (2) Energy availability as about 600 calories of heat energy to change 1 g of liquid water into a water vapor. (3) The wind speed directly above the surface which moves the vapor from the place of evaporation and in clam days when above ground layer got saturated, ET almost stops. (4) Water availability which is a must parameter as at the global scale, most of the ET of water on the Earth's surface occurs in the subtropical oceans where high quantities of solar radiation convert liquid water into a gas. Further, it is reported that

. In the Western Pacific and the Indian Ocean values

have been observed. Thus it varied a lot depending on the special

Evapotranspiration (ET) is an important soil water balance component and is playing a major role in determining the potential yields in the agricultural sector. Being affected by a number of factors, viz*.* soil temperature, soil moisture and vapor pressure gradients, ET remains almost remains similar for a particular soil textural class and agro-climatic conditions. Regarding estimation of ET, in field conditions, evaporation is generally judged by installing the lysimeters in the field which actually represent the true conditions of the field. Mini-lysimeters were quite effective in understanding the fluctuating behavior of evaporation under different treatments [26, 27]. Mini-lysimeters prepared by using PVC pipes of 8-inch length and with 2.5 inches diameter. Mini-lysimeters were filled from a particular treatment with the help of chain pulley arrangement, an end cap fixed on one side and then finally filled and capped mini-lysimeter was placed inside the outer pipe of the bigger diameter which was already fixed in the sampled plot (**Figure 4**). Daily mini-lysimeters were weighted at field using the digital balance to have an idea of evaporation [29]. After calculating the evaporation T is calculated from the soil water equation where the right-hand side has irrigation and rainfall while left-hand

. Together with

, this results in a

average ET for the northern hemisphere is around 944 mm year<sup>−</sup><sup>1</sup>

the southern hemisphere, with an average ET of 1064 mm year<sup>−</sup><sup>1</sup>

side constituted by seepage, drainage, profile soil moisture and ET.

With this technology, E reduction trends could be very easily monitored because of practiced different resource conservation technologies and thereby for a region the most effective one could also be identified which further be advocated the farmers for improving their livelihoods [30]. Some earlier studies

**102**

*Demonstrating filling of lysimeters (a); pulling out filled lysimeters with specially designed chain-pulley arrangement (b); and weighting of filled and capped lysimeter (c) [28].*

had shown the promising results of some of the technologies, viz*.* straw mulching caused 70–300 mm of irrigation savings in different crops and benefits of mulching depend upon seasonal rainfall, irrigation regimes and soil texture [31]. These irrigation savings are due to a reduction in soil water evaporation component of ET. However, among the various technologies, zero tillage is emerging as the viable option for planting wheat while retaining surface residues. Earlier there were problems with the direct drilling of wheat seed into combine harvested paddy fields as loose straw accumulates in seed drill furrow openers, seed metering and its placement were non-uniform which is now solved with the Lucky drill directly drilled wheat seeds into anchored and loose rice residues. Major advantages of this technology include about 5–10% increase in yield, 60–70% less weed growth, 30% water saving particularly pre-sowing irrigation and 45 mm reduction in evaporation losses. In spite of these advantages, it solved the problem of straw burning and the leftover paddy straw on the long run improved the soil health and its fertility levels. In the agricultural sector, irrigation efficiency generally is tried to improve by depressing the evaporation share and enhancing the T which further directly linked with the land as well as water productivity.
