It is the ability of crop plants to utilize water, it is the reverse of transpiration ratio. It is the ratio of water used effectively to irrigate the crops and the water entering the irrigation scheme. The term describes the effective water loss that occurs during the conveyance in the system. Through the distribution canals, as well as in the farms. In C3 plants for the uptake of one molecule of CO2, 500 molecule of water are transpired. So, WUE will be 0.002.
Similarly, in C4 and CAM plants for the uptake of one molecule of water are transpired, respectively. Therefore, value of WUE will be 0.004 and 0.02 respectively.
Improving water use efficiency is a critical response to growing water scarcity, including the need to leave enough water in river and lakes to sustain ecosystems and to meet the growing demands of cities and industries.
Types of WUE
– Photosynthetic water-use efficiency: Also called intrinsic or instantaneous water-use efficiency, which is defined as ratio of the rate of carbon di-oxide assimilation(photosynthesis) to the rate of transpiration.
– Water-use efficiency of productivity: Also called integrated water-use efficiency, which is typically defined as the ratio of biomass produced to the rate of transpiration.
– Water Use Efficiency can be improved through:
• Soil factors.
• Climatic factors.
• Methods of irrigation.
• Time of irrigation.
• Water harvesting methods.
• Type of crop.
– Water Use efficiency relies on:
• The soil’s ability to capture and store water.
• The crop’s ability to access water stored in the soil and rainfall during the season.
• The crop’s ability to convert water into biomass.
• The crop’s ability to convert biomass into grain.
– Organic Farming and Water Use Efficiency: Indeed, agriculture is identified as the largest user of groundwater reserves and responsible for significant pollution of water resources and environments. Some, progress has been achieved in the domain of pesticides leaching, but poor management practices continue to have a negative impact on water quality.
Organic farming system have much to offer in terms of water holding capacity, as they contribute to the preservation and restoration of water quality. Organic agriculture has significantly reduced its nitrate leaching rates. But organic farming system have the potential to continue to reduce leaching through sophisticated crop rotations, the use of green manures and maintenance of catch and cover crops. Organic farming also demonstrates effective water conservation capabilities. Organic farming impacts positively on soil structure and enhances the water holding capacity and hence availability of water.