Water-Use Efficiency: Advances and Challenges in a Changing Climate

Abstract

Water use efficiency (WUE) is defined as the amount of carbon assimilated as biomass or grain produced per unit of water used by the crop. One of the primary questions being asked is how plants will respond to a changing climate with changes in temperature, precipitation, and carbon dioxide (CO 2 ) that affect their WUE At the leaf level, increasing CO 2 increases WUE until the leaf is exposed to temperatures exceeded the optimum for growth (i.e., heat stress) and then WUE begins to decline. Leaves subjected to water deficits (i.e., drought stress) show varying responses in WUE. The response of WUE at the leaf level is directly related to the physiological processes controlling the gradients of CO 2 and H 2 O, e.g., leaf:air vapor pressure deficits, between the leaf and air surrounding the leaf. There a variety of methods available to screen genetic material for enhanced WUE under scenarios of climate change. When we extend from the leaf to the canopy, then the dynamics of crop water use and biomass accumulation have to consider soil water evaporation rate, transpiration from the leaves, and the growth pattern of the crop. Enhancing WUE at the canopy level can be achieved by adopting practices that reduce the soil water evaporation component and divert more water into transpiration which can be through crop residue management, mulching, row spacing, and irrigation. Climate change will affect plant growth, but we have opportunities to enhance WUE through crop selection and cultural practices to offset the impact of a changing climate.

Row spacing of alfalfa interseeded into native grass pasture influences soil‐plant‐water relations

“…Ritchie (1972) reported that canopy development and growth affect transpiration, which increases linearly with leaf area. However, row spacing of a crop would affect the partitioning of the ET by reducing the soil water evaporation and increasing canopy transpiration in a monoculture (Hatfield & Dold, 2019). Nevertheless, deeply rooted crops increase the contribution of transpiration to ET even in semiarid and arid environments (Kizito, Dragila, & Sene, 2006), which mainly drives total ET.…”

UAV Multispectral Imagery Combined with the FAO-56 Dual Approach for Maize Evapotranspiration Mapping in the North China Plain

“…The change in the air temperature surrounding the leaf will change the leaf temperature and directly affect the gradient of water vapor between the leaf and the atmosphere. Water deficit stress and heat stress may be induced by changes in available water, VPD, and increased ambient air temperature [65].…”

Role of fixing nitrogen in common bean growth under water deficit conditions

“…We were also interested to find a possible association between capability to fix nitrogen and efficiency to use water (WUE), which increases under drought (Hatfield & Dold, ). WUE is defined as the amount of carbon assimilated as biomass or grain produced per unit of water used by a crop.…”

“…However, we still have to find out whether better drought tolerance of BAT 477 solely depends on a more favorable root angle or whether this line has simply more roots and therefore accesses more water, which in turn would permit more N-fixation. We were also interested to find a possible association between capability to fix nitrogen and efficiency to use water (WUE), which increases under drought (Hatfield & Dold, 2019). WUE is defined as the amount of carbon assimilated as biomass or grain produced per unit of water used by a crop.…”