Abstract
Higher transpiration efficiency (TE) has been proposed as a mechanism to increase crop yields in dry environments where water availability usually limits yield. The application of a coupled radiation and TE simulation model shows wheat yield advantage of a high-TE cultivar (cv. Drysdale) over its almost identical low-TE parent line (Hartog), from about -7 to 558kg/ha (mean 187kg/ha) over the rainfed cropping region in Australia (221-1,351mm annual rainfall), under the present-day climate. The smallest absolute yield response occurred in the more extreme drier and wetter areas of the wheat belt. However, under elevated CO2 conditions, the response of Drysdale was much greater overall, ranging from 51 to 886kg/ha (mean 284kg/ha) with the greatest response in the higher rainfall areas. Changes in simulated TE under elevated CO2 conditions are seen across Australia with notable increased areas of higher TE under a drier climate in Western Australia, Queensland and parts of New South Wales and Victoria. This improved efficiency is subtly deceptive, with highest yields not necessarily directly correlated with highest TE. Nevertheless, the advantage of Drysdale over Hartog is clear with the benefit of the trait advantage attributed to TE ranging from 102% to 118% (mean 109%). The potential annual cost-benefits of this increased genetic TE trait across the wheat growing areas of Australia (5year average of area planted to wheat) totaled AUD 631 MIL (5-year average wheat price of AUD/260t) with an average of 187kg/ha under the present climate. The benefit to an individual farmer will depend on location but elevated CO2 raises this nation-wide benefit to AUD 796 MIL in a 2°C warmer climate, slightly lower (AUD 715 MIL) if rainfall is also reduced by 20%.
Highlights
Higher transpiration efficiency (TE) has been proposed as a mechanism to increase crop yields in dry environments where reduced water supply limits biomass and yield (Craufurd, Austin, Acevedo, &Hall, 1991; Ehdaie, Hall, Farquhar, Nguyen, & Waines, 1991; Martin & Thorstenson, 1988; Passioura, 1977)
It is difficult to separate the genetic components of TE from the environmental components, but as Sinclair (2012) showed, it is possible to do this by defining TE as an inverse function of vapor pressure deficit (VPD) (TE = kd/VPD)
Crop TE itself can vary more than the assumed constant kd, when water stressed under high VPD or under increasing atmospheric CO2
Summary
Higher transpiration efficiency (TE) has been proposed as a mechanism to increase crop yields in dry environments where reduced water supply limits biomass and yield The complexity comes from disproportionate changes in transpiration and biomass, with changes in assimilate partitioning considered independent of those factors that primarily control TE (e.g., VPD) This partitioning is important when considering grain yield, because grain growth occurs later in the season when crops are typically water-limited and experiencing terminal drought and crops have the capacity to shift varying amounts of C assimilated earlier in the season into the grain. This early work showed significant advantage of related high-TE lines over low-TE lines in drier locations (e.g., Rebetzke et al, 2002) but the benefits over a wider range of environmental conditions remain largely unknown. This study region represents a large proportion of global wheat production areas and is typical of many rainfed cropping environments throughout the world experiencing significant changes in climate (e.g., CIMMYT Mega environment 1, 2, 4, and 8; CIMMYT 2014)
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
