Using strategic deficit irrigation to increase water productivity under limited water availability

Authors: Comas, Louise; Gleason, Sean; Zhang, Huihui; DeJonge, Kendall; Trout, Thomas

Submitted to: Annual American Geophysical Union Hydrology Days
Publication Type: Abstract Only
Publication Acceptance Date: 2/22/2019
Publication Date: 3/27/2019
Citation: Comas, L.H., Gleason, S.M., Zhang, H., DeJonge, K.C., Trout, T.J. 2019. Using strategic deficit irrigation to increase water productivity under limited water availability. Annual American Geophysical Union Hydrology Days. http://hydrologydays.colostate.edu/wp-content/uploads/2019/03/HD-2019_Program-FINAL.pdf.

Interpretive Summary: n/a

Technical Abstract: Water shortages are responsible for the greatest crop losses around the world and are expected to worsen. In arid areas where agriculture is dependent on irrigation, various forms of deficit irrigation management have been suggested to achieve high yields with less water used by the crop (i.e. evapotranspiration, ET). The observed relationship between crop yield and ET can be curvilinear or linear with the majority of ET being crop transpiration. In arid regions, crops may have limited capacity to reduce transpiration without significant yield losses. However, strategic application of deficit irrigation can improve the yield-ET response. In the high plains of Colorado in the US, application of greater deficit during the late vegetative stage with full or nearly full ET during the rest of the season consistently maintained yield similar to full ET treatments while saving approximately 17% of ET. Maize given 40% of full ET during the late vegetative stage had reduced plant height but little reduction in final leaf area index. Stress treatments showed conservative hydraulic control (e.g. midday stomatal closure) with efficiency of photosystem II (quantum yield) in maize fluctuating with water stress. The ability of photosystem II and stomatal conductance to recover when well-watered after stress suggests that reductions in biomass and yield resulted from stomatal closures, reduced photochemistry, or xylem dysfunctions that were temporary. With little indication of permanent decline in carbon assimilation after reducing ET by 45% of full ET in vegetative stages, maize appears able to achieve high grain yield if soil water is available during the reproductive and maturation stages. However, when plants were given full or nearly full irrigation during the entire vegetative period, deficits during the maturation period resulted in a greater proportion of yield losses than there were ET savings. Strategic deficit irrigation shows promise for increasing water productivity and buffering crops against yield losses in water limited environments if flexibility exists in irrigation scheduling. However, even the slightest reductions in yield are only economically viable at a relatively high cost of water at current grain prices.