Soil Water Dynamics and Evapotranspiration under Annual and Perennial Bioenergy Crops

Abstract

Understanding soil water dynamics and evapotranspiration (ET) is imperative to predict the interactions between bioenergy cropping systems and water resources; yet measurements of these variables under bioenergy crops in the U.S. Southern Great Plains (SGP) are limited. The objectives of this study were to quantify and compare soil water dynamics and ET under switchgrass (Panicum virgatum L.), biomass sorghum [Sorghum bicolor (L.) Moench], and mixed perennial grasses managed for biofuel production. Soil water content was measured from 2011 through 2013 at Stillwater, OK, and from 2012 through 2013 at Chickasha, OK, and ET was estimated using the soil water balance approach. For these crops, soil water depletion occurred mainly above the 2.0‐m depth, suggesting negligible root water uptake below 2.0 m. Growing season soil water depletion ranged from 4 to 287 mm and was greater (α = 0.10) for sorghum than switchgrass in 2 out of 5 site‐yr, while mixed grasses exhibited the greatest soil water depletion in 1 out of 3 yr. Growing season soil water depletion was positively related to initial soil water content. Crop year ET ranged from 493 to 846 mm and was greater for switchgrass than sorghum in 2 out of 3 site‐yr. At Stillwater, average crop year ET measured for 2 yr was 676 mm for switchgrass, 630 mm for sorghum, and 717 mm for mixed grasses. In the SGP, rainfed bioenergy production systems based on biomass sorghum may consume less water per unit land area than systems based on perennial grasses.

Cellulosic biofuel crops alter evapotranspiration and drainage fluxes: Direct quantification using automated equilibrium tension lysimeters

“…The cellulosic biofuel crops (switchgrass, miscanthus, and hybrid poplar) exploited initial and early growing season soil water under dry conditions allowing for a greater growing season ET. This was similar to the responses seen under prairie land cover (Burba & Verma, ), hybrid poplar (Petzold et al, ), and switchgrass (Yimam et al, ). Each cellulosic crop was well established prior to the 2012 drought with the resulting root structures allowing transpiration to begin ~60 days earlier than maize.…”

“…However, studies conducted across a wide range of climate and soil conditions including the US Great Plains (Burba & Verma, 2005), Germany (Petzold, Schwärzel, & Feger, 2011), and China (Sun et al, 2011;Zhou et al, 2014) show that water use within the growing season is determined in large part by water availability and antecedent conditions, especially during periods of water stress. Furthermore, a close relationship between longer growing seasons and greater water use has been observed-which is significant because perennial grasses emerge and begin transpiring much earlier than maize (Garcia & Strock, 2016;Hickman, Vanloocke, Dohleman, & Bernacchi, 2010;Ryu, Baldocchi, Ma, & Hehn, 2008;Wagle, Kakani, & Huhnke, 2016;Yimam, Ochsner, Kakani, & Warren, 2014).…”

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

“…Without irrigation, soil water deficit in the root zone is a major limiting factor for plant growth and development in arid and semiarid environments (Yimam, Ochsner, Kakani, & Warren, 2014). Interseeding alfalfa into semiarid grassland may intensify soil water depletion (SWD) and exacerbate competition with grasses for water.…”

Hydrological responses of land use change from cotton (Gossypium hirsutum L.) to cellulosic bioenergy crops in the Southern High Plains of Texas,USA

“…The potential for the use of cellulosic crops such as Alamo switchgrass (Panicum virgatum L.), Miscanthus 9 giganteus (Miscanthus sinensis Anderss. [Poaceae]), big bluestem (Andropogon gerardii) and biomass sorghum as bioenergy crops was studied by several researchers in different parts of the world through field experimentation and modeling (Wright, 2007;Heaton et al, 2008;Jain et al, 2010;Qin et al, 2011Qin et al, , 2014Zhuang et al, 2013;Yimam et al, 2014Yimam et al, , 2015Zatta et al, 2014;Oikawa et al, 2015;Zhang et al, 2015a). Alamo switchgrass is a perennial C4 warm-season bunch grass native to North America, and it is found in low, moist areas and prairies of north-central Texas (Diggs et al, 1999).…”