Long‐term evapotranspiration rates for rainfed corn versus perennial bioenergy crops in a mesic landscape

Abstract

Perennial cellulosic crops are promoted for their potential contributions to a sustainable energy future. However, a large-scale perennial bioenergy production requires extensive land use changes through diversion of croplands or conversion of uncultivated lands, with potential implications for local and regional hydrology. To assess the impact of such land use conversions on ecosystem water use, we converted three 22 year-old Conservation Reserve Program (CRP) grasslands and three 50+ year-old conventionally tilled corn-soybean crop fields (AGR) to either notill continuous maize (corn) or perennial (switchgrass or restored prairie) bioenergy crops. We also maintained one CRP grassland without conversion. We measured evapotranspiration (ET) rates on all fields for 9 years using eddy covariance methods.Results show that: (a) mean growing-season ET rates for perennial crops were similar to the ET rate of the corn they replaced at the previously cultivated (AGR) field but ET rates for perennial crops at CRP fields were 5-9% higher than ET rate for corn on former CRP fields; and (b) mean nongrowing season ET rates for perennial fields were 11-15% lower than those for corn fields, regardless of land use history. On an annual basis, mean ET rates for perennial crops tended to be lower (4-7%) than ET rate of the corn that they replaced at AGR fields but ET rates for perennial crops and corn at CRP fields were similar. Over 9 years, mean ET rates for the same crop across land use histories were remarkably similar for corn, whereas for the perennial crops they were 4-10% higher at former CRP than at former AGR fields, mainly due to differences in growing season ET. Over the 9 years and across all fields, ET returned~60% of the precipitation back to the atmosphere. These findings suggest that large-scale substitution of perennial bioenergy crops for rainfed corn in mesic landscapes would have little if any (0 to −3%) impact on terrestrial water balances. K E Y W O R D S eddy covariance, maize, perennial cellulosic bioenergy, restored prairie, seasonal evapotranspiration (ET), smooth brome grass, switchgrass Hydrological Processes. 2020;34:810-822. wileyonlinelibrary.com/journal/hyp 810 SUPPORTING INFORMATIONAdditional supporting information may be found online in the Supporting Information section at the end of this article.How to cite this article: Abraha M, Chen J, Hamilton SK, Robertson GP. Long-term evapotranspiration rates for rainfed corn versus perennial bioenergy crops in a mesic landscape.

Challenging a Global Land Surface Model in a Local Socio-Environmental System

“…Each tower was equipped with an infrared gas analyzer (LI-7500, LI-COR Biosciences, Lincoln, NE, USA) and a 3D sonic anemometer (CSAT3, Campbell Scientific Inc., Logan, UT, USA), with sensor heights 1.5–2.0 m above canopy heights [ 67 ]. Fluxes were processed following Ameriflux guidelines, with 30-min average fluxes (i.e., net ecosystem production, NEP) computed with EdiRe [ 68 ] and then gap filled and partitioned into gross primary production (GPP) and ecosystem respiration using REddyProc [ 69 ].…”

Root water uptake of biofuel crops revealed by coupled electrical resistivity and soil water content measurements

“…(2015) and Abraha et al. (2020) found that this was not necessarily the case at a southern Michigan site, where ET from the perennial grasses was comparable to maize in both wet and dry years based on measurements of soil water uptake and eddy covariance, respectively. They proposed that this discrepancy could be attributed to development of water‐limited conditions during most years in the well‐drained sandy loam soils of the Michigan site.…”

Hydraulic redistribution by deeply rooted grasses and its ecohydrologic implications in the southern Great Plains of North America

“…Field studies that have compared ET in annual crops to that of perennial biofuel crops are fairly limited, and the results have been mixed. For well-drained soils, some studies have found that both crop types have similar growing-season ET rates (Abraha et al, 2015;Abraha et al, 2020;Hamilton et al, 2015;Parish et al, 2019), while perennials have higher growing-season ET rates than annual crops in soils with high water tables (Hickman et al, 2010;Zeri et al, 2013).…”

“…Field studies that have compared ET in annual crops to that of perennial biofuel crops are fairly limited, and the results have been mixed. For well‐drained soils, some studies have found that both crop types have similar growing‐season ET rates (Abraha et al, 2015; Abraha et al, 2020; Hamilton et al, 2015; Parish et al, 2019), while perennials have higher growing‐season ET rates than annual crops in soils with high water tables (Hickman et al, 2010; Zeri et al, 2013). Similarly, mixed results come from modelling studies, as some show no difference in growing‐season ET rates (Song et al, 2016), while others show higher growing‐season ET rates for perennials than for annuals (Le et al, 2011; Schilling et al, 2008; VanLoocke et al, 2012; Zhuang et al, 2013).…”