Net ecosystem exchange of CO2 and H2O fluxes from irrigated grain sorghum and maize in the Texas High Plains

Pradeep Wagle; Prasanna H Gowda; Jerry E Moorhead; Gary W Marek; David K Brauer

doi:10.1016/j.scitotenv.2018.05.018

Net ecosystem exchange of CO₂ and H₂O fluxes from irrigated grain sorghum and maize in the Texas High Plains

Sci Total Environ. 2018 Oct 1:637-638:163-173. doi: 10.1016/j.scitotenv.2018.05.018. Epub 2018 May 8.

Authors

Pradeep Wagle¹, Prasanna H Gowda², Jerry E Moorhead³, Gary W Marek³, David K Brauer³

Affiliations

¹ USDA, Agricultural Research Service, Grazinglands Research Laboratory, El Reno, OK 73036, USA. Electronic address: pradeep.wagle@ars.usda.gov.
² USDA, Agricultural Research Service, Grazinglands Research Laboratory, El Reno, OK 73036, USA.
³ USDA, Agricultural Research Service, Conservation and Production Research Laboratory, Bushland, TX 79012, USA.

PMID: 29751299
DOI: 10.1016/j.scitotenv.2018.05.018

Abstract

Net ecosystem exchange (NEE) of carbon dioxide (CO₂) and water vapor (H₂O) fluxes from irrigated grain sorghum (Sorghum bicolor L. Moench) and maize (Zea mays L.) fields in the Texas High Plains were quantified using the eddy covariance (EC) technique during 2014-2016 growing seasons and examined in terms of relevant controlling climatic variables. Eddy covariance measured evapotranspiration (ET_EC) was also compared against lysimeter measured ET (ET_Lys). Daily peak (7-day averages) NEE reached approximately -12 g C m^-2 for sorghum and -14.78 g C m^-2 for maize. Daily peak (7-day averages) ET_EC reached approximately 6.5 mm for sorghum and 7.3 mm for maize. Higher leaf area index (5.7 vs 4-4.5 m² m^-2) and grain yield (14 vs 8-9 t ha^-1) of maize compared to sorghum caused larger magnitudes of NEE and ET_EC in maize. Comparisons of ET_EC and ET_Lys showed a strong agreement (R² = 0.93-0.96), while the EC system underestimated ET by 15-24% as compared to lysimeter without any corrections or energy balance adjustments. Both NEE and ET_EC were not inhibited by climatic variables during peak photosynthetic period even though diurnal peak values (~2-weeks average) of photosynthetic photon flux density (PPFD), air temperature (T_a), and vapor pressure deficit (VPD) had reached over 2000 μmol m^-2 s^-1, 30 °C, and 2.5 kPa, respectively, indicating well adaptation of both C₄ crops in the Texas High Plains under irrigation. However, more sensitivity of NEE and H₂O fluxes beyond threshold T_a and VPD for maize than for sorghum indicated higher adaptability of sorghum for the region. These findings provide baseline information on CO₂ fluxes and ET for a minimally studied grain sorghum and offer a robust geographic comparison for maize outside the United States Corn Belt. However, longer-term measurements are required for assessing carbon and water dynamics of these globally important agro-ecosystems.

Keywords: Bioenergy; Eddy covariance; Evapotranspiration; Gross primary production; Lysimeter; Net ecosystem exchange.

Published by Elsevier B.V.