Soil respiration from winter wheat-based cropping systems in the US Southern Great Plains as influenced by tillage managements

Authors: KANDEL, TANKA - Oklahoma State University; Gowda, Prasanna; Northup, Brian; ROCATELI, ALEXANDRE - Oklahoma State University

Submitted to: Acta Agriculturae Scandinavica
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/11/2019
Publication Date: 2/22/2019
Citation: Kandel, T.P., Gowda, P.H., Northup, B.K., Rocateli, A.C. 2019. Soil respiration from winter wheat-based cropping systems in the US Southern Great Plains as influenced by tillage managements. Acta Agriculturae Scandinavica. https://doi.org/10.1080/09064710.2019.1582691.
DOI: https://doi.org/10.1080/09064710.2019.1582691

Interpretive Summary: Tillage and grazing are important managements to affect soil respiration (SR) from agroecosystems. Although reduced tillage systems are widely adopted for winter wheat based cropping systems in the US Southern Great Plains, influence of tillage and grazing management practices on SR fluxes are scarcely reported. In this study, we compared SR fluxes from reduced and conventional tillage systems of winter wheat based cropping systems in the SGP. The study area consisted of four paired paddocks that were either assigned to conventional or reduced tillage systems. During the study year, three paired paddocks were cultivated with winter wheat managed as forage-only, dual-purpose, grain-only crop and a pair were cultivated with winter canola. Heterotrophic SR fluxes were measured using a plant and root exclusion method on eight permanently deployed PVC cores in each paddock. Fluxes were measured manually on the plant-free cores using a closed chamber connected with an infra-red gas analyzer on 12-13 dates during a full growing season of the crops. As expected, there was strong seasonal pattern of SR fluxes with lower rates during dry and cold periods and higher rates during warm and wet periods. Large rainfall induced pulses of SR fluxes were also observed from both tillage systems. However, there was no consistent and remarkable difference in SR fluxes between paired paddocks assigned to CT and RT treatments. Overall, the results from this study indicate that SR fluxes from winter wheat grazing systems are mostly controlled by environmental factors than the tillage manipulations.

Technical Abstract: Tillage and grazing are important management tools that affect cycling and turnover of carbon in agroecosystems. Reduced tillage systems are becoming more widely adopted in cropping systems applied to winter wheat in the US Southern Great Plains. However, reports of the influence of tillage and grazing management on soil respiration (SR) are scarce. This study compared SR fluxes from reduced and conventional systems of tillage applied to winter wheat-based cropping systems used in the SGP. The study consisted of four sets of paired paddocks that were either assigned to conventional or reduced tillage. During the 2016–17 study year, three sets of paired paddocks were cultivated with winter wheat managed as: forage for grazing, dual-purpose (grazing and grain production), and grain-only. An additional pair of paddocks were planted to winter canola. Heterotrophic SR fluxes were measured using a plant and root exclusion method on eight permanently deployed PVC cores per paddock. Fluxes from the cores were measured manually using a closed chamber connected to an infrared gas analyzer on 12–13 dates during the winter wheat growing season (October through May). We used the data to evaluate a process-based model (DNDC; DeNitrification-DeComposition) for its capacity to predict SR fluxes. There were strong seasonal patterns of SR fluxes, with lower rates during dry and cold periods, and higher rates during warm and wet periods. Large rainfall induced pulses of SR fluxes were observed from both tillage systems. There was no consistent difference in SR fluxes between paired paddocks assigned to tillage treatments. The DNDC model could not accurately simulate SR fluxes and therefore was not effective in estimating cumulative SR. Overall, results from this study indicate SR fluxes from management systems applied to winter wheat are controlled more by environmental factors such as soil temperature and moisture than tillage systems.