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Title: Variability in carbon dioxide fluxes among six winter wheat paddocks managed under different tillage and grazing practices

Author
item Wagle, Pradeep
item Gowda, Prasanna
item Northup, Brian
item Turner, Kenneth
item Neel, James
item Steiner, Jean
item MANJUNATHA, PRIYANKA - Oklahoma State University

Submitted to: Grazinglands Research Laboratory Miscellaneous Publication
Publication Type: Abstract Only
Publication Acceptance Date: 11/16/2017
Publication Date: 5/26/2018
Citation: Wagle, P., Gowda, P.H., Northup, B.K., Turner, K.E., Neel, J.P., Steiner, J.L., Manjunatha, P. 2018. Variability in carbon dioxide fluxes among six winter wheat paddocks managed under different tillage and grazing practices [abstract]. Association of Nepalese Agricultural Professionals of America (NAPA)Conference 2018. Available at: http://napaamericas.org/downloads/first-biennial-conference-proceedings-2018.pdf.

Interpretive Summary: Abstract only

Technical Abstract: Understanding the variation of CO2 fluxes in wheat (Triticum aestivum L.) fields under different tillage and grazing practices is crucial to evaluate the role of different management practices on CO2 dynamics. Six eddy covariance systems were used to measure CO2 fluxes in grain only, graze-grain, and graze-out winter wheat under conventional till and no-till conditions during the 2016-2017 growing season. Wheat fields were carbon sinks from October/November to April in general, with near carbon neutral during cold winter (December-January) and maximum rates in March/April during peak vegetative growth and early reproductive phase. However, large variations in CO2 fluxes [growing season net ecosystem CO2 exchange (NEE) ranged from -137 to -542 g C m-2, gross primary production (GPP) ranged from 705 to 1547 g C m-2, and ecosystem respiration (ER) ranged from 505 to 1030 g C m-2] were observed among wheat sites. Maximum daily rates (7-day averages) of NEE ranged from -3.39 to -8.68 g C m-2, GPP ranged from 6.71 to 16.35 g C m-2, and ER ranged from 4.89 to 9.26 g C m-2. Across-site analysis showed that Canopy% and NEE were linearly correlated (R2 = 0.76). The NEE-Canopy% relationship was slightly improved (R2 = 0.79) when leaf area index (LAI) was included in multiple regression. LAI was linearly correlated with GPP (R2 = 0.71). The relationship was slightly improved (R2 = 0.75) when dry biomass (DW) was included in multiple regression. Canopy% and LAI explained 72% of variations in ecosystem light use efficiency (ELUE). Preliminary results showed that spatial variability in vegetation characteristics were major drivers for spatial variability in CO2 fluxes. Moving forward, our clustered and paired EC towers can provide insights into the effects of tillage and different grazing management practices on CO2 dynamics in wheat.