Carbon budget and seasonal carbon dioxide emission from a central Ohio Luvisol as influenced by wheat residue amendment

Enhancement of soil organic carbon (SOC) stocks through mulching has been proposed, and although this practice can alter several soil properties, its impact on the temporal variability of carbon dioxide (CO2) emission from soils has not been widely investigated. To that end, we monitored CO2 fluxes from a central Ohio Luvisol (fine, mixed, mesic Aeric Ochraqualf) amended with wheat (Triticum aestivum L.) straw applied at rates of 0 (MO), 8 (M8) and 16 (M16) Mg dry matter ha-1 per year and supplemented with fertilizer (244 kg N ha-1 per year) or without. The experimental design was a randomized complete block design with three replications. The intensity of CO2 emission was higher in the late winter (mean: 2.79 g CO2-C m-2 per day) and summer seasons (2.45 g CO2-C m-2 per day) and lowest in the autumn (1.34 g CO2-C m-2 per day). While no significant effect of N fertilization on CO2 emission was detected, soil mulching had a significant effect on the seasonal variation of CO2 fluxes. The percentage of annual CO2 emitted during the winter and spring was similar across treatments (17-22%); however, 43% of the annual CO2 loss in the MO plots occurred during the summer as opposed to 26% in the mulch treatments. A close relationship (F = 0.47X + 4.45, R2 = 0.97, P < 0.001) was found between annual CO2 flux (F, Mg CO2-C ha-1) and residue-C input (X, Mg C ha-1). Litter and undecomposed residue amounted to 0.32 and 0.67 Mg C ha-1 per year in the M8 and M16 plots, respectively. After 4 years of straw application, SOC stocks (0-10 cm) were 19.6, 25.6 and 26.5 Mg C ha-1 in the MO, M8 and M16 treatments, respectively. The results show that soil mulching has beneficial effect on SOC sequestration and strongly influence the temporal pattern of CO2 emission from soils. © 2002 Elsevier Science B.V. All rights reserved.