Soil Carbon Flux Characteristics in Tobacco Fields of Guizhou under Different Mulching Methods

To investigate the effect of different mulching cultivation methods on soil carbon flux, continuous monitoring of soil carbon flux was conducted in tobacco fields in Kaiyang County, Guizhou Province, using the static chamber-gas chromatography method under three cultivation modes: no mulching (CK), mulching during half of the growth period (T1), and mulching throughout the full growth period (T2). The characteristics of soil carbon flux (including CO2 and CH4) were analyzed in combination with various environmental conditions. Results showed that the peaks of CO2 and CH4 fluxes under different mulching methods occurred on the 35th and 56th days after transplanting, and the fluxes followed an "M-shaped" double-peak curve during the tobacco growth period, with similar trends. Compared with CK, T1 and T2 increased the cumulative CO2 emissions by 16.49% and 48.75%, respectively, while T1 resulted in a 27.69% reduction in cumulative CO2 emissions compared to T2. The cumulative CH4 emissions under CK and T1 showed a net absorption effect, while T2 displayed a net CH4 emission effect. The diurnal CO2 flux maxima and minima occurred at 12:00-14:00 and 4:00-6:00, respectively, which corresponded closely to the variations in sampling temperature. The CH4 flux under CK, T1, and T2 peaked during the high-temperature period of the day (12:00-14:00). In summary, mulching cultivation methods significantly affect soil carbon flux in tobacco fields. Among these methods, mulching during half of the growth period (T1) achieves better carbon sequestration and emission reduction, making it a recommended cultivation practice for tobacco production in this region.