Rice paddies are a major source of agricultural greenhouse gas emissions, primarily caused by the proliferation of anaerobic, methanogenic bacteria during prolonged inundation. Phototrophic bacteria utilize light energy for metabolism and are potential candidates for carbon and nitrogen fixation, and reduction of methane gas emissions. We investigated the effect of applying the phototrophic bacterium Rhodopseudomonas palustris (PNSB) during the cropping period on soil organic carbon (SOC) and methane emissions for second-crop rice in the Tainan Guantian region. In the experimental group, PNSB was applied five times during the rice cultivation period. Compared to the control group, the experimental group demonstrated a significant reduction in methane emissions, especially in the tillering stage, where emissions averaged 37.26 ± 12.97 g-CH₄/m²/season compared to 49.48 ± 25.06 g-CH₄/m²/season of the control group. Over the entire growing season, the experimental group reduced the emission of 3.05 Mg·CO₂e/ha. Additionally, administering PNSB improved soil carbon sequestration, from 4.89 tons-C/ha in the control group to 17.45 tons-C/ha. The phototrophic bacterium PNSB was beneficial for soil carbon sequestration and reducing greenhouse gas emissions. However, further research is required to optimize the methodology of applying phototrophic bacteria for agricultural purposes.

With the acceleration of climate change in recent years, enhancing the carbon sequestration capacity of agricultural soil has become an important strategy for achieving sustainable agriculture and carbon neutrality. This study aimed to investigate the effects of multiple experimental factors on the soil carbon fixation efficiency of corn cultivation using the Taguchi method of experimental design. The following factors were investigated: amount of fertilizer, amount of irrigation, as well as soil supplementation with Rhodopseudomonas sp. strain AKW01 and Rhodoplanes sp. strain AKW02. We designed an L9(3⁴) orthogonal array with three levels for each factor, and conducting nine sets of experimental plantings for each element in the array. Various outcomes were measured during different growth stages, including soil pH, soil electrical conductivity, soil organic carbon (SOC); as well as the height, chlorophyll content as determined using a Soil Plant Analysis Development (SPAD) meter, fresh weight, and dry weight of plant matter. The results of this study showed that the addition of the AKW01 strain significantly improved crop growth and carbon sequestration and was the primary factor affecting crop performance among the experimental factors studied, with a total variance contribution of 41.55%. Another significant factor was irrigation water amount, with a total variance contribution of 35.78%. Crop performance was optimal when the addition of the AKW01 strain was at 10 mL/plant, which led to a mean height of 138.1 cm, SPAD of 29.8, SOC increase of 0.01%, and fresh and dry weights of 95.38 g and 48.03 g, respectively.