Short-chain fatty acid producers in compost tea as affected by brewing time and aeration condition

PurposeThe objectives of the present paper were to (1) investigate the effect of compost tea on pakchoi; (2) illustrate the microbial community and metabolite variations under different aeration treatments and brewing time; and (3) figure out the response mechanism of compost tea to fermentation procedure.Materials and methodsThe effects of compost tea with varied compost/water ratio on pakchoi yield were investigated first. Then, compost tea under different aeration treatments (aerobic or anoxic treatment for 48 h and then switched aeration treatments for another 48 h) was conducted, and physicochemical properties and microbial community were analyzed. This study also investigated the effects of brewing time on microbial metabolisms when compost tea was fermented for 72 h in total with intermittent ventilation.Results and discussionIt was interesting that compost tea could improve pakchoi yield by 46.59% compared to control treatment. Short-chain fatty acid (SCFA) was found noteworthy during compost tea fermentation, and its producers were key microbes in response to aeration conditions. It also was found that acetic acid (a typical SCFA) was prone to accumulation under anoxic conditions especially at earlier period of fermentation. The total fermentation process is suggested to be divided into three stages according to microbial metabolic characters including initial stage, exuberant stage, and mature stage, respectively. It was also found that vitamin B6 metabolism, which indirectly related to SCFA metabolism, played an important role during all the 3 stages.ConclusionsSCFA was found noteworthy during compost tea fermentation, and its producers were the key microbes in response to aeration conditions. The total fermentation process is suggested to be divided into three stages according to microbial metabolic characters including initial stage, exuberant stage, and mature stage, respectively.