Production of artificial humic acid from rice straw for fertilizer production and soil improvement

In this study, artificial humic acid (AHA) was produced from rice straw at room temperature. The response surface methodology was used to investigate the response of artificial humic acid to time, liquid-solid ratio, and KOH concentration. The optimal reaction conditions were determined: reaction time of 2 h, liquid-solid ratio of 6, and KOH concentration of 1.5 mol/L. The artificial humic acid content under these conditions was 32.29 g/L, which satisfied the Chinese agricultural industry standard for water-soluble humic acid fertilizers (humic acid content >= 30 g/L). Compared with chemical fertilizers, artificial humic acid fertilizer promoted chard growth and increased soil organic matter and humic acid. The stability of artificial humic acid was better, with a retention rate of 60.47 % in the soil. Water-soluble humic acid fertilizer also promoted chard growth by increasing the relative abundance of growth-promoting bacteria such as Glutamicibacter and Pseudomonas and, as well as growth-promoting fungi such as Mortierella. The application of water-soluble humic acid fertilizers has implications for both soil improvement and the reduction of agricultural carbon emissions.