Effects of different fermentation synergistic chemical treatments on the performance of wheat straw as a nursery substrate

Abstract

Wheat straw is rich in organic matter and nutrients and has the potential to replace peat as the primary raw material in organic nurseries. Using straw as a peat substitute can also aid in reducing the CO2 emissions that result from peat mining. Furthermore, this can avoid resource wastage and eliminate the practice of burning wheat straw, thereby causing pollution. The conventional composting treatment has a long cycle and inability to control substrate properties in a targeted manner. Thus, this study analyzed the physicochemical properties, material science properties, and biological toxicity of straw substrate at the end of fermentation to achieve rapid and targeted regulations of the substrate's overall performance. Wheat straw treated with two types of fermentation (aerobic/anaerobic) and five chemical conditioners (1% CH3COOH, 1% H2SO4, 1% NaOH, 1% K2CO3, and H2O) under different temperature conditions was used. Adjusting the pH of straw substrate to acidic levels (4.47–6.51) reduced the organic matter consumption by 0.27–5.82% under anaerobic digestion than under aerobic composting. Meanwhile, aerobic composting retained more nitrogen (0.12–8.23 mg/g) than anaerobic digestion. The co-fermentation of wheat straw pretreated with 1% H2SO4 resulted in 14.18–46.12% hemicellulose degradation. Co-aerobic straw composting with H2SO4 and K2CO3 at 35 °C reduced the crystallinity of the straw substrate by 6.66 and 7.33%, respectively, as compared to other conditioning agents. CH3COOH lowered the electrical conductivity values of the straw substrate at the end of fermentation (2.33–3.49 mS/cm). Overall, the findings revealed that CH3COOH-cooperative aerobic composting pretreatment at 35 °C is a suitable replacement for the traditional composting process as a method of utilizing straw substrate.