Optimizing measurement of soil potential high-affinity H2 uptake activity across pH

Abstract

Soil high-affinity H₂ uptake activity can be affected by many factors, including the soil pH. However, the method to determine how pH affects high-affinity H₂ uptake activity should be updated. The effect of pH on the biological high-affinity H₂ uptake in agricultural soils was compared using three pH buffer systems in the pH 4–8 range. Soil pH was adjusted to the target pH using a buffer system (1 g soil/5 mL pH buffer). Soil slurries were treated with heat (autoclaving) or a chemical (25% v/w of toluene addition, microbial inhibitor) to inhibit biological activity. Sterile pH buffer was used as a negative control. The sterile soil slurry (heat sterilization) was the optimal reference control for measuring biological high-affinity H₂ uptake activity. Biological H₂ uptake activity was resistant to toluene, particularly at extreme pH levels. Overall, soil pH (p = 0.95) and pH buffer systems (p = 0.46) did not affect the high-affinity H₂ uptake activity in the tested agricultural soils. We provide an updated method to accurately measure the potential high-affinity H₂ uptake activity in soil, with an emphasis on the importance of controlling the soil pH.