Towards a Mechanistic Understanding of Peroxidase Controls on Soil Carbon and Nitrogen Mineralization.

Our previous study has showed that soil C and N mineralization in diverse farming systems were significantly correlated with soil peroxidase activity, but such an association could not be ascertained from a limited number of field samples due to variations in soil properties. The objectives of this study were to assess fundamental relationships between soil peoxidase activity and soil C and N mineralization as well as the underlying mechanisms in controlled experiments. First, soils were amended with different dosages of commercial peroxidase. Soil C mineralization was found to be tightly associated with the dosage of peroxidase used (r = 0.80, P < 0.01). Second, autoclaved soils were amended with commercial cellulase, protease, peroxidase or their combination to reveal regulation pathways of peroxidase on C and N mineralization. We found that dissolved reducing sugars or amino acids as a fraction of dissolved organic C or N were increased in cellulase or protease treatments with the addition of peroxidase. After days of enzyme additions, sterile soils were inoculated with a small amount of unautoclaved soil for additional 7-day incubation.  Soil C mineralization in the treatment of both cellulase and peroxidase addition was about 15% than the treatment of cellulase alone and 40% than the treatment of peroxidase alone and control soil. Similarly, soil N mineralization in the treatment of protease and peroxidase addition was about 60% greater than protease alone and 70% greater than the treatment of peroxidase alone and control soil. Our results indicated that peroxidase controls soil C and N mineralization via its enhancement on soil C and N substrates for hydrolytic enzymes.