Combined bamboo-derived biochar and DCD improves the catalytic potentials of ureases in forest and agricultural soils

Abstract

Soil urease kinetics reflects the affinity and catalytic reaction rate of urease. However, an incomplete understanding on soil urease kinetic hampered the optimisation of soil N management practices for agricultural and forestry ecosystems. In the present study, different soils from farmland and forest land were subjected to the following four treatments: (1) blank control (CK), (2) bamboo-derived biochar application (BC), (3) DCD application (DC), and (4) combined application of bamboo-derived biochar and DCD (CBAD). In the forest soil, the urease kinetic half-saturation constant (K_m) values decreased significantly by 28 %, 73 % and 45 % in the BC, DC and CBAD treatments, respectively. Similarly, in the agricultural soil, these values decreased by 46 %, 29 %, and 46 %, respectively. However, no significant difference in urease decomposition rates at saturated substrate concentrations (V_max) was observed among the four treatments. The contribution percentages of soil abiotic and biotic (the composition of bacterial and fungal community) properties to the variability in K_m were 58.6 % and 41.4 %, respectively. Biochar and DCD application improved the catalytic potential of urease in the agricultural and forest soils, which would not be conducive to the retention of nitrogen in soils. The increases in the catalytic potential of urease were associated with the increased content of mineral N and fungal community diversity under the application of biochar or DCD. Abiotic factors outweighed the microbial community composition in altering urease kinetics in various soils. These findings highlighted the necessity of nitrogen-fixing measures in soils amended with biochar or DCD and advanced our comprehension of how abiotic and biotic factors influence the urease kinetics in agricultural and forest soils.