Table 1.
The physical and chemical properties of experimental soil and biochar.
Fig 1.
FTIR spectra of maize straw biochar at 450°C.
Fig 2.
Scanning electron microscope (SEM) images of maize biochar produced at 450°C (a, b). (a) denotes the cross section of biochar, (b) denotes longitudinal section of biochar.
Fig 3.
Energy spectrum analysis for biochar surface produced at 450°C.
Fig 4.
Dynamic variation of soil pH (a) and electrical conductivity (b) in different treatments over a 56-day incubation. Vertical bars in the figures represent standard error of the means (n = 3).
Fig 5.
Dynamic variation of the contents of soil organic carbon (a), soil total nitrogen (b), dissolved organic carbon (c), and (d) C/N ratio in different treatments over a 56-day incubation. Vertical bars in the figures represent standard error of the means (n = 3).
Fig 6.
Response of soil respiration to additions of biochar and urea during a 56-day incubation: soil CO2 emission rate (a), cumulative CO2 emissions (b).Vertical bars in the figures represent standard error of the means (n = 3).
Table 2.
Parameter of first-order kinetic model (Cmin = C0 [1-e-Kt]) fitted to the cumulative values of CO2-C mineralized from different amounts of BC application.
Fig 7.
Response of C-cycle enzyme activities to additions of biochar and urea during a 56-day incubation.
(a) β-glucosidase activity, (b) β-cellobiosidase activity, (c) β-xylosidase activity, (d) α-glucosidase activity and (e) phenol oxidase activity. Vertical bars represent the standard error of the means (n = 3) and lower case letters indicate significant differences between treatments at the P< 0.05 level.
Fig 8.
Redundancy analyses (RDA) of the correlations between soil parameters and enzyme activity.
The red arrows indicate the soil parameters that had a significant impact on enzyme activities (P < 0.05), and the corresponding explained proportion of variability is shown in the lower right corner. Abbreviations: TN, total nitrogen; TOC, total organic carbon; DOC, dissolved organic carbon; TDN, total dissolved nitrogen and EC, electrical conductivity.