Postulated N balance in the UREA soil with and without biochar addition.

<p>Total amounts of urea N in the soil were assumed to be lost through N_<b>2</b>O emission, NH_<b>3</b> volatilization and leaching and be remained in the soil as organic N and mineral N (NH_<b>4</b>^<b>+</b> + NO_<b>3</b>^<b>-</b>). The amount of NH_<b>3</b> volatilization, plant biomass N and soil organic N were assumed to be the same between NO CHAR and CHAR treatments and not shown in the graph. Different letters beside the bars indicate significant differences between the NO CHAR and CHAR treatments at a 5% probability level.</p

The N₂O emissions represented as a) the temporal changes from the soils with biochar and amendments and b) the average of the interactive effects between biochar and amendments.

<p>Four solid arrows show the urea and compost application events and two thick open arrows indicate the timing for biochar application. Error bars in b) represent the standard errors among the average data of the sampling dates.</p

The temporal change of a) soil temperature, gravimetric soil water content, and water filled pore space (WFPS), b) CO₂ evolution from the soil with biochar and amendments.

<p>c) Average soil CO_<b>2</b> emissions by different amendments. Four solid arrows show the urea and compost application events and two thick open arrows indicate the timing for biochar application. Error bars in c) represent the standard errors among the average data of the sampling dates.</p

Effect of biochar and fertilization on soil water holding capacity (WHC).Bars with different letters indicate significant differences among treatments at a 5% probability level.

<p>Effect of biochar and fertilization on soil water holding capacity (WHC).Bars with different letters indicate significant differences among treatments at a 5% probability level.</p

Physicochemical properties of the soil and biochar.

<p>^*HWC stands for hot water extractable C</p><p>Physicochemical properties of the soil and biochar.</p

Interactive effect between biochar and amendments on a) microbial activity and b) microbial biomass C in the soil.

<p>Bars with different letters indicate significant differences in the average values of sampling dates among treatments at a 5% probably level.</p

Pearson correlation coefficients among CO₂ emission rate, N₂O emission rate, soil temperature, gravimetric water content, and hot water extractable C.

<p>Numbers in parentheses are the probability to reject the null hypothesis.</p><p>*, **, ***, significant at the P = 0.1, P = 0.05, P = 0.001 probability levels, respectively.</p><p>Pearson correlation coefficients among CO₂ emission rate, N₂O emission rate, soil temperature, gravimetric water content, and hot water extractable C.</p

Temporal change in total C contents influenced by biochar and amendments.

<p>Bars with different letters indicate significant differences among treatments at a 5% probability level.</p

Effects of biochar and amendments on the average amounts of NH₄⁺ + NO₃^-.Bars with different letters indicate significant differences among treatments at a 5% probability level.

<p>Effects of biochar and amendments on the average amounts of NH₄⁺ + NO₃^-.Bars with different letters indicate significant differences among treatments at a 5% probability level.</p