The role of biochar in reducing nitrous oxide emissions and nitrogen leaching from soil

摘要

This study examined the influence of four biochars on nitrous oxide (N_2O) emission and nitrogen (N) leaching from the two contrasting soils (an Alfisol and a Vertisol) using repacked soil columns over three wetting-drying (W-D) cycles and two leaching events spanning five months. A control (acid-washed sand) was also included for each soil. The four different biochars used were:(i) W400 - woodchip (Eucalyptus, saligna) biochar prepared at 400 °C, non-activated(ii) PM400 - poultry manure/rice hull biochar prepared at 400 °C, non-activated(iii) W550 - woodchip (Eucalyptus saligna) biochar prepared at 550 °C, activated(iv) PM550 - poultry manure/rice hull biochar prepared at 550 °C, activatedDuring the first two W-D cycles, W400 and W550 had inconsistent effects on soil N_2O emissions; however, the soils amended with poultry manure biochars, especially PM400, generally produced higher soil N_2O emissions, relative to the control. The greaterinitial N_2O emissions from the PM400-amended soils (cf. control) can be ascribed to its higher intrinsic N content, which may be relatively labile, compared with the other biochars. Notably, during the third W-D cycle, all biochars, including PM400, consistently decreased soil N_2O emissions (cumulatively by 14-73% from the Alfisol and by 23-52% from the Vertisol) than the control soil. In the first leaching event, after two months, none of the biochars influenced the leaching of NPL/-N and NO_3~--N,except for PM400, which caused higher leaching of N03"-N than the other treatments. In the second leaching event, after four months, the leaching of N03"-N was not affected by the biochar treatments; whereas, leaching of NTi4+-N was significantly reducedby 55-93% from the W550- and PM550-amended Alfisol and Vertisol, and by 87-94% from the W400- and PM400-amended Vertisol. We hypothesize that the increased effectiveness of biochars in reducing N_2O emissions and NH4+-N leaching over time is due to an increase in sorptive properties as biochar 'ages' in soil through oxidative reactions on the biochar surfaces.