Biochar as a soil amendment has been shown to improve
soil quality and crop growth. However, biochar’s effect on
urea-N use efficiency in long term is not well elucidated.
Here we studied urea-N (
15N isotope) allocation in
plants and soil in the presence of maize (
Zea mays
L.)
stover biochar (equivalent to 46 t ha
-1) during a 4-yr
pot trial. Results showed that biochar only increased
maize biomass (about 9%) with high amount of urea
addition, which indicates the increased maize dry weight
by biochar application could be attributed to synergistic
effects between biochar and urea. Soil total N contents
and fertilizer N retention were increased by 20% and
10.47% to 94.52%, respectively, indicating that biochar
was more capable for fertilizer N retention than promote
plant adsorption. Moreover, inorganic N content in
biochar treatment was greatly increased, which implies
the increased N mineralization. In total, we concluded that
biochar application was a potential urea enhancer during
plant production.