Surface application of fertilizers and residue biochar on N<sub>2</sub>O emission from Japanese pear orchard soil

Abstract

This study investigated soil N<sub>2</sub>O emissions following the application of fertilizers and pruning residue biochar on the soil surface of the Japanese pear orchard. Completely randomized design was laid out with four treatments: (1) control (unfertilized); (2) pig manure 300 kg N/ha and ammonium sulfate 200 kg N/ha with no biochar (F + BC0); (3) the same amount of manure and nitrogen (N) fertilizer with 2 t/ha biochar (F + BC2), and (4) with 10 t/ha biochar (F + BC10). The results showed that high N<sub>2</sub>O fluxes were observed after fertilization. Soil temperature and moisture were major controlling factors for N<sub>2</sub>O emission from the orchard soil. The lowest cumulative N<sub>2</sub>O emission (0.46 kg N/ha) was observed in the unfertilized control. Application of manure and N fertilizer significantly increased cumulative N<sub>2</sub>O emission compared to unfertilized control. Surface application of biochar (1.68 and 1.77 kg N/ha in F + BC2 and F + BC10, respectively) had no effect on soil N<sub>2</sub>O emission compared to F + BC0 (1.68 kg N/ha). Our results indicated that biochar pyrolyzed from orchard pruning residues can be returned to orchard soil as surface application without affecting soil N<sub>2</sub>O emissions.