▎ 摘　　要

NOVELTY - Method for preparing bio-fertilizer involves (a) preparing graphene-chitosan suspension by soaking natural graphite powder in acetic acid, adding chitosan to obtain chitosan-acetic acid solution, performing liquid phase ultrasonic stripping reaction, and mixing natural graphite powder and chitosan, and (b) adding hydrogen peroxide, performing ultrasonic degradation to generate chitosan oligosaccharide containing graphene, diluting chitosan oligosaccharide suspension, and obtaining chitooligosaccharide suspension containing graphene. USE - The bio-fertilizer is useful for horseradish tree. ADVANTAGE - The bio-fertilizer exhibits synergistic effect, and enables to obtain selenium-enriched, and superoxide dismutase-enriched horseradish tree with stress-resistance. DETAILED DESCRIPTION - Method for preparing bio-fertilizer involves (a) preparing graphene-chitosan suspension by soaking more than 300 mesh size natural graphite powder in 3-8% acetic acid with pH less than or equal to 5, adding chitosan to obtain 1-2% chitosan-acetic acid solution, performing liquid phase ultrasonic stripping reaction at 10-60 degrees C for 2-24 hours, and uniformly mixing natural graphite powder and chitosan in a mass ratio of 1:1-10, and (b) adding 20 times 30% hydrogen peroxide to the prepared graphene-chitosan suspension, performing ultrasonic degradation at 10-60 degrees C for 6-8 hours to generate chitosan oligosaccharide containing 0.1-2 wt.% graphene, diluting chitosan oligosaccharide suspension containing graphene, and obtaining chitooligosaccharide suspension containing 0.05-0.5 wt.% graphene.