『Abstract
　Biochar can play a key role in nutrient cycling, potentially affecting nitrogen retention when applied to soils. In this project, laboratory experiments were conducted to investigate he adsorption properties of bamboo charcoal (BC) and the influence of BC on nitrogen retention at different soil depths using multi-layered soil columns. Results showed that BC could adsorb ammonium ion predominantly by cation exchange. Ammonium nitrogen (NH4⁺-N) concentrations in the leachate of the soil columns showed significant differences at different depths after ammonium chloride application to the columns depending on whether BC had been added. Addition of 0.5％ BC to the surface soil layer retarded the downward transport of NH4⁺-N in the 70-day experiment, as indicated by measurements made during the first 7 days at 10 cm, and later, in the experimental period at 20 cm. In addition, application of BC reduced overall cumulative losses of NH4⁺-N via leaching at 20 cm by 15.2％. Data appeared to suggest that BC could be used as a potential nutrient-retaining additive in order to increase the utilization efficiency of chemical fertilizers. Nonetheless, the effect of BC addition on controlling soil nitrogen losses through leaching needs to be further assessed before large-scale applications to agricultural fields are implemented.

Keywords: Bamboo charcoal; Nitrogen leaching; nitrogen retention; Ammonium nitrogen; Adsorption』

1. Introduction
2. materials and methods
　2.1. Soil and bamboo charcoal
　2.2. Ammonium ion adsorption by BC
　2.3. Multi-layer column device
　2.4. Leaching experiment
　2.5. Sample analysis
　2.6. Statistic analysis
3. Results and discussion
　3.1. Adsorption of ammonium ion on BC
　3.2. Effect of BC on NH4⁺-N concentration in leachate
　3.3. Effect of BC on cumulative losses of NH4⁺-N through leaching
　3.4. Effect of BC on EC in the leachate
4. Conclusions
Acknowledgement
References