Short-Term Effect of the Combined Application of Rice Husk Biochar and Organic and Inorganic Fertilizers on Radish Growth and Nitrogen Use Efficiency

Research on soil biochar fertilization has mainly been conducted on cereal crops, and information on its potential for radish production remains inconsistent. Therefore, a pot experiment was conducted to examine the short-term effects of rice husk biochar on radish growth and nitrogen use efficiency (NUE). An investigation was conducted with two application rates of biochar alone, (10 t ha^-1 (B10) and 25 t ha^-1 (B25), and biochar + chicken manure application with and without NPK fertilizer. The results indicated that the application of biochar 25 t ha^-1 + chicken manure (B25:CHM) and the combination of biochar 25 t ha^-1 + chicken manure + NPK fertilizer (B25:CHM:NPK) significantly increased root yield by improving NUE, fertilizer recovery efficiency (RE_N), agronomic efficiency (AE), nitrogen harvest index (NHI), and retaining soil NH₄⁺-N. Although biochar application alone did not significantly influence radish growth on a short-term basis, B10 and B25 increased root yields by 10% and 20%, respectively, compared with the control. Notably, the role of biochar application when combined with organic and inorganic fertilizers was to retain fertilizer N and promote N uptake efficiency by radishes, as higher rates of biochar resulted in higher NUE. Our results suggest that B25:CHM is a suitable combination for organic farming.