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Biochar is stable in soil and can have long-term effects on its physicochemical properties. Hence, a pot experiment was conducted with medium-fertility (MF) and low-fertility (LF) soils after 1 year of rice husk biochar and organic fertilizer application to determine biochar's residual effects on soil chemical properties, grain yield, and greenhouse gas emissions. In previous years, biochar alone (at application rates of 5 and 10 t ha−1) and biochar combined with chicken manure (CHM) or cow manure (at application rate of 5 t ha−1) were applied to the soil. In the present year, the soils were fertilized with only chemical fertilizers. Results indicated that application of 10 t ha−1 biochar combined with 5 t ha−1 CHM (B10:CHM) produced the highest grain yield and total global warming potential (GWPtotal) in both soils. Regarding grain yield, non-significant results were detected for B10:CHM, B5:CHM, and B10. This study revealed that biochar retains nutrients without annual reapplication and has long-term effects. Although biochar application can suppress N2O emissions effectively, the combined application of biochar 10 t ha−1 and organic manure significantly increased CH4 emissions. Overall, B5:CHM can be recommended for rice cultivation since it improves grain yield without increasing GWPtotal. [ABSTRACT FROM AUTHOR]

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 (REN), 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. [ABSTRACT FROM AUTHOR]

The application of biochar is considered an alternative amendment strategy for improving soil fertility. In this study, we performed pot experiments using soils of low and medium fertility to assess the effects of different combinations of biochar and organic manure on the chemical properties of paddy rice soils and determined the best combination to improve the grain yield without increasing N2O and CH4 emissions. The applied treatments were without biochar (control), the application of rice husk biochar alone (5 and 10 t ha−1), and biochar combined with chicken or cow manure. The results indicated that for both soils, the application of 5 t ha−1 biochar combined with 5 t ha−1 chicken manure increased grain yield by improving soil total nitrogen and soil NH4+-N without increasing cumulative N2O and CH4 emissions. Multiple regression analysis showed that when combined with biochar, chicken manure significantly contributed to a higher grain yield and was negatively associated with cumulative CH4, N2O emissions, and total GWP. Furthermore, regardless of soil type, combined applications of biochar and cow manure promoted significant increases in soil available P. Our findings indicate that the C/N ratio of organic manure influences CH4 fluxes, and soil type was identified as a factor driving greenhouse gas emissions. [ABSTRACT FROM AUTHOR]