Abstract
Biochar as a soil ameliorant has generated great interest for scientists in improving soil quality and carbon sequestration. The objective of this study was to investigate the persistent effects of biochar application on soil organic carbon (SOC) mineralization and soil-resistant carbon (Cr) in upland red soil. This experiment was conducted from September 2011 to May 2016. Biochar was applied only once in September 2011 at rates of 0, 2.5, 5, 10, 20, 30 and 40 t/ha in the field experiment, designated as treatments B0, B1, B2, B3, B4, B5 and B6. The chemical properties, dynamics of SOC mineralization and soil-resistant carbon (Cr) were measured at the 1st and 6th year after biochar application. The results were as follows: biochar application at rates of 30 and 40 t/ha (B5 and B6 treatments) distinctly increased soil pH value and available P relative to B0 in 2011. The pH value, available P, SOC, total N and C/N ratio in B4, B5 and B6 treatments were significantly higher compared with the B0 treatment, where the B6 treatment increased the pH value by 0.80 and C/N ratio by 3.88 while increasing available P, SOC and total N by 24.18, 76.29 and 19.78%, respectively, compared with the B0 treatment in 2016. The cumulative SOC mineralization (Cm) occupied around 4.62–6.91% of total organic carbon (Ct), which showed a declining trend in 2016 as compared to 2011. The Cm/Ct ratio also showed a declining trend with biochar amendment at both samplings. The Cr occupied around 26–46% of SOC and showed obviously increasing trends both in 2011 and 2016. We further found that Cm/Ct showed highly significant (p < 0.01) negative correlations with the rates of biochar application both in 2011 and 2016. The Cr, however, showed very significant (p < 0.01) positive correlations with the rates of biochar application both in 2011 and 2016. This study suggested that biochar application to upland red soil persistently improved soil properties and resistant carbon. Cumulative SOC mineralization was clearly restrained by biochar amendment. This study can provide scientific support for improving soil fertility and enhancing carbon sequestration by application of large amount of biochar (40 t/ha) in upland red soil.
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