Short-Term Effects of Bamboo Biochar and Oyster Shell Powder on Soil Organic Carbon Fraction, Microbial Respiration, and Enzymatic Stoichiometry in a Lei Bamboo Plantation

Abstract

Both biochar and oyster shell powder have been known as promising amendments to ameliorate soil acidity and enhance soil fertility. However, it is still unclear how their application alone and in combination affect the soil organic carbon (C) fraction and microbial activity in subtropical bamboo plantations. Therefore, to investigate the effects of biochar and oyster shell powder on soil microbial respiration, organic C fractions, microbial biomass, and enzyme activities related to C, N and P cycling, topsoil samples were collected from plots in a bamboo (Phyllostachys praecox) plantation that has been amended with oyster shell powder at 4 t ha−1 (T), bamboo biochar at 10 t ha−1 (B), and their combination (TB, with 4 t ha−1 T and 10 t ha−1 B) for 8 months. Our results showed that T alone significantly increased soil microbial respiration by 21.5%, whereas B alone and TB significantly decreased soil microbial respiration and metabolic quotient compared with T. T alone also increased soil pH, the size of labile C pool and the activities of β−glucosidase and cellobiosidase, whereas TB rather than B increased soil pH, the recalcitrant C pool size and declined these enzyme activities relative to T. T alone significantly enhanced microbial C limitation by 28.6% and decreased P limitation by 13.0%, while TB decreased microbial C limitation and increased microbial C use efficiency (CUE). Structural equation modeling indicated that T enhanced soil microbial respiration through increasing soil pH and enzyme activity, while biochar co-addition weakened the stimulation of T on microbial respiration by increasing soil recalcitrant C pool size and microbial metabolic quotient. Our study suggests that adding bamboo biochar together with oyster shell powder could be a better strategy to decrease soil C loss and ameliorate soil acidity in bamboo plantations compared with the application of oyster shell powder alone.