Soil dissolved organic carbon regulates the impact of biotic and abiotic factors on soil acidity and acid buffering capacity in the lateritic red soil

Abstract

Soil susceptibility to acids is commonly assessed by soil pH buffering capacity (pHBC), which is often estimated in an acid buffer curve and considered to be mainly regulated by abiotic factors. This study was conducted to evaluate the sensitivity of soil pH thresholds and range to exogenous acids and examine the effects of biotic and abiotic factors on the acid buffering capacity of the lateritic red soil in a 90-day-period incubation, with addition of biochar or earthworms in either of sterilized or unsterilized soils as three treatment factors. The results showed that soil pH thresholds and range were highly sensitive indicators of soil susceptibility to pH change, compared with pHBC,and that soil microorganisms significantly regulated soil acid buffering capacity (p<0.05). Earthworm activities lowered soil pH by regulating soil microbial communities, while biochar application significantly increased soil pH. However, neither earthworm nor biochar additions substantially change soil acid buffering capacity. Content and fractions of soil dissolved organic carbon were significantly related to soil acid buffering capacity indices. Our results evidence the feasibility of soil pH thresholds and range to indicate soil susceptibility to external acids and assess soil acidification trends and dissolved organic carbon is of high importance in regulating acid buffering capacity.

Graphical abstract

Keywords

soil acidification / soil remediation / soil microbial community / soil organic carbon / global change

Highlight

	● Soil pH thresholds and range were highly sensitive to indicate soil acid buffer capacity.
	● Soil microorganisms regulated effects of earthworm or biochar additions on soil acidity.
	● Soil DOC content and fractions greatly regulated soil acidity and acid buffering capacity.

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