Elevated soil organic carbon lability by continuous singly amending alkaline materials in an acidic purple paddy
The impact of continuous amending of alkaline materials on soil organic carbon(C)lability remains unknown.The typical acidic purple paddy of double-cropped rice in eastern Hunan province was selected.A paired field experiment was applied to study the labile organic C fractions and extracellular enzyme activities in topsoil at 0-15 cm depth in response to 5 years continuous singly amending alkaline commercial organic fertilizer,quicklime,and Si-Ca-Mg soil conditioner.Comparing to the CK,the content of coarse particulate organic C(cPOC),fine particulate organic C(fPOC),and light fraction organic C(LFOC)in soil increased by 57%-136%,27%-77%and 51%-60%(P＜0.05),respectively,after continuous amending alkaline materials.The ratios of soil labile organic C fractions to total organic C were increased.The content of Ca-SOC raised by 22%and 34%,respectively,after continuous amending lime and soil conditioner.The enzyme activities of β-glucosidase(βG)and N-acetyl-β-D-glucosaminidase(NAG)in soil were significantly reduced by 20%after continuous amending organic fertilizer.The soil labile organic C fractions contents were significantly correlated with soil organic C and available nutrient contents.Continuous input of alkaline materials in paddy enhanced the soil organic C level and lability,which was beneficial to soil C sequestration.The POC and LFOC fractions in soil were sensitive to the alkaline materials input,which could effectively indicate the early change in paddy soil organic C.
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