Rapid estimation of microbial biomass in acid red soils with and without substrate incorporation
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A rapid and alternative measurement of microbial biomass in acid red soils with and without substrate incorporation is proposed for soil quality evaluation.
Materials and methods
Soil microbial biomass C (SMBC) and N (SMBN) in 24 typical red soil samples developed from two parent materials (granite and arenaceous shale) were measured using fumigation-extraction followed by dry combustion method in comparison with ultraviolet (UV) spectrophotometry (increase in absorbance at 280 nm, ΔUV280). The reliability of microbial biomass estimation by UV spectrophotometry was verified using six representative red soils amended with biochar (0, 1, 3 and 5%) and glucose (0, 100, 500 and 1000 mg kg−1) separately.
Results and discussion
ΔUV280 was strongly correlated with SMBC and SMBN measured by dry combustion, regardless of biochar/glucose incorporation. Validated conversion equations from unamended soil data were dependent on confounding effects of organic C and particle size and can be described as follows: SMBC = 27.08 × ΔUV280 (R2 = 0.67, n = 24) and SMBN = 3.62 × ΔUV280 (R2 = 0.69, n = 24). Regression models for rapid estimation of microbial biomass in red soils from different parent materials had to be calibrated separately in case of amendments. In most cases, SMBC (R2 of 0.75–0.76 and root mean square error (RMSE) of 22.2–29.3 mg kg−1) and SMBN (R2 of 0.74–0.80 and RMSE of 2.60–14.2 mg kg−1) can be predicted from ΔUV280 in biochar/glucose-amended soils using these equations. The slope of the regression of SMBC against ΔUV280 shifted in biochar-amended granite soils, mainly due to uncoordinated changes of SMBC in response to the difference in parent material-induced nutrient availability, while shifts of SMBC (or SMBN) against ΔUV280 in glucose-amended arenaceous shale soils were attributed to particle size distribution.
Soil microbial biomass (SMBC and SMBN) in red soils can be rapidly predicted by fumigation-extraction with UV spectrophotometry detection and corresponding correction of calibration curves, depending on soil nutrient availability, particle size distribution and organic C levels.
KeywordsAcid red soils Biochar amendment Microbial biomass estimation Ultraviolet spectrophotometry
This work was supported by the Natural Science Foundation of China (grant numbers 41471246; 41561074); the Guangdong Provincial Natural Science Foundation of China (grant numbers 2014A030313703; 2014A030313570); the Guangzhou City Science and Technology Plan Project (grant number 201510010187); and the Guangdong Provincial Science and Technology Plan Project (grant numbers 2015A020208009; 2014B020206001).
- Cong HJ, Cheng Y, An SS, Li DH (2010) Changes of soil nutrient and soil microbial biomass C, N and P in different plant rehabilitation on the loess hilly area of Ningxia. J Soil Water Conserv 24:217–221 (in Chinese with English abstract)Google Scholar
- Grace C, Hart M, Brookes PC (2006) Laboratory manual of the soil microbial biomass group. Rothamsted Res:5–6Google Scholar
- He R, Wang JS, Shi Z, Fang YH, Xu ZK, Quan W, Zhang ZX, Ruan HH (2009) Variations of soil microbial biomass across four different plant communities along an elevation gradient in Wuyi Mountains, China. Acta Ecol Sin 29:5138–5144 (in Chinese with English abstract)Google Scholar
- Liu A (1993) Red soils in Guangdong. Science Press, BeijingGoogle Scholar
- Liu M, Li Z, Zhang TL (2009) Changes of microbial biomass and functional diversity in red soil under different land use types. Soils 41:744–748 (in Chinese with English abstract)Google Scholar
- Lu RK (2000) Methods for soil and agricultural chemistry. Chinese Agricultural Press, BeijingGoogle Scholar
- Yao H, He ZL, Wilson MJ, Campbell CD (2000) Microbial biomass and community structure in a sequence of soils with increasing fertility and changing land use. Microb Ecol 40:223–237Google Scholar
- Yu WT, Ma Q, Xu YG, Zhou H, Jiang CM (2012) Rapid estimation of microbial biomass nitrogen in agricultural soils by ultraviolet spectrophotometry method. Chin J Soil Sci 43:1131–1135 (in Chinese with English abstract)Google Scholar