Liming effects on microbial carbon use efficiency and its potential consequences for soil organic carbon stocks

• Published in: Soil biology & biochemistry Vol. 191; p. 109342
• Main Authors: Schroeder, Julia, Dǎmǎtîrcǎ, Claudia, Bölscher, Tobias, Chenu, Claire, Elsgaard, Lars, Tebbe, Christoph C., Skadell, Laura, Poeplau, Christopher
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.04.2024; Elsevier
• Subjects: Agricultural sciences; Agricultural soil; Climate change mitigation; Environmental Sciences; Isotopic labelling; Life Sciences; Long-term field experiment (LTE); Microbial soil carbon; Organic C inputs; Soil study; Agricultural soil; Isotopic labelling; Microbial soil carbon; Climate change mitigation; Organic C inputs; Long-term field experiment (LTE)
• ISSN: 0038-0717; 1879-3428
• DOI: 10.1016/j.soilbio.2024.109342

Climate-smart agriculture aims amongst others at protecting and increasing soil organic carbon (SOC) stocks. The allocation of metabolised carbon (C) between soil microbial growth and respiration, i.e. C use efficiency (CUE) is crucial for SOC dynamics. We hypothesised that raising soil pH would alleviate CUE-limiting conditions and that liming could thus increase CUE, thereby supporting SOC accrual. This study investigated whether CUE can be manipulated by liming and how this might contribute to SOC stock changes. The effects of liming on CUE, microbial biomass C, abundance of microbial domains, SOC stocks and OC inputs were assessed for soils from three European long-term field experiments. Field control soils were additionally limed in the laboratory to assess immediate effects. The shift in soil pHH2O from 4.5 to 7.3 with long-term liming reduced CUE by 40 %, whereas the shift from 5.5 to 8.6 and from 6.5 to 7.8 was associated with increases in CUE by 16 % and 24 %, respectively. The overall relationship between CUE and soil pH followed a U-shaped (i.e. quadratic) curve, implying that in agricultural soils CUE may be lowest at pHH2O = 6.4. The immediate CUE response to liming followed the same trends. Changes in CUE with long-term liming contributed to the net effect of liming on SOC stocks. Our study confirms the value of liming as a management practice for climate-smart agriculture, but demonstrates that it remains difficult to predict the impact on SOC stocks due its complex effects on the C cycle. [Display omitted] •Liming altered CUE depending on the initial soil pH and the span of the pH shift.•At low pH, CUE declined with liming likely due to microbial community shifts.•At high pH, CUE increased with liming likely due to altered nutrient availability.•Liming increased microbial biomass C in all cases.•Changes in CUE with liming were not the primary cause for changes in SOC stocks.