Biochar addition rate influences soil microbial abundance and activity in temperate soils

Abstract

Biochar (BC) amendment to soils is a proposed strategy to improve soil fertility and mitigate climate change. However, before this can become a recommended management practice, a better understanding of the impacts of BC on the soil biota is needed. We determined the effect of addition rates (0, 1, 5, 10 and 20% by mass) of a fast-pyrolysis wood-derived BC on the extraction efficiency (EE), abundance and temporal dynamics of phospholipid fatty acids (PLFAs, microbial community biomarkers) in four temperate soils during a 1-year incubation. Additionally, the effects on microbial mineralization/incorporation of BC-C were determined by measuring CO 2 efflux and the BC contribution to CO 2 and PLFA-C using the natural 13 C abundance difference between BC and soils. Biochar addition proportionally increased microbial abundance in all soils and altered the community composition, particularly at the greatest addition rate, towards a more gram-negative bacteriadominated (relative to fungi and gram-positive) community. Though chemically recalcitrant, the BC served as a substrate for microbial activity, more so at large addition rates and in soil with little organic matter. Microbial utilization of BC-C for growth could only partially explain the observed increase in microbial biomass, suggesting that other, potentially abiotic, mechanisms were involved. The strong decrease in PLFA EE (−77%) in all soils with biochar addition emphasizes the need to measure and correct for EE when using PLFA biomarkers to estimate soil microbial responses to BC additions. Overall, our study provides support for BC use as a soil amendment that potentially stimulates microbial activity and growth.

Fire affects root decomposition, soil food web structure, and carbon flow in tallgrass prairie

“…Soil subsamples for PLFA analysis were sieved to 2mm, with any visibly remaining plant material carefully removed with forceps. The PLFA extraction, quantification, and δ 13 C analysis methods were based on previous studies (Bossio and Scow, 1995;Denef et al, 2007;Gomez et al, 2014). For all treatments, approximately 6 g soil subsamples from the bulk soil were lyophilized and extracted in duplicate using a modified Bligh-Dyer method (Gomez et al, 2014) at each harvest.…”

“…The PLFA extraction, quantification, and δ 13 C analysis methods were based on previous studies (Bossio and Scow, 1995;Denef et al, 2007;Gomez et al, 2014). For all treatments, approximately 6 g soil subsamples from the bulk soil were lyophilized and extracted in duplicate using a modified Bligh-Dyer method (Gomez et al, 2014) at each harvest. Fatty acid methyl ester (FAME) derivatives were analyzed by capillary gas chromatography-combustion-isotope ratio mass spectrometry (GC-C-IRMS) (GC-C/TC DELTAplus XP, Thermo Scientific) via a GC/C III interface.…”

“…Changes in the microbial community composition were evaluated based on relative PLFA abundance data, which were calculated as in Gomez et al (2014).…”

Dynamics of microbial community composition and soil organic carbon mineralization in soil following addition of pyrogenic and fresh organic matter

“…Recent research has only begun to identify PyOM effects on soil microbial communities, and it is clear that PyOM additions to soil can induce changes in soil microbial community composition. Most current evidence has been gathered using fingerprinting approaches, such as terminal restriction fragment length polymorphism (Bingeman et al, 1953;Jin, 2010;Kolton et al, 2011) or denaturing gradient gel electrophoresis (Kolton et al, 2011;Chen et al, 2013), or by surveying phospholipid fatty acids to assess microbial diversity at low phylogenetic resolution (Dunavin, 1969;Jindo et al, 2012;Gomez et al, 2014;Watzinger et al, 2014;Mitchell et al, 2015). In addition, clone libraries targeting functional genes (Song et al, 2014) and some highthroughput DNA sequencing approaches have been applied to survey microorganisms in PyOM systems.…”

Opportunities and constraints for biochar technology in Australian agriculture: looking beyond carbon sequestration

“…Limitations of existing laboratory soil and plant methods for biochar or biochar-amended soil analyses have been highlighted in several research studies (Novak et al 2009;Singh et al 2010b;Enders and Lehmann 2012;Farrell et al 2013;Kameyama et al 2014;Gomez et al 2014). Researchers need to address this issue collectively by customising and streamlining the analytical procedures for the analysis of biochars.…”