Biochar effect on the mineralization of soil organic matter

Abstract

The objective of this work was to verify whether the addition of biochar to the soil affects the degradation of litter and of soil organic matter (SOM). In order to investigate the effect of biochar on the mineralization of barley straw, soil was incubated with 14C-labelled barley straw with or without unlabelled biochar. To investigate the effect of straw on the mineralization of biochar, soil was incubated with 14C-labelled biochar with or without straw. In addition, to investigate the effect of biochar on old SOM, a soil labelled by applying labelled straw 40 years ago was incubated with different levels of biochar. All experiments had a control treatment, without any soil amendment. The effect of biochar on the straw mineralization was small and nonsignificant. Without biochar, 48±0.2% of the straw carbon was mineralized within the 451 days of the experiment. In comparison, 45±1.6% of C was mineralized after biochar addition of 1.5 g kg-1. In the SOM-labelled soil, the organic matter mineralized more slowly with the increasing doses of biochar. Biochar addition at 7.7 g kg-1 reduced SOM mineralization from 6.6 to 6.3%, during the experimental period. The addition of 15.5 g kg-1 of biochar reduced the mineralized SOM to 5.7%. There is no evidence of increased degradation of either litter or SOM due to biochar addition; consequently, there is no evidence of decreased stability of SOM.

Mineralização e efeitos de biocarvão de cama de frangosobre a capacidade de troca catiônica do solo

“…Na pesquisa de Wardle et al (2008), conduzida por dez anos, em condição de campo na Suécia, ou seja, sob variação da distribuição de chuvas, efeitos indiretos do biocarvão sobre a manutenção da umidade na interface solo-liteira, bem como sobre a retenção de nutrientes, podem explicar o favorecimento à degradação do material vegetal, em presença do pirolisado (Bruun & El-Zehery, 2012). Em laboratório, cujas condições de temperatura e umidade para degradação dos compostos orgânicos são controladas, o efeito "priming" pode ocorrer como consequência de compostos orgânicos solúveis no biocarvão (Luo et al, 2011).…”

“…Em laboratório, cujas condições de temperatura e umidade para degradação dos compostos orgânicos são controladas, o efeito "priming" pode ocorrer como consequência de compostos orgânicos solúveis no biocarvão (Luo et al, 2011). Esses compostos são responsáveis pelo estímulo à atividade microbiana, em curto período, na incubação do biocarvão com solo, o que define inclusive a taxa de mineralização de C do biocarvão (Smith et al, 2010;Cross & Sohi, 2011;Bruun & El-Zehery, 2012). A ocorrência ou não de efeito "priming" é associada a características quantitativas e qualitativas da matéria orgânica do próprio solo, à dose de biocarvão utilizada e à fração solúvel de C no biocarvão (Luo et al, 2011).…”

Towards a global assessment of pyrogenic carbon from vegetation fires

“…Thevenon et al, 2010;. Critically, however, the MRTs of PyC products are generally one or two orders of magnitude longer than those of their unburnt precursors (Baldock & Smernik, 2002;Knoblauch et al, 2011;Brunn & EL-Zehery, 2012;Santos et al, 2012;Maestrini et al, 2014a;Naisse et al, 2015a). Furthermore, PyC, together with fossil C, is the only form of non-mineral-associated organic matter that shows long-term persistence in mineral soils (Marschner et al, 2008).…”

“…Studies testing the hypothesis that PyC can prime the decomposition of soil organic matter have had mixed results, with effects being negative (e.g. Cross & Sohi, 2011;Jones et al, 2011;Zimmerman et al, 2011;Whitman et al, 2014;Naisse et al, 2015a), positive (Wardle et al, 2008;Zimmerman et al, 2011;Singh et al, 2014;Naisse et al, 2015a) or absent (Hilscher et al, 2009;Kuzyakov et al, 2009;Cross & Sohi, 2011;Brunn & EL-Zehery, 2012;Santos et al, 2012). The direction of the priming effects depends on several factors such as soil type, original soil organic matter quantity and quality, climate/ incubation conditions, and PyC amount and characteristics (Stewart et al, 2013;Michelotti & Miesel, 2015).…”

The stability of low- and high-ash biochars in acidic soils of contrasting mineralogy

“…There could be various plausible explanations for the positive priming observed in the biochar amended soils. When considering the properties of the biochars used in this case, the most likely reason for this positive priming is due to the creation of favourable soil environment for microbial colonisation (Zimmerman, 2010;Zimmerman et al, 2011;Bruun and El-Zehery, 2012). The alkaline nature of the biochars used here, increased the soil pH that encouraged microbial activity.…”