TY - JOUR
T1 - Critical comparison of the impact of biochar and wood ash on soil organic matter cycling and grassland productivity
AU - Reed, Eleanor Y.
AU - Chadwick, David R.
AU - Hill, Paul W.
AU - Jones, Davey L.
PY - 2017/7/1
Y1 - 2017/7/1
N2 - Wood represents the single most important source of renewable energy worldwide and depending on the mechanism of energy production can lead to the production of by-products with vastly different properties (i.e. wood ash (WA) from incineration and biochar (BC) from pyrolysis). These are typically applied to land, however, a critical comparison of their impact on soil quality and carbon (C) cycling is lacking. To address this, we generated biochar (450 °C) and wood ash (870 °C) from the same mixed hardwood feedstock and added it to an agricultural grassland at comparable rates under both laboratory and field conditions (10 t ha−1 and 571 kg ha−1 for BC and WA, respectively). We hypothesized that alkaline, nutrient-rich wood ash would stimulate microbial activity, resulting in the loss of soil organic matter (SOM), while biochar which is recalcitrant to microbial attack would promote the stabilization of native SOM. The effects on the soil microbial community and soil C and N cycling were determined over 1 year. Overall, biochar promoted soil quality by enhancing nutrient availability (P and K), moisture retention and increasing soil C content. However, it was also associated with an increase in below-ground CO2 loss. As plant productivity was unaffected and laboratory incubations of biochar with 14C-labelled SOM showed no indication of priming, we deduce that this CO2 originates from the biochar itself. This is supported by the lack of effect of biochar on soil N cycling, microbial biomass and community structure. Wood ash had almost no effect on either soil quality or vegetation quality (yield and foliar nutrient content) under field conditions but did induce negative SOM priming under both laboratory and field conditions. We conclude that when applied at field-relevant rates, neither amendment had a detrimental effect on native SOM cycling. While wood ash promotes the retention of native SOM, biochar may be a better strategy for enhancing SOM levels because of its intrinsic recalcitrant character, however, this needs to be offset against the reduced amount of energy derived from pyrolysis in comparison to incineration.
AB - Wood represents the single most important source of renewable energy worldwide and depending on the mechanism of energy production can lead to the production of by-products with vastly different properties (i.e. wood ash (WA) from incineration and biochar (BC) from pyrolysis). These are typically applied to land, however, a critical comparison of their impact on soil quality and carbon (C) cycling is lacking. To address this, we generated biochar (450 °C) and wood ash (870 °C) from the same mixed hardwood feedstock and added it to an agricultural grassland at comparable rates under both laboratory and field conditions (10 t ha−1 and 571 kg ha−1 for BC and WA, respectively). We hypothesized that alkaline, nutrient-rich wood ash would stimulate microbial activity, resulting in the loss of soil organic matter (SOM), while biochar which is recalcitrant to microbial attack would promote the stabilization of native SOM. The effects on the soil microbial community and soil C and N cycling were determined over 1 year. Overall, biochar promoted soil quality by enhancing nutrient availability (P and K), moisture retention and increasing soil C content. However, it was also associated with an increase in below-ground CO2 loss. As plant productivity was unaffected and laboratory incubations of biochar with 14C-labelled SOM showed no indication of priming, we deduce that this CO2 originates from the biochar itself. This is supported by the lack of effect of biochar on soil N cycling, microbial biomass and community structure. Wood ash had almost no effect on either soil quality or vegetation quality (yield and foliar nutrient content) under field conditions but did induce negative SOM priming under both laboratory and field conditions. We conclude that when applied at field-relevant rates, neither amendment had a detrimental effect on native SOM cycling. While wood ash promotes the retention of native SOM, biochar may be a better strategy for enhancing SOM levels because of its intrinsic recalcitrant character, however, this needs to be offset against the reduced amount of energy derived from pyrolysis in comparison to incineration.
KW - Black carbon
KW - Charcoal
KW - Life cycle assessment
KW - Nutrient cycling
KW - PLFA
UR - http://www.scopus.com/inward/record.url?scp=85016274535&partnerID=8YFLogxK
U2 - 10.1016/j.soilbio.2017.03.012
DO - 10.1016/j.soilbio.2017.03.012
M3 - Article
AN - SCOPUS:85016274535
SN - 0038-0717
VL - 110
SP - 134
EP - 142
JO - Soil Biology and Biochemistry
JF - Soil Biology and Biochemistry
ER -