Abstract
Although association between mineral and biochar carbon have been speculated in some studies, still there is no direct evidence for the influence of individual clay minerals on the mineralization of biochar carbon in soils. To address this, we conducted an incubation study using monomineralic soils constituted by separately mixing pure minerals, i.e., smectite, kaolinite, and goethite, with a sandy soil. Switch grass biochar (400 °C) was added to the artificial soils and samples were incubated for 90 days at 20 °C in the laboratory. The CO2-C mineralized from the control, and biochar amended soil was captured in NaOH traps and the proportion of C mineralized from biochar was determined using δ13C isotopic analysis. The clay minerals significantly decreased the cumulative total carbon mineralized during the incubation period, whereas biochar had no effect on this. The least amount of total C was mineralized in the presence of goethite and biochar amended soil, where only 0.6% of the native soil organic carbon (SOC) (compared to 4.14% in control) and 2.9% of the biochar-C was mineralized during the 90 days incubation period. Native SOC mineralization was significantly reduced in the presence of biochar and the three minerals. Goethite was most effective in stabilizing both biochar and the native soil organic carbon. The short-term data from this study demonstrate that biochar application in Fe oxide rich soils may be an effective strategy to sequester biochar carbon, as well as to stabilize native soil carbon.
Highlights
In recent years many studies have been conducted on biochar application to the soil to evaluate its potential multiple benefits, for increasing soil carbon storage, and mitigating climate change, and improving soil quality, and promoting and sustaining crop production [1,2,3].Woolf et al [4] modelled that biochar has the potential to substantially reduce greenhouse gas emissions, in the order of 1.8 Pg CO2 -C per year
Only the soil mass basis data are presented here because the native organic carbon concentration was the same in all treatments and the total C mineralized data on soil mass basis better reflect the effects resulting from different mineral compositions, which is the main objective of this research
Biochar had no significant influence on the cumulative total C mineralized (CO2 -C produced per unit soil mass basis) after 90 days of incubation (Table 2, Figure 1)
Summary
In recent years many studies have been conducted on biochar application to the soil to evaluate its potential multiple benefits, for increasing soil carbon storage, and mitigating climate change, and improving soil quality, and promoting and sustaining crop production [1,2,3]. Woolf et al [4] modelled that biochar has the potential to substantially reduce greenhouse gas emissions, in the order of 1.8 Pg CO2 -C per year. This potential is, largely dependent on the stability of biochar-C in the soil. Several researchers have evaluated biochar mineralization in soils, in relation to the influence of biochar addition on the stability of native soil organic carbon (SOC), referred to as “priming”. Negative and neutral priming effects of biochar have been reported on the mineralization of native SOC [5,7,8,9,10,11]
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