Stability and stabilisation of biochar and green manure in soil with different organic carbon contents

Abstract

Abstract. Due to its recalcitrance against microbial degradation, biochar is very stable in soil compared to other organic matter additions, making its application to soils a suitable approach for the build-up of soil organic carbon (SOC). The net effects of such biochar addition also depend on its interactions with existing organic matter in soils. A study was established to investigate how the status of pre-existing soil organic matter influences biochar stabilisation in soil in comparison to labile organic additions. Carbon loss was greater in the C-rich sites (C content 58.0 g C/kg) than C-poor soils (C content 21.0-24.0 g C/kg), regardless of the quality of the applied organic resource. Biochar-applied, C-rich soil showed greater C losses, by >0.5 kg/m 2 .year, than biochar-applied C-poor soil, whereas the difference was only 0.1 kg/m 2 .year with Tithonia diversifolia green manure. Biochar application reduced the rate of CO 2 -C loss by 27%, and T. diversifolia increased CO 2 -C losses by 22% in the C-poor soils. With biochar application, a greater proportion of C (6.8 times) was found in the intraaggregate fraction per unit C respired than with green manure, indicating a more efficient stabilisation in addition to the chemical recalcitrance of biochar. In SOC-poor soils, biochar application enriched aromatic-C, carboxyl-C, and traces of ketones and esters mainly in unprotected organic matter and within aggregates, as determined by Fourier-transform infrared spectroscopy. In contrast, additions of T. diversifolia biomass enriched conjugated carbonyl-C such as ketones and quinones, as well as CH deformations of aliphatic-C mainly in the intra-aggregate fraction. The data indicate that not only the stability but also the stabilisation of biochar exceeds that of a labile organic matter addition such as green manure.

Biochar and Manure Effects on Net Nitrogen Mineralization and Greenhouse Gas Emissions from Calcareous Soil under Corn

“…A change in N partitioning associated with a decrease in soil nitrification is strongly implicated because the biochar-only treatment maximized the soil NH 4 / NO 3 concentration ratio (Supplemental Table S1) relative to other treatments on average. The overall effect of these changes would result in the apparent stabilization of soil C (Kimetu and Lehmann, 2010). The decreased root biomass of biochar-only treatment (Fig.…”

Effect of biochar on the greenhouse gas emissions from farmland and its physicochemical properties

“…Other researches showed that biochar application could led to an increase of CO 2 emission from SOC-rich soil [13]. When applied pasture waste biochar(10 t·hm -2 ) into soil, it showed increased CO 2 and N 2 O emission than CK whereas net absorption of CH 4 [14].…”

Impacts of Biochar on Agriculture Soils and Environmental Implications

“…However, there are some reports about the biochar related to products of short duration pyrolysis at higher temperatures known as"fast pyrolysis"and even novel techniques such as microwave conversion. During the process of production of biochar, the transformation from energy to heat is relatively low which resulted in high storage of carbon in biochar and significantly low emissions of global warming gases into atmosphere [6].…”