Rice (Oryza sativa L) plantation affects the stability of biochar in paddy soil.

Mengxiong Wu,Hailong Wang,Gerty Gielen,Qibo Feng,Xue Sun,Weixiang Wu

doi:10.1038/srep10001

Mengxiong Wu, Hailong Wang + Show 4 more

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https://doi.org/10.1038/srep10001

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Abstract

Conversion of rice straw into biochar for soil amendment appears to be a promising method to increase long-term carbon sequestration and reduce greenhouse gas (GHG) emissions. The stability of biochar in paddy soil, which is the major determining factor of carbon sequestration effect, depends mainly on soil properties and plant functions. However, the influence of plants on biochar stability in paddy soil remains unclear. In this study, bulk and surface characteristics of the biochars incubated without rice plants were compared with those incubated with rice plants using a suite of analytical techniques. Results showed that although rice plants had no significant influence on the bulk characteristics and decomposition rates of the biochar, the surface oxidation of biochar particles was enhanced by rice plants. Using 13C labeling we observed that rice plants could significantly increase carbon incorporation from biochar into soil microbial biomass. About 0.047% of the carbon in biochar was incorporated into the rice plants during the whole rice growing cycle. These results inferred that root exudates and transportation of biochar particles into rice plants might decrease the stability of biochar in paddy soil. Impact of plants should be considered when predicting carbon sequestration potential of biochar in soil systems.

Highlights

Recent studies have shown that TG could be used to estimate the labile fraction of carbon in biochar and evaluate the thermal stability of soil organic matter by using the fraction of volatile matter with respect to the sum of volatile matter content and fixed C24,25
It has been suggested from the elemental composition that a biochar material containing lower O/C ratios would be more stable than a biochar material with higher O/C ratios[26]
The O/C ratio of the biochars significantly decreased after pre-incubation (Table S1)

Summary

Introduction

For the direct utilization of biochar carbon within soil microbial communities, microbial degradation of biochar has been shown to occur through co-metabolism. While abiotic and microbial degradation of biochar has been shown to significantly influence biochar stability, the effect of plants on biochar stability is not known. Rooting systems provide a source of organic carbon to soil microbes, which enhance microbial biomass, leading to a promotion of microbial co-metabolism that can increase biochar degradation[17]. Plants are able to directly influence biochar decomposition rates through abiotic or indirectly influence biochar through microbial oxidation. The adsorption onto biochar contributes to soil organic carbon stabilization and, in turn, plant roots can impact on biochar stability in a soil ecosystem. We hypothesized that rice plants would stimulate RS biochar degradation via roots exudates and microbial oxidation

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