Biochar-Compost Interactions as Affected by Weathering: Effects on Biological Stability and Plant Growth

Marie-Liesse Aubertin,Cornelia Rumpel,Cyril Girardin,Sabine Houot,Sarah Bena,Yann Le Brech,Cécile Nobile,David Houben

doi:10.3390/agronomy11020336

Abstract

Biochar addition to compost is of growing interest as soil amendment. However, little is known about the evolution of material properties of biochar-compost mixtures and their effect on plants after exposure to physical weathering. This study aimed to investigate the physico-chemical characteristics of fresh and weathered biochar-compost mixtures, their biological stability and their effect on ryegrass growth. To this end, we used the contrasting stable isotope signatures of biochar and compost to follow their behavior in biochar-compost mixtures subjected to artificial weathering during 1-year of incubation. We assessed their impact on ryegrass growth during a 4-week greenhouse pot experiment. Weathering treatment resulted in strong leaching of labile compounds. However, biochar-compost interactions led to reduced mass loss and fixed carbon retention during weathering of mixtures. Moreover, weathering increased carbon mineralization of biochar-compost mixtures, probably due to the protection of labile compounds from compost within biochar structure, as well as leaching of labile biochar compounds inhibiting microbial activity. After soil application, weathered mixtures could have positive effects on biomass production. We conclude that biochar-compost interactions on soil microbial activity and plant growth are evolving after physical weathering depending on biochar production conditions.

Highlights

We evaluated the effect of weathering on dissolved organic carbon content (DOC) and elemental content
We investigated the effect of two biochar-compost mixtures and weathering on their material properties, biological stability and on plant growth after addition to two contrasting soils
Our results showed that the physical weathering led to the alteration of material properties of the mixtures, in particular through leaching of labile compounds

Summary

Introduction

According to the last report of the Intergovernmental Panel of Climate Change (IPCC), global temperatures have increased by 1 ◦ C above pre-industrial levels due to human activity [1]. Further increase should be limited to 1.5 ◦ C in order to prevent dangerous climate change. To achieve this goal, active carbon dioxide removal from the atmosphere and its storage is needed [1]. Soil carbon sequestration and biochar application to soils may be used for this purpose. As negative emission technologies (NETs), their implementation may be able to achieve long-term carbon sequestration and may have advantages over the other NETs related to their effect on land use, water use and energy requirement [2]

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