Biochar Treatment Resulted in a Combined Effect on Soybean Growth Promotion and a Shift in Plant Growth Promoting Rhizobacteria.

Elsayed F. Abd_Allah,Gabriele Berg,Stephan Wirth,Undine Behrendt,Dilfuza Egamberdieva

doi:10.3389/fmicb.2016.00209

Abstract

The application of biochar to soil is considered to have the potential for long-term soil carbon sequestration, as well as for improving plant growth and suppressing soil pathogens. In our study we evaluated the effect of biochar on the plant growth of soybeans, as well as on the community composition of root-associated bacteria with plant growth promoting traits. Two types of biochar, namely, maize biochar (MBC), wood biochar (WBC), and hydrochar (HTC) were used for pot experiments to monitor plant growth. Soybean plants grown in soil amended with HTC char (2%) showed the best performance and were collected for isolation and further characterization of root-associated bacteria for multiple plant growth promoting traits. Only HTC char amendment resulted in a statistically significant increase in the root and shoot dry weight of soybeans. Interestingly, rhizosphere isolates from HTC char amended soil showed higher diversity than the rhizosphere isolates from the control soil. In addition, a higher proportion of isolates from HTC char amended soil compared with control soil was found to express plant growth promoting properties and showed antagonistic activity against one or more phytopathogenic fungi. Our study provided evidence that improved plant growth by biochar incorporation into soil results from the combination of a direct effect that is dependent on the type of char and a microbiome shift in root-associated beneficial bacteria.

Highlights

Biochar is a fine-grained charcoal that is rich in organic carbon, produced by pyrolysis or by heating biomass in a low oxygen environment and has been used worldwide as a soil amendment to increase soil fertility (Lehmann and Joseph, 2009; Schomberg et al, 2012)
Our study showed that shoot and root biomass of soybeans were not significantly affected by either maize biochar (MBC) or wood biochar (WBC) amendments in all concentrations (1, 2, and 3%; Figures 1A,B)
There was a slight but not significant increase in shoot and root growth in the soybeans grown in soil amended with MBC at 1 and 2% concentrations compared with control plants (Figure 1A)

Summary

Introduction

Biochar is a fine-grained charcoal that is rich in organic carbon, produced by pyrolysis or by heating biomass in a low oxygen environment and has been used worldwide as a soil amendment to increase soil fertility (Lehmann and Joseph, 2009; Schomberg et al, 2012). Other topics are about improving soil nutrient availability and the growth and development of Biochar Effects Soybean and Rhizobacteria agriculturally important crops, inducing systemic resistance in plants against soil borne fungal pathogens (Elad et al, 2010). There are several studies explaining an indirect effect of biochar on root growth and development by altering soil properties, such as porosity and pore size distribution, water holding capacity, mechanical stability, sorption properties and the bioavailability of nutrients and trace elements (Laird et al, 2010; Spokas et al, 2010), but the functional response of soil microbial populations after biochar amendments are not well-understood (Lehmann et al, 2011). Despite numerous reports on microbial changes induced by biochar application in various cropping systems, there have been no studies on how biochar affects the diversity and physiological activity of plant growth stimulating rhizobacteria, especially in legumes

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