Evaluating the combined effect of biochar and PGPR inoculants on the bacterial community in acidic sandy soil

András Kari,Zsuzsanna Nagymáté,Csaba Romsics,Balázs Vajna,Erika Tóth,Rita Lazanyi-Kovács,Boglárka Rizó,József Kutasi,Botond Bernhardt,Éva Farkas,Károly Márialigeti

doi:10.1016/j.apsoil.2020.103856

Abstract

Biochar is used to improve soil fertility and mitigate climate change by carbon sequestration. The potential of using biochar together with plant growth promoting rhizobacteria (PGPR) as a soil fertilization technique, offers an alternative way for sustainable agriculture. In the present study biochar and acid stress adapted PGPR inoculants were applied in three different quantities in order to improve soil fertility to enhance maize growth and crop yield in an acidic sandy soil (pH 4.4). The objective of the study was to monitor the effect of biochar on soil biota and on the inoculated PGP bacteria. Soil bacterial community structure was characterized with the genotyping sequence-aided terminal restriction fragment length polymorphism (T-RFLP) technique and the phenotyping phospholipid fatty acid analysis (PLFA). T-RFLP method was applied also for detecting and estimating the relative abundance of the inoculated PGP bacteria. Inocula immobilized on the biochar surface, as well as high doses of biochar treatments positively influenced the applied Azospirillum brasilense and Arthrobacter crystallopoietes abundances. In case of Azospirillum brasilense, the positive effect proved to be statistically significant (1–6 times higher relative abundances as compared to the control and small dose). The bacterial community structure in the rhizosphere was significantly influenced both by maize growth stage and by high doses (15 and 30 Mg ha−1) of biochar treatment. In the case of the immobilized PGP bacteria on the biochar surface treatment the maize above-ground biomass was significantly enhanced (2.6–3.2 times of the control). This study revealed that high doses of biochar treatment influenced the abundance of those bacterial groups that might play important roles in soil nutrient cycles.

Highlights

Sustainable agriculture aims to preserve environmental quality, and provides safe and healthy food in adequate quantities to overcome the needs of the growing population (Benbrook, 1999)
In the case of the 5 applied plant growth promoting rhizobacteria (PGPR) strains, four strains were identical to those applied in our previous research (Kari et al, 2019), only Azo spirillum brasilense 242/9 was a new strain
In our study we examined the correlation between the plant biomass and the relative abundances of the inoculated PGPR’s

Summary

Introduction

Sustainable agriculture aims to preserve environmental quality, and provides safe and healthy food in adequate quantities to overcome the needs of the growing population (Benbrook, 1999). Due to its environ mental benefits and being a renewable resource, biochar offers a promising material for sustainable agriculture. As Bonanomi et al (2017) reported that biochar amendment to lithic haplustolls soil improves soil quality, retain nutrients and enhance plant growth. As a soil amendment, has been described to have multiple benefits in improving soil fertility, enhancing crop yield and even sequestering carbon to mitigate climate change (Lehmann et al, 2006; Liu et al, 2013; Baiamonte et al, 2015; Ding et al, 2016). According to Ding et al (2016), several mechanisms can explain how biochar application can influence the soil microbiota: i) changes nutrient availability; ii) forms habitat and protects from grazers; iii) causes alterations in plantmicrobiome signalling; iv) modifies “other” microbial communities

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