Benefits of Corn-Cob Biochar to the Microbial and Enzymatic Activity of Soybean Plants Grown in Soils Contaminated with Heavy Metals

Samir A. Haddad,Joanna Lemanowicz

doi:10.3390/en14185763

Samir A. Haddad, Joanna Lemanowicz

Open Access

https://doi.org/10.3390/en14185763

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Abstract

Synchronous effects of biochar on heavy metals stress, microbial activity and nodulation process in the soil are rarely addressed. This work studied the effects, under greenhouse conditions, of selected heavy metals Cd2+, Pb2+ and Ni2+ on soybean plants grown in two different soils amended with biochar, and studied their effect on the microbial and enzymatic activity. As a result of the interference between heavy metals and biochar, biochar overcame heavy metal problems and maintained a microbial population of major groups (bacteria–fungi). There was an increase in the degree of resistance (RS) of the major microbial groups to heavy metals when biochar was added to the soil under study. Numbers of bacterial nodules significantly increased, particularly by using the higher rate of biochar compared to the control, either by adding biochar alone or by mixing it with the selected heavy metals. The arginase activity was increased by 25.5% and 37.1% in clay and sandy soil, respectively, compared to the control. For urease (UR), the activity was increased by 105% and 83.8% in clay and sandy soil, respectively, compared to the control. As a result, considerations of using biochar as a soil amendment should be first priority.

Highlights

There is increasing trepidation about soil pollution by heavy metals because of their harmfulness to plants, animals and human beings and their deficiency of biodegradability [1,2]
The values of the resistance index (RS) for selected soil microorganisms were positive throughout the experiment
They differed depending on the type of heavy metal applied, the experimental time and the soil texture (Tables 6 and 7)

Summary

Introduction

There is increasing trepidation about soil pollution by heavy metals because of their harmfulness to plants, animals and human beings and their deficiency of biodegradability [1,2]. Previous studies showed that heavy metal contamination has both long-term [6] and short-term [7] toxicity effects on soil microbial communities. As natural catalysts of many soil processes connected with decomposition of organic substances, participate in the processes of releasing and making minerals available to plant roots in the rhizosphere. Enzymatic activity is an early indicator of changes in the level of intensity of biological processes and the level of soil degradation and it is usually correlated with its physical and chemical properties [8,9]. Certain biochars have been shown to change soil biological community composition and abundance [10]. The influence of biochars on soil enzyme activities, is still poorly documented

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Results

Conclusion