Effects of different concentrations of biochar amendments and Pb toxicity on rhizosphere soil characteristics and bacterial community of red clover (Trifolium pretense L.)

Abstract

Amending soil with biochar can reduce the toxic effects of heavy metals (HM) on plants and the soil. However, the effects of different concentrations of biochar on the properties and microbial activities in lead (Pb)-contaminated soils are unclear. In this study, two Pb concentrations were set (low, 1000 mg/kg; high, 5000 mg/kg), and five corn straw biochar (CSB) concentrations (0, 2.5, 5, 10 and 15%) were used to determine the response of the growth and rhizosphere of red clover (Trifolium pretense L.) (in terms of soil properties and bacteria) to CSB and Pb application. The results showed that 5% CSB better alleviated the toxicity of Pb on the shoot length of red clover, the biomass increased by 74.55 and 197.76% respectively and reduced the enrichment factor (BCF) and transport factor (TF) of red clover. Pb toxicity reduced soil nutrients, catalase (CAT), acid phosphatase (ACP) and urease activity, while the addition of CSB increased soil pH, soil organic matter (SOM) content and soil enzyme activity. 16S rDNA amplicon sequencing analysis showed that Pb toxicity reduced the diversity of rhizosphere bacteria in red clover and reduced the relative abundance of plant growth-promoting rhizobacteria such as Gemmatimonas, Devosia and Bryobacter. Spearman correlation analysis showed that the addition of alkaline CSB restored the relative abundance of rhizobacteria positively correlated with pH, such as Chitinophaga, Sphingomonas, Devosia and Pseudomonas, and thus restored the rhizosphere soil environment. This study demonstrates that 5% CSB can better alleviate the toxicity of Pb to red clover and soil. We also provide a theoretical basis for the subsequent use of beneficial bacteria to regulate the repair efficiency of red clover.

Dynamic microbial regulation of triiron tetrairon phosphate nanomaterials in the tomato rhizosphere

“…45 Gemmatimonas can fix atmospheric nitrogen, enhance nutrient availability in the soil, enhance soil structure, prevent diseases and insect pests, stimulate plant growth, and increase the availability of P and potassium (K). 46 Plants exhibit distinct functional needs during various developmental stages and possess specific recruitment requirements for the rhizosphere microbiome. For instance, during the seedling stage, the immune system of the plant is insufficiently robust to defend against pathogen invasion.…”

Microbial mediated remediation of heavy metals toxicity: mechanisms and future prospects

“…In another study, it was documented that Pb stress altered the bacterial community structure. These authors found that Pb 2.5% and 5% increased Actinobacteria abundance by 118.56 and 147.25% while 5% Pb stress Bacteroidota and Myxococcota increased abundance by 280.76 and 138.54%, respectively ( Meng et al., 2023 ). In another study, a significant change in microbial abundance and diversity was observed in Cd-polluted soil.…”