Biochar and Rhizobacteria Amendments Improve Several Soil Properties and Bacterial Diversity

Abstract

In the current context, there is a growing interest in reducing the use of chemical fertilizers and pesticides to promote ecological agriculture. The use of biochar and plant growth-promoting rhizobacteria (PGPR) is an environmentally friendly alternative that can improve soil conditions and increase ecosystem productivity. However, the effects of biochar and PGPR amendments on forest plantations are not well known. The aim of this study is to investigate the effects of biochar and PGPR applications on soil nutrients and bacterial community. To achieve this goal, we applied amendments of (i) biochar at 20 t hm−2, (ii) PGPR at 5 × 1010 CFU mL−1, and (iii) biochar at 20 t hm−2 + PGPR at 5 × 1010 CFU mL−1 in a eucalyptus seedling plantation in Guangxi, China. Three months after applying the amendments, we collected six soil samples from each treatment and from control plots. From each soil sample, we analyzed several physicochemical properties (pH, electrical conductivity, total N, inorganic N, NO3−-N, NH4+-N, total P, total K, and soil water content), and we determined the bacterial community composition by sequencing the ribosomal 16S rRNA. Results indicated that co-application of biochar and PGPR amendments significantly decreased concentrations of soil total P and NH4+-N, whereas they increased NO3-N, total K, and soil water content. Biochar and PGPR treatments increased the richness and diversity of soil bacteria and the relative abundance of specific bacterial taxa such as Actinobacteria, Gemmatimonadetes, and Cyanobacteria. In general, the microbial composition was similar in the two treatments with PGPR. We also found that soil physicochemical properties had no significant influence on the soil composition of bacterial phyla, but soil NH4+-N was significantly related to the soil community composition of dominant bacterial genus. Thus, our findings suggest that biochar and PGPR amendments could be useful to maintain soil sustainability in eucalyptus plantations.

Effects of Plant Growth Promoting Rhizobacteria Microbial Inoculants on the Growth, Rhizosphere Soil Properties, and Bacterial Community of Pinus sylvestris var. mongolica Annual Seedlings

“…Chloro exi is a Gram-negative bacteria that can potentially autotrophically metabolize through photosynthesis. This study found that after inoculation with PGPR, the relative abundance of Chloro exi in the rhizosphere soil was signi cantly negatively correlated with soil AN content (p < 0.05), which is similar to the results of Ren et al (Ren et al 2020) who found that after inoculation with biochar + PGPR, the soil nitrogen content increased, while the abundance of Chloro exi decreased. The cluster analysis results showed that the bacterial communities treated by strains A20 and A36 differed signi cantly from those treated with strains A13 and CK at the genus level, indicating that inoculation with strains A20 and A36 altered the soil bacterial community.…”

Long-Term Bacterial Fertilizer Application Improves Eucalyptus Growth and Yields through Altering Soil Quality

“…Besides, PGPR may stimulate the synthesis of secondary metabolites that may increase the accumulation of potassium compounds in eucalyptus roots (Tinna et al 2020). Han et al (Ren et al 2020a) also reported that major increases in soil potassium content occurred in PGPR treatment over uninoculated control. Consistent herewith, we observed that soil available K content increased with PGPR applied in the soil.…”

“…Besides, Acidobacteria has been reported to be a predictor of soil health status and generally negatively correlated to soil quality, especially in relatively barren soil (Liu et al 2020). PGPR potentially decreased soil Acidobacteria phylum abundance in a eucalyptus seedling in south China (Ren et al 2020a). These ndings are consistent with the increase in soil quality after the application of BF in our study.…”

“…foliar N). Proteobacteria has been reported to be a predictor of soil health status and generally negatively correlated to soil quality, especially in relatively barren soil (Liu et al 2020), however, soil TN was certi ed to be positively affected by the activity of soil Proteobacteria in a 3-month eucalyptus seedling plantation (Ren et al 2020a). These ndings are consistent with the negative correlation between soil TN and soil quality, and further soil TN negatively and signi cantly in uenced plant yield in our trial.…”

“…Plant Growth Promoting Rhizobacteria (PGPR) has been widely reported to improve crop yield and soil quality via improving soil fertility (Han Ren, Chengqun Lv, Víctor Fernández-García, Baoling Huang, Jiangming Yao 2019), soil microbial composition diversity (Ren et al 2020a), and plant nutrient uptake capacity (Ren et al 2020b). Bacillus megaterium, such as B. megaterium var.…”