Different fertilization treatments in coal mining-affected soils change bacterial populations and enable soil reclamation

Effects of coal-derived compound fertilizers on soil bacterial community structure in coal mining subsidence areas

The land damaged by coal mining can be recovered to healthy condition through various reclamation methods. Fertilization is one of the effective methods to improve soil fertility and microbial activity. However, the effects of coal-derived compound fertilizers (SH) on bacterial communities in coal mining subsidence areas still remain unclear. Here, we studied the effects on the nutrient characteristics and bacterial communities in fertilizer-reclaimed soil (CK, without fertilizer; CF, common compound fertilizers; SH, coal-derived compound fertilizers) in coal mining subsidence areas and we applied SH with four different nitrogen application rates (90, 135, 180, and 225 kg/hm²). The results showed that the application of SH significantly increased the contents of available nitrogen (AN), available phosphorus (AP), available potassium (AK), total phosphorus (TP) and soil organic matter (SOM) compared with CK, as well as the bacterial richness (Chao1) and diversity (Shannon) in reclaimed soil that increased first and then decreased with the increase of nitrogen application. Under the same nitrogen application rate (135 kg/hm²), the nutrient content, Chao1 and Shannon of SH2 treatments were higher than those of CF treatment. Meanwhile, SH increased the relative abundance of Proteobacteria, Actinobacteria and Gemmatimonadetes. LEfSe analysis indicated that the taxa of Acidobacteria and Actinobacteria were significantly improved under SH treatments. Canonical correspondence analysis (CCA) and Variance partitioning analysis (VPA) showed that SOM was the most important factor affecting the change of bacterial community structure in reclaimed soil. In conclusion, application of SH can not only increase nutrient content and bacterial diversity of reclaimed soil, but also improve bacterial community structure by increasing bacterial abundance.

Biotechnology of Microorganisms from Coal Environments: From Environmental Remediation to Energy Production

Simple Summary

Despite the wide perception that coal environments are extreme habitats, they harbor resident microbial communities. Coal-associated habitats, such as coal mine areas/drainages, spoil heaps, and coalbeds, are defined as complex ecosystems with indigenous microbial groups and native microecological networks. Resident microorganisms possess rich functional potentials and profoundly shape a range of biotechnological processes in the coal industry, from production to remediation.

Abstract

It was generally believed that coal sources are not favorable as live-in habitats for microorganisms due to their recalcitrant chemical nature and negligible decomposition. However, accumulating evidence has revealed the presence of diverse microbial groups in coal environments and their significant metabolic role in coal biogeochemical dynamics and ecosystem functioning. The high oxygen content, organic fractions, and lignin-like structures of lower-rank coals may provide effective means for microbial attack, still representing a greatly unexplored frontier in microbiology. Coal degradation/conversion technology by native bacterial and fungal species has great potential in agricultural development, chemical industry production, and environmental rehabilitation. Furthermore, native microalgal species can offer a sustainable energy source and an excellent bioremediation strategy applicable to coal spill/seam waters. Additionally, the measures of the fate of the microbial community would serve as an indicator of restoration progress on post-coal-mining sites. This review puts forward a comprehensive vision of coal biodegradation and bioprocessing by microorganisms native to coal environments for determining their biotechnological potential and possible applications.

A critical assessment on the short-term response of microbial relative composition in a mine tailings soil amended with biochar and manure compost

Phytomanagement of tailings requires the use of soil conditioners to favour plant establishment, but their benefits on soil microbial composition need to be assessed. The goal of this work was to evaluate the effect of two organic amendments, manure compost and biochar, on soil bacterial and fungal composition at metallic mine tailings. The addition of compost caused stronger effects in most of soil parameters and microbial composition than biochar, especially at the initial stage of the experiment. However, the higher dependence on labile organic carbon for some bacterial groups at the treatments containing compost determined their decay along time (Flavobacteriales, Sphingobacteriales) and the appearance of other taxa more dependent on recalcitrant organic matter (Xanthomonadales, Myxococcales). Biochar favoured bacterial decomposers (Actinomycetales) specialised in high lignin and other recalcitrant carbon compounds. Unlike bacteria, only a few fungal orders increased their relative abundances in the treatments containing compost (Sordariales and Microascales) while the rest showed a decrease or remained unaltered. The mix biochar-compost may result the best option to support a more diverse microbial population in terms of soil functionality that is able to decompose both labile and recalcitrant carbon compounds. This may favour the resilience of the system against environmental stressors.

Smallholder Farmers' Practices and African Indigenous Vegetables Affect Soil Microbial Biodiversity and Enzyme Activities in Lake Naivasha Basin, Kenya

Simple Summary

Smallholder farmers in Sub-Saharan Africa (SSA) are food insecure. Underexploited African indigenous vegetables (AIVs) are consumed locally without being considered a primary source of food and income. However, AIVs hold great potential for the future challenges of food security and climate change. We investigated the effects of different cropping systems and inclusion of AIVs in farming on the soil biodiversity and fertility status of smallholder farmers in Naivasha, Kenya. Compared to mainstream farming approaches, soil microorganisms under AIV cultivations differed significantly. Tillage, fertilization, soil amendments, and traditional homemade plant protection were singled out as the most important factors. The soil alteration index based on enzyme activity offered a reliable way to determine the alteration status for the first time in SSA. These findings could be useful for farmers to integrate AIVs with correct sustainable practices for a sustainable future and may contribute to the mitigation of food insecurity.

Abstract

Loss of soil biodiversity and fertility in Sub-Saharan Africa (SSA) may put the food security of smallholder farmers in peril. Food systems in SSA are seeing the rise of African indigenous vegetables (AIVs) that are underexploited but locally consumed without being considered a primary source of food and income. Here we present a field study, a first of its kind, in which we investigated the effects of different cropping systems and inclusion of AIVs in the farming approach on bacterial and fungal biodiversity and community structures, enzymatic activity, and the alteration status of soils of the smallholder farmers in Kenya. When compared to mainstream farming approaches, the composition and biodiversity of bacteria and fungi under AIV cultivations was significantly different. Tillage had a significant impact only on the fungal communities. Fertilization and soil amendments caused shifts in microbial communities towards specialized degraders and revealed the introduction of specific microorganisms from amendments. Traditional homemade plant protection products did not cause any disturbance to either of soil bacteria or fungi. The soil alteration index based on enzyme activity successfully differentiated the alteration status for the first time in SSA. These findings could be useful for farmers to integrate AIVs with correct sustainable practices for a sustainable future.