Coupled effects of elevated CO2 and biochar on microbial communities of vegetated soil

Biochar for ameliorating soil fertility and microbial diversity: From production to action of the black gold

This article evaluated different production strategies, characteristics, and applications of biochar for ameliorating soil fertility and microbial diversity. The biochar production techniques are evolving, indicating that newer methods (including hydrothermal and retort carbonization) operate with minimum temperatures, yet resulting in high yields with significant improvements in different properties, including heating value, oxygen functionality, and carbon content, compared to the traditional methods. It has been found that the temperature, feedstock type, and moisture content play critical roles in the fabrication process. The alkaline nature of biochar is attributed to surface functional groups and addresses soil acidity issues. The porous structure and oxygen-containing functional groups contribute to soil microbial adhesion, affecting soil health and nutrient availability, improving plant root morphology, photosynthetic pigments, enzyme activities, and growth even under salinity stress conditions. The review underscores the potential of biochar to address diverse agricultural challenges, emphasizing the need for further research and application-specific considerations.

Plant-soil hydraulic interaction and rhizosphere bacterial community under biochar and CO2 enrichment

The increasing atmospheric CO2 concentration is a global concern that affects the plant-bacteria-soil system. Previous studies have investigated plant growth and bacteria activity under CO2 enrichment. However, the effects of coupled elevated CO2 and biochar amendment on the interactions of soil and medicinal plants are not well understood. This study aims to investigate the medicinal plant-soil hydraulic interactions and rhizosphere bacteria communities under coupled CO2 enrichment and biochar conditions. Two levels of CO2 concentration (400, 1000 ppm) and two biochar dosages (3%, 5% by mass) were considered. Pseudostellaria heterophylla was used as the tested medicinal plant. During plant growth, coupled CO2 enrichment and biochar at 3% and 5% dosage increased the volumetric water content at a matric suction of 33 kPa by 97% and 82% respectively, which indicates enhanced water retention. The transpiration rate of P. heterophylla was slightly reduced by 11-30% with an increase in biochar dosage due to higher total suction, while it was significantly reduced by up to 57% due to CO2 enrichment. In the rhizosphere of P. heterophylla, elevated CO2 (1000 ppm) coupled with 3% biochar dramatically increase the relative abundance of Thaumarchaeota, which played an important role in C and N cycles. Moreover, coupled CO2 enrichment and biochar addition resulted in the highest bacterial richness, while 3% biochar at ambient CO2 induced the highest bacterial diversity. This study provides a basis for understanding the medicinal plant-bacteria-soil system under CO2 enrichment and biochar conditions.

Mechanistic and future prospects in rhizospheric engineering for agricultural contaminants removal, soil health restoration, and management of climate change stress

Climate change, food insecurity, and agricultural pollution are all serious challenges in the twenty-first century, impacting plant growth, soil quality, and food security. Innovative techniques are required to mitigate these negative outcomes. Toxic heavy metals (THMs), organic pollutants (OPs), and emerging contaminants (ECs), as well as other biotic and abiotic stressors, can all affect nutrient availability, plant metabolic pathways, agricultural productivity, and soil-fertility. Comprehending the interactions between root exudates, microorganisms, and modified biochar can aid in the fight against environmental problems such as the accumulation of pollutants and the stressful effects of climate change. Microbes can inhibit THMs uptake, degrade organic pollutants, releases biomolecules that regulate crop development under drought, salinity, pathogenic attack and other stresses. However, these microbial abilities are primarily demonstrated in research facilities rather than in contaminated or stressed habitats. Despite not being a perfect solution, biochar can remove THMs, OPs, and ECs from contaminated areas and reduce the impact of climate change on plants. We hypothesized that combining microorganisms with biochar to address the problems of contaminated soil and climate change stress would be effective in the field. Despite the fact that root exudates have the potential to attract selected microorganisms and biochar, there has been little attention paid to these areas, considering that this work addresses a critical knowledge gap of rhizospheric engineering mediated root exudates to foster microbial and biochar adaptation. Reducing the detrimental impacts of THMs, OPs, ECs, as well as abiotic and biotic stress, requires identifying the best root-associated microbes and biochar adaptation mechanisms.

Role of Soil Microbiota Enzymes in Soil Health and Activity Changes Depending on Climate Change and the Type of Soil Ecosystem

The extracellular enzymes secreted by soil microorganisms play a pivotal role in the decomposition of organic matter and the global cycles of carbon (C), phosphorus (P), and nitrogen (N), also serving as indicators of soil health and fertility. Current research is extensively analyzing these microbial populations and enzyme activities in diverse soil ecosystems and climatic regions, such as forests, grasslands, tropics, arctic regions and deserts. Climate change, global warming, and intensive agriculture are altering soil enzyme activities. Yet, few reviews have thoroughly explored the key enzymes required for soil fertility and the effects of abiotic factors on their functionality. A comprehensive review is thus essential to better understand the role of soil microbial enzymes in C, P, and N cycles, and their response to climate changes, soil ecosystems, organic farming, and fertilization. Studies indicate that the soil temperature, moisture, water content, pH, substrate availability, and average annual temperature and precipitation significantly impact enzyme activities. Additionally, climate change has shown ambiguous effects on these activities, causing both reductions and enhancements in enzyme catalytic functions.