Factors Boosting Microbial Biomass in the Soil Profile:

Microbial biomass, essentially the living portion of soil organic matter, plays a crucial role in maintaining soil health and fertility. Various factors can influence its abundance and composition, broadly categorized into:

1. Organic Matter Inputs:

• Increased plant residues and cover crops: These provide readily available carbon and energy sources for microbes.
• Compost amendments: Introduce diverse microbial communities and readily decomposable organic matter.
• Manure application: Adds both organic matter and nutrients, stimulating microbial activity.

2. Reduced Disturbance:

• Minimizing tillage: Preserves soil aggregates where microbes thrive and protects fungal networks.
• Mulching: Moderates soil temperature and moisture, creating favorable conditions for microbes.
• Rotational grazing: Minimizes soil compaction and allows time for organic matter accumulation.

3. Optimal Environmental Conditions:

• Moderate temperature and moisture: Warmth and moisture enhance microbial activity, but extremes can be detrimental.
• Neutral pH (around 7): Acidic or alkaline soils can limit microbial diversity and abundance.
• Balanced nutrient availability: Adequate levels of N, P, and K are essential for microbial growth and metabolism.

Key Microorganisms in Biomass Utilization:

A diverse community of microorganisms contributes to biomass decomposition and nutrient cycling in soil. Some prominent players include:

• Bacteria: Decompose various organic compounds, with specific groups specializing in cellulose, lignin, proteins, and other substrates.
• Fungi: Their filamentous networks break down complex organic matter and contribute to soil aggregation.
• Actinomycetes: Produce potent enzymes that degrade lignin and other recalcitrant materials.
• Protozoa: These micro-predators graze on bacteria and fungi, releasing nutrients while regulating microbial populations.

The specific composition of this community varies depending on soil type, organic matter inputs, and environmental conditions. Understanding these factors can help us cultivate a thriving microbial population for robust soil health and sustainable agricultural practices.

For further details or specific questions regarding individual microorganisms or soil management strategies

Dr Murtadha Shukur thank you for your contribution to discussion

The microbial biomass is affected by factors that change the water or carbon content of soil, and include climate, soil type and management practices. The microbial biomass grows best in warm and moist conditions. Consequently areas with warm moist climates will have a greater microbial biomass than cold or dry areas. Soils with higher clay contents generally have a higher microbial biomass as they retain more water and often contain more organic C. Soil pH is also important as microbial growth declines under conditions that are too acid or too alkaline. A soil pH near 7.0 is most suitable for microbial growth. The microbial biomass can be increased by adding effective organic matter such as compost, solid manure, green manures or cultivating grains (incl. straw). Other examples of measures are reduced soil tillage, permanently covering the soil, temporary grassland or less ploughing up of permanent grassland. Microbial biomass is substantially lower in deeper soils compared to surface soils by as much as two orders of magnitude, and microbial turnover is also significantly slower. Soil pH, total phosphorus, climate and distance are the major factors influencing microbial activity at a regional spatial scale. Three types of microorganism are used for microbial biomass production: bacteria, fungi (including higher fungi) and microalgae. Bacteria are the most abundant organisms in soil, second only to fungi in their contribution to global soil microbial biomass (7 Gt C).