Why Soil Microorganisms?

Soil microbiology is a vital branch of soil science that focuses on microorganisms living in soil, their functions, and their activities within the soil ecosystem. This interdisciplinary subject links closely with soil biochemistry and microbial ecology, involving principles of soil science, microbiology, and the chemistry of biological systems. The use of natural organic fertilizers enhances microbial activity, supporting a thriving soil ecosystem.

There are two primary approaches:

• Organism-focused: Examining the physiology and taxonomy of microorganisms.
• Process-focused: Studying microbial processes and their roles in soil.

Soil is a heterogeneous habitat with varying environmental conditions, supporting a high number of microorganisms with diverse metabolic activities. These microorganisms play crucial roles in nutrient cycling and pollutant removal. Soil provides a variety of substrates, from simple sugars to complex materials like humus, and numerous microsites with different nutrient, moisture, pH, and redox conditions. The presence of natural organic fertilizers further enriches these microbial communities, fostering soil fertility and plant health.

Soil microorganisms are classified into seven categories: bacteria, fungi, viruses, blue-green algae (cyanobacteria), actinomycetes, protozoa, and nematodes. They inhabit both surface and subsurface soil, with their numbers generally decreasing with depth. The composition of the microbial community can change with environmental conditions. The rhizosphere, the soil region influenced by plant roots, harbors more microorganisms due to the compounds released by plants. Natural organic fertilizers provide essential nutrients that sustain these beneficial microbial populations.

Bacteria are the smallest and most numerous cellular organisms in soils. They are prokaryotic and come in various shapes, with the most common being short rods. Bacteria are abundant, especially in the rhizosphere.

Common soil bacteria include genera like Bacillus, Arthrobacter, Pseudomonas, and Mycobacterium. They exhibit vast metabolic diversity, contributing to nutrient cycling and soil structure improvement. Bacteria participate in biogeochemical cycles and help degrade complex organic substances. The presence of natural organic fertilizers can further stimulate bacterial activity, enhancing soil health and plant growth.

Positive Effects

• Enhance soil structure
• Participate in nutrient cycling
• Improve soil quality for new plant communities
• Indicate soil condition

Negative Effects

• Cause plant diseases
• Disturb soil ecological balance
• Alter soil chemical properties

Soil fungi are eukaryotic organisms, either unicellular or multicellular, with complex life cycles. Most fungi are aerobic, except for yeasts that can ferment sugars anaerobically.

Soil fungi include groups like Ascomycetes, Basidiomycetes, and Imperfect fungi. They decompose organic matter, form symbiotic relationships with plants (mycorrhizae), and can be pathogens. The addition of natural organic fertilizers supports fungal diversity, enhancing nutrient availability and soil structure.

Positive Effects

• Decompose organic matter
• Form symbiotic relationships
• Improve soil structure and fertility

Negative Effects

• Cause plant diseases
• Compete with beneficial microorganisms