Soil Flora

Soil microbial populations consist of autotrophs, decomposers, and mutualists. Their distribution is influenced by soil conditions and plant interactions.

A. Bacteria:

• Most abundant soil microorganisms.
• Classified as autochthonous (indigenous) and zymogenous (fermentation) types.
• Major genera: Arthrobacter, Bacillus, Pseudomonas, Agrobacterium, Alcaligens, Flavobacterium.

B. Actinomycetes:

• Gram-positive bacteria with filamentous growth.
• Dominant genera: Streptomyces, Micromonospora, Nocardia.
• Play a role in decomposition and antibiotic production.

C. Fungi:

• Second most abundant microflora after bacteria and actinomycetes.
• Common genera: Penicillium, Aspergillus, Fusarium.
• Significant for decomposition, mycorrhizal associations, and disease suppression.

D. Archaea:

• Previously classified as archaebacteria, reclassified based on molecular studies.
• Found in extreme environments and cropland soils.
• Important in methane production and ammonia oxidation.

E. Algae:

• Less abundant but present in moist, well-lit soils.
• Groups: Cyanophyceae (blue-green algae), Chlorophyceae (green algae), Xanthophyceae (yellow-green algae), Bacillariaceae (diatoms).
• Found mostly in the top 10 cm of soil.