What is the role of soil microorganisms in nutrient cycling and plant health?

• A. Microbes decompose organic matter and can promote nutrient uptake in plants
• B. Microbes decompose litter and do not influence nitrogen cycles
• C. Microbes fix nitrogen
• D. Microbes solubilize phosphorus

Answer: (C)

Nitrogen fixation is a key way soil microorganisms support nutrient cycling and plant health. Certain bacteria convert atmospheric nitrogen (N2), which plants can’t use, into ammonia or ammonium that plants can take up through their roots. This adds new nitrogen to the soil ecosystem, helping plants build proteins, enzymes, and chlorophyll—fundamental for growth and vitality. Nitrogen is often the nutrient most limiting to plant growth, so this process directly boosts plant health and productivity. While decomposition and nutrient release from organic matter and phosphorus solubilization are also important microbial roles, the ability to introduce usable nitrogen into the soil makes fixation a particularly crucial driver of nutrient cycling and plant health.