Only microbes can convert the organic forms of plant and animal wastes into inorganic forms. Crops can absorb food only in the inorganic form. Only microbes can balance the favorable C: N ratio in the soil to help plants get nitrogen in available forms. Only microbes can prevent climate change.

Dr Girish Panicker thank you for your contribution to the discussion

In their natural environment, plants are part of a rich ecosystem including numerous and diverse microorganisms in the soil. It has been long recognized that some of these microbes, such as mycorrhizal fungi or nitrogen fixing symbiotic bacteria, play important roles in plant performance by improving mineral nutrition. Soil microbes provide significant strength to crop plant growth and development against the soil-born pathogens in agriculture. Initially, the plant releases some root excreted exudates in the soil and root interface that helps migrate soil microorganisms towards the root hairs. Beneficial microorganisms have been shown to play a role in atmospheric nitrogen fixation, organic wastes and residues decomposition, detoxification of pesticides, suppression of plant diseases and soil-borne pathogens, enhancement of nutrient cycling, and production of bioactive compounds such as vitamins, hormones. Beneficial soil microbes perform fundamental functions such as nutrient cycling, breaking down crop residues, and stimulating plant growth. While the role of microbes to maintain soil health and contribute to crop performance is clear, the soil biological component is extremely difficult to observe and manage. Beneficial microbes improve plant growth by enhancing the availability of nutrients, the regulation of phytohormones, and increasing plant tolerance against stresses. PGPM act as biofertilizer, increasing macro and micronutrient availability. By far, the most numerous microbes in soil are bacteria, which have just one cell. Also abundant are fungi, which produce long, slender strings of cells called filaments, or hyphae. The actinomycetes are in-between these two organisms. They are advanced bacteria that can form branches like fungi. Soil microorganisms are responsible for most of the nutrient release from organic matter. When microorganisms decompose organic matter, they use the carbon and nutrients in the organic matter for their own growth. They release excess nutrients into the soil where they can be taken up by plants. Rhizosphere include the use of plant growth-promoting organisms and the suppression of plant diseases and weeds using biocontrol agents. Rhizosphere organisms can also be used to enhance the formation of stable soil aggregates and as bioremediation agents of contaminated soils. The rhizosphere is the soil region influenced by plant roots where complex biological and ecological processes occur. The Rhizosphere Function Integrated Research Platform (RF IRP) investigates the molecular mechanisms of interactions between roots, the soil, and microbes.

"Why?" is an inappropriate question. Plants have not made a decision.