Why does dirt smell

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Have you ever thought about the feeling when you take off your shoes and dip your feet into a clear rippling stream? We feel something deep in the smell of that fresh-soil, and it is one of those mysteries that takes us back to a place in time.

The smell of soil invokes something so deep that it never really can be described. Can you describe the smell of soil in a forest, freshly tilled field, or in a swamp? Foul odor in the soil is often caused by overwatering, improper drainage, and lack of aeration. Bacterial or fungal contaminations in the soil or the use of under-processed manure can also create an unpleasant smell in soil.

Continue reading to learn about the problems associated with smelly soil and how to resolve them before your plants suffer. These nutrients are made available by the beneficial microorganisms in the soil that break down organic matter into simple nutrients that plants can absorb. These healthy activities within the soil layers give it the natural, earthy smell we are fond of.

Bad-smelling soil is typically indicative of anaerobic soil — soil that lacks oxygen. Overwatering induces soil compaction, reducing the number of air pockets so that the environment becomes anaerobic rather than aerobic.

Anaerobic soil diminishes the activity of healthy microbes and harbors anaerobic bacteria that are harmful to the plants and give off a bad smell. Other than promoting unhealthy bacteria that can kill plant roots, lack of aeration directly affects plant health. Plant respiration requires oxygen from the soil , and without enough oxygen from the air pockets within the soil layers, the plants will lose vigor and, eventually, die.

The bad smell from indoor plants is indicative of one or more problems associated with overly wet soil. In this connection it is worth remembering that the majority of antibiotics we use are produced by streptomycetes.

A Petri dish with colonies of Streptomyces and the structures of the two compounds are shown in the Figure at right.

The smell of these compounds can cause reduced quality of drinking water. Geosmin and MIB also have been found to reduce the quality of fish in freshwater aquacultures as the odours penetrate and accumulate in the fish, thereby lowering the commercial value. The characteristic odor of soil was first investigated by Berthelot in 1. In the structure of the responsible compound geosmin was determined by Gerber 2. It was not until that the pathways for the biosynthesis of these compounds determined.

Bentley and I determined on the basis of isotopic labeling experiments that geosmin is a degraded sesquiterpene and MIB is a methylated monoterpene 3.