Healthy soil contains millions of fungi and bacteria many of which are beneficial to plant growth. It is often said that the salts in synthetic fertilizers kill these microbes resulting in sterile soil. The research does not support this claim. In one study researchers looked at fungal and bacterial populations in soil before and after an application of synthetic fertilizer, an application of Organic fertilizer and in a control plot to which nothing but water was applied. In the field treated with synthetic fertilizer the bacterial population remained unchanged while the population of fungi increased as compared to the untreated control plot. In the field treated with Organic fertilizer there was a slight increase in both fungi and bacteria. A second long term study found no significant detriment to microbial populations in soil treated with synthetic nitrogen over ten years.
