How do commercial fertilizers impact soil biology?

Answer: The following ATTRA resources should be of interest to you:Sustainable Soil Management https://attra.ncat.org/attra-pub/summaries/summary.php?pub=183Drought Resistant Soilhttps://attra.ncat.org/attra-pub/summaries/summary.php?pub=118Alternative Soil Amendmenthttps://attra.ncat.org/attra-pub/summaries/summary.php?pub=284Sources of Organic Fertilizer and Amendmentshttps://attra.ncat.org/attra-pub/org_fert/In the Sustainable Soil Management publication, Part I includes a section on conventional fertilizers that discusses how several types of fertilizers affect soil. This is mainly through soil compaction and increased acidity and salinity of the soil. Alternative Soil Management discusses non-chemical inputs such as plant and animal by-products, rock and mineral powders, and microbial inoculants.In addition, the Rodale Institute conducted a 22-year experiment on Farming Systems Trial farm in Pennsylvania. The research found statistically significant differences between the organic systems and the conventional system soil carbon levels. In regards to soil biology, using arbuscular mychorrhize (AM) as an indicator of microbial activity and thus overall soil health, the study found the organic systems had a greater population of AM spores and greater colonization of plant roots than the conventional system. The charts and graphs included in the project report, while not specifically answering your question about the effect of chemical fertilizers on soil, provide good visual aids when discussing variability between conventional and organic systems. You can learn more about the project, and read the project report, at http://rodaleinstitute.org/our-work/farming-systems-trial/.Finally, I suggest looking into The Organic Materials Research Institute (OMRI) website at www.omri.org. Certifiers for the National Organic Program utilize OMRI for determining allowable substances for certified organic operations. When looking for alternative products on the market that have a less harmful effect on the environment (e.g., soil biology), I suggest using those with the OMRI seal.