This article talks about commercial chickens, but included the following info on baking soda: http://www.bookrags.com/tandf/chickens-layer-nutrition-tf/ The substitution of sodium biocarbonate (NaHCO3) for a portion of the salt (NaCl) is often beneficial for improving eggshell strength. Many experiments were conducted to measure the potential benefits of this practice. It was assumed that the CO3 from the NaHCO3 was useful in deposition of calcium (CaCO3) in the eggshell. However, it was found that sodium reduced the plasma phosphorus and was responsible for improving eggshells. This article is long because it includes info on gardening, and it talks about using baking soda to inhibit fungal growth. Not kill a fungus, but keep it from producing spores. http://www.puyallup.wsu.edu/~Linda ...ths_files/Myths/magazine pdfs/Baking soda.pdf It cites studies and says that baking soda is not effective against aspergillus fungus, HOWEVER, the study I saw showed that baking soda was as effective at inhibiting growth as the other salts listed once it was at a high enough concentration. This was measured in mols, so in normal measures worked out to 1/8 tsp to a quart of water. Using oil, according to the above article, made the baking soda more effective. Aspergillus is a bad fungus that likes grains and hay, and can colonize in humans who have weakened immune systems.