http://www.puyallup.wsu.edu/~Linda%2...ycorrhizae.pdf
by Dr. Linda Chalker-Scott, Washington State University.
"When the soil chemistry is significantly changed by the addition of pollutants or contaminants including salts, lime, heavy metals, and fungicides, many mycorrhizal species are unable to function. But by far the most damaging to mycorrhizal health is excessive fertilizer application, especially of those containing phosphate; this includes composted manure and many soilless potting mixes."
"Stop using soluble phosphate fertilizer! If soil tests show you’ve got too much phosphate already, research has found that conservative additions of nitrogen fertilizer or organic material can increase mycorrhizal infectivity."
"Yet numerous studies have demonstrated that phosphate fertilizer is deadly to mycorrhizal associations."
"Healthy soils naturally contain indigenous mycorrhizae. Adding packaged mycorrhizae to such soils is a waste of money and resources."