High rates of fertilizers, especially inorganic and soluble phosphorus fertilizers, can hinder the formation of mycorrhizae.
Mycorrhizal fungi are sensitive to soil phosphorus levels because if there is already a surplus of phosphorous available to the plant, mycorrhizae have less reason to perform. High phosphorus contents will therefore also cause the mycorrhizae to be delayed or not perform other important duties such as increasing water and other nutrient uptake into the plant. Available phosphorus levels should be kept in the low to moderate range per soil type, especially at the time of mycorrhizal inoculation (when the mycorrhizae attach to the plant roots).
However, organic forms of fertilizers have been shown to have less inhibitory effects on mycorrhizae than inorganic, soluble fertilizers. The use of organic fertilizers, kelp, humic acids and other carbon sources have been shown to be suitable when combined with mycorrhizal fungi. Composts are mostly compatible with mycorrhizal fungi, but caution should be taken as some compost sources may have high salt or other nutrient content that can inhibit Trifecta Myco Supreme.