I have been using fish bone meal for over 20 years. We have fields that have only had fish bone meal for the duration of that time. Soil testing and tissue testing has not demonstrated any depreciation using this practice. The production has been very adequate. I have organic hay fields that are also only getting applications of bone meal and production has not diminished. Nutrient testing of the hay itself through the first three years of this project indicates a slight improvement in the TDN which suggests to me that this practice may be sustainable.