All fertilizers can cause injury to plants when applied in excess.
Unless diluted with water, most liquids of comparable formulation are as toxic as dry fertilizers. Liquid fertilizers made specifically for application to the foliage of plants, to seed or to household plants should have a low salt index value. Double nutrient salts, such as ammonium phosphate and monopotassium phosphate, help keep the salt index down. This information is for educational purposes only. References to commercial products or trade names does not imply endorsement by MSU Extension or bias against those not mentioned.