A method for using a new liquid fertilizer comprising potassium derived from potassium phosphate, organic sources of potassium, animal manure, carboxylic acid salts of potassium, potassium silicate and combinations thereof, and having a slightly alkaline pH and relatively low salt index compared to other sources of potassium for liquid fertilizer products is disclosed. The fertilizer composition may further comprise additives such as sulfur, zinc, boron, calcium, manganese, iron, copper, cobalt, magnesium, or a combination thereof.