The present invention provides for a method for producing an aqueous monoammonium phosphate containing fertilizer solution. The method provides for means to control the temperature of a reaction zone as measured at a reagent entry point and a product exit point. The pH of the reaction is monitored and the reaction is terminated when the reaction mixture has reached a pH of between about 5.5 and about 7.5. The invention further provides for a method of treating crops with a monoammonium phosphate solution having a pH of between 6 and 7.