What is the best deep-root feeding technique. have a friend with an 18 gpm Bean Pump and a deep-root feed gun. What pressure is correct for deep-root feeding? How far apart should the injections be made for azaleas, arorvitaes, and larger evergreens? What is the best liquid fertilizer to use, and at what cost? He is leary of a water-soluble granule because of agitation and clogging issues. Finally, roughly how many gallons per working day would he be using? Thanks!