What is going on is the well pressure is keeping up for a short time and the pressure tank can not keep up with the flow. Unfortunately there is little you can do other than change the pump size in your well which can get expensive. You must first figure out how many gallons per minute your well is putting out then take a pressure reading on your well as your irrigation is running. Most wells have a 40/60 psi pressure switch which you could adjust the low side of the pressure switch up a little ...
