Get to the root of it all with K-Rain® pressure compensating bubblers.  Bubblers are small irrigation heads designed to flood the ground surface around the tree or shrub. The water sinks down into the root ball (a string of roots, including dirt and soil, at the base of the tree), helping to establish a deep root system.  Pressure compensation ensures consistent flow rates over lower pressure ranges and eliminates excess runoff or waste.
This model is adjustable. .1-4.5 GPM.