Hydraulic technology, used to wash away the soil from the roots of growing almond trees, has yielded surprises for a UC Davis nut tree expert. Conventional wisdom has held that water stress encouraged trees to establish root systems that are deeper than those of well-watered trees. But during a recent experimental orchard demonstration, using a fire hose and large sewage-sludge truck to wash away the soil from the tree roots and remove excess mud and water, pomology associate professor Ken Shackel found that the poorly irrigated trees had sparse, unhealthy root systems that were no deeper than those of the well-watered trees. For years, the effects of different levels of irrigation on the tree roots have remained hidden beneath the soil. Some growers use backhoes to dig away the dirt, but this method is a rather crude approach to examining the tree's delicate root zone, according to Shackel. He hopes that use of the high-powered hydraulic technology will provide a better understanding of the basic physiology of tree roots and give growers the information needed to make appropriate irrigation decisions.