Drip was installed in April 1994, and since then Nichols has seen reduced conditions on the drip blocks. Those same block have increased edible in-shell nut yields this past season by 10 percent over rows that remained on flood irrigation. Starling said that while increased yields are not dramatic, the ranch is confident enough in results to convert the entire 80-acre block to drip this year. Nichols Farms shanked in thick-wall drip tubing at a depth of about 28 inches and 5 feet away from the tree row. If you wet the surface it defeats the primary purpose of having buried drip' David Goldhamer, UC Water Management Specialist Starling said in a report last year that he would have used shanks that were 6 inches longer to compensate for the uplift of the compacted soil and help work through impacted roots.
Roots can play a major obstacle in converting a mature orchard to underground drip.
Nichols used Geoflow drip tubing that has Treflan herbicide incorporated into the emitters to help prevent root intrusion, but roots continued to create a challenge. Excessive root pruning from the shanking affected canopy growth during the installation season. With initial impacts to canopy and roots, it appears conversion should be done during an off year in the alternate-bearing cycle. The pump was a 100-horsepower turbine moving 1,400 gallons per minute. Starling said he would bury the drip tubing farther down in future applications to keep water from seeping to the surface.