MICROIRRIGATION OF ALMONDS

Abstract

A large scale field trial was conducted at the Nickels Soils Laboratory in the Sacramento Valley of California to evaluate three microirrigation systems; Surface Drip, Subsurface Drip (SDI) and Micro-jet on four cultivars of almonds, ’Nonpareil’, ’Butte’, ’Carmel’ and ‘Monterey’ (Prunus dulcis [Mill.] D.A.Webb.). Ten years of evaluation has shown that high commercial yields (2500 kg/ha) of high quality almonds can be produced using all three types of microirrigation. Micro-jet irrigated trees tended to outyield drip irrigated trees by about 10% in some years for some cultivars. No consistent yield differences were found. Tree growth under SDI, as measured by trunk size, was comparable to surface drip irrigation but slightly smaller than micro-jet irrigated trees when equal amounts of irrigation water were applied. Root development was more extensive under micro-jet irrigated trees compared to both single hose drip systems. No significant root intrusion was found in trifluralin impregnated SDI emitters but standard SDI emitters were plugged by almond root growth after five years of field operation. Minor root pinching was evident on the buried flexible supply hoses in both SDI and surface drip systems. Micro-jet irrigation increased system maintenance and resulted in higher herbicide use to control vegetation on the orchard floor.