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Slip Plow Tillage Effects in Almonds John P. Edstrom
Expansion of orchard plantings in California has exhausted the supply of prime orchard ground forcing new plantings onto poorer soils. These are often characterized by stratified layers of hardpan, clay or gravel and a shallow topsoil. More powerful diesel tractors have allowed deep subsoil tillage using slip plows to partially mix soil layers creating a more uniform soil profile. Substantial new almond acreage has been established using slip plows at considerable expense -- $300-500/acre. At the same time, improvements in microirrigation performance have allowed growers to supply tree roots with a more optimal and continuous supply of moisture making soil physical characteristics less critical to tree performance. Soil limitations have to some extent been overcome by this technology. Limited almond field tests in the 1970s at the Nickels Soil Lab showed no yield response to various soil modification treatments under single hose drip irrigation. More recent slip plow tests with walnuts also failed to show tree growth, crop yield or quality benefits under double hose drip conditions. The benefits of slip plow soil modification to almond orchard development and crop production have not been adequately evaluated, particularly under current microirrigation practices. This field trial will evaluate the effects of slip plow soil modification on three varieties of almonds, NonPareil, Carmel and Aldrich planted in 1997 on Marine Ave. (M-3). Prior to planting, the area was first leveled and planted with a cover crop. Replicated areas of this 20 ac. planting then received a commercial slip operation on a 10 foot. grid to a depth of 6 feet in a north/south direction and with a diagonal pass (SE-NW), the locally recommended practice. The planting receives irrigation via microsprinklers, trees are planted to either Lovell or peach almond hybrid rootstocks. Tree performance will be evaluated by various measurements, including tree height and trunk size and crop yield and quality. The first commercial harvest is expected in the year 2000. |
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