Sustaining Yields in Almond Hedgerows

Long term yields from this 19 year old hedgerow continue to be monitored. Production for 1998 can be seen in Table I, which shows substantial yields continue to be produced in this tightly spaced block. Yield declined somewhat this year in the Unpruned Hedge compared to other 7' x 22' spacing treatments. We have not found this difference before since we began collecting data in 1981. Lack of pruning for 17 years did not depress yield until this season (see table). Data show that the Unpruned tree yield is close to the typically low yielding Temporary Hedge. Production from the Two-Scaffold and Permanent Hedge treatments (7' x 22') continues to exceed the Temporary Hedge (14' x 22') where alternate trees were removed in 1986. These 14' x 22' trees have never replaced the fruitwood lost from past alternate tree removal. Accumulative yields continue to favor the permanently spaced trees. The alternate tree removal scheme has resulted in an accumulative production loss of 7000 lb./Ac.

TABLE I.

The continued low yield from the Temporary Hedge treatment suggests that alternate tree removal may be a questionable practice, even in tightly spaced hedgerow almonds. However, the peculiarities of this test site should be considered when interpreting these yield figures. This two cultivar planting (Nonpareil and Price) has developed on Class II/III gravelly loam soils under a single hose drip irrigation system. These limitations have resulted in a restricted root zone and have possibly reduced or delayed the growth of permanent trees into their expanded space (from 7' spacing to 14' spacing). Additionally, the adjacent tightly spaced pollenizer rows created heavily shaded conditions, further inhibiting fruitwood regrowth on the 14' x 22' spaced Nonpareil plots. Given more favorable "regrowth" conditions, this hedge removal treatment may have regained high productivity and proven, over time, to be an economically viable system. Certainly under our conditions with nearly 7000 lbs. in accumulated lost production, this is not an advisable hedge management strategy. (A UC trial in Butte County on Class I soil also resulted in a major crop loss from an alternate tree removal strategy.)

At this site, close spaced almond hedgerows appear to be quite forgiving with respect to pruning/training methods. Accumulative yields show no difference between trees pruned to Two-Scaffold, Permanent (3-scaffold) or left Unpruned after scaffolds established. Loss of lower fruitwood continues in this planting, especially in the unpruned trees. Apparently, fruiting capacity in the upper canopy has compensated for this loss and yields have been sustained.

As the trees age, however, increasingly more crop remains high in the trees after harvest, especially in the unpruned trees. The inter-twined branches may not receive sufficient force from the shaker for complete crop removal. Mummy removal and navel orangeworm could become more of a problem but as yet this has not occurred.

We know of no other experimental data that shows unpruned almonds to produce yields equal to standard pruned trees over this length of time. Excessive overgrowth and shading has not occurred in the unpruned trees under these low vigor conditions created by tree crowding and soil/root limitations. A new study using a modified version of minimal pruning is currently underway at Nickels to better our understanding. However, the sustained productivity in this test of the Unpruned Hedge merits consideration when planning a pruning strategy for all almond plantings in addition to hedgerows. Our savings, in pruning costs over the span of this trial have been considerable.

Leaf/Year

1/ Accumulative Yields Since 1984.