    |
|
|
|
|
Pruning High Density
Almonds John Edstrom Bill Krueger
Almond tree training and pruning practices haven't changed all that much for decades. Traditional concepts stressed careful selection of primary and secondary branches to develop a strong evenly spaced framework capable of supporting heavy crops. Large trees developed during the 30-40 year life span especially at wide spacings. Yearly pruning was needed on old trees to increase light into the tall canopies, stimulate growth and replace unproductive fruitwood (to keep trees "forever young"). Considerable time, equipment (pruning towers) and expense ($100-200/ac) is required to complete this type of pruning operation (if the weather cooperated). However, today tree densities have increased to 100+ trees/ac, twice what they used to be and many new orchards are planted on weaker ground. Both trends result in smaller sized trees which don't need to support such heavy weight (crop) per tree to be productive per acre. So, scaffold number, position, orientation, or strength is not as critical without large expansive canopies. Younger trees, typical of more tightly spaced orchards are inherently more vigorous so yearly pruning is not as critical to maintain vigor . Shorter statured trees naturally allow more light to penetrate deeper into the canopy promoting fruit bud formation without much pruning to "open up the centers". Big cuts may not be necessary. Improvements in water management using microirrigation bring orchards into production fast (and impart vigor to older trees). Good yields are obtained in the 4th year compared to year 6 to 8 as in the past. Many growers don't expect today's almond orchards to last longer than 20 years. We will want to replace blocks at a younger age simply to exploit new superior technology. These factors should all be considered when devising a profitable training/pruning strategy for today's high density orchards. The objective of this field trial is to evaluate various tree training/pruning methods which promote maximum early production while maintaining long term orchard yield in tightly spaced almonds. Four training systems were selected using 4
replicates of 33 trees on Nonpareil, Carmel, Monterey and Aldrich:
Progress Trunk size as measured 2 years after planting showed a slight increase for trees with temporary limbs. Trees from all other methods were equal in size. During April, 1998, strong northerly winds damaged most local 2-3 year old orchards. Trees in the test with temporary scaffold training experienced no limb breakage, while all other training methods resulted in significant loss of primary limbs. Temporary Scaffold Method Nonpareil scaffolds developed satisfactorily the first year even with competition from the temporary limbs. Some removal of upright growth on temp limbs was needed to deinvigorate these branches and a few temp scaffolds needed complete removal to insure permanent scaffold and secondary limb development. During the 2nd year more competition from temp limbs occurred. Numerous upright branches interfered with permanent limbs and may have reduced there size. These trees have very large canopies. (Many problems are expected to develop with this system. Avoiding one problem involves planting large trees to allow heading high at 40 inches. This would give enough room on the trunk for both permanent scaffold development on top and temporary scaffold positioning while still leaving space for the shaker head to clamp below pruning wounds left after temp limb removal.) Carmel and Monterey varieties were more difficult to train using the temp scaffold idea. More flattening and removal of temp limbs was necessary to maintain the dominance of permanent primary limbs. These two varieties, now at the end of the 3rd leaf, look like short bushes. The upright growth habit of the Aldrich variety proved incompatible with the temp scaffold technique. The temp limbs competed too severely with the permanent scaffolds and were completely removed at the 2nd dormant pruning. Mechanically Hedged Trees of all 4 varieties were topped removing 2/3rd of past seasons top shoot growth with the intention of developing a shorter and more compact, dense tree. More was removed from the taller Nonpareil and Aldrich plots than the Monterey and Carmels. Looking at these trees now, the temptation is great to do some dormant hand pruning to thin excessive branches and open the centers. However, we plan to "bite the bullet" and watch these develop.
|
|
Send mail to jlschmierer@ucdavis.edu with questions or comments about this web site.
|
