With respect to spacing, Carmel yields in this trial have been significantly higher on closely planted trees (10’ and 14’ feet down the row), and the increase in cumulative yield ranges more than 1,500 to 2,400 pounds per acre compared to wider spacing. On the other hand, there has been no obvious cumulative yield advantage to close planting of the Nonpareil variety, which is a larger tree than Carmel. Cumulative yield represents the total of annual yields from fourth leaf through 12th leaf, except for one year in which yield was not recorded, for a total of eight harvests.

In most cases, tree spacing has a greater effect on tree failure and breakage than pruning technique. More-closely spaced trees are less likely to have scaffold breakage, which may ultimately lead to longer orchard life, though we won’t know for sure until we look at this trial orchard as it progresses into the latter portion of its lifetime.

Advantages of Closer Spacing

Closer spacing, which produces shorter trees, may also provide better spray coverage and a better shake at harvest, providing fewer mummies and less shaker injury. Trees that are too closely spaced, however, can create problems related to access and worker safety. Duncan said a general rule, on good ground, is to plant trees in the neighborhood of 21- or 22-foot row spacing with 14 or 16 feet down the row to optimize light interception without creating problems. Weaker ground might benefit from closer spacing down the row.

With respect to pruning, Duncan notes that in most years, Nonpareil yields are statistically similar in conventionally pruned, minimally pruned and non-pruned trees. Cumulatively un-pruned Nonpareil trees have yielded 1,330 pounds/acre more than conventional pruning, but this is not statistically significant.  In contrast, cumulative Carmel yields in minimally trained and pruned trees is significantly higher by 1,500 to 2,400 pounds/acre compared to conventional programs. However, young trees trained to multiple scaffolds are more prone to scaffold failure and tree blow over, particularly in wider spacings. Taking pruning costs and yields into account, Duncan estimates that conventional training and pruning would have reduced gross income in his trial orchard under a commercial setting by $4,800 per acre.

Pruning/Training Strategies

Duncan concluded that a good compromise to develop tree structure and minimize pruning costs is to train trees to three scaffolds the first year, prune trees for open centers the next year and leave trees unpruned afterwards, except where needed for breakage, worker safety other factors.

We will continue to learn more about orchard pruning and tree spacing and their impacts on efficient almond production as this trial orchard progresses into the later part of its productive life. For now, consecutive years of consistent results in this trial, which confirms results from previous trials, are offering promising recommendations for growers for planting, training and pruning young orchards.

To view the 2011 season results and detailed data from this trial,  go to www.AlmondBoard.com/FarmPress28. Roger Duncan can be reached at the UC Cooperative Extension office in Stanislaus County at (209) 525-6800 or raduncan@ucdavis.edu.