David Doll, UCCE Farm Advisor, Merced County and Carolyn DeBuse, UCCE Farm Advisor, Yolo and Solano counties: editors

A fertilization program is typically designed for a specific crop and orchard. At establishment, the soil is sampled for existing available nutrients. After the application program is initiated, leaf analysis in mid-July is used to monitor it. Growers are advised to keep long-term records of their application program for an orchard, including applications of fertilizer and soil amendments, results of leaf sampling, and yield. These records provide information for decision-making in orchard management.

Application Program: Nutrients are best applied to the root zone when the tree can use it efficiently and in amounts that will not be leached past the root zone. Apply the first application of fertilizer during spring when rapid growth occurs followed by smaller amounts throughout the growing season and post harvest. Nutrient demand is determined by crop demand — a heavy crop year removes more nutrients from the system than a light crop year. General fertilization schedules for nitrogen (N), potassium (K), boron (B), and zinc (Zn) below should be modified for extremes in soil type. On sandy soils, nitrogen applications should be made more frequently at smaller doses, while in heavy soils, monthly applications can be made. Interactive models (link) have been developed to customize a fertilization program to a specific site. The schedules below provide a generic fertilization schedule, applicable for mature orchards in most almond growing areas in California.

Table 1. Fertilization schedule for almond (lbs/acre)

Leaf Sampling for Nutrients: This is an extremely useful tool to measure the adequacy of the fertilization program and to diagnose nutrient deficiencies and toxicities. Annual leaf sampling is advised. Samples are analyzed at commercial labs. To provide an acceptable sample:

• collect the sample from late July through mid-August
• sample non-fruiting spurs, 6 ft. (1.8 m) from the ground
• choose fully expanded sub-terminal leaflets
• collect 4 - 10 leaflets per tree
• sample 10 - 20 trees/orchard block
• do not include leaflets that have received in-season nutrients sprays
• deliver the sample to the lab within 24 hours

Critical Values (CV) are minimum concentrations for adequate tree growth and yield. Suggested Range also refers to the concentration for optimal growth. These values are part of the leaf analysis report. CV and Suggested Range values for essential nutrients are provided in the Table 2 below.

Table 2. Nutrient concentrations in August leaf samples

Nutrient Deficiencies: For symptoms and susceptibilities please see Table 4 on the pistachio nutrients and fertilization page. The Almond Toxicities and Deficiencies photos are also helpful for identifying symptoms.

Source: Almond Production Manual (1996), UC Division of Agriculture and Natural Resources.

David Doll, UCCE Farm Advisor, Merced County, Carolyn DeBuse, UCCE Farm Advisor, Yolo and Solano counties, and Bob Beede, UCCE Farm Advisor, Kern County: editors

Typical Types of Pruning Cuts

• Thinning cuts remove limbs by severing at point of origin from parent limb. They are used to open up and thin out canopies and control tree height. Thinning cuts, by reducing wood, reduce competition for nutrients and result in overall invigoration of remaining wood.
• Heading cuts remove a portion of an existing limb. The removal of terminal buds temporarily releases remaining buds from apical dominance. Because buds are concentrated near shoot tips, heading cuts remove a relatively large number of potential growing points and thus stimulate the remaining buds. Removal of only the tips means that the carbohydrates stored in the basal portion of the shoots are still available to growing points.

Training

The First Year (Training video¹ Year one pruning)

• Planting: Nursery-grown rootstocks, approx. 1 year old, are planted from late spring to early summer. These newly planted trees should be pruned at about 36 inches from the ground. Plants should be immediately staked and irrigated. Subsequently, a program of regular fertilization and irrigation is begun when trees begin to grow. 
• Staking: Note that stakes are manually placed next to the root ball, not into it. Use 2 x 2 in. stakes, 6 ft. long, placed 12 - 18 in. into the soil.  Locate the stake so the tree blows into the stake with the prevailing wind.
• Field Budding: Almond scions are typically budded to rootstock in early summer, but may continue as long as the rootstock bark slips. T-budding it the most common.  Bud the tree at a height of 24 -28 inches. At harvest, the shaker attaches at 19 - 22 in., and the bud should be placed above this zone.
• First Dormant Season: This first pruning is critical in determining the ultimate shape and performance of the tree. Now is the time to select the three permanent primary scaffolds, or main limbs that will form the framework. Once these primary scaffolds are determined, remove all other limbs that originate from the trunk and all growth below the lowest primary limb. Growers use one of three methods for pruning the remaining lateral branches: long pruning, short pruning, or intermediate pruning.

The Second Year (Training video¹ Year Two pruning) 
Trees will typically have several growing laterals destined to become secondary scaffolds – two each should be selected per primary limb. A secondary scaffold is a vigorous, upright lateral that forms a “Y” off a primary limb.

• Second Dormant Season: Remove all but two of the secondary lateral branches. These secondary branches should be evenly spaced around the canopy and have an upward and outward extension. They do not need to be headed unless excessively long.
• Other than pruning limbs that compete with the selected secondaries, removing badly crossing branches, and cutting an excess of internal water sprouts, additional limb removal is usually unnecessary.

Years 3 - 4 
Trees now have primaries, branching to secondaries, branching to tertiaries. Let these grow.

• Third and Fourth Dormant Season Pruning: Implement the pruning strategies applied in the second year dormant pruning at one or two levels higher in the tree.
• The key is to fill the upper periphery of the canopy while maintaining a somewhat open center that allows sunlight to penetrate.

Years 5+  Pruning Mature Bearing Trees A systematic pruning program encourages steady production. 
Mature almond trees are pruned to:

• Invigorate and Renew Fruitwood: Fruiting spurs generally live about 5 years. Pruning this old, minimally productive wood stimulates renewal of fruiting wood.
• Manage Light Distribution: The ability of light to penetrate the canopy maintains productive fruitwood in the lower part of the tree.
• Reduce Alternate Bearing: If trees are in an alternate bearing cycle, pruning more heavily in advance of a heavy crop year will help balance the cycle.
• Control Tree Size: Mature trees are pruned to facilitate spray coverage, nut removal, and light penetration, and to restructure the trees to allow scaffold shaking.

¹Produced by: EU Perennial Horticultural Dev. Project

Source: Almond Production Manual (1996), UC Division of Agriculture and Natural Resources.