Almond Nutrients & Fertilization
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)
|Nutrient||Date (lbs/acre)||Date (lbs/acre)||Date (lbs/acre)||Total lbs/acre for year|
|N||Mid-March (85)||Early May (90)||Postharvest (75)||250|
|K||May (25)||June (50)||Postharvest (75)||150|
|B||Dormant (2 - 5)||2-5|
|Zn||Dormant - Broadcast (10-15)||Postharvest - Foliar (10-15 lbs/100 gallon)||10-15|
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||Critical Value (CV)||Suggested Range|
|Nitrogen (N)||2.0%||2.2 - 2.5%|
|Phosphorus (P)||0.14%||0.1 - 0.3%|
|Potassium (K)||1.0%||1.4 - 2.0%|
|Calcium (Ca)||1.9%||2.0 - 4.0%|
|Magnesium (Mg)||0.25%||0.6 - 1.2%|
|Manganese (Mn)||20 ppm||30 - 80 ppm|
|Boron (B)||80 ppm||80 - 150 ppm|
|Zinc (Zn)||15 ppm||15 - 20 ppm|
|Copper (Cu)||4 ppm||6 - 10 ppm|
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.