Fertilizing First Year Almond Trees: Major Nutrients

Determining fertilizer needs for newly planted orchards is challenging. This is due to the desire to grow the trees as rapid as possible while considering the risk of uptake burn and irrigation system inefficiencies. To determine the optimal fertilizer plan, the amount and type of nitrogen and other nutrients need to be considered.

The first fertilization for first year almond trees should occur after 8-12" of growth.

Nitrogen: Ratestudies conducted in California have found that tree growth seems to peak with 3-4ounces of nitrogen application per tree. This is based on three differentstudies – one located near Arbuckle, CA and the other two in Merced County. Withinthe most recent studies in Merced County, applications were made every threeweeks from April through July for a total of six applications. A total of 0, 1,2, 4, and 6 ounces of actual nitrogen was applied during this period toreplicated plots using a NPK blended fertilizer.

The source of nitrogen did not create a difference in trunkcaliper in the multiple studies within Merced County. Very simply stated, “nitrogenis nitrogen.” There are benefits, however, to the various nutrients that arewithin fertilizers. If soil levels of phosphorous or potassium are low,utilizing an NPK blend would provide an addition of these major nutrients. Thesame could be said about calcium-containing fertilizers. If these nutrients areat sufficient levels for plant growth, however, there is minimal benefit fromadding additional amounts.

The effect of different nitrogen fertilizer rates on the change of first year almond trunk diamater. The nitrogen rate was applied as 6 split-applications over a four month period. The 120 controlled release was a single application.

Potassium andPhosphorous: Within California conditions, phosphorous (P) and potassium(K) do not appear to be the limiting factor with most soils. The two triallocations within Merced County were located on sandy soil and found no increasein growth from the inclusion of P and K within the fertilizer programs. Thisdoes not mean that these major nutrients are not important, rather that manysoils contain adequate levels of P and K to support first year growth.

Many soils world-wide are deficient in these major nutrients.Due to these variations, pre-plant soil tests should be conducted to determinethe amount of P and K needed. Amending the soil pre-plant provides an opportunityto apply lower cost fertilizers at higher rates without impacting the plant. Ifsoil sufficiency levels are variable or unclear, adding additional P and Kwithin the fertilizer program does not appear to negatively impact tree growthand, depending on soil type, may build a reserve for future year’s use.

The effect of 6 different fertilizers on first year almond growth. There were no differences across treatments.

Application method:This study did not account for the inefficiencies of fertilizing through thewater. In these situations, water containing fertilizer may be applied outsideof the rootzone of the tree. In these situations, it may be needed to increasethe amount of nitrogen applied to make sure that the proper rate is beingapplied to the root zone. In any single application, however, the rate ofnitrogen should not exceed 1 ounce of actual nitrogen for the first year ofgrowth. Applying less nitrogen more frequently will reduce the risk of uptake toxicity.

Use of granular fertilizers will require water to move thenitrogen into the rootzone. This can be accomplished using micro-sprinklerirrigation or rain. Use of granular fertilizers with drip systems can createcomplications in moving the material into the rootzone. If drip is being used withinthe orchard, and there are no other options for fertilizing, apply the materialwithin the wetting pattern of the irrigation system.

Controlled release fertilizer was also utilized in theMerced study. It found that a large, single application providing the entireseason’s fertilizer needs can be made. This single application provided thesame growth response as multiple applications of the conventional blendedfertilizer. Application costs, however, were reduced significantly, offsettingthe increased cost of the fertilizer. This may provide a reduced laboralternative for growers who wish to apply fertilizer by hand.

Fertilizer rate. Firstyear fertilizer needs are described as rate per tree. This will allow the site-specificamount to be determined as higher densities will require more nitrogen todevelop the orchard. For example, at one ounce of nitrogen per tree, this wouldequal 8 and 10 pounds of nitrogen per acre for a 128 and 160 tree/acreplanting, respectively. Inefficiencies of nitrogen and the application methodneed to be added to this amount to reach the application total.

Application timing.The first application of nitrogen to young trees should occur when there is8-12 inches of growth. Fertilizing too soon may lead to tree damage by uptakeand increased salt concentrations in the rootzone. Fertilizing too late maylead to lost growth for the season. Once the first application has beenproperly timed, application can continue on an every three-to-four-week basis,with the last application being applied in late summer. Multiple, small applicationswill have a greater efficiency than fewer, larger applications.