![]() In addition, almond trees need nutrients for the growth of perennial parts, such as roots, trunk and branches. In a four-year study carried out at multiple sites, Brown and coworkers found that the amount of N removed at harvest with hulls, shells, leaves, debris, and kernels ranges from 50 to 75 lbs/1000 lbs of kernels, averaging 68 lbs/1000 lbs of kernels. Therefore, careful irrigation management is important to prevent nitrate from leaching below the root zone. However, nitrate is very mobile and may move quickly below the still small root zone of the young trees. In early spring, when the soil is still cooler, nitrate based fertilizers may be more efficient than urea or ammonia fertilizers. To ensure sufficient P and K availability, a granular NPK fertilizer may be used for the first application of the year. To second-leaf trees, liquid fertilizers, such as UN-32 or CAN 17 can be applied. Blends, such as 15-15-15 or 12-12-12 also supply K and P. Therefore, as a measure of caution, granular fertilizers should be used for first-leaf trees. The risk of root burn is increased with liquid fertilizers, as their application may result in high concentrations in the root zone. Once trees produce nuts, the optimal N application rate depends highly on the yield level (see Soil Applied N). Meyer suggested the following annual N rates for drip-irrigated trees on non-fertile soils: Ī total annual application of up to 4 ounces/tree (20-35 lbs/acre) to first-leaf trees may increase growth, while higher rates have no benefits. Under these conditions, lowering the rates per application and instead increasing the number of applications reduces the risk of leaf burn. The rate should also be reduced for stunted trees and in hot weather when the trees take up a lot of water. For the first application to first leaf trees, even less than one ounce of N should be applied. One ounce of N per tree corresponds to 5-9 lbs N/acre, depending on tree density. A good rule is to apply no more than one ounce of N per tree per year of growth with a single application. Nitrogen fertilizers need to be applied with care to young trees, as high N concentrations in soil solution may burn the roots. Contact your local farm advisor for more information. ![]() The almond fertilization model suggests reducing the N application rate by 14 lbs/acre for each 0.1% increase in leaf N concentration above 2.3%. If leaf N concentrations are well above the sufficiency level, the post-harvest application rate should be reduced, but not eliminated. ![]() However, by maintaining an orchard at 2.5% field average, the majority of the trees will most certainly be over-fertilized (Brown, personal communication). For this reason it is important to divide an orchard into uniform blocks with respect to soil type, age of trees, variety, location and management and sample each block separately.Ĭritical nutrient levels in almond leaves sampled in July. In a heterogeneous orchard, some trees may be deficient even when the leaf N concentration of the orchard is well above 2%. In contrast, the results from leaf analyses refer to the average of all trees sampled in the orchard with some trees being below and others above the average. Therefore, the critical values refer to a tree. This may be due to the fact that most critical values for almonds have been determined on the basis of visual symptoms. However, in some cases almond yields have been found to be reduced with leaf N concentrations of 2.2 to 2.3%. A leaf N concentration of 2.2% is generally adequate (see Table). With measured or predicted July leaf N concentrations below 2%, almond trees are considered N deficient, and yield may be reduced by 20% or more. The information together with the laboratory analyses and yield data can help with future fertility planning. It's good practice to bring a notepad along to record tree vigor in the different blocks. ![]() Keep the leaves cool and send or deliver the samples to the lab as quickly as possible.įor spring samples, ask for a full nutrient analysis (N, P, K, B, Ca, Zn, Cu, Fe, Mg, Mn, S).įor samples taken in spring, predict the July leaf N concentrations using the leaf N model. Place the samples in paper bags (use separate bags for each block) and label the bags. In each tree collect leaves around the canopy from at least 8 well exposed spurs located at a height of 5 to 7 feet. Avoid collecting from sick, injured or stunted trees.Ĭollect leaves from 28 trees, which are at least 30 yards apart. A separate sample should be submitted for analysis from each block. The following collection procedure has been recommended for a representative leaf sample :ĭivide the orchard into uniform blocks of trees with respect to soil type, age of trees, variety, location and management.
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