David Doll6 CommentsSeptember 1, 2009Horticulture, Nutrient

Postharvest Care for Almonds

We are mid way through almond harvest. As we finish up shaking our Nonpareils, we need to keep in mind the list of orchard tasks to help maintain crop production for the next year. For almonds, flower bud differentiation takes place during the month of September. This means that next year’s bloom and subsequent crop is being formed in the middle of this year’s harvest. During this time period, there are three important cultural practices that need to be considered by almond growers.They include irrigation, nitrogen fertilization and pruning. 1. Post-harvest irrigation is very important to keep the leaves active and functioning until normal leaf drop, which typically takes place at the end of October, early November. By preventing premature defoliation, we let the tree transition its nutrients from the leaves back to the fruiting spurs. The nutrients that are known to migrate from the leaves to the spurs at the onset of leaf fall are nitrogen, potassium and phosphorous. These nutrients play major roles in bloom development and fruit set. If the orchard does prematurely defoliate due to lack of water, irrigate to encourage re-growth. This may reduce yields in the following year, but yield loss will not be as significant as not watering at all. If watering does not occur, not only will fruit bud differentiation be poor, the orchard will suffer from premature flower drop in late winter. The best advice is to avoid this situation all together by properly managing your water during the harvest period. 2. After irrigation, nitrogen fertilization is the most important cultural practice in an almond orchard. For most of our orchards, split nitrogen applications provide the most efficient use of nitrogen. A post-harvest nitrogen application can be of 20 to 40 pounds per application – dependent upon tree age- totaling no

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David Doll2 CommentsJuly 20, 2009Nutrient

Potassium thiosulfate toxicity on almond

During periods of high heat and the corresponding high evapo-transpiration, several unique orchard problems can occur. Most of these are due to fertigation methods which have been widely adopted to increase fertilizer application efficiency. The benefits of fertigation greatly outweigh most negative impacts, but caution must be used as a simple mis-calculation can cause orchard damage. A field call from a grower in late June demonstrated the potential problems that can occur with fertigation. Observations of yellowing leaves, leaf drop, and death of lower limbs raised concerns by the grower and pest control advisor (PCA), prompting an orchard visit. Initial Observations: Upon arriving to the 11th leaf Sonorra/Nonpareil/Carmel (all on Nemaguard) orchard I noticed excessive leaf drop across all varieties (Picture 1). Most of these leaves were coming from the interior of the canopy, suggesting the possibility of drought stress from improper irrigation scheduling. Lower leaves found on the interior of the canopy were burnt back, with a crispy texture. Leaves closest to the trunk that were completely yellow were beginning to abscise, while leaves on the tips of the branches remained green (Picture 2). This is in contrast to lower limb dieback, which causes soft yellow leaves found on the ends of interior branches. Picture 1: Leaf drop associated with the over-application of potassium thiosulfate. Picture 2: Leaf wilting and “dieback” associated with the over-application of potassium thiosulfate. Note how the interior branches are more affected than the branches on the outside edge of the canopy. Up-Close Observations: Close inspection of the leaves revealed a necrotic tip, or burnt region of the leaf. This leaf was surrounded by a yellow halo (Picture 3). Typically, a yellow halo around a necrotic area would suggest the possibility of almond leaf scorch, but due to the widespread occurrence of the problem, this

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David Doll7 CommentsJuly 13, 2009Nutrient

Mid-July Leaf Sampling for Almonds

Leaf analysis of almond is a useful tool in diagnosing deficiencies, toxicities, and future nutrient needs of the tree. It provides an up to date analysis of the mineral composition of the tree, with desirable concentration of different elements known through extensive University of California research. Reasoning for sampling. As almond trees increase in size, their demand for nutrients also increases. Tree nutrient concentration is dependent upon the growth rate of the crop and the amount of nutrients that have been supplied naturally or through fertilizer. Under certain conditions, plant tissue may become deficient which could limit further growth and crop quality. Depending upon the nutrient and level of deficiency, remediation is possible in the current season, dormant period, or early spring of the following year. Leaf concentrations of major elements (nitrogen, phosphorous, and potassium) can be used along with kernel yield per acre to determine the nutrient budget for the next season. Process of sampling. Sampling should be distributed in a regular pattern across the block, with fully expanded leaves pulled from non-fruiting spurs on branches at least 6 feet high. About 100 leaves are needed for each sample. Leaves should be picked from trees of the same variety, age, rootstock, and soil type. Trees samples should be at least 100 feet apart and 20 trees are needed to ensure accuracy and confidence with the results. Partitioning of larger sampling blocks is advised to determine tree size and yield variability. Label the samples so the sampling location is known, and keep cool until they are sent to an analytical lab. Interpreting the results. Leaf analysis results are recorded either in percentages (%) or parts per million (PPM) of each element in a given weight of dried leaves. The table below contains the critical values for almond leaves sampled in

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David Doll1 CommentJune 4, 2009Nutrient

Zinc Deficiency in Almond

A farm call in early April yielded a problem that proved to be difficult to diagnose due to complicating factors. The orchard was three years old with three varieties planted on nemaguard rootstock: 50% Nonpareil, and two pollinators Monterrey (25%) and Avalon (25%). The soil was loamy sand to sand, very coarse, and a hardpan was present. Tree sites were backhoed before planting to remove the hardpan within the tree site. The previous cropping cycle was almond, but methyl bromide was used to fumigate the soil to kill nematodes, soil pathogens, and weeds. Irrigation is by moveable sprinklers. Initial Observations:Overall the orchard has variable growth overall. Some trees are large, some trees are smaller. Branches in the top of the tree have sparse growth. This growth, however, seems to be limited to one variety – the nonpareil. The symptoms are therefore found in every other row. Photo 1 shows the symptoms of sparse growth in the upper trees of one row. Photo 1: Overview of the orchard showing symptoms. Note that the symptoms are more severe on one row of trees. Up-Close Observations:Sparse tree growth has tufts f leaves that are “bootstrapped.” Leaves are deformed are have not completely formed physiologically. Photos 2 shows a symptomatic tree and photo 3 shows a close up of effected leaves. Photo 2: An individual tree showing symptoms of poor leaf growth and development. Photo 3: An isolated branch showing “bootstrapped” leaves. Possible causes:Glyphosate (Herbicide) damage (Round-up)Dormant applications of chloropyrifos (insecticide) (Lorsban)Zinc Deficiency Diagnosing:The applications of chloropyrifos, a broad spectrum insecticide, can sometimes lead to similar growth responses in almond when applied in the delayed dormant stage. Questioning of the grower yielded that no chloropyrifos was used within the orchard – in fact, he doesn’t use chloropyrifos in any of his orchards. Good –

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