David Doll4 CommentsDecember 5, 2021Nutrient

Managing low hull boron: late season corrective measures before next year’s bloom.

Recently, boron hull analysis was provided by an almond farmer. The analysis consisted of two samples from his ~300 acre (~125 ha) third-year farm. The results were 62 and 84 ppm from the cultivars Nonpareil and Monterey, respectively. Both values were under our targeted hull analysis of 95-105 ppm, with the Nonpareil sample also being deficient (<80 ppm). This orchard has followed a boron program since the beginning of its development. Initial soil samples had indicated very low boron (<0.2 ppm, undetectable), high soil pH (7.7-8.2), and a clay loam texture across the operation. Prior to planting, soil sulfur was applied to lower the pH, as well as diammonium phosphate and potassium sulfate. After establishment, boron in the form of disodium octoborate tetrahydrate (20.5% boron, tradename: Solubor®) was applied at 5 lbs/acre (~5.5 kg/ha) twice a year (spring and fall) through the drip system. A foliar application of sodium tetraborate was also made at 1.8 lbs/acre (2 kg/ha) in the fall after the second year of growth and pink bud. As a result, soil boron levels have improved slightly, with some detectable boron within the wetting pattern. Boron deficiency can greatly impact almond yields. Boron improves pollen tube germination and growth, helping to increase the number of flowers fertilized during pollination. Being deficient in boron can lead to very low nut set and yield, and a willowy- look to the trees. More on this can be found in previous articles (here and here are a few). Given that the most recent hull samples indicate deficiency or borderline deficiency in boron, a new plan has been developed. This plan will utilize additional foliar sprays and soil boron applications and will be applied through dormancy and into the next year. The grower has already applied 5 lbs/acre (5.5 kg/ha) and 2 lbs/acre

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David Doll0 commentsOctober 30, 2021Nutrient

Major Nutrient Fertilizers: Thoughts to Reduce Operational Costs without Impacting Productivity

Increasing input prices are being observed across the farming sector. Fertilizer prices have increased due to demand, government regulations, weather, trade issues, and energy prices. Prices are some of the highest in a decade, with nitrogen and phosphate fertilizer prices nearly double what they were in 2020. Within almonds, maintaining the proper fertilizer status within the tree is important to maintain yields. Research projects have determined how much of each major nutrient is needed for the tree to maximally produce. These studies first occurred in the early 1990’s and were re-done between 2008-2013. In summary, the projects concluded that for every 1000 lbs of almond kernels harvested, 68 lbs of nitrogen, 92 lbs of K2O, and ~12 lbs of P2O5 are removed from the orchard. These nutrients need to be re-applied to maintain yields. Leaf tissue, soil samples and other in-season assays and monitoring can be used to determine if optimal levels have been achieved. If optimal levels are present, input levels should only match crop demand, while if excess amounts are present, applications can be reduced. These adjustments will help reduce waste, run-off, and leaching.   More on this here and here. Nitrogen (N) usage and uptake occurs when there are leaves on the tree. As such, N applications should only occur in-season. When applying N, more than 68 lbs/1000 kernel pounds of production is applied – typically around 85 lbs/1000 kernel pounds of production. This inefficiency of about 20-30% considers the N lost to NOx conversion, run-off, and leaching. Fortunately, I have observed many orchards much more efficient than this. These orchards have been able to reduce N amounts applied based on the observation of high N within leaf samples.  They have found that maintaining N levels at 2.5% in mid-July allow for the maintenance of high yields (>3000

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David Doll2 CommentsSeptember 26, 2021Horticulture

Reduced Kernel Size – 2021 Harvest

There have been several reports of smaller than expected nut size for the 2021 harvest. Nonpareil sizes have been reported to be in the range of 28-30/ounce rather than the typical 24/25 nuts per ounce. Many have suggested that this is due to drought induced water shortages, but this has occurred even on fully irrigated orchards. Water stress has played a role, but earlier conditions of the season should also be considered. Nut weight is influenced by a few different factors. These include: Reduced number of cells; Reduced cell size; Reduced cell weight. Cell number is mostly impacted by temperatures that occur during cell division, which occurs early in the season, typically within 6-8 weeks following fertilization. Cell enlargement is influenced by plant stress. It begins in April and continues through May. Lastly, weight accumulation begins in May and continues until early August. It is influenced by plant stress, which reduces the production of carbohydrates. To maximize nut size, carbohydrates (sugars) must be available during these periods for cell building processes. Carbohydrate availability is influenced by the rates of photosynthesis and respiration. These two processes are heavily influenced by plant temperature, which are influenced by ambient air temperature and water availability. Temperature influences photosynthesis and respiration. Both processes increase rapidly as temperatures warm, and begin to drop as temperatures increase above a certain point. The peaks, however, are different, with 86F and 103F for photosynthesis and respiration, respectively (figure 1). Since these peaks are different, there is a net gain of carbohydrates when temperatures are below 86F, but a net loss as temperatures increase above this point. Furthermore, as temperatures warm towards 86F, there is more energy being directed towards respiration, which reduces availability to be used for other processes, like nut development and plant growth. Internal plant temperature is

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16 Aug, 2021
David Doll3 CommentsAugust 16, 2021Irrigation, Salinity

Post-harvest Leaching Fractions to Manage Soil Salinity

Drought years are tough. Limited water supplies create several challenges that impact the current and future year’s crop. Several articles have been constructed to help manage almond orchards with limited water supplies, but as harvest starts, focus needs to shift to post-harvest management of the orchards. Many orchards relied on groundwater at some point through this year. This may have been sourced directly from a well on the property, or from wells within an irrigation district. Groundwater often contains elevated levels of salt, in particular sodium and chloride. These salts accumulate in the soil from the irrigations that occur during the season. Due to almond roots generally excluding salts, salt levels within the soil could climb as high as 10-15 times the concentration of the irrigation water within a single season. These higher levels of salt will impact growth and productivity as well as lead to tissue toxicity and leaf loss. To manage these salts, they need to be removed from the active rootzone of the tree. Salinity management for various soil types have been described previously for sandy and finer texture soils. These programs rely on winter leaching to reduce the salinity levels within the active rootzone of the tree. This process, however, can be improved by taking actions in the post-harvest to increase soil moisture levels. At this time of year, a leaching fraction should be added to each water applications to increase soil moisture levels. An increase of 15-20% of the irrigation duration should be sufficient. This additional water will refill the soil profile during this period, increasing the effectiveness of leaching by winter rains. The value of applying a leaching fraction in the post-harvest is greater than leaching fractions applied earlier in the season. This is due to the irrigation practices associated with harvest – a

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