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 commentsApril 25, 2021Nutrient

Iron Deficiency of Almond

It is common to observe iron deficiency within new growth of almonds. Iron is an essential micronutrient that is used to build chloroplasts. Without iron, the leaves fail to turn green. More obviously, iron deficiency causes interveinal chlorosis – or yellowing between the veins – on new growth. Severe deficiency will reduce growth and lead to increased susceptibility to minor leaf pathogens. Iron deficiency is not observed on older tissues due to lack of mobility within the plant. Iron deficiency is commonly observed in the spring as yellowish looking trees. This is due to wet and saturated soil conditions that limit fine feeder root development. These roots serve as the primary point for iron absorption. Secondly, too wet of soils increases the amount of carbon dioxide (CO2), which forms carbonate (HCO3-) leading to a temporary increase in soil pH, which reduces iron’s availability. The solution for this cause is simple – withhold irrigation until soil moisture levels drop and good aeration can occur. It is very common to see recovery within 7-10 days after the soils have dried to field capacity. The second primary cause of iron deficiency is “lime induced iron chlorosis.” Since higher pH restricts iron uptake, it can create deficiencies. This is very common in poor quality soils in which the pH is greater than 7.5. A soil test or soil pH meter can help determine if high pH is the cause of the observed deficiency. Soil acidification or modification is recommended to resolve the symptoms. When dealing with “lime induced iron chlorosis,” there are a few strategies to manage. These include the use of acids or acid forming fertilizer to lower soil pH. Injecting acids into the fertilization system can be complicated, but tend to direct the acid to the area which contains the most roots

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David Doll0 commentsMay 30, 2020Pistachio

Copper Deficiency in Pistachio

Copper is a micronutrient of plants. In certain situations, soil levels may be low enough or plant growth demand high enough that deficiency may occur. Within pistachio, this deficiency often occurs in the middle of the season (July-August) on young, fast growing trees. Symptoms include the die-back of new growth, forming a “shepherd’s crook.” Most, if not all, new growth will show this deficiency. In these cases, a foliar spray containing copper can help remediate the deficiency. Ideally, deficiency should be prevented to maximize growth. To prevent copper deficiency, plan to apply 0.1 lb/acre or 0.100 kg/ha of a chelated copper as a foliar spray when the new canopy is 50-90% expanded. This spring-time application will prevent the symptoms from occurring later in the summer. Soil applications should also be considered if soil values are low. Cooper sulfate can be fertigated in acidic soils, while a chelated product (EDDHA, or similar) should be used in alkaline soils. Soil applied rates of 1-2 lbs/acre or 1-2 kg/ha should be sufficient.

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