21 Aug, 2022
David Doll2 CommentsAugust 21, 2022Nutrient

Using Mid-summer Leaf Samples to Guide Fertilizer Decisions: Part 2- Potassium

Potassium fertilizers have seen major increases in price over the past year. This is due to multiple factors, including increased demand, trade embargos with Belarus, and shipping constraints from Russian suppliers. Due to this price increase, many operations are trying to determine the appropriate amount of potassium needed for a specific orchard. Potassium fertility management is different than nitrogen. Potassium moves into the root through diffusion and mass flow. This means that it must be within the active rootzone to be utilized by the tree. Additionally, potassium is a cation (K+) and will respond differently based on the type of soil. High cation exchange capacity (CEC) soils have many charge sites, which can prevent potassium from being available to the plant. This can be further complicated by the presence of micas and other clay minerals. In low CEC soils, the opposite is true, the reduced number of charge sites in the soil mean higher potassium uptake for the plant. However, keep in mind that this higher availability in the soil can also lead to more potassium leaching below the rootzone, increasing costs, or reducing tree productivity. Potassium programs vary. Almonds use a significant amount of potassium, with 92 lbs of K2O needed for every 1000 lbs of kernels produced (92 kg of K2O/metric ton). Potassium is often applied as one of several products, including potassium sulfate, potassium chloride, potassium thiosulfate, and potassium nitrate. These materials may be applied blended with other fertilizers. For example, potassium chloride is commonly used within blends as it is easy to dissolve and stays in solution.  Other sources are available, but are often more expensive and, regardless of the sales pitch, equal in performance. The only exception is compost, which can be cheaper per unit depending on the source and the analysis. Due to the soil

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David Doll2 CommentsAugust 1, 2022Nutrient

Using Mid-Summer Leaf Samples to Guide Fertility Programs, Part 1

By this time, mid-July leaf tissue sample results should be available. These tissue results are critical for any nutrient management plan. They should be taken annually to determine if the nutrient program is adequate for the orchard, and the values should be used to tune the orchard´s nutrient program. Research has shown that once an orchard reaches sufficiency of a specific nutrient, increasing it further will not improve yields. This has been demonstrated several times, both within nitrogen and potassium. Second-guessing and adding more fertilizer beyond sufficient levels to address existing yield problems will not improve the situation. This fact is relatively unpopular as it is easier to add more fertilizer than it is to fix the problems that limit orchard production, or assure oneself during a period of second guessing.  More on that can be found here (slide 17) and here (slide 20), and this article will focus on nitrogen The typical nitrogen program often budgets for 20% of the nitrogen to be applied during the post-harvest period. Mid-summer leaf samples should be used to determine if the post-harvest fertility plan should be changed. Within nitrogen, leaf tissue samples that exceed 2.5% can reduce or even eliminate the need for postharvest nitrogen applications. This is based on: Many orchards with leaf levels above 2.5% often have high residual nitrogen within the soil that will meet post-harvest needs, The reduced transpiration rates of the postharvest period reduce uptake of nitrogen, There is significant canopy loss from the harvest process, reducing nitrogen uptake, Nitrogen remobilization back into perennial tissues is happening earlier than previously thought – probably sometime between hull-split and harvest (or maybe even earlier!). Additionally, a long-term study in Arbuckle found that postharvest nitrogen applications did not improve yields in a reasonably high producing almond orchard. Nitrogen levels within

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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 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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