Knowledge grows The Nutrition of Almonds
Yara Nutrition of Almonds Crop Characteristics Almonds, like all plants require adequate quantities of all essential plant nutrients if they are to achieve their genetic potential. Optimum nutrient management results in the highest yields, greatest profits and least environmental impact. Yara Crop nutrition fertiliser programs are based on optimum nutrient management which implements the Four Rs of nutrient stewardship: apply the Right rate of nutrient, using the Right source, at the Right time, and in the Right place. While all sixteen essential plant nutrients must be available to almonds, Nitrogen (N), Phosphorus (P), Potassium (K), Calcium (Ca), Magnesium (Mg), Boron (B) and Zinc (Zn) are the most commonly applied nutrients to Almonds. Deficiency of any essential nutrient, even for short periods of time, can adversely affect nut yield and harvest quality. For Almond trees to achieve their genetic potential, sound crop nutritional programs must be supported by good overall orchard management practices, such as timely irrigation scheduling, pest, disease and weed management and soil preparation for harvesting. 2 Yara
Nitrogen Almonds are among the most efficient crops studied in terms of nitrogen (N) uptake. The requirement for N fertiliser application is based on crop demand which is driven by crop yield. Hence, higher yields require more N than lower yielding crops. General fertiliser N applications rates should be 0.1 Kg N / Kg of targeted nut yield. Rates may need to be increased if trees are still actively expanding, as additional N will be needed for permanent tissue or if there are other losses/ inefficiencies. Shortages of N will reduce growth and yields. The acidifying effect of nitrogen fertiliser is well documented. Low soil ph can cause many nutrient issues, reducing plant growth and crop yields. Supplying nitrogen as nitrate can reduce soil acidification and lower the requirement for lime as can been seen in Figure 1. The lime requirement for individual nitrogen fertiliser is presented in Table 1. Table 1: Lime requirement to neutralise acidifying effect of various fertilisers Product Lime required when N leached (Kg CaCO3 / 100 Kg N) N-CAL 15+18Ca/ YaraLiva CALCINIT 0% 50% 100% -360-180 0 YaraLiquids N-CAL 28+9Ca -70 100 290 YaraLiquids N-CAL 35+6Ca -50 130 310 YaraLiquids N-CAL 23+12Ca -150 30 210 UAN/ Urea 0 180 360 Ammonium Sulphate 360 540 720 N25 0 180 360 A negative value indicates a positive liming effect from the addition of fertiliser. Some additional acidification can occur if basic cations are leached with anions in the soil solution e.g. sulphate. Source: Moore, G., Dolling, P., Porter, B and Leonard, L. (1998). Soil Acidity. In Soilguide. A handbook for understanding and managing agricultural soils. (ed. G. Moore), Agriculture Western Australia Bulletin No. 4343, pp. 127 140. Figure 1. Impact of N form on soil ph in wet zone under drip irrigation Yara I 3
Important growth stages for N application are: End of bloom to full leaf expansion Aim to apply 20% of the total N required by the tree during this growth period. Small and frequent applications of N through fertigation systems is the ideal method to match nutrient supply with crop demands. Nitrate (NO 3 ) based N fertilisers are the preferred choice for spring applications when soil temperatures are still cool. Nitrate is immediately available for plant uptake and also supports calcium uptake. Fertilisers containing urea and ammonium (NH 4 ) forms of N have to undergo conversion to nitrate, which can be slow under low soil temperatures and/ or dry soils. Fruit growth Between full leaf expansion and shell hardening, target approximately 30% of the total N to be applied. Kernel Filling For this growth stage, target 30% of total N required by the crop. Adjustments for total N rate should have been made during the fruit growth stage to reflect seasonal yield potential. Under application will potentially reduce yield and over application will lead to high soil N concentration, which may be lost to the production system and possibly cause environmental impacts. Hull split to early post-harvest The post-harvest period should have 20% of total N rate. Nitrogen uptake during the post-harvest period is critical for optimum yields in the following year. Nitrogen is stored in roots, the trunk and branches during the winter dormant period and is then remobilised for early spring growth. Mid-season N applications need to be adjusted to reflect any change in estimated yield. Apply the N applications over a number of applications to improve N uptake efficiency. One of the keys to achieving the greatest N use efficiency is to apply the right rate of N based on the yield potential of the trees. We know that nut yields vary within orchards in response to changes in soil conditions, diseases and other environmental factors. Yield variations of +/- 50% from the average are common within an individual orchard, thus the optimum N rate will vary +/- 50% within that block. While options to vary N rate may be limited, the N rate should vary depending on the yield potential of individual blocks within the orchard. 4 Yara
Phosphorus Calcium Almonds have a low requirement for Phosphorus (P) but P is essential for plant growth, especially for energy transport and production of carbohydrates. Trees suffering from P deficiency have stunted growth and leaves and shoots remain smaller than normal. Phosphorus applications need to replace P removed in harvested nuts, approximately 6-13 Kg P/ton and provide additional P for permanent tissue if the trees are still growing. Application of P should be made during the End of bloom to mid fruit development Calcium improves potato tolerance to diseases and during Post-harvest in fertigated systems. Potassium Almond trees take up almost as much Potassium (K) as nitrogen (N) and a K deficiency will reduce nut yields and quality. Each ton of almonds removes 50-75 Kg of K depending on variety. Potassium is needed for starch formation, translocation of sugars and to regulate turgor pressure (opening and closing of stomata). A mild to moderate K deficiency is unlikely to be seen except for overall slow growth, which reduces yield potential. A more severe K deficiency causes leaf margins to die and leaf tips to curl upward and overall health is adversely affected. Significant yield loss will result if the K deficiency is severe enough to cause leaf symptoms. Almonds are known to be sensitive to salinity buildup in the root zone, which can reduce yield potential. An increase in root zone salinity can be caused by many reasons. Common contributing factors include; irrigation water quality, soil type and structure, soil drainage, annual rainfall and K fertiliser source. By having a good understanding of the relative influence of each of these factors, root zone salinity can be managed, allowing all K fertiliser sources (chloride, sulphate, nitrate and phosphate) to be considered when designing a crop fertiliser program. With this in mind, K can be supplied to almonds in the most cost effective manner. The majority of Calcium (Ca) in plants is found in the cell membranes and cell walls where it plays a critical role in maintaining cell membrane integrity and cell wall strength. Localised Ca deficiencies are usually found at the growing points because Ca is immobile within the plant. These disorders caused by localised Ca deficiencies are referred to as physiological diseases because the physiology of the plant is adversely affected but no pathogen is involved. An adequate concentration of Ca in plants helps reduce or eliminate physiological disorders and also helps plants resist fungal and bacterial pathogens by suppressing the extracellular enzymes that the pathogens secrete. The beneficial effects of Ca on nut crop diseases is shown in research of hazelnuts. Results from 3 years of field research have shown that applying 40 or 80 kg/ha of Ca as YaraLiva Tropicote in early spring markedly reduced the incidence of mouldy nuts at harvest and after 10 or 18 days in storage (Figure 2). The same rate of nitrogen was applied in all treatments but YaraLiva Tropicote replaced the growers standard practice which supplied no Ca. Calcium is essential for nut retention and applications are most effective in early season and post-harvest. Figure 2. Summary of 3 year study investigating the benficial impact of soluble calcium on mould incidents in Hazelnuts Monitoring orchard K status Leaf samples provide a good window into the K nutritional status of Almond orchards. Minimum critical leaf value for K is 1.4% and values less than this are likely to be associated with yield loss and adverse effects on overall health. Recent research has shown that leaf K levels should be in the 1.6-1.8% K range for optimum tree health and top yields. Yara I 5
Magnesium Magnesium (Mg) is required for many plant processes, with particular importance for chlorophyll production. Deficiencies reduce the plant s ability to produce energy, resulting in less energy for growth and nut development. Applications of between 20-30 kg/ha should be applied to keep balance between K / Ca / Mg and spread throughout the growing season. Boron The main functions of boron (B) in the plant are related to cell wall development and cell division, seed and fruit development, sugar transport and hormone development. Boron is mobile in Almond trees (unlike Walnuts or Pistachio trees) and can be translocated from leaves to other organs. This allows the plants requirements for B to be supplied with both soil and foliar applications, to adequately supply periods of peak demand. The mobility of boron in Almonds allows hull analysis to be used as a better indicator of the plant boron status than leaf analysis (Table 2). Table 2. Hull analysis standards for interpretation of plant Boron status (ppm) Deficient Adequate Excessive Toxic <80 100-160 >200 >300 Zinc Zinc (Zn) plays an important role as it is part of N metabolism, amino acid production, required for the synthesis of auxins for growth and pollen viability for flowering and seed set. Deficiencies at budbreak will reduce fruit set and nut size, leading to low yields. Zinc deficiency is common on low organic matter soils, sandy soils, and heavily manured orchards. Zinc is generally foliar applied to Almonds with the first application from budburst and again at late postharvest. This late application assists in leaf drop and can be counted for as a soil application, building soil zinc levels for the next season. Yara s fertiliser range for Almond production Yara has a comprehensive range of high quality fertilisers that can adequately supply the nutritional requirements for Almond production (refer to www.yara.com.au for product information). Presented on the next page is a fertigation program that can be used as a base and modified according to individual circumstances. Please contact your local Yara Sales Agronomist for more information. 6 Yara
Almond Crop Program (Liquid) Crop Stage Bud Burst End of Blosson to Full Leaf Expansion Fruit Growth Kernel Filling Hull split to Early Post Harvest N-CAL 35+6Ca+B 250 L/ha 150 L/ha 150 L/ha N25 200 L/ha K-FLOW 0-7-36 140 L/ha 140 L/ha 120 L/ha K-FLOW 4-0-12 400 L/ha 1200 L/ha K-FLOW 18-0-10 300 L/ha Mg-SUL 100 L/ha 150 L/ha 150 L/ha Zn-SUL 6 L/ha YaraVita BORTRAC 1 L/ha 1 L/ha 1 L/ha YaraVita ZINTRAC 1 L/ha Yara I 7 Disclaimer: The information contained herein is to the best of Yara s knowledge and believed to be accurate. For customised crop plans please contact your local agronomist.
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