11 10 The benefits of foliar feeding THE aim of undertaking foliar fertiliser applications is to “cover the bases” during when plants cannot uptake soil-applied nutrients due to adverse weather or soil conditions, or in peak demand times. Foliar fertilisers should be applied every seven to 14 days, or at key demand periods, to ensure fresh growth receives the necessary nutrients. Choosing products that are tank-compatible saves time and money compared with separate foliar passes. Using Haifa Calmaster that is chelated, and the silicon-based Wall-Up with Haifa Bonus or Poly-Feed Foliar provides tank compatible solutions, helping you cover the bases of different crop stages and ensuring high quality and shelf life of produce, as well as resilience to pests and disease. Foliar applications are a fast way for uptake, as plants readily take up nutrition via leaves and it is faster-acting than roots. Plant mobility of nutrients Transpiration moves immobile nutrients via the xylem and mobile nutrients relocate through the phloem. Mobile nutrients (N, P, K, Mg) relocate from older to younger growth, while immobile nutrients like calcium and many micronutrients remain fixed in the plant, leading to deficiencies in new crop growth when under adverse conditions for root uptake. Deficiency symptoms The location of symptoms indicates nutrient mobility. Mobile nutrients show deficiencies in older leaves, whereas immobile demand is indicated in young leaves. Foliar applications Mobile nutrients can stimulate growth by relocating as needed, whilst immobile nutrients remain near the application site. Regular foliar applications should align with crop stages and soil applications should match the foliar nutrient needs. Foliar nutrition applications are a back-up for soil plant nutrition and cover the circumstances of: • Fast corrective nutrition where deficiencies are noticed. • Poor uptake due to underperforming roots due to low temperatures, poor aeration, water logging or root damage from disease or nematodes. • Poor transpiration in windy, hot, cold, cloudy or humid conditions, making plant immobile nutrients unavailable. Budbreak Apply Haifa Bonus to enhance budbreak, helping reduce dormancy-breaking agents (oils) in warm climates. This results in earlier, uniform budbreak and increased first harvest. Vegetative growth Haifa Foliar (green bag) 21-9-17 elemental (21-21-21 oxide) is the ideal solution, containing low-bi urea for foliar performance and uptake, with low phytotoxicity risk. Urea is the ideal form of nitrogen for foliar uptake in vegetative stages of plant development, and yet, urea in soil needs to be converted to ammonium or nitrate for root uptake, relying on weather and soil conditions, including temperatures. Flowering During reduced metabolic activity and nutrient uptake, apply high phosphorus foliar formulas (Poly-Feed or MKP) to boost flowering and fruit-set. Fruit sizing After fruit-set, use high potassium-to-nitrogen ratio (Haifa Bonus) and calcium (Calmaster) for better nutrition, quality and size. Early applications can reduce biannual bearing and promote larger fruit. They also support stomatal function for optimal sugar production, which is especially important during low root activity in fruit production. By Sheri Robinson Southern Sales Agronomist, Haifa Australia Potassium applied via foliar applications can ensure the efficient function of stomata for optimal sugar production and leaf performance. Potassium has low mobility in soil, and root activity is low during fruit production, when potassium is heavily sought by the crop. During periods of high sink from leaves to fruit, leaf stress can cause less resilience to hot windy conditions if stomata potassium levels are declining. Testing petiole levels will show the relocation, not the lack of leaf potassium. Foliar applications of Haifa Bonus, therefore, can improve leaf performance and aid crop ripening by helping minimise plant stress. Excessive potassium in soils can interfere with the uptake of other cations, so a foliar application during key crop phases of high demand ensures you are covering the bases of peak demand periods, when soil potassium application is not desirable. Diluted spray Slow di usion K+ K+ K+ K+ K+ K+ K+ K+ K+ Higher concentration Fasterdi usion K+ K+ K+ K+ K+ K+ K+ K+ K+ K+ K+ K+ K+ K+ K+ K+ K+ K+ K+ K+ K+ K+ K+ K+ K+ K+ 50% 45% 40% 35% 30% 25% 20% 15% 10% 5% 0% 50 55 60 65 70 75 80 85 90 95 Mean fruit diametre (mm) Fruit size share in treatment The effect of Bonus NPK on fruit size distribution – Jaffa oranges Control – 0 application Bonus NPK Ca B Fe Zn S Cu Mn Mo N P K Mg Young leaf tissue Old leaf tissue Dehydration at low K Stomata remains open and more water is lost Minimal transpiration at adequate K Closed stomata prevents further water loss 1. Haifa BonusTM is sprayed and forms droplets on the leaf surface. 2. A portion of the fertiliser is absorbed immediately. 3. When air gets hot and dry, the fertiliser droplets dry and nutrient uptake temporarily stops. 4. At night, the dew re-dissolves the fertiliser. Nutrient uptake is renewed. Product benefits & wetter formulations of Poly-Feed Foliar and Haifa Bonus These are 100 per cent water soluble, contain plant nutrients only, and are free of chloride, sodium and any other detrimental materials. They are ideal, pH 5 to 6, formulas for optimal absorption and tank-mix compatibility (potassium nitrate is normally a pH of 9). The wetter allows for higher concentrations with lower risk of phytotoxicity, improving leaf hold, absorption and length of action (up to 7 days). The special Bonus inside The special Bonus ingredient in Poly-Feed Foliar enhances adhesion to the leaf’s surface, improves absorption of nutrients and helps the fertiliser to remain on the leaves and nourish the plant over time. How it works Passive diffusion: Uptake is proportional to spray concentration • The need to boost growth at critical stages, or boost fruit sizing and quality. • The need to assist special jobs, eg, dormancy breaking or flowering performance. • The need for additional resistance under biotic stress from pest and disease. Key growth stages for targeting foliar applications The growth stage and foliar nutrition solution should be matched to the same nutritional ratios you apply to your soil. Cont. page 12
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