10 11 Irrigation amount and timings affects the soil solution and, thus, the availability of nutrients to the plants. In well-draining soils of lower organic matter, careful application of fertilisers is essential to maximise efficiencies of fertiliser use. Leaching of fertilisers can occur during over-irrigation applications and soil moisture monitoring is therefore an important factor in management of nutritional programs. Checking soil, water and plant tissues for nutrients and pH, and tracking tree performance at multiple times of the year, and between different performing areas within a block, will give us a clear indication if fertiliser use and availability is optimised at the tree level. Remember, a positive nutritional leaf test does not always indicate the future indication of crop performance, as a balance will be found by the plant, so nutritional results need to be factored alongside canopy replacement wood and fruiting bud levels. Haifa NutriNet So, how do I get the right application over the right irrigation and the mix right? Haifa NutriNet is a program available from the Haifa website. It gives growers the ability to plug-in irrigation data and fertiliser data to come up with the correct application rates. Potassium carbonate, although highly soluble with no sodium or chloride, still requires the presence of nitrate to optimise uptake (or will it uptake other undesirable anions?), so it is not considered the best option early in the season, when nitrate may be scarce. It may have its place to adjust pH with very careful monitoring of soil pH effects and careful product handling (due to high risks to safety in mixing). Haifa would suggest Poly-Feed or careful, balanced NPK complex recipe feeding to maintain leaf health. Including micro elements is always the most efficient use of fertiliser. With good choices in fertiliser products, you maximise solubility, plant uptake and leaf health, and the price is justified in the performance of tree yields in the year of application, its ability to store carbohydrates, and, hence, future cropping. Fertiliser choices affect the soil acidity and balance of anion and cations of the nutrients in solution. Combined with irrigation strategies, it is essential we Potassium sources If we look at the advantages of the sources of potassium, we see that “apples are not apples”. K Source KCl (50% K) Agronomic Advantages • Relatively cheap • Highly soluble • Neutral in solution Agronomic Disadvantages • Reduces yield due to excessive Cl Ref Patrick Browns work • Chloride accumulation in soil K Source PN (38%) Agronomic Advantages • Highly soluble, best at 20C or more. • Wider compatibility to mix • Contains both nitrogen and potassium • Haifa makes low sodium potassium nitrate • The disassociation of the cation and anion allows a balanced absorption by plants, with no energy exertion • No residual chloride, carbonate or sulphate in the soil • Neutral – alkaline in solution 10% solution = 9.9pH 5% solution 6.5pH • No pH influence on soils due to balanced feed • Not waiting for increased nitrate: Ammonium ratio for availability in soil for efficient uptake of K Agronomic Disadvantages More expensive, yet plant efficiency is optimal due to nitrate counter ion Solubility in cold water K Source SOP (42%) Agronomic Advantages • Contains Sulphur and Potassium Agronomic Disadvantages • Not very soluble, time consuming to mix • Additional sulphate not required by the plant • Higher sodium commonly found in SOP • Acidic in solution 10% solution = 2-4pH K Source Potassium Carbonate Agronomic Advantages • Extremely soluble • The carbonate uses two hydrogen ions to make water and CO2 to adjust pH in acid soils • Carefully watch soil pH, as it will bind calcium and magnesium and have lime induced chlorosis effects due to micro element unavailability if used in 6.5pH plus soils Agronomic Disadvantages • 11.4pH in drippers may lead to reactions to calcium and magnesium in irrigation water, causing precipitations, leading to blocked drippers • CO2 emissions when it reacts with acid soil or water • Ammonia gas release/ loss if reacting with ammonium nitrate – similar to lime and ammonium reaction losses of 50% nitrogen can occur. • Reactive with ammonium or any acidic based formula, ie, can cause excessive foaming or ammonia and carbon dioxide loss if mixed with acids – hazardous to mix and safety precautions are essential K Source Potassium Thiosulphate Agronomic Advantages • Acidifying • In alkaline soils, the acidification caused by thiosulphate may be advantageous. Careful monitoring of soil pH in the drip zone is required Agronomic Disadvantages • In acid soils or in the situation of high ammonium-based fertilisers causing acidity, more acidity could be a problem K2CO3 KCI KN03 K2SO2 180 160 140 120 100 80 60 40 20 0 g/100mL solubility 0 20 40 60 80 13.25 7.33 11.11 14.79 18.2 21.29 31.66 63.9 105.5 111.5 117 109.9 127 140 169 Temperature degrees celcius POTASSIUM SOLUBILITY CHART meet crop demand to optimise yields without costs to irrigation equipment or long-term sustainability of soils. Nutritional testing is important to understand the interactions of fertiliser programs with tree uptake, yet a strong nutrition program is indicated by healthy trees with strong replacement wood and fruiting bud numbers. Click for further info Haifa Bonus Poly-Feed NutriNet
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