Chelated Fertilisers

Nutrient management is crucial for optimal productivity in commercial crop production.

Micronutrients such as Iron, Manganese, Zinc, Copper and Molybdenum, are easily oxidized or precipitated in soil, and their utilization is, therefore, not very efficient. Chelated fertilizers have been developed to increase micronutrient utilization efficiency.

Chelated micronutrients are protected from oxidation, precipitation, and immobilization in certain conditions.

Medias are complex, traditional micronutrients are readily oxidized. Chelation protects a micronutrient from undesirable reactions in solutions. A chelated nutrient improves the availability of micronutrients such as Copper, Iron, Zinc and Manganese, and helps in the productivity of the crop.

Vegetable and fruit crop dependence on micronutrients varies significantly. Chelated fertilizers are often required for those plants in the susceptible categories. For those with low susceptibility chelated fertilizers are generally not required. Media and soil pH is a major factor influencing micronutrient availability, therefore a soil pH greater than 6.5, may have limited micronutrient availability thus requiring the use of chelated nutrients.

There are three ligands of chelated nutrients most often used:  EDTA, DTPA and EDDHA. Generally EDDHA chelated Iron (Fe) is most stable at a pH of greater than 7. Chelated fertilizer stability is desired because it means the chelated micronutrient will remain in an available form for much longer and thus increasing its efficiency in the crop. DPTA chelated Fe is therefore more stable between 7 and 6 whilst EDTA chelated Fe is more suitable to lower pH’s.

Chelated Fe should always be used in fertigation and when foliar application is undertaken.  The most commonly used copper chelate is EDTA as is Manganese.  Calcium chelate is commonly used when plants are suffering in cold conditions when the uptake of calcium by the root system can be low.  This also applies when tomatoes are nearing the end of their life and as their root system is struggling with uptakes the plant can suffer from Calcium deficiency which results in blossom end rot of the fruit.  An application of Calcium Chelate at 1gm per litre of water can be beneficial.

At all times when foliar feeding ALWAYS do a trial application first to ensure that plant damage is not occurring.

A full range of chelated fertilisers is available online, Click here to view


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