Chelated fertilizers have been developed to increase micronutrient utilization efficiency.

Copper use efficiency is improved if the fertilizer is water soluble and the particle size of the fertilizer is small. A single application of copper can last for many years. Foliar application of copper can also be an effective way to correct copper deficiency in small grains and vegetable crops.

Chelation keeps a micronutrient from undesirable reactions in solution and soil. The chelated fertilizer improves the bioavailability of micronutrients such as Fe, Cu, Mn, and Zn, and in turn contributes to the productivity and profitability of commercial crop production. Chelated fertilizers have a greater potential to increase commercial yield than regular micronutrients if the crop is grown in low-micronutrient stress or soils with a pH greater than 6.5. To grow a good crop, crop nutrient requirements (CNRs), including micronutrients, must be satisfied first from the soil. If the soil cannot meet the CNR, chelated sources need to be used. This approach benefits the plant without increasing the risk of eutrophication.

@ Eduardo, actually chelated compounds are more stable than non-chelated compounds. Therefore, metallic chelates with Cu, Fe, Mn, Zn are widely used in agriculture as micronutrient fertilizers to supply the desired micronutrients in plants. The most common chelates used in agriculture are EDTA, DTPA and EDDHA. As Dr. Prem Babu has rightly mentioned that chelated fertilizer have greater potential.

Dear Eduardo, this is a very interesting technical question of great practical importance. The use of chelated micronutrient in agriculture is well established. In particular, the hexadentate chelating ligand ethylenediamine tetraacetic acid (EDTA) is useful in this respect. As a synthetic chemist I'm not an expert in this discipline, but I assume that your problem with "sediment" formation could result from unreacted copper oxide. Thus my suggestion would be to use a soluble copper precursor like CuSO4x5H2O (hydrated copper sulfate) instead of CuO. This will easily form a chelate complex with EDTA. For more information about this please have a look at the following potentially useful article:

Examining the fixation kinetics of chelated and non-chelated copper micronutrient and the applications to micronutrient management in semi-arid alkaline soils

Article Examining the fixation kinetics of chelated and non-chelated...

This article has been posted by the authors as public full text on RG and can be freely downloaded as pdf file.

Good luck with your work and best wishes, Frank Edelmann

In agricultural crop production, nutrient management is essential for maximum productivity. Copper and other micronutrients are easily precipitated in the soil where it utilize inefficiently due to soil heterogeneous and complex nature where micronutrients present as a positively charged metal ions and it will easily react with oxygen and hydroxide ions, form a new component which may not bioavailable to plants.In that cases, chelation keeps the micronutrient from undesirable reaction in soil. Metal chelation is important because it makes metal ion more available for uptake by plants and the chelated copper and micronutrients can be use as a chelated fertilizer. For the commercial crop production, foliar application of chelated copper fertilizer could be more effective than the direct application in soil.

In agricultural crop production, nutrient management is essential for maximum productivity. Copper and other micronutrients are easily precipitated in the soil where it utilizes inefficiently due to the soil's heterogeneous and complex nature where micronutrients present as positively charged metal ions and it will easily react with oxygen and hydroxide ions, form a new component that may not be bioavailable to plants. In that cases, chelation keeps the micronutrient from the undesirable reaction in soil. Metal chelation is important because it makes metal ions more available for uptake by plants and the chelated copper and micronutrients can be used as a chelated fertilizer. For commercial crop production, foliar application of chelated copper fertilizer could be more effective than the direct application in soil.

In general, chelated fertilizers are less reactive to soil conditions and can significantly enhance nutrient uptake and utilization efficiencies.