What if the weakest link can’t be addressed by simply applying more pounds on the ground? Your soil report shows that a nutrient is present in adequate quantities but for some reason it’s just not getting into the plant. What’s going on? The odds are that the nutrient in question isn’t available to the plant because of the unique characteristics of the soil. pH levels play a big role in determining the solubility of nutrients. At lower or more acidic soil pH levels (< 6.0) you generally see a greater availability of micronutrients like Fe, Mn, B, Cu and Zn but run the possibility of macronutrient deficiencies with N, P, K, S, Ca and Mg. At higher or more alkaline soil pH levels (> 7.5) you generally see the micronutrients become highly unavailable and deficiencies pop up regularly; Mo is the lone exception here.
By farming at an ideal soil pH around 6.5-7.0 we can maximize nutrient availability across the board. However, real life doesn’t always allow for ideals so when your soil pH is 7.8 and the vast majority of Fe, Mn, Z, and Cu have oxidized or precipitated in soil, how do you get around that reduced utilization by plants? In order to increase the utilization efficiency, chelated fertilizers can be used to address the problem.
Chelates protect metal nutrient ions by encircling them with larger molecules so that the nutrient no longer has an exposed electrical charge. This prevents it from interacting with the environment and protects it from oxidation, precipitation, and immobilization under certain conditions. This “bond” formed between the chelate and the nutrient varies in strength…a chelate with more bonds is usually considered to be stronger.
A true, reacted chelate generally has 4 or more bonds. This includes EDTA, DTPA, EDDHA, EDDHSA and reacted LSA (all have 4-6 bonds). When there are less than 4 bonds the terminology shifts from being a chelate to be a complexing agent. LSA, glucoheptonate, citric acid, and amino acids (1-3 bonds) all provide some protection to nutrients but it’s a much more short-term and weaker level of protection.
So, do we just need the strongest chelate for all micronutrients? Unfortunately, the answer is yes and no. Most micronutrients can be adequately chelated with EDTA (4-6 bonds) for soil applications. For foliar applications, the complexing agents are usually enough to do the job and protect from tank incompatibilities. The big exception for the soil is Fe.
Many types of chelates have been used on Fe with little success until EDDHA (6 bonds) chelated Fe products hit the market. This chelate provides strong protection for Fe even under extremely alkaline conditions where EDTA tends to break down. EDDHA is almost too strong sometimes because the chelate holds onto the Fe ion for up to weeks. This is good for longer term Fe nutrition but short term, not so much. This is where EDDHSA comes into play, this chelate provides a high level of protection for Fe but a slight change in chemical makeup allows for a much faster rate of release of Fe for plant uptake and utilization.
Chelated fertilizers provide a way to protect your investment and ensure proper plant nutrition!