We are often asked why it is necessary to invest in chelated products rather than simple sulfate-based trace elements, so we finally decide to invest some research funds in a comparison. We decided to use manganese as an example, as this is a deficiency we see so often when analysing dairy pasture. It is also a common deficiency in many horticultural crops, particularly strawberries, where several of the more recent hybrids seem to struggle with manganese uptake.
To achieve identical rates of manganese, we applied 2 kg per hectare of manganese EDTA and 3 litres per hectare of both Nutri-Key Manganese Shuttle™ and Farm Saver® Manganese Fulvate. The control was obviously not foliar treated with manganese. The EDTA application cost AU$49.80 per hectare, the Manganese Shuttle™ cost AU$32.80 per hectare and the Manganese Fulvate cost just AU$17.35 per hectare. The crop involved in this trial was apple cucumbers.
It is important to note that the Manganese Sulfate treatment was not successful, as it appeared to induce a deficiency of nitrogen and potassium, which actually killed the plants. The naturally chelated products delivered much more vigorous and healthy plants. In fact both the EDTA treated plants and the control developed problems with powdery mildew which were not present on either of the naturally chelated treatments. It makes me wonder if we should not conduct further research looking at a potential protective role for manganese in mildew management.