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  • Benny Thompson

    May 27, 2023 at 12:33 am

    Iron and Manganese are the two nutrients that are most susceptible to becoming unavailable because of oxidation. Copper and cobalt are also susceptible to oxidation/unavailability. So these are the nutrients that should be in a solution with less oxygen (reduced), more hydrogen (lower pH), and chelated. Chelation doesn’t necessarily reduce a nutrient, The chelation surrounds the reduced nutrient as an extra protection against oxidation, because when you make a foliar application, naturally the solution is going to be exposed to a lot of oxygen when it gets sprayed.

    Buy these powders: Iron Sulfate Heptahydrate, Manganese Sulfate Monohydrate, Copper Sulfate Pentahydrate, Cobalt Sulfate Heptahydrate

    to make the iron and manganese available on a foliar, you can 1) reduce the oxidation and/or 2)lower the pH. (raises the hydrogen concentration, which usually also reduces oxidation). I simply put appropriate* amount manganese sulfate and/or iron sulfate in 1 gallon RO water (or any water without carbonates, chlorines, ozone, peroxides) + 1 teaspoon 5% vinegar + 1/8 teaspoon humic acid + 1/8 teaspoon fulvic acid + 1/8 teaspoon citric acid. You’re good to go.

    If you have access to OMRI Agrothrive 3-3-2 or 3-3-5, you can instead: use appropriate amount manganese sulfate and/or iron sulfate in 1 gallon RO water + 1 tablespoon Agrothrive. The Agrothrive is a lactic ferment complete organic fertilizer. It contains lactic acid, amino acid and humates (humic, fulvic and other goodies) that will all help to both reduce and chelate the foliar. From my immature understanding, the best chelation agents are amino acids. Citric acid, lactic acid, humic acid, fulvic acid and acetic acid also have some chelation strength. I think humic acid and fulvic acid will also slow down oxidation from UV. I just throw a little of each one in, not knowing which one is doing the most work.

    *appropriate amount, depends on the plant and how bad the deficiency is. A lot of plants probably have a sap level of Iron 5ppm and Manganese 4ppm. That’s probably a good starting point…spray the same concentration as the target sap level. Then I would try 10x that level on a few plants and see if the results are better or worse. (I suspect 10x the sap level is best, but better be safe than sorry)
    Here’s an estimate:So 1 gallon is about 4L = 4kg =4,000g of RO water.

    Ferrous Sulfate Heptahydrate(FSH) is 12% Iron.

    Manganese Sulfate Monohydrate(MSM) is 19% Manganese

    a little algebra with 4,000g of H20:

    5ppm = 5g/1,000,000g = .12*(FSH)/4,000g FSH=.17g

    4ppm = 4g/1,000,000g = .19*(MSM)/4,000g MSM= .08g

    Typically, we have iron and manganese deficiency at the same time. Here’s a good A/B trial for a combined iron/manganese foliar:

    A) 4L of RO water + .17g of FSH + .08g of MSM, and

    B) 10x concentration 4L of RO water + 1.7g of FSH + .8g of MSM

    somebody check my math, I did this quickly.

    Take your RO water, check the EC before adding anything. Let’s say EC of clean water is about 100uS/cm. Add your micronutrients first! (not your acids or chelators). They should dissolve within 5 minutes. Check the EC again. For MSM the conductivity will change about 100uS/cm for every 1g MSM added to 10L H20. It’s more or less the same for FSH. This will help you sleep at night! A heavy dose of a micronutrient will raise the EC about 100uS/cm. A low dose will raise the EC about 10uS/cm. If for some reason you added your micronutrients and the EC went up by more than 100uS/cm…triple check all your calculations…you are entering a risky range. If your EC went up by about 10uS/cm, you are definitely safe** for any Iron, Manganese, Copper, Zinc, Boron (Cobalt and Nickel should max be 10uS/cm…Molybdenum, I’m not sure but I would guess a max of 50uS/cm). **Safe, meaning you definitely aren’t going to over-apply. You may however, not apply near enough.

    After the micronutrients are dissolved, add your reducing, acidifying and chelating agents.

    For lettuce, I typically use .4g FSH + .2g MSM + 1 Tablespoon Agrothrive per 1 gallon RO water. Then I add a surfactant like yucca extract to make it wet the leaf out.

    Copper applications are typically 50% ppm of a Manganese application. Cobalt is typically 10% ppm of Manganese application.

    I’ve listed a lot of approximations. You should be doing sap analysis before and after to verify the efficacy.