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North Carolina | I have searched the internet for hours and called ever agronomist i can and cant get straight answers.
Tissue samples at r5 show im at threshold of copper deficiency. 8 ppm if i remember correctly. I gotta apply a foliar spray of other stuff too, possibly insecticide for kudzu bugs as well, but my question is only on copper.
5ppm jump of copper on tissue would need .028 units of copper per acre.
Im getting agronomists telling me .11 pounds copper sulfate (.028 units copper) per acre is safe, all the way to some saying only throw 2 tablespoons copper sulfate into 1000 gallon tank because of toxicity.
The .11 rate would be 5.5 lbs of copper sulfate added to a 1000 gallon tank sprayed at 20 gpa. That a big difference between 2 tablespoons.
Heres the kicker...im adding citric acid and AMS to the tank to drop my spray solution to a pH of 5. All foliars absorb much better at that low of a pH. But i found two studies that said never spray any fixed copper (copper sulfate,copper oxide, etc) on a crop with an acidified spray solution. The copper ions are too available and absorb into plant tissue too fast and become toxic.
Anyone have experience? Surely a reduced rate of one pound of copper sulfate in a 1000 gallon tank, but i eont get my 5 ppm jump im after.
Verbatim example 1
"Spray solutions should not be acidified if they contain lime, lime sulfur, or fixed copper products where copper may become solubilized by the acidity resulting in possible plant injury."
Verbatim example 2
"Copper fungicides are more soluble in water with a lower pH, which releases more copper ions. When the pH of the water or spray solution is below 6.5, too many copper ions can be released, which can burn plant tissue. This is especially true for formulations with high amounts of soluble copper, such as copper hydroxide."
Edited by JumpStartRider 8/16/2024 06:08
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Copper defecient in beans. Foliar Copper Sulfate toxicity at low pH spray solution
