Soil pH and calcium are usually related, Harris says, and “this is super-critical with peanuts. Once you get to 5.5 pH, aluminum becomes available, but with pH below 5.5 aluminum becomes toxic to most plants, including peanuts. Zinc is also very toxic at that level, and peanuts are very sensitive to zinc toxicity. Unless you bring the pH up, there’s not much you can do in these situations.

“Luckily, we have soil test guidelines that show which pH levels are needed to offset zinc toxicity. For example, if you have a soil test zinc level of 10, a pH level of 6.1 to 6.2 should avoid toxicity. There are correlations between various pH levels and zinc levels to avoid toxicity.”

High oleic peanuts: An opportunity for some growers?

Zinc can be a concern in using chicken litter on peanuts, Harris says. “There is about 1/2 pound of zinc per ton of chicken litter. While we don’t recommend applying chicken litter directly on peanuts, it does contain some calcium carbonate that will help maintain pH. It also has a lot of phosphorus, which interacts with zinc and helps keep down toxicity. We’ve not seen as many issues with zinc toxicity with chicken litter as we had expected, and as long as you keep the pH and zinc levels in balance, it shouldn’t be a problem.”

One possible issue, Harris says: “If you raise your pH too high to offset zinc toxicity, you could create a manganese deficiency. We see this fairly often — yellowing between veins is a symptom. If you bring your pH up enough to tie up the zinc, you’re also tying up the manganese.”

“If you have a a pH of 6.0, you need at least 8 pounds to 10 pounds of soil test manganese to avoid deficiency; for a pH of 7.0, you need around 15 pounds of manganese.”