Question to Soil Chemists and Fertility Experts about Increasing Phosphorus to Mitigate Issues with Zinc

Jordan Question

I had a grower asking if excessive phosphorus could be applied to create a situation where zinc is less available for plant uptake and potential damage to peanut. They are trying to plant peanuts in a field that has higher than recommended levels of zinc.  Our index is 250 - I have not done the math but is that 10 pounds zinc/acre? I can run that down in my orange NCDA book.  My impression from the conversation is that he has about 28 pounds zinc/acre that is concentrated in the upper 4 inches or so of the profile and that he intends to conventionally till to reduce the concentration by spreading it throughout the soil (he is a conventional tillage grower, so he is going to make that tillage operation either way.  Are there fertilizers that can be used to alter nutrient dynamics in a way to reduce risk of zinc for peanuts?  I am not aware of anything other than increasing pH.

David Hardy

I don’t think there are significant interactions in the soil between these two nutrients to think about this as a preventative. Much of what I have read usually points to P interacting with Zn in the plant, under very high P soil levels, causing P deficiency. It’s physiological for the most part, although there could be some soil interactions from my reading.

The 250 index is about 18 pounds per acre Zn. So, 28 pounds of Zn = 394 index.  Managing pH is the only way that I would feel comfortable doing.

He needs to remember, average value of 394 means some spots higher and some spots lower.

Luke Gatiboni

I agree with David Hardy. The precipitation of Zn-P in soils is very limited and it will not move the needle to alleviate potential Zn toxicity. As DH said, the antagonism of P and Zn is something more on the plant physiology side of things. I don't see P application as something that could help prevent Zn toxicity.