Monday, December 12, 2011

Potassium


Most of us eat bananas as a tasty source of potassium for our bodies. Bananas grow well in tropic areas where banana trees are able to pick up lots of free potassium in the soil there. I didn't meet an agronomist type person on our banana plantation tour a year ago to learn more about it but I get the general drift.

A farmer asked on Crop Talk how to manage potassium on his low CEC soil. Our soil is much the same way so I wrote this reply:

"That's a good question. I ought to add up what I have put on the last 7 years and then add up what my supposed crop removal is.

I think I have taken as much as I put on and perhaps more.

Whether it is red, pink or white potash, we all know it is not broken down in one crop. It's like feeding the soil continuously, sometimes I have more and sometimes I have less but my low CEC like yours can hold less and requires less. The big thing is as CEC goes up, usually the organic content is higher and it needs and can hold more potassium. I am not sure how that interacts with soil micro organisms but it does.

Dr. Himes taught us the black box theory at Ohio State in Soils 410. We only studied those concepts, you had to take other classes to study soil microbiology which were also intriguing to me.

This is where the tissue test helps me find hidden hunger. It may not show the total K absorbed all season but gives me a snapshot of where I am at. Some hybrids may need more than others. I would rather be Sufficient to High in Potassium than Sufficient to low."

That post should make farmers think who read that. That is what I have learned in 40 years. This morning another farmer asked what cover crop would help release free potassium into soil.

I found this link which helps describe etching of potassium from soil in a very scientific manner. Maybe one of you can help me decipher it into a good response.

It is a complex matter but we know crops grow better after tillage radish. We don't know all the reasons why. Basically, the radish "harvests" all of the free nutrients in the soil and dies over winter here in the north and the action of the tuber against the soil profile etches some of the potassium out of the mineral rock.

Potassium is a vital nutrient for plants and works with boron for maximum yield and quality. Soil tests and tissue tests help me prevent "hidden hunger" of potassium and other crop nutrients.

Ed

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