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help me understand plant tissue test
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Hay Wilson in TX
Posted 6/24/2006 17:55 (#21763 - in reply to #21735)
Subject: Some observations as to alfalfa may help.



Little River, TX
First one thing nice is the work of one lab will be compatible with that of another lab. Exception is California. The interesting part comes when looking at the desired range of elements.

It is my thinking that there is more interaction between essential elements than is generally thought. I do know that copper and molybdenum work together to some extent. Too much copper will show create a molybdenum deficiency. That little gem took me 5 or so years to digest.

Using my experience with alfalfa, correct a copper deficiency and Moly became a problem, (This showed up as a nitrogen deficiency, so may be of interest to the bean growers). Get the Mo into the desired range and then (& only then) did a potash deficiency make it's self known. Graveled one field with Murate of Potash and that helped, but then magneesium started to look low. Added some magneesium and the uptake of potash jumped from low/criticle levels to strong sufficient levels. Don't ask me how or why.

I presume all cation's interact some in a positive way, but I am not sure. With my high pH, high CEC soils ( some may call then excessively high) bringing up the soil test levels of K & Mg also brought the soil test levels of phosphate, though the tissue test results did not change. Why I have not the least idea. The alfalfa has always found the phosphate, maybe now the Lab was able to find the same phosphate. Might be something else also, who knows.

Tissue testing should tell you which element (singular) is the one limiting productivity. Fix that and the next limiting element will make it's self known. To bypass some of this there is a long string of ratio's (N/S 14/1). You will need a better understanding of mathematics than I do to get the most out of these ratios. Therefore I keep it simple and look at only 6 or 8 ratios. These ratios are referred to as DRIS. Easy to compute the ratios, understanding is not, for me.

I use soil and tissue test results for next years fertility decisions. That and to pass judgement on last years application.
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