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Little River, TX | I printed off a copy for my notebooks. Copied it first to an Email Format to change the font size. Wish I had noticed the spelling errors and used spell check to clean the spelling.
A few comments.
The equation to determine desired potassium levels is a little different from 2 others I have used. First used (5 x CEC + 250) + K ppm. I now use 10.44 x X CEC = sufficient potassium. Or a level where there is less than a 20% probability of a positive crop response from additional potash. The bottom or critical range is 8.07 x CEC = range where there is an 80% probability of a positive crop response. Something to look at is the desired values are non linier. These factors are for a CEC of 50 meq/100g. You can do the math to find what I fertilize my soil to. The higher the CEC the smaller the factors are.
Not only are cation's attracted to a negative charge but in clay soils cation's as well as anions can become trapped between clay platelets.
Look at the equation to compute CEC. They use the 3 essential cation's. So if one is excessively high or low it will slant the number from the real value. That and it is not unusual to see a 30% natural variation in soil test results for these elements. The one I use also uses sodium and pH is not a factor with an 8 pH. Think what a 6,000 or even a 9,000 ppm Ca would do to a CEC value. Because of this I pay $17.10 per sample to have a measured CEC determined. My observation is on average the computed and measured are close, BUT that is an average not real world. Real world shows the computed to be 40% high as well as 40% lower than the measured. Sort of like Central Texas summer rains. Some years it floods and most years there is no, zero, rain. The average looks good.
Saturation ratios are a joke here. Our Ca will run 90% to 95%. How much potash and magnesium would be required to drop the Ca ratio to 80%?
For reasons not fully understood K-Mag, 0-0-22-11-22, encourages potassium uptake more than Murate of potash. Depending on soil and plant analysis from an alfalfa's last year, I apply 1,000 lbs of K-Mag and 500 lbs MOP, or 2,000 lbs K-Mag, prior to planting the next stand of alfalfa.
All the above bovine scat is not meant to be a receipt, but just for something to consider. Remember my soil CEC runs from 40 to 60 meq/100g. Nor is an 8 pH much help.
Edited by Hay Wilson in TX 7/24/2006 21:50
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Potash and drought proofing?
