bgunzy - 10/7/2011 22:00 A few pages back we had a discussion about gypsum and its effect on the soil. Being made up of calcium and sulfur (as sulfate), a school of thought is that soil acids break apart the calcium and sulfate, the sulfate pulls a magnesium ion off the soil colloid, forms epson salt, leaches away, and the calcium takes up where the magnesium was.
However, I believe Joel Gruver mentioned that it is possible that the sulfate would attract a potassium ion off the soil, forming potassium sulfate, and leaching away.
How likely would it be that the potassium ion would be lost? More or less so than the magnesium? Of course, in most soils, magnesium is more plentiful than potassium (20-30% vs 2-5% of the cation exchange capacity), but would a greater percentage of potassium be lost due to application of sulfates?
And, is it a good idea anyway to be attempting to remove magnesium from the soil and replacing it with calcium and potassium? I've read that excessive Mg causes the soil to be tight, especially in clay soils. More Ca will flocculate the soil, creating more "peds" than dust/grease.
Thanks for any ideas. as Joel pointed out so well. and I agree. the issue of K or Mg. Leaching to never never land is determined by 100 s of issues. my opinion as stated. many times. 1. the soil Biology. the soil Humus content and soil O.Matter content. 100% dependent. 2. the soils physical property's . % of sand, silt and or clay. 3. Drainage, tile or natural. 4. soil Porosity. dependent on all of the above. 5. soil Chemistry. % Cations available. maybe Cation ratios ? in specific soils. very much Clay content suitable. driven. type of clay, Blue or grey clay. smeary. never dries. ? Hmmm High Magnesium content. DEAD soil syndrome. septic soils -0- percolation rate clay. 6. WATER , annual rainfall and or irrigation amounts applied. Personally, I have never observed, nor documented over very long term, 40 plus seasons of observations, soil and tissue analysis and Crop production issues. the actual leaching of K. IF anything has been observed by myself and Individual farmers. the K going into solution after the application of Calcium allows more Lush feeding of the K by the Plants. such as Corn, Soybeans and Alfalfa. allowing the crop to be more drought and disease. think stalk rot symptom's. http://images.search.yahoo.com/search/images?_adv_prop=image&fr=yfp-t-701-s&va=corn+anthracnose and there are many trends of thought that low soil K. or the available soil K is, ( and Zinc. I like at least 4 to 8 ppm soil Zinc levels. ) or can be responsible for such diseases. So I personally see the K and Mg going into the soil solution, a stated concern of MattH. as Mg. can be an issue if not available to the plant. as well as K. so as stated by Joel. the application of Calcium, on High Magnesium soils can, and does allow much needed Nutrients to become soluble for Plant feeding as necessary. from my observations, and many farmers having observed the positives. and why many Thousands of farmers are spreading Calcium products this Fall. across the Corn belt regions. and why so many soil and crop advisers getting paid for results, On the Farm. are so intuhttp://images.search.yahoo.com/search/images?_adv_prop=image&fr=yfp-t-701-s&va=corn+anthracnosene to when and where the appropriate rates and sources of Calcium Products are to be applied for the best ROI of the individual farmer. It would be an extreme case if K or Mg. were to be leached excessively any more than Calcium or any other soil Cation. Certainly NOT Like soil applied Nitrogen would Leach. under all and even Normal situations. and NO one will argue the point of NOT applying Nitrogen for the good well being of the Farmer. So in NO way do I see an issue with Cation Leaching. and in Fact. I like to see some deep leaching of Calcium. for many reasons. in my opinion. John | 
Sulfates, potassium, and magnesium
