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nafex - Re: [NAFEX] Epsom salts and nitrogen

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  • From: "Donna &/or Kieran" <holycow@cookeville.com>
  • To: "North American Fruit Explorers" <nafex@lists.ibiblio.org>
  • Subject: Re: [NAFEX] Epsom salts and nitrogen
  • Date: Fri, 5 Oct 2007 21:51:16 -0500

Regarding dolomite and Mg, according to CEC notions, Dr. Albrecht and that lot, the ideal Ca to Mg ratio is 6 or 7 to 1. However, it seems that God in his infinite wisdom did not make lime in that ratio, giving us a bit of a juggling act to do. Dolomite runs 2:1 Ca:Mg. All other limes run about 10:1 or higher, we can even get a 33:1 from the Franklin mine near Nashville. Ca and Mg do different things inside plants, and at very skewed ratios you can get deficiency symptoms, like blossom end rot in tomatoes when the soil pH is as high as you would want it to be. Ca pushes soil particles apart, while Mg draws them together. For this reason a tight clay soil will be improved by the higher 7:1 ratio, but will become much stickier if given only 2:1 dolomite. We did this the first year, big mistake. In the end we used the 33:1 lime to drive the pH just a trifle higher than I wanted it, but it brought the ratio back into line. Sandy soils will do better with a 6:1 ratio to hold the particles a bit closer together.
Another way to get some Ca into the soil is to use gypsum or calcium phosphate, which won't do much to the pH but will bring up the Ca without adding any Mg. A local farmer near Carthage TN (source of our local dolomitic lime, so only dolomite had ever been used on his farm) found that his tomatoes did much better after the CaP, as much from the Ca he thinks as from the P. I don't know any way to take out excess Mg after it's in. Plants will eventually use up some of it, so long as you don't keep adding more. In Nova Scotia there may be mostly dolomitic lime, but it's possible that if there is some bigger city not too far away that some garden center may carry some bagged lime from further away. That's what we have found here, that the nearest quarries sell it to farm supply stores loose to haul by the ton, but there are bags for your garden from places further away. Another choice, if you can find it, is any ground rock. Mixed rock dust is supposed to be fantastic stuff. The "glacial till" stuff. Lots of minerals for your plants to choose from. We can't get any such thing down here. My son says that the really fine stuff, what Harvey Lisle calls rock dust or rock flour, is composed of such small and angular particles that it hangs onto water through simple mechanical attraction. He claims their water holding capacity is greater than that of clay. Maybe some of you folks with sandy or excessively well drained soils should try a test plot and let us know what you think. He is also advising us to try the very fine granite dust from tombstones and countertops to seal our leaky pond. He says the stuff is so heavy it will sink down into any holes. He says he throws a handful into any potted plant that is letting water run through too quickly. This implies you could actually make trouble for yourself with it, but so far my practice of throwing it in planting holes doesn't seem to have drowned anything. Of course, it hasn't rained normally in several years... As for the discussion some years back about some of the polishing materials being aluminum oxide, he says a bucketful of that will give off no more aluminum than a bucketful of clay. He does say that in very acidic conditions there will be some dissolved, which does describe our soil, but then the soil would be a menace too, behooving us to add more lime! Donna




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