Magnesium is a very essential element in the growth of plants because it helps in photosynthesis. The chlorophyll molecules contain magnesium ions and a deficiency causes yellowing of leaves. Furthermore, magnesium is used in sugar synthesis, increase of iron utilization and in starch translocation.
Magnesium supports plants by facilitating the distribution of phosphorous throughout the plant. Since phosphorous is essential for developing flowers, fruit and roots, a lack of magnesium results in plants that fail to produce fruit or that are unable to take in enough other nutrients due to an underdeveloped root system. The oldest leaves of a plant with a magnesium deficiency will have edges that appear yellowish, and in the center of each will be a light green area shaped like a lance.

I've never seen a Mg deficiency in Texas field or fruit crops. Even my sand in CA tested very high, 400 ppm. Here 300-500 ppm. Blueberry media 130 ppm. The critical limit is 50 ppm.

Mg and Ca in my mind go together as both tend to be present in limestone. But as I said even my blueberry media test high in Mg.

Magnesium and calcium will tie-up Nickel in soil Nickel not available has big affect on plants, things that happen small round leafs no point mouse-ear called. Terminal die back fruit set none. Diseases come into plant leaf spots, scab, bacterial spots and others. Nematodes love plant root low in Nickel. Spraying Nickel on foliage after first flush growth best then ten days later on Vegetable after seed leaf forum on try-fold leaves then ten days later. Search Nickel on web until find nickel Ni look at images as well read reports all can find. In search you find nickel found a long time ago understanding still going on, but what out there is big help so far you find a lot on Pecans there new info out there that states Magnesium and manganese been call wrong a long time when Nickel instead. You find its more of Gulf Coastal problem sandy land and large pieces sand, but I see more places. Nickel and Copper makes good combo in spray. Nickel used in small amount by plants a table spoon 5% nickel in gallon water all needed are 1 pint to 1 1/2 pints to acre foliage spray. I find on web that gallon Nickel 65.00 and quart way more 1/4 that. I find only one manufacturer Ni and one place sells quarts and gallons mail-order.

Drew that was what I was looking for. I know magnesium is a cation and its essential. You might check out this article http://www.ctahr.hawaii.edu/mauisoil/c_relationship.aspx. Fruitnut to your point I think the magnesium is there at most sites but could be locked up in the soil by some other mineral at my site thus making a deficiency.The leaves here are sometimes slightly yellow but with the introduction of magnesium turn deep green. The plants are not picked on by insects any longer etc.. I add 10 year old composted cow manure around the fruit trees and work it in the soil every several years and add wood chips or hay a couple of inches thick on top of that area to hold moisture http://www.planetnatural.com/composter-connection/soil-science/compost-soil/. I do the same when I plant fruit trees except add the compost several feet down in the hole when i plant the tree. Magnesium is the one cation that if you add it on my land you see an immediate positive response. 3 years ago I started an experiment with biochar and added some to 10 or so nanking cherries and left 10 or so cherries without biochar. Those cherries with the biochar produced three times the fruit and were then highly picked on by rabbits during winter. The results on leaves , fruits etc was similar to what i see if I add magnesium. The other nanking cherries were not touched by the rabbits which to me indicates they were considered by the rabbits to not be as nutrient rich. There is still a lot I don't understand about things such as biochar and magnesium but am getting a better understanding. Biochar once added seems to make a very long term change in the soil in a good way if added in sufficient amounts. My suspicion is that because biochar is made from old wood that the tree was up taking trace minerals from 40 feet down and those minerals exist in the charcoal. There is much more to soil than NPK for sure. Great info gator rider thanks for posting that I had never considered nickel at all! I will research that further. Fruitnut I'm suspicious that the soil test tells me whats there but does not tell me whats usable. This clay soil is sometimes hard to figure because it is very high in macro and micro nutrients and wont give you any of them.

This post was edited by ClarkinKS on Sun, May 4, 14 at 8:44

Our ph is 8- 8.5 so we are very alkaline

The sulfur in the Epsom Salts ( MgSO4 ) lowers soil pH and frees up some minerals.

Try adding plain soil sulfur for a pH decrease without the added magnesium

lazygardens that makes sense but it is not the case because i did try sulfur because i suspected the same thing several years ago and even tried it in large quantity and it made no difference at all except it did lower the ph. I abandoned the project and planted blueberries there for a few years. The ph has now returned to normal in that spot and this year i went from growing bushes there to apple trees.

This post was edited by ClarkinKS on Sun, May 4, 14 at 15:47

MgSO4 has a neutral reaction. It doesn't decrease pH.