Only when you need the Mg...the plants will show you when you need it with chlorotic leaf margins (on most plants). It's not to be confused with K deficiency which usually starts at leaf tips.

Too much Mg can inhibit K uptake because they compete for the same uptake sites.

This post was edited by nc-crn on Sat, Feb 1, 14 at 11:07

Agree with above. E. salts are only used when your soil test shows there is a Mg deficiency or the plants display the symptoms of Mg deficiency.

My garden soil has a chronic Mg deficiency but even then I only need to add it at the beginning of the season before planting and again in late July. No way would it need to be added on a regular basis.

Dave

Contact your county's Extension Service office to ask if local soils are in need of magnesium.
And/or have a professional soil test.

Locate that office with this map
http://www.csrees.usda.gov/Extension/

Here is a link that might be useful: locate your county's Extension Service office

I don't know in what form or chemical composition magnesium is normally present in natural soil and how stable it is. But Epsom salt (Magnesium Sulfate) is water soluble, like nitrogen in the fertilizers. This means that it can be depleted and leached by watering and frequent rain, the same way it happens to nitrogen. I usually apply it in small amounts few times in the season. The normal recommendation is ONE TBspoon per gallon. I use ONE TBspoon per two gallons and with that I water an area of about 20-30 square foot.

JMO

Here you will fine an article written by WSU

Here is a link that might be useful: Adding Epsom salts to garden

This post was edited by seysonn on Sun, Feb 2, 14 at 8:26

Florida sand is remarkably consistent throughout the peninsula, though the underlying substrates can vary. I tested two plots in central florida, one high in very deep sand, the other lakeside.

They showed 62% and 58% of the optimum Mag level. Many elements are far lower than that in florida sand, so Mag is a pretty easy one to bring up - probably a couple of applications over a few years will do it.

Mix that OM into the sand!