First, those DIY kits are notoriously error prone, especially on calcerous alkaline soils, as are typical in the western U.S. I urge you to get a proper soil test before adding much of anything to your soil.

Yellowing is a symptom that fits many conditions. It could be low N, low sulfur, low Mg, too much moisture, etc. If your soil is alkaline and if it were high in P, the first thing I would suspect as a soil condition is poor iron and zinc availability. In that case a very reasonable treatment that is unlikely to adversely affect anything in the soil would be a foliar spray with chelated iron and zinc. A modest addition of an organic N source, like bloodmeal, should also be safe while you wait for the results of a soil test.

Yellowing of a plants leaves, chlorosis, is the result of plant not making chlorophyll and that happens for a number of reasons. In spite of all the myths there are about the benefits of Epsom Salts, Magnesium Sulfate, you cannot add enough to your garden to even start to benefit the plants.
Before starting to do something about the chlorosis fins out what is causing it.

Here is a link that might be useful: About plant chlorosis

"In spite of all the myths there are about the benefits of Epsom Salts, Magnesium Sulfate, you cannot add enough to your garden to even start to benefit the plants. "

Kimm, why do you keep trotting this stuff out? When you say stuff like that it might make someone think they can't possibly do harm with mag sulfate, when in fact it's pretty easy to toxify plants with it. The reality is the exact opposite from what you are saying, especially for a small garden space S and Mag can certainly be raised significantly with epsom salt (and in many cases that would be a benefit). Any such strong salt would be a heavy application at 2-300 lbs per acre so do a little math.

A quick calc using amendment standards commonly employed by soil labs:

- average soil mass at nominal "plow depth" ~ 2 million pounds/acre
- 1 acre = 43, 560 sq. ft
- 1 ppm addition to soil = 2 lbs per acre
- Epsom salts is ~ 10% Mg, so 20 lbs of Epsom salts supplies 2 lbs of Mg
- the acceptable normal soil range for Mg is about 50-300 ppm, depending on soil type and extraction method

Putting that together, to raise the level of Mg by 50 ppm would take 50 x 20 = 1000 lbs of Epsom salts per acre, or 2.3 lbs per hundred sq ft, or 23 lbs per 1,000 sq ft.

It's worth noting that soil Mg levels are influenced by soil type, pH and irrigation much like Ca - Mg is generally considered a mobile element.

TropicalChallange - since you're trying to diagnose soil issues based upon plant symptoms/appearance, I'll pass this along -- it comes from a self-study continuing ed program that was put on by Montana State University. As you go through it note how many different potential contributors there are to chlorosis and interveinal chlorosis. The decision trees under both Mobile and Immobile nutrients may be both insightful and helpful.

Here is a link that might be useful: Plant Nutrient Functions and Deficiency and Toxicity Symptoms

FWIW, unless you have a magnesium deficiency, Epsom salts as a garden amendment is worthless. Magnesium deficiencies tend to occur almost entirely in heavily cropped soils and/or acidic soils. While yellowing leaves can be an indication of a lack of magnesium, it is also an indicator of various other nutrient deficiencies as well as improper cultural care or disease issues. You need to nail this problem down to the proper cause before you consider attempting to correct.

Before you randomly start sprinkling stuff like this around, probably unnecessarily, get your soil test done and get an accurate diagnosis of what is causing the yellowing foliage.

In low-S soils (common in the east) there will be a benefit from the sulphate content. Most soils don't need mag, especially where they have been limed with dolomitic. I'm not encouraging the use of expensive (when speaking of acres) salts, just pointing out that it entirely untrue that it is difficult to use enough epsom salt to make a difference.

Looking at TX's calculation, we can easily see that tossing down a standard 4 lb package of epsom salt on a 10x10 plot would be a heavy dose. Going by Kimm's statement, a person might think that doing that would be inconsequential.

Sulfate is one of those fairly high mobility anions - in high rainfall areas it is quite subject to depletion via leaching. It is also one of those things that comes with rainfall as sulfurous gases are absorbed in rainwater and deposited.

Epsom salts is better source of S or sulfate than it is magnesium - you get 13% S, or 39% sulfate, with Epsom salts. With gypsum you get even more (~18.6% S or 56% sulfate), and it's cheaper. Then there is also elemental sulfur if you want a big hit and nothing else, but it will lower pH.

I really appreciate all the advice. Where I live on Maui it's HOT, and rains maybe once a month/every other month. The soil is sandy, and cakes hard on top. I water in the am only now. I have dealt with tons of new issues I have never had in my northwest gardens. Powdery mildew, tomato plants getting yellow curl virus from the hordes of white flies, tinny caterpillars eating all my greens and broccoli, it's too hot for sugar snap peas, peppers either have nematodes, or board mites, and the ones that don't have that are yellowish.
I have a 100 sq ft plot at least with many box stuff around it. I went ahead and got a nice 10-7-7 fertilizer, and epsom salt. I only put about a 1.5lb around the whole thing. We will see. You all may have convinced me to get a soil test, but I'm going to have to wait now since I already put stuff around the plants.
I'll post in a week or two and let you all know how it went.

Maui, eh? Okay, now I'm really jealous!

See the link below for some good background information about your soil. Use the map at the bottom to figure out the soil taxonomy, then click on the soil type to get some better understanding of what you're dealing with. My SWAG, not knowing where you're located on Maui, would be Aridisol.

Here is a link that might be useful: Soils of Maui County

Supposedly the good old days of getting enough S for crops merely from acid rain are no more.

pat - yeah, but the paint on your car last longer

Just a thought here -- no matter how much of anything you add to your soil, if the pH is wrong, the plants won't be able to take up what they need. Alkalinity is the more common problem, but it can happen with overly acid soil, too.

The link below is my favorite illustration of that. Always make sure the pH is correct. Get a soil test at your Extension office. The meters and home tests from Home Depot are spectacularly inaccurate.

TXEB, that link is wonderful -- takes me back to soil science class. I always wanted to buy a place with mollisols, and I think we did, only to discover that the home builders had stripped off every ped of topsoil. Cost a fortune to buy it back.

Here is a link that might be useful: {{gwi:299086}}