I think it is well understood that BER can be produced by low soil Ca, but that high soil Ca doesn't prevent it. As well as watering irregularities, I believe extreme pH can produce it. Are you considering iron sulfate to acidify your soil? Also, over-use of nitrogen fertilizer creates excess foliage, which suck up calcium that should go into the fruit. I gather that over-watering can also produce it. These things are all laid out in extension literature.

These were my soil results (wish it would let me have attached them to begin with!). I think the pH (which is surprisingly still in the optimal range) could withstand some iron sulfate (which I'm low on)? That's my plan this year. And to actually keep an early eye out for BER as I had assumed since my calcium was high that my poor tomatoes wouldn't suffer from such an issue.

If you had your soil tested by a lab to determine those levels of Ca, Mg, etc did they also include the pH level? A pH test is fairly routine for soil samples and as Dan points out pH can be an important factor. Typically a pH of 6.5 is ideal for most vegetables and a reading above 7 (on the alkaline side) may inhibit mineral availability for the plants.

eta, just saw your results after my post. pH seems ok..

Looking at that pic above your problem may go far beyond a simple BER problem if that tomato plant is still in the ground and growing? I'll assume it was pulled and tossed into a pile seeing as how the leaves are wilted?

Oh yes! The tomatoes were pulled and the leaves are pruned zucchini leaves!

I believe that's a birds eye view of OP's compost heap. The leaves are mostly squash, not tomato. But there is a bit of tomato foliage bottom right which could be blighted from what I can see ... which isn't much.

eta OP's comment wasn't there when I posted.

Ha, my bad, should have recognized those squash leaves. That's quite a BER problem and I wish I had an solution for you.

Well, keeping soil moisturized is the most important thing. Sounds like you're doing that. In dry, high heat conditions, fluids flow to the leaves, which are evaporating water rapidly, and dissolved calcium is diverted away from the fruit, which can result in BER. But I'm assuming that isn't an issue for you in Zone 4. Turns out that BER is almost uncorrelated with soil calcium. If you don't have any, that's a problem. If you have a little or a lot, it should be enough. Most everyone has at least a little. There are varieties that are more resistant to BER. Might try those. Some people think that foliar calcium sprays help. But I don't think that's been proven.

Please try following my method to control BER. Save all your used coffee grounds and at tomato planting time work several large handfuls into the soil around each tomato plant. At the first sign of tomatoes forming on the plants scratch more used coffee grounds lightly into the soil surface around them. Organic and should solve your problem.

I can't exactly tell from the picture, but is it possible it's buckeye rot instead of blossom end rot?

Nothing magic about coffee grounds. Though they do hold soil moisture, and acidify slightly (though that's somewhat of a myth). Very acidic or very alkaline soil can tie up your calcium making it inaccessible to the plants. Though your pH looks close to neutral. But compost will serve the same purposes.

A fungus infection damaging the fruit is an interesting possibility, though you'd see that all around the fruit, not just at the blossom end, and it usually happens where the fruit is in contact with the soil.

Here's a crazy idea (does no harm). I posted a few years ago that I'd add a little calcium chloride (environmentally friendly ice melt) to my fert regimen. One teaspoon per tomato plant appears to prevent BER or at the very least does no harm. You could experiment with a couple of your plants this season to see for yourself it it makes a difference. Also if your tomato clusters set 7-8 fruits then thinning them out to 3-4 may help.

What is not entirely clear is the form that your soil calcium is in. If, for example, your calcium is tied up in a mineral carbonate (think eggshells) it will have zero nutritive value to the plants. I believe the standard measurement strategy is to use an extractant (ammonium acetate, probably) to release the Ca cation (Ca++) from soil carbonates. Ca++ is what has nutritive value to plants. As such, in carbonaceous soils, Ca++ is overestimated using the extractant. What you're told you have is what you POTENTIALLY have, but don't ACTUALLY have. By that token, calcium chloride might be useful, since when it is dissolved in water, what you get is Ca++.

OK, I asked my soil test lab (TAMU Agrilife) about their calcium analysis. They say they use the Mehlich3 process, which most analysis labs probably use. This involves a weak acid that will dissolve some limestone materials, but not much of it. So most of the calcium assessed that way is actually the Ca++ cation nutrient. That is, if you have limestone (calcareous) soil, some of your measured calcium will indeed be non-nutrient calcium, but much of it will be the Ca++ nutrient. So with a high value of measured calcium in your soil, even with a lot of limestone, you're probably good to go, calcium-wise.

This is just a reminder of why eggshells are NOT a way to add calcium nutrients to your soil. Eggshells are rocks and, until they dissolve, which won't happen for a long long time, they won't add any calcium cations to the soil. Eggshells as an effective calcium nutritive supplement for soils is a total myth.

I should add that there is some controversy about whether foliar calcium sprays help avoid BER in tomatoes. They are commonly used in fruit to extend post-harvest lifetime, though.

I watered consistently as possible.

What does that actually mean? How were you watering? As in how often, how much water when you were watering. How much dry was there between waterings, be they by you or nature?

Other things to consider. If you aren't using mulch, you could be getting uneven watering zones between the upper and lower root areas. If you are using mulch, you may be watering the much more than the plant and so you aren't watering like you think.

How do you handle your root mass.. what does it look like when you pull the plant at the end of season? Sometimes BER can be caused by root issues. Damaged, mishandled, or stunted roots can't take up the water and nutes like they need to. Since they can't take up the water and nutes, BER can result. If you have small or poor root masses or very shallow root masses at the end of season, your plants probably aren't intaking as well as they should.

Depending on what you are amending your garden with, you could be contributing to salt shock. Like if you use calcium nitrate, that's a salt. Not the same kind of salt or potency as table salt... but if you are using a lot of it, that can build up and could cause salt shock.

Your report says your low on nitrogen. Nitrogen is really important to plant health, things like cell structures and how the plant is able to interact with calcium and take up water.

Does temperature affect calcium uptake as well?

And I agree that variety may be a factor.

Good question about temperature. Some interesting findings. First of all, calcium tends to protect plants from heat stress. Calcium, along with potassium, regulates the opening and closing of the guard cells around the stomates in leaves. Those stomates open to allow evaporation and cooling. Secondly, it's been found that the calcium content in plant cells rises somewhat dramatically when it gets cold. Not clear why they do that, and the effect is greater the faster it gets cold. That all being said, calcium deficiency in soil is very rare, so I wouldn't necessarily shovel calcium on your soil to protect against heat.

Just wanted to mention that despite the damage, the rest of those green tomatoes are likely still OK to eat - I like to cook with mine after trimming off any bad parts. I make a yummy pasta topper with sauteed sausage, onions, garlic, parsley and chopped green tomatoes - I also add them to stews, taco meat, chicken & rice, etc...

THANK YOU EVERYONE for such thoughtful, helpful, and insightful responses!!! I'll try to provide answers to any asked questions (sorry if I miss some) and will keep everyone updated on my progress this year!!

Watering - I tended to water every 3 or so days - sometimes more when the weather was hot - not so much after it rained a good deal. Running drip hoses isn't ideal in my set-up so it was mostly by hose. I would water a great deal at the base of the plants (trying to avoid the leaves) until the area seemed nice and saturated. Sorry - not greatly scientific - but I'm definitely open to suggestion. The weather here gets pretty hot (upper 80s. low 90s), windy, and was mostly dry last year.

I fertilized before the season started with a 12-0-0 fertilizer (Blood meal) - per the instructions for my square footage - so I'm assuming it started low - was somewhat replenished with what I added - then was quickly depleted by the heavy feeders I planted (10 tomato plants, green beans, corn, a zucchini plant, cucumbers, carrots, marigolds and a pepper plant!).

The tomato plants seemed pretty healthy minus the BER - lots of production, no cracks to the fruit, deep roots. I planted Sun Golds, Brandy Boys (which had the rot), Pineapple (which had the rot), some mystery cherry tomato plants, and a Sart Roloise (which REALLY REALLY sadly had the rot).

Is CALCIUM PHOSPHATE easily broken down in the soil to Ca++??? My organic chemistry is pretty poor at this point lol. I think given my soil analysis - I think it would be likely that the calcium is bundled with the phosphate since they are both high.

I've never cooked green tomatoes before but thanks for the tip that they're still good despite the rot!! I'll have to find some recipes to use them up (if I can't figure out how to solve my problem this year lol).

THOUGHT ON ADDING CALCIUM CHLORIDE to the soil?? At least when planting or at some point??

THANKS AGAIN!!!

Calcium phosphate is insoluble in water, so I can't imagine it would do anything for your calcium nutrient-wise. It's pretty much a mineral. I guess if you dissolved it in acid it might contribute calcium ions. Now, if your soil has been tested, and has loads of calcium, why would you be inclined to waste your time adding more? Your BER problem is NOT calcium deficiency.

MIght be worth noting that magnesium can interfere with calcium uptake, and your soil seems to have an overabundance of that. Adding extra calcium won't fix it. Gypsum can reduce magnesium by producing magnesium sulfates, which are easily leached. FWIW, gypsum will also flush out manganese, but your soil has plenty of that.

You don't need to add calcium. Your readings are so high it might be contributing to the BER issue. Do not add anything more that you are already high on. It's like if someone is anemic and needs iron- they can eat a steak, but dropping 50 steaks on the table isn't going to make them eat them all immediately. They can only consume so much at a time.

If you want to add, add nitrogen. You are extremely low on it. It's really important for many functions in the plant, including the processes for nutes to get around.

" THOUGHT ON ADDING CALCIUM CHLORIDE to the soil?? At least when planting or at some point?? "

As I mentioned it would be best to experiment on a couple of plants this season to judge the outcome compared to your untreated plants. CaCl is typically the main ingredient in those commercial BER sprays where the Ca solution is absorbed through the plant foliage. Whether it works as advertised is questionable but transporting Ca via the root system seems like a more reasonable approach. I add a teaspoon of CaCl to my regular fertilizer soil application about 2 weeks before planting but probably the most critical timing would be to apply it during the initial blooming period. It dissolves easily in water and can be used in that manner too when watering the plants.

Again, adding calcium to soil that is already rich in calcium is just avoiding what might be the real problem. Yes, calcium deficiency is what can cause BER, but you appear to have loads of it. Now, if you don't trust your soil analysis, all bets are off. Not having air to breathe can cause asphyxiation and death, but as long as you have air to breathe there isn't much point in trying to get more.

I contacted MySoil as they did the soil testing and I asked them about my calcium (whether it was calcium phosphate, etc) - and this is what they replied "We are evaluting plant available calcium. Based on the results and sample provided, the soil certainly has enough Calcium." I included the youtube link they sent as well https://youtu.be/1FL4Z20uOUc?feature=shared

So I think this Spring I'll plan on trying to add some Iron sulfur and some gypsum and watch my tomatoes carefully to see what happens. Any suggestions as to how much to add? I have a 300 square foot garden . . .

Thanks!!!!

Yes, calcium that is not plant-available is often quantified in what the soil analysis people call "mineral analysis". But good to be sure that what they are measuring for you is actually plant-available calcium. As to detailed recommendations for application-rates, you can just look on the label, but I'd send a question to your local extension folks. Not sure where you are, but most states have ag extension services that are WONDERFUL in giving plant-growing advice. I send questions to mine and, within a day, I have an answer back from a certified horticulturalist. That's their job. Tell them where you are. They will likely have insights into your local soil chemistry and, in your case, might have local wisdom about BER mitigation.