Calcium Deficiency Damages Apple Crop

This has been a very good crop year and most orchards I manage have a bumper crop of beautiful apples, but the late varieties in my own trees are a complete mess. Most apples are disfigured and rendered unfit for storage with corking- the unsightly dimples presumably the result of calcium deficiency.

Why this year for the first time after over 20 years of cropping mostly sound apples? I’ve had problems with a couple varieties- a Jonagold that gets too much water because it sits by the runoff from my cistern and a Braeburn just below it have had problems in the past. This year even Goldrush has 75% of its apples showing these symptoms.

So what gives? My theory is that my acidic subsoil along with the heavy crop have created a calcium deficiency as a result of Aug drought. I’m guessing the roots were unable to draw calcium from the much sweeter topsoil at a time when they needed lots of it because the soil was dry where the calcium was available.

Years ago I read that liming the subsoil before installation can be important for this very reason. All I’ve ever done is lime the base of holes and backfill during installation and kept the top soil close to neutral with surface apps beyond this. It has taken 20 years of cropping before my trees suffered from lack of calcium below. Now I have to figure out how I will prevent this from happening again. Probably calcium sprays during summer drought would be easier than getting it into the subsoil now.

As you know according to reports in Good Fruit grower the commercial growers spray lots of Ca even in WA state with high pH soils. I’ve never had serious issues on my medium to high pH soils. I think Calcium Nitrate is a favorite spray material but my memory might be bad.

Your hypothesis as to why now makes sense to me.

I have told by local growers that our clay soil gradually becomes more acidic over time and thus to apply lime around your fruit trees every few years. My thought is to spread a few hand fulls of lime around the perimeter of the trees but no doubt calcium sprays would have a much more immediate impact.

This article may help It lists a few minerals that may tie up calcium. I have always heard a calcium shortage will be seen in apples or tomatoes first because of the negative affects . Each apple contains 6 mg of calcium

I actually bought a jug of foliar (and fruit) calcium this spring intending to use it on Honeycrisp apples to help control bitter pit. Instead I decided to lean on Captan to see if that would solve the problem by itself which in the case of HC it pretty much did. If I’d gone with both I wouldn’t have learned anything specific.

I think it may require a perfect storm for this to happen on my site with my trees- my top soil is exactly at the pH where I want it. I will probably try a couple of experiments including the spray on a couple of trees. I might also try trenching in some calcium to get it low in a few spots, but I realize that commercial growers usually rely on spraying it onto the fruit directly every single season.

I’m trying to keep things as simple as possible but it all just gets more complicated as new problems arrive.

If this only happens when there is a period of long drought (preventing CA uptake from the upper soil), maybe it can be solved by irrigating a bit during the worst periods? I usually go around with a hose once or twice a summer. While I haven’t picked most of my Goldrush, I haven’t noticed any corking. I have seen one with cracking and all the un-bagged ones are cosmetically ugly due to sooty blotch & flyspec (I don’t mind that- it gives them character :slight_smile: ).

I don’t have a great well. I can water all I want as long as the soil is wet! I may go back to mulching my trees. I’ve stopped since they became more than big enough and excessively vigorous. I can certainly mulch the Goldrush.

I collected some leaf samples a few years ago and had them tested when I had a similar problem. The recommendation from the lab were for boron and calcium sprays. There is a very fine line with boron and its easy to go from a beneficial level to a toxic level. I considered adding gypsum to the soil as a source of calcium, but never got around to it.

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That got me wondering what the best ph would be for apples and a concern for adding too much calcium. Various recommendations on the internet range from PH 5.0 to 7.0.
My mostly shady yard only has room for one apple tree at the moment. The natural ph of my land is 5.5. The one apple tree I planted hasn’t produced fruit yet so I don’t know how it will do at 5.5.
My plum, pluot and peach trees are doing OK at 5.5 but now that I’ve done some research I’m thinking I’d be better off at 6.5 with more calcium.

5.5 is more like a blueberry pH. I’d agree apply enough every few yrs to achieve and maintain 6.5

Cornell suggests pushing pH up to 7 as the ideal for apples- more commonly the recommendation is around 6.5.

I was surprised that some websites said 5.5 and even 5 was OK for apples. Perhaps the meaning was that they won’t die at that PH. I’ll be adding some calcium this week to get into the 6.5 to 7 range.

My land is sand topped with 4 inches of topsoil from thousands of years of plant decay. My PH readings of 5.5 were from the topsoil. I decided to dig down about 8 inches to were the soil changes color. PH is 6.5 to 7.0. As they say, things are not always as they appear on the surface.
So my apple tree is fine but now I have to look closer at my blueberries.

I have very healthy blueberry plants growing in the reverse. Most of the roots are undoubtedly in the top 12 inches where pH is in the low 6’s but the pH drops to about 5.6 below. It doesn’t seem to matter where the plants get their iron as long as its in some part of their rhizophere. That’s my anecdotal take, anyway. Seems to be an inadequately researched issue although Whitcomb has done experiments with surface apps of sulfur and cured iron deficiency chlorosis in pinoaks before pH readings showed an improvement. Free iron was apparently obtained from narrow sliver of soil on surface.

We had a perfect storm like that ten years ago, and the commercial orchards had to throw out a lot of fruit. I don’t recall what made that year different.

Proceed slowly with soil pH changes using lime until you have a good series of soil tests that give you a CEC(cation exchange capacity) measure, lime needed per acre and the soil pH. Soils with a low CEC can become hard to manage if the exchange sites are overloaded with Ca. cations making P, K, and Mg. deficiencies more prevalent. Gypsum (Calcium sulfate) may give you better short term results w/o changing soil pH radically. Always moderation with lime.
Something else to think about maybe a sulfur deficiency. Here in the midwest, some of the highly productive soils are experiencing sulfur deficiencies from the lack of coal burning, at least that’s what experts in growing corn and beans are saying. I wouldn’t think you would see that in your acid soils but having sulfur checked in soil testing isn’t expensive and could lay to rest another question.

Chikn, NY apple growers don’t tend to delve into minutiae on the issue. Just follow the pH and that seems to be all required in most situations- growers in acid soils apply ground limestone to their soils as a routine without negative consequences as long as they are following guidelines based only on pH and soil texture.

Of course, part of orchard management includes a certain amount of soil testing which I used to do by the score (but now usually only when diagnosing a problem) but I don’t remember a single soil test that affected prescribed calcium app rates beyond the question of pH and texture. No legitimate laboratory I work with has ever prescribed the use of gypsum around here. Mostly it is used in sodic, alkaline soils, which are not prevalent in my region.

I don’t even believe there is usually a problem when dealing with trees with using massive quantities of lime to change the pH quickly. They have roots above and below and are much less sensitive to temporary imbalances in the very top soil than annual crops that begin root establishment in the very top.

I wonder if your Ca deficiency expressed itself due to water issues, like blossom end “rot” on tomatoes. On tomatoes that is typically the causal factor.

I’ve used calcium nitrate in my foliar sprays for many years. Mostly as an N source, but it also adds Ca. I also use lime in some of them as well (when not using the Ca nitrate). In the greenhouse, these have worked well on tomatoes, but even with them, highly susceptible varieties can get blossom end rot if the watering schedule is disrupted and they get water stressed.


Steve, I suggested it was a water issue in my topic note. What is mysterious is that we’ve had drier Augusts and drought is usually a harbinger of superior quality. I expect it was the result of more than a single issue.

Alan, could it be a combination of a very wet spring/early summer with late season drought? I’m not suggesting that is the case, just wondering if the combination might make a difference.