Soil at 7.8 can be lowered in pH by applying sulfur but only if the soil doesn't contain free carbonates. You can determine if it has free carbonates via soil test or by testing it yourself with a strong acid. It will fizz if you apply a strong acid to soil with free carbonates.

What makes you think the pH killed your trees? Usually what you see is iron chlorosis. I've grown apples for years at pH 7.5 to 7.8 without much issues.

'Fruitnut'.
I have been dumping ACT on my garden, not thinking! Ph is very high, plus I find 'Corky Root Rot' is now a major problem, I have inoculated the whole garden by the ACT. Killed the raspberries, strawberries, two young Apple trees. Managed to save the Blueberries, mainly because I treated with sulphur.
Now I'm trying to correct the problem. At the moment both trees are in tubs, waiting for the snow to leave!
You mention iron cholrosis, what would be the signs?
I have a soil test but it doesn't mention carbonates. Could you give more information please?

What's ACT?

Iron chlorosis shows up as leaves with green veins and yellow to even whitish between the veins.

Carbonates in soil are mostly calcium carbonate and magnesium carbonate, also called limestone.

'fruitnut'
ACT? Activated Compost Tea.
I didn't see any chlorosis. The soil test I have had in the past doesn't mention carbonate. It does mention calcium quotes '2470 VH'. I assume that is 'very high'?
Whether this has any bearing or not, the plot is also lacking in magnesium '185 L'.
We live on the Canadian shield which is a limestone area, so I have always assumed the garden was alkaline, but it's only this winter I have discovered how much.
Would appreciate any help you can give me to correct this error.

This post was edited by beeman_gardener on Sun, Apr 21, 13 at 9:34

'fruitnut'
ACT? Activated Compost Tea.
I didn't see any chlorosis. The soil test I have had in the past doesn't mention carbonate. It does mention calcium quotes '2470 VH'. I assume that is 'very high'?
We live on the Canadian shield which is a limestone area, so I have always assumed the garden was alkaline, but it's only this winter I have discovered how much.
Would appreciate any help you can give me to correct this error.

None of that should kill your tree. You could apply some epsom salt, magnesium sulfate, to supply magnesium. And sulfur to lower pH. But don't go overboard on either. There are places you should be able to find online that will estimate application rates of sulfur based on current pH and soil texture. Don't apply more than that recommended to lower pH to 6.5.

If you're not seeing chlorosis then your trees should grow fine even at pH 7.8.

ACT could not be the cause of your problems. My suggestion is to keep looking for the real cause. Did you have a lab do a soil test? Al

beeman:

Al gave good advice. Neither the ACT, pH, nor anything else you mentioned would likely kill all those different plants. Does your soil drain poorly? Too wet kills plants. Salt kills plants as in ACT spiked with strong fertilizer.

Another soil test would be a good place to start. Make sure the salts aren't too high although that is unlikely in a humid climate.

'fruitnut'
I did mention in an earlier post that I have 'Corky Root Rot' in my garden.
In using ACT from compost made in my garden which had also been infected with CRR, I successfully innoculated the whole garden. Now I have a problem with stuff dying all over the garden. My big concern is starting off these apple trees in the right direction and a Ph of almost 8 is not the best.
Corky Root Rot does affect all of the plants I've mention, as well as apple trees.
I haven't ever added fertilizer to my ACT, so salt is not a problem.
I firmly believe that the tress were killed by possibly a number of factors. High Ph, lack of magnesium, Corky Root Rot and the effect of two years of drought.
I intend to add sulphur to lower the Ph for later in the year, a small amount of peat, and mulch with Pine bark nuggets. Plus, I have found a product called Biotamax a bacteria/fungal treatment, used like ACT, but without the disease problems from my compost, which should help with the CRR.
Comments?

My soil typically runs 7.8 to 8.1 and I don't have any problems with apples. Sometimes I will see some iron chlorosis, but this seems to affect some trees and not others so I assume it is related to the rootstocks.

You mention you are in a high lime area, so it is unlikely you will ever be able to fully drop the pH due to the soil reserves of lime. Keep the soil well mulched around the trees, the rotting mulch at the soil surface will carry a lower pH which the tree roots will invade and be better able to extract iron.

I doubt the pH would be the cause of the tree loss or prevent you from establishing new trees. Something else caused the dead trees.

I live in Florida AKA one big limestone. It has been a pain for me to grow blueberries here in the ground. What I have done to correct the issue is site treat the ground with flower of sulfur heavily and wait a few months for the soil to stabilize a bit. At planting a cover the top of the roots with peat moss and mulch with fine pine shavings the break down pretty fast. Every year I replace the peat at shavings that have been composted down. This has kept the soil at a low enough PH for my blueberries to thrive. That being said I grow Florida apple trees (Anna and Tropic sweet) in the soil with a ph level around 7.6 just fine⦠like everyone else said it sounds like your issue is else where.