Sometimes I see or work on fruit trees that just aren't getting much fruit. I think a lot of times this is the variety and wonder why more people don't plant something like an Akane apple that seems to produce something every year.
But it is not always the variety....and it is not always a cross-pollination problem....and it is not a pruning problem when I work on them....and it is not an inadequate bee problem, either.
So, what is it? I confess the next thing I need to learn more about is how to understand "soil samples" but I want an easier answer....if that is possible.
I wonder if anyone has noticed a recurrent "culprit" in the way of inadequate nutrients? Not enough phosphorus, perhaps....too much nitrogen? not enough boron? not enough magnesium?
I have limited success with "scoring" to make trees more fruitful....and am now trying Epsom salts (magnesium)......
How does the homeowner get his backyard tree to produce when there is no other known culprit? That is my question.
(shrug) some varieties are more prolific than other varieties.
People tend to plant either what they like or what was available that day at the big box store. If they plant a variety that is a shy producer, they really have no one to blame but themselves.
You get out of it what you put into it, and if you've put in no thought or effort, perhaps the results are going to be thin.
You don't say where you are located. In some areas, it is cold enough to freeze the fruit buds during winter, and then there will be no fruit or flowers that spring.
Apple trees must be carefully matched to the climate and growing conditions, which goes right back to making the effort to plant the correct tree.
I’d say the last 3 out of 4 years have been poor fruit producing years for me… and that’s with a solid 25 year history. The trees are healthy and nothing’s changed in the soil, but it seems the spring weather, or perhaps hard & early freezes, or even exceptionally hot spells in summer may be to blame? Some trees are ‘biennial bearers,’ meaning they’ll set far too heavy one year – and barely anything the next. Gravenstein apples are like that…
Some trees are shaded out by massive evergreens folks planted around the same time as their ‘orchard’ (often next to them). Trees need sunlight nearly all day to prosper, if not, they’ll survive, but fruit production is very limited. Pruning is important too, yearly, not once every decade... If a tree is allowed to continually put it’s energy into new growth, it will. Pruning stresses the tree into thinking it had better set fruit or perhaps die.
A lot has to do with pollination, though. I’ve got magnificent Asian plum trees consistently barren due to the lack of an adequate pollinator. Sure, they’ll bloom like crazy, but without the perfect mate, nothing – year after year. They’re pruned, watered and fertilized, but without that perfect pollen …they’re labor-intensive specimen trees…
I think the ‘scarring’ of trees is an outdated concept; if the conditions are right, they’ll produce to the best of their abilities. And, some just don’t set all that heavy. Inbred, many new varieties are simply weak trees prone to all kinds of maladies and dependant on very specific pollinators, as they’re related to most. ...and then some trees, like peaches and nectarines only produce so long…
Lot’s of possibilities! That’s why most of us just keep diggin and plantin until we finally get it right… The never ending hobby 
I'm leaning to wondering why we just don't plant Liberty and Spartan apples to avoid the scab problem ......
and then why don't we plant Akane apples if we want to be sure we have a good crop every year.......
I don't care so much about the exacting taste of a particular variety....I just want a variety that can be counted on for our wet Pacific Northwest.....and then not have to try to figure out the "puzzle" of what specifically ails the tree.....
Liberty and Akane trees for me......let the Eastern Washington growers plant the varieties that sell in the stores. 
Idyllwild
simplepress
jafar
Marsha H
Viron
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