My apple tree doesn't have apples every second year.

[ve3wou]

My old apple tree has plenty full apples one year,then next year nothing apples---just within 10 apples. Do you know how to do for equal apples every year?

[rainbowgardener]

"There are a few things to understand about the behavior of an apple tree. Most apple trees, when left to their own devices, only produce a large amount of fruit every other year. In other words, they are naturally biennial. We can change that to a large extent through fruit thinning. Thinning involves removing excess fruit to allow space for remaining fruit to grow large, and to allow flower initiation and development for the following year."

https://www.marshallindependent.com/page/content.detail/id/510301/Bearing-fruit--taking-care-of-apple-trees.html

see article for more information

[JONA878]

I would just add one other thing to RG's reply.
There are some vars that are just plain Bi-annual in nature.
Blenheim Orange and Millers Seedling come to mind straight away.
No matter how much we tried to get these two to crop regularly they just will not.
In fact in the case of Blenheims we planted some two years apart to see if they would give us a crop on alternate years......the blasted things had a chat and within a couple of years had reverted to the same year for their ' off ' year. gg`

But as RG has said usually thinning is the critical reason.