New fence posts splitting

It depends on the size of the split, I suppose. Frost can also become a factor with splits in wood. The moisture in the tree will take years to reduce plus the treatment if it's treated. I have seen many posts during my career and some with large cracks over 2-3ft long. New and old. Still the post has great structural integrity. If the post has much movement during applied pressure, yet the bottom doesn't move. Then the post may not last long. If the post has minor movement, plus no indication the split/crack is the cause. Then I'd say the post should still last year's. Hope this helps.

If your fence posts start to split and twist And are not pressure treated Damp and and rot will set in much faster At ground level and being set In concrete Don’t put concrete underneath the post this will speed up the rotting So treating the bottom third of post before installing rot would be much slower So treat posts more frequently if splits are at ground level

Hi all timber posts will crack and open up this being a natural product but it is expected to return to normal in the colder wet times as the wood shrinks and expands ! As long as the crack doesn’t go more than halfway through the post as British standard states Hope this is helpful

If you feel posts are bad then I would paint them and that would seal and prevent water get in