To reduce splitting ends in frame timber, I soak the ends of the
individual pieces in  water, at a depth of 2 inches (5 cm.) for 15
minutes.
Doesn't work all the time, but does limit splitting in timber that has
been cut and stored.

Also, the type of soft wood used influences the % of splits.
During my travels in Canada, I have been told which is best for frames,
boxes etc., but not being used to the range available - have
forgottenwhat's what.
Maybe others may comment on this!

Peter