|my 4 inch maple tree has a split in the bark the length of the trunk it is open to a depth of 3/4
|Splitting bark isn't as much of a concern as if the entire trunk is split and you are able to see daylight through the split. If it's just the bark, it will callous over on its own as the tree heals the damage. If the split is entirely through the trunk, the tree may not be able to heal the wound. A three-quarter inch split is probably due to sunscald. You might try using a protective tree wrap over the trunk until the tree develops more mature and harder bark, which will be less prone to splitting. Good luck with your maple.