Sounds like over watering could be the cause. I generally only water my trees (which are in small pots which requires more water) daily for about 25 minutes during the summer (this too is on drip).

A good test is to check the soil down near the bottom of the root ball right before the next scheduled watering. If it is wet enought that water can be squeezed out it is definetely getting to much. It should be lightly moist, but not wet at all. The top 2 inches or so of the rootball should dry out some between waterings. If this is not the case (which I would doubt as much as you are applying), we probably have another issue that may be more difficult to diagnose.

Generally it is not a good idea to plant trees like this in early summer because it is so difficult to get the watering cycle down. Our heat drains all of the water out so you need a constant supply to the roots to prevent burning, but overwatering can kill them quicker than anything else. You really have to have very well drained soil and plenty of water to plant in late spring or summer.

If you can save the tree until fall you will want to back off tremendously in the amount of watering. By next year, you will only want to water it about twice a week or so for about a half hour assuming that the roots have become established. After the tree has been in the ground about a year it is usually safer to not water at all (barring extreme draught like we had last month) than it is to water daily for a JM.

I think Matts watering suggestions are good ...for his area and other similar areas...but I would caution others reading this thread not to "necessarily" adapt this watering regimen for other less dry areas recieving weekly or regular rainfall or not in drought conditions ...You must adapt your watering to YOUR local conditions.