The pilot reported that, during a practice soft field take off in light wind conditions, as the airplane's nose wheel lifted off the runway, he released the aft pressure on the yoke. The airplane "found" ground effect and "all felt normal". The airplane then began to drift left, he applied right rudder, but the rudder input had little effect. Since the landing gear was not yet retracted, he landed the airplane on the grass off the end of the runway. During the ground roll, the left wing hit a tree and went through a barbed wire fence. The airplane sustained substantial damage to the left wing. The pilot reported that there were no preaccident mechanical failures or malfunctions with the airplane that would have precluded normal operation. The automated weather observation system at the accident airport reported that, about the time of the accident, the wind was from 100° at 5 knots. The pilot departed on runway 32.