The pilot took off without first performing the calculations that would determine if the aircraft could out-climb the surrounding terrain under the ambient conditions. Because of the gusty winds, turbulence, downdrafts, and high density altitude, it became evident soon after takeoff that the aircraft might sink into the unfavorable terrain along the departure route. The pilot therefore elected to make a precautionary landing in an open field. During the landing roll on the rough/uneven terrain, one main gear collapsed and the aircraft sustained substantial damage.