The pilot reported that, following an aerial application on field, he was returning to a private [air]strip, when the engine began to run rough and lost power at an altitude of about 100 ft above ground level. The pilot initiated a forced landing to a wheat field, however, the airplane impacted terrain about 75 ft short of the field, which resulted in substantial damage to the fuselage. The pilot reported that there were no preaccident mechanical malfunctions or failures with the airplane that would have precluded normal operation. The pilot added that carburetor ice “was not even considered at the time of power loss” and that the conditions favorable to carburetor ice were not taken into account. Carburetor heat was not used. Weather conditions reported at the time of the accident were conducive for serious carburetor icing at cruise power.