From the late 1960s to the early 1970s, Oppenheim was engaged mostly in two art forms, that is, land art that involved large-scale outdoor projects and body art that employed, in most of the cases, his own body. "Directed Seeding－Canceled Crop", a typical example of the former, was a work that consisted of the act of planting seeds along the contour of the land (the curving line of the road that connected the wheat filed to the silo where wheat was usually stored and processed), and when the wheat was grown, harvesting the crop in the shape of an enormous X. The huge scale of the work, which makes it uncontainable in an art museum, is a counter to the existing system, and at the same time, the act of harvesting the wheat, and processing it into food, is presented here as a parallel to the act of painting which turns paint into an illusion upon a canvas. The enormous X, which cancels and denies the crop, is thus doing the same to painting and art in a complex irony. Another type of work, "Ground Level Push-ups on Mud", was presentation with performance, sound, and slides given at the "Information" Exhibition at the Museum of Modern Art, New York. In this work, he projected slide images from past push-ups onto the place where he had done them, and again did push-ups this time in the snow. Both of these works were by nature impossible to be preserved in their original forms, and when they are presented again as records, scenes from different times and places are juxtaposed. This adds a new level of conceptual depth to them.rn