Abstract: A cultivator adapted to straddle a windrow of material such as compost. A frame has an improved disintegrator and aerator comprising a horizontal drum crosswise of the windrow with a plurality of cultivator blades disposed in two helical arrays between opposite ends of the drum, the arrays being circumferentially spaced 180.degree. apart about the drum and extending equal distances on opposite sides of a central, longitudinal, vertical plane along the center of the frame. The blades on the right and left sides of the drum have paddle portions at their ends transversely offset toward the central vertical plane and contoured to move material sidewise and heap it up into a peak along the center of the windrow.