Wikipedia
In farming and gardening, the broadfork, also called a U-fork or grelinette, is a tool used to manually break up densely packed soil, like hardpan, to improve aeration and drainage.
It consists of five or so metal tines, approximately eight inches long, spaced a few inches apart on a horizontal bar, with two handles extending upwards to chest or shoulder level, forming a large U-shape.
The operator steps up on the crossbar, using full bodyweight to drive the tines into the ground, then steps backward while pulling backwards on the handles, causing the tines to lever upwards through the soil. This action leaves the soil layers intact, rather than inverting or mixing them, preserving the topsoil structure.
A broadfork can be used in a garden, or practically for one to two acres (4,000 to 8,000 m²). For larger areas, a tractor- or animal-powered chisel plow or similar tool is usually employed.