System for the opening and closing of hail protection nets, protective sheets or the like in agricultural systems which a support structure consisting arranged inclined from vertical piles, from parallel to the rows of plants strained wires, from strained across these ridges wires, and anchored to the ground wires and from networks or conveyors, these being spreadable over the plants, or einholbar by rolling, each of said individual networks (8) between a pair of rods (7) which is arranged rotatably at both ends (5r) of profiles (4) which are transverse to the rows of plants and the nets (8), stored (5s) and each of said grids (8) along one of the longitudinal edges is fixed to one of the rods (7) while the opposite longitudinal edge with a thin, spaced among themselves , cables or bands (8c) is provided a second end of the corresponding rotary bar (7) be is fastened.
