Farm machinery for distributing treatment products on the ground, which comprises: - a support frame; - at least one tank, fixed to said support frame and adapted to contain products to be distributed on the ground, said tank being provided with at least one dispensing opening of said products to be distributed; - distribution means, mechanically connected to said support frame, placed below the dispensing opening of said tank and comprising at least one spreader plate which is intended to receive the dose of said products from said tank and is actuatable to rotate in order to distribute said dose of products on said ground; - closure means, mechanically connected to the external surface of said tank at said dispensing opening and comprising at least one metering plate, which is provided with a perimeter edge having at least one shaped section and is movable, along a movement trajectory, at least between multiple different operating positions in which it is placed with said shaped section to at least partially close said dispensing opening, in order to allow the dispensing of corresponding predetermined doses of said products from said tank; wherein said closure means comprise at least one regulation plate, which is interposed between said metering plate and said tank, is mechanically connected to the latter, is provided with at least one first through opening and with at least one second through opening and said regulation plate is movable between at least: - one first position, in which said first through opening is placed at the dispensing opening of said tank and the shaped section of said metering plate is placed at least to partially close said first through opening; and - one second position, in which said second through opening is placed at the dispensing opening of said tank, and the shaped section of said metering plate is placed to at least partially close said second through opening. - a support frame; - at least one tank, fixed to said support frame and adapted to contain products to be distributed on the ground, said tank being provided with at least one dispensing opening of said products to be distributed; - distribution means, mechanically connected to said support frame, placed below the dispensing opening of said tank and comprising at least one spreader plate which is intended to receive the dose of said products from said tank and is actuatable to rotate in order to distribute said dose of products on said ground; - closure means, mechanically connected to the external surface of said tank at said dispensing opening and comprising at least one metering plate, which is provided with a perimeter edge having at least one shaped section and is movable, along a movement trajectory, at least between multiple different operating positions in which it is placed with said shaped section to at least partially close said dispensing opening, in order to allow the dispensing of corresponding predetermined doses of said products from said tank; - one first position, in which said first through opening is placed at the dispensing opening of said tank and the shaped section of said metering plate is placed at least to partially close said first through opening; and - one second position, in which said second through opening is placed at the dispensing opening of said tank, and the shaped section of said metering plate is placed to at least partially close said second through opening.