SRI recommends planting rice in a square pattern to allow for mechanical weeders to be used in perpendicular directions. Mechanical weeders like rotary hoes and cono-weeders aerate the soil while turning weeds back into the soil to decompose. An engineer in Madagascar designed an adjustable two-row weeder based on drawings from IRRI. A new weeder design developed in Sri Lanka greatly reduces weeding time from 5-10 days per acre to 1-2 days per acre. This weeder has teeth similar to cono-weeders that do not get clogged like other hand weeders.