The Grillo rotary tiller is suitable for deep tillage, even in very hard and stony soil.
The first rule for working this type of soil is to keep the spur facing forward so that the user can maneuver the machine effortlessly. In these situations, a first pass breaks the surface crust; a second pass works deeper. The side discs of the tiller should be removed to facilitate penetration into hard soil.
Two factors determine working depth: the pressure exerted by the operator on the spur and its height adjustment. If the spur is high, the machine's center of gravity is forward and will tend to advance rather than sink. With a low spur, on the other hand, the machine will try to work "in place," sinking.
The lateral discs keep the machine in position and precisely define the tilled area. In some types of tillage, they serve to limit the lateral flow of soil that would otherwise cover vegetable crops, but also to prevent damage to the plant roots.
In very soft soil, the lateral discs ensure good flotation and uniform advancement of the machine, preventing it from sinking.
In very hard soil, it is advisable to till without discs to allow the blades to work deeply, as well as in moist soil, which tends to clog the tiller.
