Seed drills and planters

Seed drills can be attached to certain models of rotary tillers so that primary seedbed preparation and the plant­ing process can be completed in one operation. Sometimes the land must be tilled once with the rotary tiller before planting. Small grain is planted in this manner. Variations of the seed drills can also be found where grass seeds are sown directly in the field in strips. If necessary, ripper tines can be mounted behind the rotary cultivator to loosen the soil to a deeper level.

Planter units, fertiliser hoppers, herbicide pumps and sprayers can be mounted on some rotary tillers, which means that seedbed preparation, planting, fertiliser application and weed control can be done in one operation (see Figure 1).

Tractor preparation

Rotary tillers require much power. The tractor must be in top mechanical condi­tion and tuned for maximum power output and optimum fuel consumption.

To provide the desired degree of pulverization, the tractor must have sufficient power to maintain standard PTO-speed at the desired operating depth and forward travel speed. Adequate hydraulic lift capacity must also be available, or the cultivator must be equipped with lift wheels.

Adding extra weights on the tractor’s rear wheels is unnecessary for normal rotary cultivation. Front-end weights on the tractor must be adequate when using three-point-mounted rotary tillers, because the tractor must be able to carry the tiller easily (see Figure 2).

If the rotary tiller’s width permits, adjust the distance between the trac­tor’s wheels to such an extent that the tread is wide enough for good tractor stability. The tractor’s rear wheels must, preferably, run on uncultivated soil rather than on loose soil, and therefore the rotary tiller must be offset to loosen the soil behind the rear wheel closest to the previously tilled strip.

Doing this will ensure that the tilled strips overlap all the time while the tractor’s wheels run on untilled soil all the time. If the cultivator is long enough to cover the whole width behind the tractor, the tilled strips will overlap every time and the tractor’s wheels will run on hard soil (see Figure 3).

To prevent damage when lowering the rotary tiller, the three-point-hitch on the tractor must be operated as slowly as possible. Side-swing when operating the tiller must also be pre­vented by installing hitch stabilizers or sway chains. No load-and-depth-control must be applied to the rotary tiller, and the three-point-hitch on the tractor must be free to float at will. The tiller will be seriously damaged if it is forced into the soil. Stops on the three-point-linkage of the tractor, must be adjusted to limit the raising of the rotary tiller as this will prevent damage to the PTO-shaft from an excessive an­gle or over-extension. PTO-shaft safety shields must be used every time.

The PTO-shaft

The PTO-shaft must always be used in as straight a line as possible. Most rotary tillers can be used on a variety of tractors by using a range of vertical hitch-attaching points. The power shaft of the rotary tiller must be connected to the PTO-shaft of the tractor, and the shaft length must be matched to the tractor being used.

To prevent universal-joint shudder and possible damage, it is recommended that the maximum PTO angle does not exceed 40 degrees when the rotary tiller is fully raised or lowered. This may require limiting the lift height of the tiller or re-arranging the hitch points. Some manufacturers recom­mend limiting the maximum distance the tiller may drop below normal ground level to about 300 mm (see Figure 4).

Because of the high power require­ments of rotary tillers, care must be taken to assure adequate lubrication of the PTO-shaft for easy telescoping as the rotary tiller moves up and down in relation to the tractor. PTO-shafts cannot telescope freely in operation, it could result in damage to the bearings of the PTO or the tiller’s gearbox. A slip clutch is usually provided in the tiller’s drive train to protect the cultivator, and the tractor, should the blades strike a solid object.

Depending on the shape of the obstacle, the blades may simply lift the tiller and walk over some objects (see Figure 5).

Next month we shall look at prepa­ration and maintenance, field op­eration and adjustments, rotor care and pasture renovation. We thank the ARC Agricultural Engineering in South Africa who made the infor­mation on rotary tillers available to the readers of ProAgri Zambia.