These are concerned with the production of a good seed bed and involve the use of one or more of the following tractor-mounted or tractor drawn implements, often referred to as cultivation machinery.
A) Disc harrows
This implement consists of a number of concave discs which are mounted on a frame in sets or 'gangs'. They can be set at various angles to the direction of travel, the greater the angle, the more the soil is disturbed.
T discs rotate as they are drawn through the soil, breaking down the larger lumps or clods. They do not expose trash or weeds which have been buried by primary cultivation machinery if they are properly used.
B) Seed harrows
This type of harrow has tines which are about 10-15 cm in length, bolted on to a frame. The tines break down the soil to the depth of the tine penetration. For heavy soils, the tines may be curved to aid soil Penetration Light seed harrows are used for covering and mixing in seed with the surface soil, they may also be used to suppress the growth of annual weeds.
C) Cultivators
These implements may be either mounted or trailed and are solidly constructed; the heavy duty rigid tines being bolted on to a strong frame. The tines are drawn through the soil at the required depth, breaking up the larger lumps of soil and bringing buried weeds and trash to the surface where they will be exposed to desiccation by the sun. The effectiveness of this operation depends on the curvature of the tines or the angle or rake at whichtine-cultivators
D) Spring tine-cultivators
The C-shaped tines of this implement are made of tempered steel and have replaceable points or tips.
They are usually mounted on a frame similar to that used for cultivators but smaller models may be bolted on to a harrow frame. The angle of the curved tines can be adjusted and locked into the required position.
Spring tine cultivators are useful for the rapid preparation of a seed bed since the vibrating movement of the tines as they are pulled through the soil effectively breaks down the larger lumps.
E) Rotary cultivators
These are available as either trailed or tractor-mounted versions, two-wheeled rotavators are also commonly used for small scale operations, such as intensive vegetable growing. The basic principle of operation of all types of rotary cultivator is similar, tines or L-shaped blades are fitted to a rotor shaft which revolves in the same direction as the tractor wheels. The tines or blades break up the surface soil to a fine tilth and may penetrate to 20 cm in depth; the degree of fineness of the soil crumbs is governed by the forward speed of the machine in relation to the speed of the rotor shaft which is operated by a separate gearbox. The overall effect of a rotary cultivator is similar to the combined effect of ploughing and cultivating; surface mulch or trash is chopped up and mixed with the soil and large clods are broken down into smaller particles.