Freshly cut grass will have a moisture content of about 75 per cent. For safe storage in the hay barn this must be reduced to approximately 20 per cent. It is important to reduce the moisture level as quickly as possible with the help of the sun and wind. Hay treatment machines help the drying process by turning and loosening the hay swaths. This work must be done with minimum loss of the valuable leafy material.
Mower conditioners combine cutting with the first treatment of the new swath. The cut grass passes to the conditioner which bruises the stem to release the sap and speed the drying process. There are several types of conditioning mechanism. Some conditioners have free swinging nylon fingers on a rotor shaft which treat the whole crop as it leaves the cutting discs.
Another systems uses a horizontal rotor which has vee-shaped spring tines: these scuff the grass stems to help release the sap as the crop leaves the cutting disc or drum.
A third type of conditioner consists of two intermeshing nylon rollers held in close contact by spring pressure. The surfaces of the rollers have grooves which mesh with each other. As the grass to release the sap and hasten drying.
The power take-off driven conditioner rotor is contained within a metal or plastic hood with rear doors. The doors can be adjusted to restrict the outflow of the crop when a greater degree of conditioning is required. The width of the conditioner will be matched to the cutting width of the mower.
Mower conditioners can be rear-mounted or attached to a front linkage and driven by the front power shaft. Both types have working widths of approximately 3 m and rear-mounted machines are usually swung round behind the tractor for transport. High work rates can be achieved with a front- and a rear-mounted mower on the same tractor. A typical rear-mounted model has side deflector plates used to vary the size of windrow. Wide windrows promote rapid drying but they will need to be narrower if the crop is to be collected with a trailed forage harvester.
Trailed mower conditioners with the cutter bar and conditioner offset behind the tractor may either be side-pulled (Plate 14.6) or have a centre-pivot hitch arrangement from the tractor drawbar. Both types are swung round behind the tractor for transport. Cutting widths are normally between 2.5 and 4.5 m leaving windrows between 0.8 and 2.4 m wide.
Some trailed mower conditioners have either a set of deflector plates or belt-driven tines used to group the swaths cut on two consecutive runs close together to make larger swaths for turning with a wide tedder or to be picked up with a high-output self-propelled forage harvester.
Plate 14.6 A 68 kW (90 hp) tractor has sufficient power to operate this side-pull 3-metre rotary mower conditioner. (John Deere)
Figure 14.4 (Top) Deflecting a second swath against one cut by a mower conditioner on the previous run. Cutting 6-metre swaths with front- and rear-mounted mower conditioners.