Several aspects have to be considered when making choices for haymaking in the field…
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The technical and technological choices for field haymaking are consequent to the agronomic choices made in the cultivation of the meadow, to its type and in particular to the prevailing botanical family, and to the system of final utilisation of the fodder to be implemented on the farm; in this context, the adoption of two-stage haymaking and silage techniques is of great importance.
The type of meadow and, ultimately, the species it is composed of, have a great influence on the haymaking process to the point of conditioning the choice of equipment operating in the field, the haymaking technique and the storage system. A second aspect that influences the choices made in haymaking concerns the amount of forage in the field. However, both these aspects vary over time.
For example, in a polyphyte lowland meadow, the high availability of nitrogen tends to favour the development of poaceae (grasses) and, within this botanical family, the more nitrophilous ones such as ryegrass, fescue, poe, dactylis and javone, which thus tend to physically dominate the fabaceae (leguminous) and other dicotyledonous species. In the meadows of northern Italy, where microtherm grasses predominate, high summer temperatures can, however, give leguminous plants such as alfalfa and clover, which often return as a share of the crop in second or third cuts. Thus, the permanent lowland meadow is dominated by grasses in the first cut, while in subsequent cuts, at least in certain situations, leguminous plants find more space. Something similar happens in alfalfa fields: with a massive presence of grasses in the first cut, which is then greatly reduced in the summer cuts where the alfalfa returns to dominate the lawn almost in purity. This alternation in alfalfa starts to be evident after the third/fourth year and this is why it is often terminated, however giving up an interesting food resource.
Simplifying, one can say that the productivity of the former is always higher than the subsequent cuts regardless of the type of lawn, and in the presence of microtherm grasses (northern Italy) this difference increases. In the south it depends very much on the availability of rainwater and irrigation.
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Choosing the mower
Disc mowers have dominated the Italian market for several years, relegating drum mowers to niche situations and reciprocating motion mowers to mountain environments.
However, the choice of mower does not end with typology. In fact, there are certain technological characteristics specific to this family of equipment that must be assessed when purchasing it to verify whether it is suitable for the type of lawn and the environmental conditions in which it will work.
The mower conditioners must allow the cutting height to be adjusted while maintaining the correct trim of the bar, i.e. limiting the bar’s inclination to a few degrees. In fact, when it is excessive, it makes the cutting height uneven and increases both the probability and the level of stress in the event of hitting an obstacle. To do this on disc mowers it must be possible to either replace the bar bearing slide by inserting a thicker one or add a spacer. This is because the cutting height should never drop below 50-60 mm under normal conditions and increase when the turf is not very dense or discontinuous, or when stones are present, and in lawns with an uneven profile (as permanent lawns often are in comparison to alternating ones). In this way, contact between the cutting organ and the reproductive centres of forage species (such as the grass crown) is avoided, thus preserving the species most suited to this environment. Choosing the cutting height appropriately means reducing damage to the crown of the plants caused by the knife, which means greater longevity of the grassland, but also of the organs of other equipment used in haymaking. In fact, by setting a high value, forage raking in spreading and turning operations and in raking operations can be conducted more effectively by reducing the probability of contact with the soil. In addition, in soils rich in stones, the increased ground clearance reduces the risk of these parts coming into contact with the cutter bar.
Vice versa, a cut that is too low risks reducing the number tillerings in the grasses, creating spaces where annual weeds can easily find room for their development, reducing not only the quality but also the quantity of production.
A second aspect to be analysed concerns the sensitivity adjustment of the device that regulates the adherence of the bar to the ground and reacts when faced with an obstacle, as well as the type of kinematic mechanism that regulates the reaction movement upon impact. An efficient device, and one that can be adjusted appropriately, makes it possible to adapt the machine to working speed, profile homogeneity, and cutting productivity.
In fact, with high forward speeds, which can reach 15 km/h, the bar must withstand heavy stresses that can cause oscillations that modify the set cutting height. This phenomenon is reduced by hydro-pneumatic or mechanical devices with calibrated springs, which also allow the bar to rise in the event of a collision. Once the obstacle has been overcome, the device automatically replaces the bar in its working position. The systems can be adapted to the operating conditions by modulating the load on the ground, normally between 30 and 50 kg. Lightening the bar is recommended when the surface is uneven or the turf is infested with moles, as it avoids direct contact between the soil and the cutting device. Conversely, making it heavier improves the bar’s grip on the turf and significantly reduces oscillations: the cutting height remains constant even with high forward speeds.
A third element to be explored concerns the opportunities offered by the device or devices for changing the arrangement of the forage after cutting and the effectiveness and convenience of the adjustments. This adjustment should be modified according to the moisture status of the turf, the planned haymaking technique, the productivity of the meadow, and the available clearance under the tractor. These devices can be distributing units, conveyor hoods, movable belts or even real belt conveyors that collect the forage from the mower conditioner and transport it to one of the two sides of the machine depending on the operator’s intentions.
Choice of the conditioner
Conditioning is an efficient technique that aims to reduce the difference between the speed of water evaporation from the leaves, which occurs very quickly, and that from the stems, which is much slower, by producing lesions on the plant. Accelerating water loss reduces the intensity and duration of cellular respiration phenomena that still persist after cutting and which are the cause of the consumption of the most digestible part of the forage. Furthermore, accelerating the drying process reduces the risk of rain.
The choice of conditioner is influenced by the characteristics of the meadow and therefore by the species that dominate it. Much applied research on conditioning was done in the 1980s and 1990s. Unfortunately, field research was carried out by European research centres that worked mainly on polyphytic or grass meadows. Only those in France and the USA have devoted themselves with some continuity to experiments on alfalfa. Unfortunately, there has been little research on conditioning in Mediterranean environments where, in addition to particular climatic conditions, species such as sulla, sainfoin, vetch and others that deserve more attention are widespread.
However, there are some general rules on conditioning that apply to any area and any type of grassland. The first is that conditioning provides an advantage that is greater, the better the environmental and weather conditions are during haymaking. Thus, under unfavourable weather conditions, conditioned forage dries slightly faster than unconditioned forage, and vice versa.
A good conditioner produces crushing and bending actions that produce longitudinal cracks and tears mainly in the stems. These allow water vapour to disperse more easily into the atmosphere without having to pass through the plant tissues and in particular the external cuticle, which is covered with waxy substances that make it not very permeable to vapour.
In the roller conditioner, the forage passes through two counter-rotating rollers, equipped with reliefs that interpenetrate with each other, undergoing abrasion, compression and bending that mainly affect the more voluminous parts, such as the stems. In this equipment, the intensity of conditioning depends (and in the best equipment it is adjustable) on the reciprocal pressure exerted, on the rotation speed of the rollers, and on the shape of the pads. Less important for effectiveness is the material with which they are made.
The flail conditioner, on the other hand, is characterized by a single rotor equipped with flails or fingers, rarely fixed, often hinged to the rotor, which pick up the forage and transport it to the rear where it is thrown to the ground. This journey is guided by a carter that can be equipped with a series of counter-flails whose task is to amplify the action. Rotation speed, clearance between the crankcase and rotor, and the position (insertion) of the counter-flails are the variables that allow the intensity to be increased or reduced. In all its configurations, this type is able to quickly dispose of the cut forage, avoiding the flooding of the conditioner itself. Because of this characteristic, it is well suited to the high forward speeds and high productivity of microthermal grass meadows at the first cut.
The flail conditioner, if technologically evolved, allows the intensity of the conditioning itself to be varied within very wide limits, and it is precisely this possibility of modulating the effect that is also favouring its diffusion on mower conditioners intended for alfalfa. However, it is hoped that field trials will be resumed to verify whether the two binomials ‘flails for grasses’ and ‘roller for leguminous plants’ can really be said to be outdated.
Lorenzo Benvenuti
