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Big prismatic balers

Forage packing operations can be carried out with different machine setups, capable of packing bales in different shapes according to farm needs. Many models are available on the market, and manufacturers are making increasingly sophisticated technological solutions

by Davide Facchinetti
October - November 2022 | Back

Haymaking is as crucial as it is a delicate process that, in line with what is happening throughout the agricultural mechanization landscape, is constantly evolving. 

Considering the data on the types of machinery sold, it is noticeable that there is a constant increase in the demand for machines used for cutting with increasingly larger dimensions. Hence, they are also more powerful, as well as those used for the subsequent stages of turning and windrowing. However, the most significant increase is, above all, for machines used for baling forage. This is a critical stage for which there is a propensity on the part of farmers to turn more and more frequently to contractors. Indeed, this solution makes it possible to profitably employ state-of-the-art machines with high working capacities without having to bear the huge expenses required to purchase them.

The haymaking technique involves several stages:  the cutting of the forage, the following field wilting of the same (or pre-wilting in the case of two-stage haying) and, finally, the product's harvesting. This last operation is rarely carried out with self-loading wagons. As a rule, in fact, baling hay in bales having different shapes and sizes is usually favored, according to the type of baling machine used and the work organization chosen. Nevertheless, the goal is always to maximize the quality of the product and minimize its losses. Therefore, it is essential to contain the contamination by foreign bodies, such as soil, dust and stones, as well as to avoid mistreating the forage too much to reduce the loss of product left on the ground. 

Although due to more favorable climatic conditions, Italian grassland farming has traditionally been much more inclined toward hay production than silage, as is the case on the other side of the Alps, it is also possible to note that the tendency to silage grassland is also rising in Italy, especially for the first and last cuts, which are known to be made in periods when weather patterns are less stable. However, a significant difference still remains concerning large European companies performing trench silage: in fact, bale wrapping is favored in Italy.

The harvesting and baling phase consists of collecting the forage (hay or more or less wilted grass) gathered in windrows and packing it into bales. Forage harvesting can be performed: when it is dry, in which case the product has 15-16% water content; in this way, the bales obtained can be stored as they were produced; when it is wilted, operating on a product that still has about 35-40% water content and which must, therefore, be dried in forced-ventilated barns or silos; in this case, it is what is known as "two-stage haying." when it is fresh or just semi-wilted: in this case, it is planned, for subsequent storage, to wrap the bales with specific plastic films, which are intended to create an anaerobic environment inside them.

This last practice is increasingly widespread, especially for alfalfa, since harvesting the product while it is still partially moist and then silage makes it possible to drastically decrease the loss of the leaflets, which are liable to break up during the drying phases in the field. The same applies to those essences where it is also important to harvest the flower. 

The main parameter defining hay bales is the degree of compression expressed in kg/m3. Depending on the type of machine used, it is possible to obtain hay bales having a density that can vary from a little more than 100 kg/m3 to almost 300 kg/m3. Where straw is baled with the same equipment, densities vary from just under 100 to less than 200 kg/m3. As far as hay is concerned, it is also necessary to consider that with bales having a density of less than 140 140 kg/m3, it is still possible to lose a few points of moisture after baling. With bales having a density of less than 140 kg/m3, this cannot occur for those bales having high densities, and it is, therefore, essential to harvest the hay only when it has reached a moisture content of less than 15%, to avoid the risks of mold and overheating.

There are basically three choices in terms of geometric shapes and the size of the bales produced.

Small parallelepiped bales: Traditional small parallelepiped bales are increasingly less used in Italy, but they are still profitably used in developing countries, small-scale animal husbandry, and mountainous areas. Typically, small balers have the advantages of being handled by even small tractors, have a low center of gravity, produce bales with volumes of 0,1-0,2 m3 and have typical densities of 130-150 kg/m3, resulting in an average weight of 15-35 kg, which allows them to be handled manually. On the other hand, the disadvantages of using this baler arise from the greater difficulty in the subsequent use of the bales in contexts involving unifeed, and the low density leads to more significant storage problems. Furthermore, due to the small size of the machinery used, the operational capacity of the harvesting site is low.

Round bales: Very much in fashion and highly valued by farmers, they are shaped with fixed- or variable-chamber round balers. Round bales volumes typically range between 1.4 e 2.1 m3, with densities for hay usually between 130 and 180km/m3, but only variable chamber round bales can achieve the highest baling values. Their typical round shape is a disadvantage in storage, as the unavoidable gaps between the round bales decrease capacity in storage and transport. On the other hand, they facilitate the rainwater drainage in the unfortunate event that it rains on them before it has been possible to take them out of the fields where they were produced. The round bales' weight and volume that they reach make them easy to lift with tractor loaders. They are well suited with unifeed wagons and can be produced with harvesting yards featuring a low workforce and high operating capacity.

Large parallelepiped bales: These are manufactured by modern balers commonly referred to as "big balers". They have been popular since the late 1980s and have proved to be highly suitable for 300 kg/m3. However, it should also be noted that since their volume is usually between 2 and 4 m3 (depending on the size of the baling chamber and the selected length), subsequent handling usually requires the use of telescopic loaders (telehandlers), especially when harvesting semi-hay forage or fresh for wrapping. Moreover, they are highly productive harvesting yards, with capacities of between 4 and 7 tons of dry matter per hour, which, however, usually entail an increase in the soil compaction index, given the need to employ significantly heavier machinery. However, their use is steadily increasing, either because their parallelepiped shape allows economies in storage as all available space can be occupied or because their greater density facilitates stacking them up to towering heights with minimal risk of collapse compared to round bales, and in the case of fresh forage to be baled it also facilitates ensiling.

The prismatic baler technique:  Whether small or large, parallelepiped balers share a classic general operating scheme. On the other hand, the machines and their components differ substantially in size and location. Forage arranged in swaths is always picked up by a pick-up with flexible teeth that rotates opposite to the wheels and sends the crop toward an infailer (customarily made with a pair of forces but sometimes also with an auger) that sends the crop inside the compression chamber having a square or rectangular cross-section. 

A hydraulically controlled knife-cutting device is fitted between the pick-up and the packer (small packers sometimes lack this device), which also usually makes it possible to select the number of knives to be used to obtain a more or less shredded product according to different requirements). More recent machines can be equipped, near this part, with devices to recognize the possible presence of foreign bodies (e.g., stones), which then enable the machine to act to expel them without encasing them in the bale.   Inside the compression chamber, a piston equipped with reciprocating motion and capable of delivering almost one blow per second compresses the harvested forage, pushing it toward the rear outlet. In this respect, it should be noted that in order to increase the pressing capacity, solutions equipped with a double piston have also recently appeared on the market.

Once the desired length of the bale is reached, a tying device steps in to package them. The bale density is set simply by adjusting the width of a bottleneck located at the rear of the compression chamber since decreasing its size causes greater resistance to the bales leaving the chamber, consequently more compression effect by the piston on the bale being formed. Once the bale is tied, it is slid to the rear of the compression chamber by the thrust produced by the new bale being produced, which causes it to slide over a chute device for unloading the bales onto the ground level.

Many manufacturers are venturing into this market, starting with American Hesston (which now also produces for AgCo brands such as Fendt and Massey Ferguson), New Holland, Vicon, Lely, Krone, Claas, Welger, and John Deere, as well as Italian companies such as Supertino, Cicoria, and Gallignani. Companies such as France's Rivierre Casalis and Italy's Laverda and Gallignani developed giant prismatic balers, later deciding to stop producing for this segment.

Among the latest features introduced on these machines, it is worth mentioning, for example, ISOBUS connectivity, which is beneficial not only to allow machine functions to be controlled directly from the tractor's on-board computer without installing dedicated control units but also to allow a dialogue between equipment and tractor that automatically optimizes working parameters (with ISOBUS class III). For example, speed to keep productivity at the highest possible levels at all times. 

Some manufacturers have also added load sensors inside the machine on the plunger to monitor and optimize the filling of the pressing chamber, as well as sensors placed near the pick-up, which allow possible repositioning of the machine with respect to the windrow in case of trajectory deviations.

Nevertheless, the big-baler market is a lively and constantly growing market, which continues to produce innovative solutions designed both to increase its operational performance and to introduce new electronic devices to control and map field activities. It also enables the analysis of forage quality in real-time, including for the purpose of possibly allowing the storage of bales according to their quality and to be able to track them even in subsequent use, to the benefit of feeding operations and the traceability of animal products.

An interesting feature is the technology that allows the bales to be weighed, and as well as the monitoring of yields to differentiate, for example, the bale price according to its weight. 

Regarding the size of the baling chamber, it should be noted that almost all manufacturers provide the same machines in several sizes to allow customers to choose according to their needs. Generally, chambers with a width of 120 cm are reported to be the most popular, mainly because the bales produced are then very convenient to transport on the trucks since placing two of them side by side gives a width of 2.4 meters.

As for height, the options are many and vary substantially between 65 and 130 cm. Lower chambers produce more stable bales to stack, while higher ones simplify subsequent logistical management, but there is a need to employ more powerful (and therefore heavy) tractors.

On the other hand, the bale length is a parameter that can be modified at will, since with the baling channels, which start from lengths of just under 3 meters and sometimes reach lengths close to 4 meters, it is now possible to form decidedly long bales, although, to simplify logistics, it is usually preferred to use lengths around 2-2.5 meters.


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