The evolution of forage balers
To produce quality forage, it is essential to be able to manage the entire technical path, in which harvesting is certainly one of the most critical phases. Today more than ever, forage balers are at the centre of the development of innovative technologies based on sensor technology aimed both at monitoring the harvesting and baling of forage in real time and at automating certain operational routines
Producing quality forage means ensuring the health and productivity of dairy and beef animals bred for human consumption. The aspects to be considered in order to make quality forage certainly concern the choice of variety and the adoption of the best agronomic practices for the management of the crops, but the technical path to be taken is also very important, including the choice of machinery used for forage production. In recent years, the machines that are used for mowing, turning and windrowing forage have seen a certain evolution, especially from a mechanical point of view, such as to best combine both the timeliness required to conclude operations in the shortest possible time, and the reduction of qualitative-quantitative losses attributable to the 'mechanical' action of the parts working on the plants. As far as the baling machine category is concerned, the evolution has concerned two aspects: a strictly mechanical one, always aimed at reducing harvest losses as much as possible, and a more innovative one, with the development of sensor systems for monitoring and controlling certain particularly critical phases of the hay baling operation.
As is well known, balers are divided into two categories according to the geometric shape that the generated forage bale takes: rotary balers and piston balers (in their more modern version known as 'big balers'), which produce cylindrical and prismatic bales, respectively.
Round balers, with a fixed or variable chamber, have the great advantage of being reliable and relatively inexpensive machines, intended purely for farm use. Coupled to a medium-power tractor, they are capable of harvesting and compacting hay, straw or forage for silage into bales with a density of 140-145 kg/m3 of dry matter, if produced by a fixed chamber machine, and up to 180 kg/m3 if produced by a variable chamber model. Big balers are designed to be able to form large prismatic bales with high density, up to 200-280 kg/m3 of dry matter. On the other hand, these machines are significantly more expensive than round balers and require more powerful tractors to drive them. For this reason, those opting for this equipment are mainly contractors, who need high performance machines. In addition to minimising qualitative/quantitative losses, the most important parameter to be monitored very carefully is the moisture content of the forage at harvest. To produce quality hay, the moisture content must not exceed 20%, to avoid abnormal fermentation and the development of mould. To produce silo hay, the moisture content is conversely usually around 35-40%. For these reasons, systems for the continuous measurement of forage moisture are available on the market, both for round balers and big balers, based either on the measurement of electrical conductivity or via microwave sensors. In some cases these are kits that can be retrofitted to machines of different makes, in other cases they are proprietary systems on balers and connected to the tractor's ISOBUS network. They can 1) regulate the amount of bale compression according to the moisture content of the forage (even creating zones of differentiated pressure in the individual bale); 2) prevent the baling of a product that is not yet suitable; 3) correctly dose any additive, added with the aim of improving the quality and shelf life of the forage. Another measurable quantity is the weight of the bale produced. In the case of balers, load cells installed on the wheel axle can be used, while in the case of big balers, sensors can be integrated in the bale discharge chute. In this way, it is possible to detect not only the weight of the individual bale, but also the total quantity of forage harvested over a certain area or in the unit of time.
All the data acquired are displayed on the virtual terminal on board the tractor and are then sent to a cloud server; if they are also geolocalised using GPS, it is possible to trace each individual bale with great precision, starting from the field and the farm where it was produced. In this regard, systems have recently appeared on the market that are able to identify each bale by means of an RFID chip that is applied, before unloading in the field, to the net or binder twine. Querying the RFID on a special application, using a tablet or smartphone, will display the weight, moisture content at harvest, date and time of baling, GPS position where the bale was created, any additives applied, etc.
Such technology can be very useful when fodder is sold by parameterising the price to its actual quality, but also to better manage the harvesting, handling and storage of the bales produced. As far as operational control is concerned, several systems are available both to increase the comfort of operation and to optimise, and partly automate, certain work steps.
The first aspect concerns big balers in particular, as the fluctuations in power and torque demand to which the coupled tractor is subjected can cause significant vibrations that put a strain on the operator. To reduce this impact, it is possible to have intelligent control of transmission operation and/or front axle suspension response on certain tractor models. In particular, by means of a self-learning control algorithm, it is possible to dampen vibrations and reduce the pitching and swaying of the tractor-packer combination. Being an on-board tractor system, it can normally work with any make of big baler. As far as pressing control is concerned, it is possible to have either systems that assist the operator by indicating whether the process is taking place correctly or not, or by having the tractor automatically adjust certain operating parameters via a class III ISOBUS system. In the first case, it is worth mentioning the system for round balers that prevents the creation of asymmetrical bales due to an uneven introduction of forage into the compression chamber. This is done by measuring the pressure inside the chamber either directly on the bale thanks to two flaps equipped with springs, or by measuring the tension on the two outermost belts thanks to spring tensioners equipped with position sensors. If the difference in tension between the two sides exceeds a predetermined threshold, the operator is prompted to correct the tractor's trajectory so that the pick-up puts more load on the part of the chamber that is under less pressure. For big balers, there is a similar system based on sensors attached directly to the plunger that can accurately measure the load acting on it. If the system detects that the product is only flowing from one side, the operator is prompted to change the driving path in order to maintain an even feed. The second is a system for big balers, which uses a LiDAR sensor to scan the swath in front of the tractor and detect its density, volume and direction. Using a class III IsoBus connection, the steering and forward speed of the tractor and the baler settings are automatically adjusted so that the baler precisely follows the swath while maintaining a constant forage supply to the pick-up. This results in optimisation of the bale shape, increased working capacity and high operator comfort. Furthermore, the risk of flooding (with the well-known risks for the operator) is avoided should the linear mass of the swath be too great and the working speed too high.
