How to avoid losses with harvesters

Inadequately adjusting the harvester, as well as harvesting under the wrong conditions of speed, rotation and crop humidity are factors that negatively influence losses during harvest.

Currently, the objective of every rural producer is to increase productivity with each harvest. However, with the increase in taxes and the increase in export prices, many, attracted by the increase in their earnings, end up preferring to invest in new technologies, often expensive, instead of improving their current production methods, such as control adequate maintenance and adjustments of equipment. Obviously, the adoption of new production technologies is becoming essential to produce on a large scale today, but it is necessary to observe the cost/benefit ratio for their implementation, in the short or long term.

According to the Brazilian Institute of Geography and Statistics (IBGE), in the last 40 years the area cultivated with grains increased from 40 million in 1980, to 67 million hectares in 2014. To confirm these data, we can highlight through records that in 1980 Brazil it was at the level of 50 million tons of grains per year and, twenty-two years later, it reached the level of 100 million tons per year. In the last ten years, thanks to the use of production technologies, the mark of 160 million tons/year has been reached. The projection of this growth is typically exponential, indicating that, if we manage to maintain growth at the same pace, we should reach 200 million in 2019/20.

According to the National Supply Company (CONAB), of the products grown in Brazil, those that achieved the greatest growth in production were soybeans with 10,1 million tons, followed by off-season corn with 5,6 million tons, according to the same, this growth is due to favorable climatic conditions and the increase in the area cultivated with soybeans and corn.

However, within the production processes, the last process carried out in the field, harvesting, which involves cutting, feeding, threshing, separation and cleaning steps, if poorly conducted can make it impossible to achieve this objective, causing considerable qualitative and quantitative losses at the end of the operation. . Currently, these represent around 4% of the entire Brazilian grain harvest, a representative figure, given the national production figures, which in 2014 reached the incredible mark of 192,8 million tons, according to IBGE. Furthermore, according to these data, it is estimated that the total that was lost was close to 7.712 million tons.

With the expansion of cultivated areas, time, which for many was already synonymous with money, became worth even more. Rushing with the harvest and needing to see their production stored away from climate threats, farmers accelerate the harvesting process without realizing the negative consequences for the quality of the grain. It is at this stage that greater production instability occurs, as the crop depends on and at the same time is subject to climatic adversities, regardless of the intensity in which they occur. These events can destroy entire crops or even delay the harvest, causing the natural dehiscence of the fruits, allowing the seeds to fall.

As a result, the need for agility in the operation, associated with the carelessness and lack of training of many operators, allows for high losses in the mechanized harvesting of grains, which, when added to the losses obtained in pre-harvest and transportation, result in significant losses.

A self-propelled harvester's function is to carry out several activities at the time of harvest, basically cutting, feeding, threshing, separating and cleaning. According to Alonço & Reis (1997), the factors associated with the machine that cause losses include: travel speed, angular speed and position of the reel, state of maintenance and adjustment of the cutting bar, elevator adjustment, track cylinder , sieves and fan. According to Alonço (2004), around 90% of these occur only on the cutting platform, in most cases due to failures in the operation of the harvesting mechanisms or even due to a lack of knowledge on the part of the operator, who is often unaware of the necessary adjustments for a good harvest. performance at the time of cutting.

These must be observed in order to reduce losses on the platform, for example: knife and counter knife system must not have vibrations or excessive gaps greater than 4 mm. This fact can cause the grain to be threshed before the plant is harvested by the system, due to the vibration of the plant and cutting inefficiency. The windlass, which is responsible for picking up the plants, should work a little faster than the harvester's forward speed. In general, this speed or rotation should be 10 to 15% greater than the machine speed. If this speed is lower, the windlass may push the plants and cause the grains to thresh before they are even picked up onto the platform.

Still regarding the reel, there are two important adjustments to be observed: the height in relation to the crop and the horizontal adjustment. In crops where there is a greater density of plants per hectare, it is recommended that the windlass be placed further forward to capture a greater quantity of plants, whereas when the densities are lower or the plants are more dispersed, it is recommended that the windlass be placed placed further back in relation to the platform bucket. This adjustment must also be carried out on the fingers of the reel bars, and for denser crops, the ideal is for these to be more inclined in relation to the plants. On the other hand, for less dense crops, this adjustment can be carried out more vertically. In horizontal adjustment, which is the working position in relation to the crop, it is recommended that the reel performs its action in the upper third of the plant, that is, from the median to the apical portion.

Regarding the platform helicoid, adjustments can also be made according to the crop being harvested. The basic adjustment of this mechanism occurs by changing the height of the helicoid in relation to the bottom of the platform bucket, being careful not to make it too high in relation to the bottom of the platform, as this This can cause the accumulation of plants not transported to the trail system, resulting in threshing on the platform and loss of grain.

Still in relation to the helicoid, the adjustment of the retractable fingers is also carried out according to the density of the crop. For large amounts of vegetable mass, your fingers may be more exposed. However, a new concept in transporting the mass to be threshed is available on the market, which are platforms equipped with rubberized conveyor belts, commercially known as Draper platforms, replacing helical conductors, carrying out the transport of the crop to the harvesting system more smoothly. trail, reducing friction with the system and consequently reducing damage to the grain.

However, despite the cutting and feeding system causing high losses, the internal systems of the machine also cause, due to the fragmentation of the material caused by friction with the internal elements, responsible for the trail and displacement of the grains, from the cutting platform to the reservoir. Furthermore, there is the so-called “grain in the straw”, which is nothing more than what is not threshed and ends up being eliminated by the separation system. This fact is due to the threshing system regulations that do not consider the characteristics of the crops to achieve adequate grain cleaning. These systems are currently represented by two types, which differ in that they are arranged longitudinally (axial), as opposed to tangential in which the mass to be threshed touches the rotor (transverse), and can be composed of one or two rotors, which leads to better operational performance and quality of the threshed product.

The adjustments of the cylinders and concaves must consider the type of crop, grains more sensitive to the action of friction between these mechanisms, such as soybeans and beans, which must be threshed at a lower rotation, so as not to cause a large amount breaking. For grains with greater resistance and vegetable mass, such as rice, it is possible to increase the rotation, always following the levels recommended by the manufacturers. The higher the cylinder rotation speed, the smaller the distance between the cylinder and the concave must be. The choice of the size of the concave grid must be made according to the grain size of the crop in question. Therefore, the larger the grain, the larger the concave grill mesh will be. Normally the concave opening is larger at the entrance than at the exit, due to the greater amount of material deposited at the beginning of the trail. Generally this measurement has a ratio of 2:1.

According to Campos et al. (2005) in their study on losses in mechanized soybean harvesting in the State of Minas Gerais, harvesters equipped with an axial threshing system showed better performance compared to those with a tangential threshing system, causing less grain breakage in addition to better threshing and , consequently, less loss.

After making these changes, it is recommended to carry out a visual inspection to indicate the quality of the trail. This can be done by observing the grain deposit, checking the cleanliness and integrity of the grains and also the presence of grains in the straw excluded at the rear of the harvester.

After observing all these variables, it is possible to realize that a sequence of small errors and/or inattention can lead to significant losses at the end of the harvesting process. However, if each professional in the role of operator fully knows the needs, limitations and possibilities that their work tool requires and offers, this will consequently result in a reduction in grain waste throughout the production chain, providing greater revenue for the farmer. .

Determination of losses

Through NBR 9740, ABNT establishes test conditions and a methodology for determining losses in self-propelled harvesters, such as: terrain slope, number of plots and repetitions, plot size, operating speeds, material collection and methodology. calculations. It also establishes how to calculate the operating capacity of each harvester, which is defined by the total feed rate at 3% of losses. However, as they are complex and time-consuming methods, their use is restricted to the preparation of technical reports and research work.

However, there is another methodology for this assessment, made available by extension agencies and presented by Machado et. al (1997). It is quite adequate and simpler to execute than that established by NBR 9740 (1987), enabling the farmer to carry out the assessment of losses more quickly, in order to check possible outbreaks and adjust them within acceptable levels. Because they are methods that use calibrated measuring cups that relate the volume of grains collected in a small demarcated area with the losses per hectare, they are called volumetric.

Vítor Pires Scherer, Airton dos Santos Alonço, Tiago Rodrigo Francetto, Dauto Pivetta Carpes, LASERG/UFSM

Article published in issue 158 of Cultivar Máquinas.