Ideal settings for mechanized tomato harvesting

The tomato (Lycopersicon sculentum Mill.) is a vegetable originating from South America, in the Andes region and is currently considered the second vegetable in volume of production and consumption in the world.

With the growing economic importance of this crop in the vegetable growing area, mechanization in the industrial tomato harvesting process has been providing some satisfactory results in the cultivated areas, where there is a greater reduction in costs per unit, which is mainly based on the reduction of labor costs. Mechanized harvesting provides greater reliability in carrying out the operation and, consequently, greater cost-benefit, making it attractive to most producers.

Not all areas currently used are suitable for carrying out this type of operation, and actions related to soil preparation and, when necessary, the windrowing process are important. Among the factors that stand out with influence on losses, there are not only soil topography conditions, but also climate conditions and cleanliness of the area. On uneven terrain, the action of the platform's collecting rods can carry a large amount of impurities to the machine's various mechanisms, where the equipment is damaged and reduces the quality of the harvested product.

Assessment work on losses caused by a tomato harvester and its mechanisms is rare, and these losses, when monitored, can serve as indicators of the quality of the harvesting process. As it is a sensitive product and involves a high hourly cost of machinery and labor, there is concern about measuring losses. In harvesters equipped with track systems used for various agricultural products, their adjustment has been highlighted so that there is good performance and efficiency during operation. In more traditional crops, such as soybeans and corn, studies on the trail system have become routine, however, the same does not occur with tomato crops. Therefore, given little information on the assessment of losses of fruits that did not detach from the branches, there was a study of different adjustments in the tomato harvester's trail system.

The study was carried out in the municipality of Morrinhos-GO in an area irrigated by a central pivot irrigation system and with a history of implementing tomato cultivation. The tomato cultivar HEINZ 9553 was used, implemented in a direct planting system, where the harvesting process took place after 125 days. The region studied is considered one of the largest producing areas in the state and has stood out on the national scene as the largest tomato producing region in Brazil.

To evaluate the loss of fruit stuck on the branches after the trail, a GUARESI self-propelled harvester was used., model G-89/93 MS 40”, with FIAT-Iveco 175 hp engine, equipped with a floating cutting and collection platform and equipped with an electronic selector of green fruits and clods on its separation mats. At the time of harvest, the soil had a water content of 18,4%, as the importance of maintaining a moist soil during harvest is based on the fact that the collecting rods of the cutting and collection platform act a little below the soil surface, avoiding losses due to uncollected fruits. The harvester has a threshing rotor equipped with fiberglass rods that, through circular movements generated by the rotor, vibrate and strike the collected mass (branches and fruits), thus carrying out the threshing operation.

The study was conducted in a randomized block design with four replications, in a split-plot scheme, where the plots consisted of three rotations of the threshing mechanism (6; 12; 18 rpm), and the subplots consisted of three vibration frequencies of the same mechanism (0.83, 2.5 and 4.17 Hz). Forty plots measuring 40 m long and 2,5 m wide were demarcated, where, in each plot, the harvester operated with the combinations to be evaluated.

During operation, the harvester operated with an engine speed of 1900 rpm and an average operating speed of 4,1 km.h¹. To quantify losses, a template with an internal area of ​​2,5 m was used.², where after the harvester passed, the necessary materials for the evaluations proposed in the present study were collected at each point. After the material was collected, it was bagged, identified and weighed.

Losses in branches were made up of fruits that did not detach from the vegetative part (branches) after passing through the trail system. Natural losses and losses on the cutting platform were not accounted for in this process, as these are loose fruits not attached to the branches. The data obtained regarding losses in the track system were subjected to analysis of variance, the effect of vibration and rotation factors on the track mechanism was evaluated through regression analysis, with the models chosen based on the coefficient of determination, the significance of the regression coefficients, and the lack of adjustment of the models using the “T” test at 5%.

From the results, it was verified that there was no significant effect on the interaction of the studied factors. When isolated individually, it was possible to verify that the vibration of the threshing mechanism significantly influenced the loss of fruits not detached from their branches (P_Aries). Based on the model obtained to evaluate the effect of the vibration frequency of the threshing mechanism on harvest losses, it can be seen that with the increase in vibration, the losses of non-detached fruits reduced linearly. This model obtained a coefficient of variation of 43,95% and a coefficient of determination of 83,9%, which indicates a great influence of vibration frequency on fruit detachment.

The use of higher vibration frequencies proved to be an efficient method for harvesting various agricultural products, such as coffee, oranges, olives, etc. In Figure 1, the values ​​were separated into estimated values ​​and observed values. Regarding losses related to fruits not detached from the branches by the machine (Pram), it was found that the estimated values ​​for these losses were greater when the vibration frequency was 0,83 Hz, where, on average, there was a loss of 7,00 tons ha¹. The values ​​observed in losses for the frequency of 0,83 Hz were slightly higher, totaling an average of 7,42 t ha¹.

When the vibration frequency was 2,5 Hz, there was an estimated loss of 4,91 t ha¹, with the observed values, for the same frequency, the values ​​were lower, totaling an average of 4,07 t ha¹. For the frequency of 4,17 Hz, the estimated loss values ​​were 2,82 t ha¹ and the values ​​observed were 3,24 t ha¹.

Removing the fruits from their branches is a process that requires several “blows” from the rods attached to the trail rotor, however, this number of blows may be greater or lesser, and may have greater or lesser vibration amplitudes. These factors depend on some determining points, such as different cultivars and fruit ripening point.

There are varieties in which the fruits detach more easily from the branches, requiring fewer blows and a lower frequency of vibration. Fruits with a late ripening point have a tendency to more severe mechanical damage when exposed to large vibrations of the threshing mechanism. In view of this problem, it is necessary to evaluate the rotation and vibration of the threshing system.

Given this scenario, it is possible to conclude that greater efficiencies in the trail system were obtained with the use of higher vibration frequencies, which made the detachment more efficient.

This article was published in issue 136 of Cultivar Máquinas magazine. Click here to read the edition.