Management of losses in mechanized cotton harvesting

Cotton harvesting is a high-cost and extremely important stage in the cotton production process, as, if carried out poorly, it could cause quantitative losses in the final product. It is at this moment that the producer awaits the return of all investments and work carried out, however, they are not always able to obtain the best yields due to the lack of suitable conditions.

Losses in the cotton harvest occur due to the most varied factors, among which the ripening point, harvesting conditions, machine settings, harvesting speed, type of machine, type of soil, variety and climatic factors stand out. .

In this sense, some errors may occur at the time of harvest, and so that these can be observed and corrected, it is important to monitor harvest losses, characterized by the presence of cotton that is on the ground and cotton that remains on the plant after the harvester has passed, as well as weight loss due to delay in harvesting.

Researchers from Unesp and the Federal University of Mato Grosso carried out field research to evaluate productivity and losses in cotton harvesting depending on two cultivars and two harvesting speeds. The research was carried out in the state of Mato Grosso, in the 2011/2012 harvest, in the production field of Fazenda Mirandópolis, located 60 km from Rondonópolis.

The cotton was produced in a conventional cultivation system, sown in December 2011 using a direct seeding system (millet straw and sudan grass), with a row spacing of 0,90 m and a population of 100.000 plants/ha.

The cultivars evaluated were cultivars FMT 705 and FMT 701, both belonging to the Mato Grosso Foundation. The harvesting speeds evaluated were 3,6 km/h and 7,2 km/h. As an experimental design in the field, we used a randomized block design in a split-plot scheme, that is, the cultivars belonged to the plots of each block and each harvester passed at a speed of 3,6 km/h or 7,2 km/h. h corresponded to the subplots, totaling four treatments, each with six replications.

Mechanical harvesting was carried out with a John Deere cotton picker, model 9970, with a power of 186 kW (253 hp), year 2001, with 3.886 hours worked, with a 4,5 m wide platform and five harvesting lines. The equipment was driven by the same operator throughout the experiment, observing each displacement speed and working rotation.

The productivity of seed cotton was determined in a useful area of ​​3,6 m2, equivalent to three rows of two meters in length in each plot, by manually collecting all the bolls present on the plants before mechanized harvesting.

The survey of losses at the time of harvest was determined by collecting pre-harvest losses (cotton falling on the ground before mechanized harvesting), soil losses (cotton falling on the ground after the harvester passed through) and plant losses (cotton that remained on the plant after the harvester passed through). The sampling area for all evaluations was 3,6 m2 (three lines measuring two meters long), totaling six replications per treatment.

The samples were duly collected, stored and identified. Subsequently, all sample weight values ​​were corrected in grams to kg/ha, and the total loss was also calculated, which was obtained by the simple sum of the average losses in the soil and plant losses. The Percentage Loss was also determined, relating the total losses with the productivity values ​​obtained by each cultivar. The average water content in seed cotton at the time of harvest was 9,5%.

Using statistics, the results obtained were subjected to analysis of variance and comparisons between means were compared using the Tukey test, at 5% probability. According to the results obtained in the experiment, according to the productivity collected manually, the FMT 705 cultivar achieved the highest seed cotton productivity, totaling 3929,5 kg/ha, surpassing the productivity of FMT 701, which resulted in 3306,2 kg /ha (Figure 1).

Figure 1. Average seed cotton productivity results before mechanized harvesting.

When manually harvesting to obtain productivity, pre-harvest losses were evaluated, verifying that they were negligible and were, therefore, not considered in the evaluations.

Evaluating the results of harvest losses (Figure 2), we saw that the cultivars showed no difference between them for losses in the soil and in the plant, however, for total losses, the cultivar FMT 705 resulted in the highest result (514,7 kg/ha) . Possibly, this result was due to this cultivar having obtained higher productivity in relation to cultivar FMT 701, consequently resulting in greater losses.

Figure 2. Average results of soil losses, plant losses and total losses for cultivars FMT 705 and FMT 701.

The average result for percentage total loss did not show a significant difference between cultivars, resulting in 13% for cultivar FMT 705 and 11% for cultivar FMT 701.

When harvesting losses were evaluated between different harvesting speeds, we observed a significant difference for soil losses and total losses. Plant losses were similar between speeds.

It was observed in the experiment that when harvesting at a speed of 7,2 km/h, soil losses increase, indicating that the fact of harvesting at a higher speed of travel of the harvester affects a greater drop of cotton on the ground by part of the harvester. of harvesting mechanisms.

Figure 3. Average results for soil losses, plant losses and total losses for speeds of 3,6 and 7,2 km/h.

It is also noteworthy that, due to increasing the speed from 3,6 to 7,2 km/h, an increase of 100 kg/ha of seed cotton falling on the ground was observed.

For total losses, a total of 385 kg/ha was observed harvesting at a speed of 3,6 km/h and 510 kg/ha harvesting at 7,2 km/h. An increase of 125 kg/ha was observed between harvesting speeds.

Figure 4. Average results for percentage total loss among harvesting speeds.

Due to the existence of few studies on losses in cotton harvesting using different speeds, we can compare with research that analyzed the influence of speed on losses in soybean harvesting, observing that with an increase in the speed of travel of the harvester, there is an increase losses, which are more significant at speeds above 7 km/h; These results are in agreement with the present work, which resulted in greater speed losses of 7,2 km/h (14,1%).

In general, the values ​​obtained are below those found by Silva et al. (2007) who observed total losses of around 16,7% in cotton harvesting, however, the results are close to the limits observed in the literature, where, in savannah conditions, as is the case of the area in question, total losses resulted between 9% and 12,5%.

The high loss rates in the present research were probably inherent to inadequate adjustments of the harvesting and shredding mechanisms; or even on the plant compression plates on the harvesting drums, in which these must be checked and adjusted so that the spindles collect the maximum amount of seed cotton, thus minimizing losses of cotton fallen to the ground.

According to everything that has been discussed, the producer must pay attention when harvesting, because, to partially avoid losses at this time, a series of precautions must be taken to maximize crop yield, such as: time of use of the machine and operator training, as these factors reduce the harvester's performance, as well as monitoring the harvesting speed and harvesting drum adjustments, as it can be concluded from the results of this research that, speeds around 7,2 .3,6 km/h cause greater losses in the cotton harvest when compared to speeds averaging XNUMX km/h, consequently meaning significant reductions in final productivity.

This article was published in issue 137 of Cultivar Máquinas magazine. Click here to read the edition.