Need for machines adapted for the cultivation of dense cotton

With the rise in the prices of fertilizers, fuel and labor, one of the alternatives found by researchers and cotton farmers, aiming to reduce production costs, was to narrow the spacing between rows in cotton. This technique, which emerged in the United States of America (USA), aims to shorten the crop cycle, enabling a reduction in phytosanitary applications, less interference from weeds, greater precocity and, consequently, lower production costs, and may therefore present some advantages over the conventional farming system.

When cotton is grown in a dense system, it requires sowing with row spacing of 0,39 to 0,76 m, with populations ranging from 173 thousand to 300 thousand plants per hectare; In the conventional cultivation system, spacings are greater than 0,76 m with populations ranging from 80 thousand to 120 thousand plants/ha.

There are two types of machines for harvesting cotton: the rotary spindle harvester (picker), which consists of removing only seed cotton from the plant, and the stripper harvester, which is equipped with a windlass and endless screw, removing entire bolls and the casings.

In reducing costs with the dense cultivation system, the main component is harvesting, as a stripper harvester ends up being two to three times cheaper than a picker, both for purchase and maintenance.

Stripper harvesters, until 2011, were the most used in the harvesting of dense cotton, as, traditionally, spindle harvesters harvested cotton grown with spacing between rows of 0,76 m to 1,01 m, therefore not being used in the dense system.

During the 2011 harvest, equipment was made available on the agricultural market to adapt existing spindle harvesters for use in cotton harvesting in dense cultivation, called Cotton 45 (Deltamaq Indústria e Comércio), capable of harvesting rows spaced up to 0,38 m. These harvesters have the operating system of cutting and transporting the plants from one row to the adjacent row where the bolls are extracted with higher harvest quality and lower levels of impurities, as this was the great villain of the dense cultivation system, where the stripper system collects fibers with a high level of impurities, reducing their quality and consequently the sales price.

Because they have different harvesting systems, harvesting machines with systems picker e stripper they can cause different harvest losses and affect the fiber yield of the harvested cotton.

A team of researchers carried out field research to evaluate the productivity of cotton cultivars in a dense system, as well as the percentage of fiber and harvest losses depending on the picker and stripper harvesting systems.

The research was carried out in the state of Mato Grosso, in the 2012 harvest, in the production field of Fazenda Mirandópolis, located 60 km from Rondonópolis. The cotton was produced in a dense cultivation system, sown in January 2012 using a direct seeding system (millet straw and sudan grass), with a row spacing of 0,45 m and a population of 250.000 plants/ha.

As an experimental design in the field, a randomized block design was used with a split-plot scheme, which consists of having two cultivars in the plots (FMT 701 and IMACD 408) and two harvesting systems in the subplots (pickere stripper), totaling four treatments with five replications.

Mechanical harvesting was carried out with a cotton harvester, John Deere, model 9970, 4,5 m wide platform adapted by DELTAMAQ (Cotton 45) with 10 harvesting lines with system picker(of spindles); and cotton harvester, Case brand, model 2555 equipped with comb platform, adaptation of the BUSA brand model, 6 m wide and harvesting system stripper(reel with endless thread).

The harvesters were driven by the same operator throughout the experiment, observing uniform travel speed and working rotation for each type of harvester. At the time of harvest, cotton seeds were manually collected to obtain maximum crop productivity and harvest losses were determined by collecting cotton that had fallen to the ground before mechanized harvesting (pre-harvest losses), cotton that fell to the ground after the harvester passed through (loss in the soil) and cotton that remained on the plant after the harvester passed through (loss in the plant). The sampling area for all assessments was 2,7 m², totaling five replications per treatment.

According to the results obtained in the experiment, the productivity collected manually did not show significant differences, resulting in 3911 kg/ha for the FMT 701 cultivar and 4108 kg/ha for the IMACD 408 cultivar.

Table 1. Average yield of seed cotton before mechanized harvesting.

Cultivar	Productivity (kg ha-1)	Productivity (@.there is-1)
FMT 701	3911,2	260,7
IMACD 408	4108,8	273,9

Cultivar

Productivity

(kg ha^-1)

Productivity

(@.there is^-1)

FMT 701

3911,2

260,7

IMACD 408

4108,8

273,9

Among the characteristics sought in cotton improvement is the percentage of fiber, as it is one of the components for the production of down. It was observed that the stripper harvesting system considerably reduced the fiber percentage of both cultivars and, consequently, resulted in reductions in the lint yield. This reduction in the percentage of fiber in the stripper system is possibly the result of the action of the mechanisms, which are quite aggressive when compared to the picker system (rotary spindles).

Tabela 2. Average fiber percentage results (%) depending on cultivars and harvesting systems

	Fiber Percentage (%)
Harvesting systems	Cultivar
	FMT 701	IMACD 408
Picker	40,5aB	42,6aA
Stripper	32,8bA	32,1bA

Fiber Percentage (%)

Harvesting systems

Cultivar

FMT 701

IMACD 408

Picker

40,5aB

42,6aA

Stripper

32,8bA

32,1bA

Means followed by the same capital letter in the line do not differ from each other using the Tukey test (p≤0,05); Means followed by the same lowercase letter in the column do not differ from each other using the Tukey test (p≤0,05).

Before starting mechanized harvesting, pre-harvest losses were evaluated, noting that they were negligible and were, therefore, not considered in the evaluations of the present experiment. It was observed that all losses did not differ between cultivars, however , for harvesting systems, the greatest total loss was observed in the harvesting system picker(13,5%). Plant losses did not differ in any of the treatments.

Tabela 3. Average results for soil losses, plant losses and total losses for harvesting systems pickere stripper

Treatments	PS (kg ha-1)	PP (kg ha-1)	PT (kg ha-1)
Cultivar
FMT 701	367,3 to	83,2 to	450,5 to
IMACD 408	379,5 to	101,4 to	480,9 to
Harvest System
Picker	478,68 to	84,8 to	563,5 to
Stripper	268, 09 b	99,8 to	367,9 b

Treatments

PS

(kg ha^-1)

PP

(kg ha^-1)

PT

(kg ha^-1)

Cultivar

FMT 701

367,3 to

83,2 to

450,5 to

IMACD 408

379,5 to

101,4 to

480,9 to

Harvest System

Picker

478,68 to

84,8 to

563,5 to

Stripper

268, 09 b

99,8 to

367,9 b

The results found in the experiment are above those observed in the literature, where, in savannah conditions, as is the case in the area in question, total losses are between 9,4%. In general, authors refer to the 10% level as being the maximum acceptable loss in the cotton harvest, with the ideal range being between 6% and 8%. The high loss rates of the picker harvesting system (13,5%) can be explained due to the adaptation of the rotating knives on the picker platform to harvest ten lines; This fact led to a greater volume of seed cotton passing through each harvesting unit, meaning that the rotating spindles and shredders were not fully efficient in processing all the cotton from the harvesting drums to the air ducts, which consequently could have causing an increase in soil loss rates. In addition to this, it may be suggested to reevaluate the working speed used (average of 5,1 km/h), as with the increase in the number of rows harvested in the same pass, lower speeds could result in lower losses.

The percentage of 9,5% for total losses in the stripper harvesting system possibly originated as a result of the height of the plants in the experiment, which resulted in an average of 0,91 m, as for the stripper harvest, it is ideal that the Plants do not exceed 0,70 or 0,80 m to avoid disturbing the stripper harvest.

With the new harvest model pickerfor dense cotton, the disadvantage of poorer fiber quality in harvesters is overcome stripper, but the advantage of reduced harvesting cost is lost, which is the main component of mitigating production costs in the dense system. Although this system achieves equal or higher productivity and lower production costs than the conventional system, dense cotton harvested with stripper has been “braked” in its development due to the higher cost of cleaning during ginning and the lower price when selling the fiber.

Finally, cultural management factors, harvester adjustment, machine operating speed as well as operator training can efficiently interfere in reducing harvest losses. In this context, the correct choice of the harvesting system and adequate adjustment of these machines associated with productive cultivars with a lower rate of losses (good lint retention) and a higher percentage of fiber can mean a greater profit margin in the cultivation of dense cotton for cotton farmers.

This article was published in issue 145 of Cultivar Máquinas magazine. Click here to read the edition.