Optimising your cotton picker spindle operation (29 April 2019)

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Cotton picking contributes about nine percent, on average, to the total cost of production, so it is hardly surprising there is a constant focus for both growers and researchers on making efficiency gains in this area.

Ensuring cotton pickers are working optimally is one area where gains can be made with little to no additional overheads.

The bulk of cotton in Australia is now harvested with the John Deere 7760/CP690 spindle pickers. Research has shown that harvesting efficiency is influenced by many in-field conditions, including variety, boll size, degree of boll opening, plant size and yield. What hasn’t been so clear in the past is the effect on quality of row unit settings such as ground and spindle speed, compressor plate pressure, spindle tip clearance and scrapping plates in a high yielding production system such as Australia’s. Although studies have been conducted to determine the effect of spindle speed on fibre quality, the effect was still unclear.

“It is generally accepted that harvesting plays an important role in determining efficiency, as well as fibre and seed quality,” CottonInfo's Fibre Quality Technical Lead René van der Sluijs said.

“However we still needed to determine the effect machine setup has on harvesting efficiency and cotton quality.”

How well set up are you?

As a result René began two lines of study: one study focused on ground and spindle speed, compressor plate pressure, spindle tip clearance and scrapping plates attached to the back compressor plates, and the second study focused on drum arrangement.

René found that ground speed and scrapping plates attached to the back compressor plates did not have an effect on gin turn out, however, the compressor plate pressure setting did appear to decrease turnout as the front and back plate tension was increased, with the highest turnout achieved with the standard setting of 0.5F/2.0B. Although the mechanically-damaged seed fell within the acceptable range, the level of damage increased as the front and back compressor plate pressures were increased.

René found that ground speed and back compressor plate pressure setting had little or no effect on fibre quality. However the addition of scrapping plates resulted in improved colour grade and a statistically significant increase in fibre length, micronaire, the trash count and size, and a decrease in elongation. The interaction between the scrapping plates and the front compressor plate setting resulted in a positive increase in strength, while interaction between the scrapping plates and the back compressor plate setting was significant in terms of nep content. A decrease in compressor plate setting resulted in an increase in total and fibrous nep content.

Drum arrangement

Spindles are attached to picker bars which are arranged on rotating drums. Conventional picking units have two opposed contra-rotating drums, one on each side of the row. The in-line drum arrangement has both drums on the right side of the row, resulting in the cotton plant being picked only from one side, and was introduced by John Deere in 1989.

René’s drum arrangement study showed that the harvesting efficiency of the opposed drum arrangement was substantially better than the in-line units and resulted in a 22 percent increase in yield. This increase in yield did not, however translate into higher gin turnout as the seed cotton harvested by the opposed drum arrangement contained more trash, which was removed during the ginning process.

“Although there were small differences in terms of fibre colour (both Rd and +b), fibre length, length uniformity, short fibre index, strength and micronaire, after ginning they were not statistically significant,” René said.

Similarly, in terms of fineness and maturity there were no significant differences between the two picker drum arrangements – trash levels, total, fibrous and seed-coat neps as well as nep and seed-coat nep size also showed no significant differences.

“These two studies have shown that harvesting machine setup and adjustment in terms of compressor plate, spindle tip clearance and addition of scrapping plates, has a substantial effect on fibre quality and turn out,” René says.

“Ground speed and drum arrangement meanwhile having little or no effect on fibre quality and gin turn out.

“It is therefore important to ensure that the harvester is in good mechanical condition and initially set up according to the manufacturer’s recommendations and changes to these settings are then made in accordance with field conditions, which include picking conditions, defoliation and yield.”

This article appears in the Autumn 2019 edition of CRDC's Spotlight magazine.