Cotton is a natural fibre grown on a plant related to the commonly-found garden species hibiscus.
Cotton seeds are planted in spring and the plant grows into green, bushy shrubs about one metre in height.
The plants briefly grow pink and cream coloured flowers that, once pollinated, drop off and are replaced with fruit, better known as cotton bolls.
Inside the cotton boll is fluffy, white lint as well as cotton seeds.
Farm and soil preparation
There are a number of locally-bred and adapted varieties of cotton that can be selected and grown. Varieties are generally chosen by growers based on yield, quality, disease resistance characteristics and biotechnology traits. Other traits such as season length, disease resistance and varietal determinacy also play important roles.
Fields are laser-levelled and graded, and if fields are not going to be planted with cotton again the following season, they can also be rotated either into another crop (often wheat) or fallowed.
Fields are prepared for planting, weeds are controlled, and nutrients are added if necessary. Most growers now leave their cotton stubble standing in the field and mulch it back into the soil to add valuable nutrients.
Soil moisture is also checked and pre-watering is undertaken if necessary.
Growers check the soil temperature regularly before planting. Cotton seed is planted in the spring, as soon as the soil is warm enough to be sure of satisfactory seed germination and crop establishment (when the temperature reaches 14 degrees Celsius measured at 8am AEST with a rising temperature forecast for the seven day period post-planting).
Cotton seeds emerge from the ground five to 14 days after planting – depending on soil temperature and moisture.
Refuge crops are also established at this time, which help slow down resistance to Bt proteins from evolving in the pest population by producing susceptible Helicoverpa moths that have not been exposed to the Bt toxins. Moths produced in the refuge crops will disperse and mate with any potentially resistant moths from the Bollgard 3 crops. This tactic is called genetic dilution.
As with many farming practices, having the right equipment is key to success when harvesting cotton. For this task, farmers have two options of which machinery to use: cotton pickers and/or cotton strippers.
Cotton pickers remove the seed cotton from the bolls and leave the dried locules behind, essentially leaving the plant intact in the field. These pieces of equipment feature a series of spindles that are round, tapered, and grooved with barbs – these are all stacked on a spindle bar in the drum of the picker. As the picker enters a cotton row, the spindle bar rotates and once the spindles come into contact with the seed cotton on the plant, the cotton itself is drawn out of the locule. The bar will then continue to rotate and make contact with a spinning doffer, which will then wipe the cotton off the spindle and transfer it to a pneumatic conveying system that moves it to the basket of the machine.
Cotton strippers, on the other hand, remove the complete boll from the cotton plant – this is achieved via two counter-rotating rollers consisting of nylon brushes and rubber bats. Similar to the cotton picking process, crops harvested with a cotton stripper are elevated into a basket in the machine. However, once this happens, the cotton stripper will then pack the cotton into 8-12 bale modules for storage.
Video resource : Complete Agriculture