Defoliation timing critical for cotton quality

Applying cotton defoliants too early can turn riches to rags – and it’s a situation Australian growers are being urged to avoid.

Speaking on CSD’s Web on Wednesday broadcast, CSIRO research scientist Dr Michael Bange said studies had revealed early defoliation may increase the incidences of neps – tiny entanglements or knots in the finished fabric – once cotton is harvested and ginned.

“The reason we get these knots or fibre entanglements is often associated with immature fibres in the processing of the fibre – they break and the small fibres get caught up with the other fibres.”

“One of the biggest issue with neps is that you can’t find them until you produce the actual fabric – so a spinner buys the cotton and makes yarn that is then used to produce a high quality fabric, a nice shirt or a nice pair of jeans, and finds white flecks through them because they will have trouble taking up the dye, and then there a little knots along the yarn itself. It’s a significant cost for the spinner and fabric manufacturers.”

“For us as an industry, we don’t want to develop a reputation for having neps because ultimately spinners will tend to choose other markets over ours if they feel we have too many neps,” he said.

Dr Bange said CSIRO research over the past decade had explored all steps in the cotton production process from the paddock to the finished product to find what practices were contributing to neps.

“Clearly the one in-field management practice that was contributing to neps was timing of application of harvest aids – the earlier you went with those, the more chance of increasing neps.”

“If we open bolls that are immature, that’s what contributes to neps and the way to avoid that is to ensure those bolls are mature by using the boll cutting technique to see that the seed coat is brown and those bolls are mature.”

“The work that we have done has supported the current recommendation for application of harvest aids – 60 percent bolls open or four nodes above cracked boll – if you’re targeting that as a point in applying harvest aids you’re reducing your chances of increasing neps overall.”

“We found that if you have around 40 immature bolls per square metre of row was when we were getting an increase in neps.”

Dr Bange said people looking for more information about neps would find it in FIBREpak – a new publication available for free from the Cotton Catchments Communities CRC.

5 March 2010

Further Information

Dr Mike Bange 0267 991500