Abstract:
Temperature plays a critical and complicated role in the growth and development of cotton. The cool starts to the last three seasons in southern regions have again highlighted of the problems of cold shock and slow crop development rates at low temperature. Low temperatures after sowing increase the time to emergence and reduce seedling vigour often leading to poor establishment, poor early growth and increased risk of seedling diseases. The timing of crop maturity, yield and fibre quality may also be affected. There has also been evidence to suggest that high crop temperatures may negatively impact on crop development.
Much of our current understanding of the impacts of cold temperature on cotton crop growth and development is based on experimental work undertaken by Dr Greg Constable in the early 70’s with cultivars quite different than those used commercially today. It was from these experiments that, the base temperature (12ºC) used in estimating crop development was derived, and the definition of a cold shock (<11ºC) was formulated. Dr Constable acknowledged even at the time there was considerable extrapolation of the information to derive these values the lowest daily temperature tested was 18ºC. His work on cooler temperatures also focussed on early season crop development, as was the need at the time in the Namoi Valley. No specific experimentation on the effects of low temperature has occurred in Australia since then. In addition there has been no definitive attempt to better understand and quantify the effects of temperature extremes on cotton growth and development at other stages and subsequent impact on crop yield (especially with current varieties and agronomic practices, particularly early season insect protection).
