Temperature increase and cotton crop phenology

Abstract

The daily outputs of the Commonwealth Scientific and Industrial Research Organisation (CSIRO) Conformal Cubic Atmospheric Model driven by four general circulation models (GCMs) were used by a stochastic weather generator, LARS-WG, to construct local climate change scenarios at nine key cotton production areas in eastern Australia. These climate change scenarios were then linked to daily temperature-driven models of cotton phenology (the CSIRO Cotton Day Degree calculator and the Last Effective Flower tools) to examine the magnitude of the effects of increased temperature on the initiation and duration of key crop phenophases and on the occurrence of heat stress (hot days ≥ 35°C maximum) and cold shocks (≤ 11°C minimum) during the growing season. The results show that when using 1 Oct. sowing (1) the timing of emergence, 1st square (flower bud), 1st flower and 1st open boll advanced 1~9, 4~13, 5~14, 8~16 days respectively for the period centred on 2030 compared to the period centred on 1990; (2) when crops were planted 10 days earlier, emergence advanced more in most of the locations while other phenological events changed only slightly (approximately 1 day) in comparison with 1st. Oct. sowing; when crops were planted 10 days later all these events generally were delayed (approximately 1.5 days) in comparison with 1st Oct. sowing depending on locations; (3) the timing of the last effective square, last effective flower and last harvestable boll were delayed 7~12, 6~9 and 3~9 days respectively across locations and GCMs; and (4) combining the effects of an earlier time of first square and a later last effective square potentially increased the time for new fruit (squares) to be produced by up to two to three weeks. This analysis highlights the challenges associated with temperature with future climate change for future cotton production in Australia. Future research will be directed to assess the combined effects of changes in temperature, rainfall and atmospheric CO2 concentration on cotton water use, water use efficiency, cotton lint yield, fibre quality (i.e. micronaire and fibre length); evaluate the effectiveness of a range of plant-based and management-based adaptation options in dealing with climate change risks; and quantify the cost and benefits of identified effective adaptation options, especially with the use of high yielding transgenic cotton with early high fruit loads in Australian high yielding (>2000kg lint /ha) irrigated systems.