Muhuddin Rajin Anwar1,2, Rebecca Darbyshire1
1 NSW Department of Primary Industries, Wagga Wagga Agricultural Institute, PMB Wagga Wagga, NSW 2650, Australia
2 Graham Centre for Agricultural Innovation (an alliance between NSW Department of Primary Industries and Charles Sturt University) Wagga Wagga, NSW 2650, Australia, Email: email@example.com
The area under dryland cotton has recently increased in Australia due to cotton providing a profitable summer rotational option. Dryland cotton is affected by climate variability, particularly extreme temperature and rainfall, which influences crop growth, development and yield. The goal of this study was to explore the influence of rainfall and extreme heat variability on yield during the cotton growing season in four important Australian dryland cotton growing regions, focussing on the summer months which coincide with critical cotton reproductive stages. Across these regions, inter-seasonal yield was found to be highly variable with coefficient of variation ranging from 33 – 49%. This yield variability can translate into large fluctuations in profits. Dryland cotton grown in soils with higher plant available soil water storage capacity and in combination with higher growing season and summer rainfall led to highest average yield (3.66 bales/ha at Dalby). The number of extreme heat events (maximum temperature ≥ 35oC) reduced yield at all sites (p < 0.05) with average reductions between 0.51 – 1.65 cotton bales/ha. Notable year-to-year variability was present and significant relationship to rainfall could be found across the sites. However the relationship between cotton yield and rainfall is weak (R2 = 0.06 – 0.48). This highlights a need to better characterise the relationship between rainfall events and timing in relation to phenology rather than to seasonal means.