10 August, 2017
The 2016/17 season will be remembered by many as a season of extremes. Excluding Central Queensland, the majority of regions experienced an abnormally cool start with many planting into rain moisture. September produced below average temperatures which continued into October. Planting opportunities presented with adequate soil temperatures, however the remainder of October leading into November saw below average temperatures (particularly nights) which resulted in slow crop growth and development. This delay in development meant an increase in the number of days after planting required to reach first square, combined with high sucking pest pressure first position retention was reduced.
Temperatures improved through December, setting the scene for the season with temperatures remaining above average, pushing the crop along. The flowering and boll filling period saw little reprieve in temperatures, with crops suffering through extended periods of heat, pushing growers to decrease irrigation deficits. This increased the number of irrigations required to keep crops cool.
The extreme heat took its toll with many crops experiencing above average hot shocks. Multiple shedding events and cavitation (boll dangle) were also observed, as crops struggled to produce enough carbohydrate due to the unrelenting heat, which ultimately impacted boll numbers. Some dryland crops were basically cooked, with evidence of bolls splitting open prematurely. The hot days and nights through flowering also impacted pollination/seed set, and as a consequence bolls were smaller and lighter.
The hot temperature during the boll filling period also saw a number of regions exceed a mean of 28°C, which for some, had the impact of pushing micronaire higher. This season also produced conditions conducive to Silverleaf Whitefly, producing several more generations. Temperatures remained mild through March into April which, when combined with crops that had high biomass, lower boll load, increased soil nitrogen, and the suggestion that cells in leaf abscission layers may have been damaged through heat and some late rain and/or cooling conditions, made for a very challenging defoliation.
By Chris Teague, Extension & Development Agronomist – Border Rivers and Balonne
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