RECORD cotton yields in central Queensland have been attributed to a lucky combination of perfect growing conditions and unorthodox crop management.
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Department of Agriculture and Fisheries Queensland principal research scientist Dr Paul Grundy, who has been involved in planting window research since 2013, said growers were unlikely to reliably replicate this year's yields of 20-plus unginned bales per hectare.
Dr Grundy said the extraordinary results came from crops grown through a second round of flowering, which was risky under normal conditions because the prolonged growing period increased potential exposure to damaging rain events.
"They just had absolutely beautiful sunny clear weather with favourable temperatures and virtually no rainfall in January, February, March," he said.
"Those crops that second flowered grew a large second crop, in addition to the already high yielding crop that was underneath.
"In essence it combined two high yielding crops into one.
"This year it was a winner. But whether you'd ever quite pull that off again - the long term weather averages would suggest that's a highly irregular set of climatic circumstances."
Dr Grundy said research into earlier planting windows was prompted by a prolonged period of stagnant cotton yields in central Queensland, following the introduction of Bollgard 2 varieties.
A climate analysis of the region found the September-October planting window commonly used across the industry exposed cotton to unfavourable weather at the wrong time.
That research identified cloudy weather, rain, heat and humidity in January and February as constraints on flowering and boll fill, while conditions from late October to December were more likely to be ideal for this crop stage.
Dr Grundy said they concluded from five years of research and field trials that soil temperatures in August were suitable for planting cotton in central Queensland.
"In our field trials we realised a 30 to 40 per cent yield increase for sowing in August compared to mid-September," he said.
"Changing that planting window and pushing that crop production period into better weather made a huge difference."
Growers still faced challenges with picking in late January when monsoonal influences increase, but Dr Grundy said it was better to at least have the yield potential on the bush, even if it suffered colour downgrade or loss of lint quality from rain.
"Better to have 12 bales of cotton with a lint colour discount compared to what they were getting, which was 8.5 to 9 bales, and the same lint colour discounts anyway," he said.
"Of course not every year's wet, either.
"On balance, we felt that planting earlier and capturing better weather for flowering and boll setting and then picking before the wettest month, which is February, would pay off more often than not."
Subsequent research into December planting to push picking back into the driest time of year from May onwards, created other challenges for crop canopy management with crops tending to direct energy into producing stem and leaf rather than bolls.
It was difficult to compensate for boll shedding due to cloud and heat for December-sown crops due to capping of yield potential by rapidly shortening day length from March.
Dr Grundy said benchmarking of Bollgard 3 crops in 35 randomly selected fields across 17 different operators had comprehensively demonstrated planting in August was better than December.
This year's record yields came despite limited irrigation allocations.
The Central Highlands has been in drought for four years, with Fairbairn Dam at just 21.6pc of capacity, forcing growers to limit their irrigated cotton production to one or two fields.
Rain in November gave a small boost to allocations allowing growers to water their crops an extra two or three times.
"With this extra water, people have elected to double crop their existing crops," he said.
"That represented a better return on that water compared to planting field of mung beans, for example. And that's how these large yields came about. The reason it's paid off so well in this particular season gone by is ... the weather's not always bad in central Queensland, and this year, they just had perfect conditions."
Dr Grundy said sunlight data recorded at meteorological stations across the region was so high in summer he initially thought the sensors were playing up.
"It turned out that they had some of the best sunlight we have recorded in the January to March period since our work began in 2013," he said.
"It was also very high compared with longer term records. This was most unexpected for a La Nina year, with the lack of cloud and rainfall defying most seasonal outlook predictions."
With some models tipping a third La Nina in a row for Australia, double cotton may not work as well in the coming season should drought breaking rain finally fall on the Central Highlands.
"It is possible we might see a repeat of one of the really problematic wet years that central Queensland experienced during the last run of La Ninas between 2008 and 2011, where a lot of those same growers' crops went under water from river flooding," he said.
"Even crops that didn't flood still suffered due to repeat periods of cloudy wet weather, which is what growers in southern Queensland industry have suffered this season.
"If you took the double cotton approach, I suspect it wouldn't produce the yields we have seen this season. In fact, it might actually work against you, underscoring there is an element of luck involved."
