Getting it right with dryland cotton

Analysis heat risk and likely summer rainfall before planting dryland cotton


Cotton
Australian croppers are turning to dryland cotton in increasing numbers.

Australian croppers are turning to dryland cotton in increasing numbers.

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With the increase in dryland cotton hectarages across the country, growers are urged to manage climatic risk as best as they can.

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FARMERS in the summer cropping belt are increasingly looking at introducing dryland cotton into their system due to the discrepancy in prices between cotton and common dryland summer crops such as sorghum.

With sorghum prices in the doldrums and cotton values still relatively strong, farmers are deciding that even accounting for the added risk due to the higher cost of production with cotton, it is worth taking the punt on the fibre crop.

However, a NSW Department of Primary Industries (DPI) senior research agronomist has said better seasonal forecasts, combined with a thorough knowledge of on-farm conditions prior to planting, could play a big role in mitigating risk.

Muhuddin Anwar said inter-seasonal yields in cotton were highly variable, with heat shock and rainfall the major drivers of yield.

Speaking at this week’s Agronomy Conference in Ballarat, Dr Anwar said prior to planting, farmers needed to have a good knowledge of their soils, their water holding capacity and plant available water (PAW).

Naturally, areas with better soils and higher in-crop rainfall had better yields, but Dr Anwar said crops could still be economically grown in more marginal areas.

He said better forecasting, predicting the intensity of heat events and the amount of rain over summer could assist farmers in less secure areas in making a decision whether it was an acceptable risk to plant.

At present, the nation’s climate forecasting resources are more concerned with finding greater accuracy for winter croppers.

El Niño / Southern Oscillation (ENSO) signals can be a useful rule of thumb for summer croppers, given ENSO is a strong driver of climate in Queensland and can be an influencing factor on when the summer monsoon begins, but there is still no model with a strong degree of skill.

Dr Anwar said information on the likelihood of searing summer temperatures would assist, especially in terms of timing of the heat.

In his research he found heat could reduce yield from between 0.5 bales a hectare to 1.6b/ha, depending on both the severity of the heat and also the crop stage at the time of the event.

Heat at flowering can reduce the viability of the pollen and later can reduce boll size, impacting yields.

While there is no dynamic modelling, Dr Anwar said growers could assess historical data to get a feel both for the number and timing of extreme heat days and likewise for rain events.

“Finer analysis of sequencing of rainfall events coinciding with key phenological stages, flowering and boll development) may show stronger relationships,” he said.

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