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Research update: CQ

There's plenty happening in the research space this season. This week, we have a look at key research projects in Central Queensland. 

Winter cotton 


A large-scale trial is underway examining the potential for late May or June sown cotton under CQ conditions. Hosted by Neek Morawitz at ‘Argoon’, the trial is taking a strategic look at this option from both a productivity and future climate adaptation perspective. The best conditions for boll setting in CQ are between October and December, with lengthening sunny days and less of the troublesome three (cloud, humidity and temperature extremes).
Yield increases from August sowing were enabled by capturing a greater proportion of this period for boll filling through earlier flowering. Sowing during early winter aims to exploit this climatic sweet spot even further by commencing flowering in early October to utilise the entire optimal period for boll filling, with picking occurring in early January. However, this strategy is not without risk. Frost during winter may cause irreparable crop damage during July/August. The winter cold also stunts early canopy development, which could impede the crop’s ability to grow away during squaring in September and lead to a small bush with high retention that cuts out prematurely despite rapidly improving conditions. If the plant lacks sufficient leaf area it will be unable to support both boll demand and canopy expansion, even under optimal radiation and temperature. The other important consideration is how winter sown Bollgard® 3 cotton will interact with the environment from an Bt expression perspective and Helicoverpa generational overlap. 
Data collected on all these aspects will help us understand how early winter sown cotton might work in CQ now or in the not-too-distant future, particularly if winters continue to become warmer and summer extremes more severe. A recent study (found here) examining implications of projected climate change for global cotton production suggests that by 2040, sub-tropical locations will face the greatest climate-based risks and will require modified agronomic practices to maintain productivity.
Neek Morawitz and Susan Maas in late May sown cotton during the first week of flowering in early October.
June sown cotton as it completes 3 weeks of flowering by the end of October 2021.
A field walk held at Neek's property last week.
Paul Grundy at last week's field walk. 

Retention for high-yielding Bollgard® 3 


During the past three seasons, DAF, in collaboration with CottonInfo and NSW DPI, have been examining the impact of early square loss on subsequent crop yield and maturity. For sites north of Narrabri, square removal (during squaring, early flowering or both) has not impacted crop yield or time to maturity. This supports a current industry IPM guideline that the lack of impact on yield from up to 40% square loss prior to flowering should be considered when making management decisions. This work is being repeated for a fourth and final season as part of an industry-wide effort to capture seasonal variability with a site also located at Neek Morawitz’s property ‘Argoon’.

Cover crops for irrigated cotton 


Increased yields produced in CQ since the introduction of sowing flexibility with Bollgard® 3 come at a cost, with a greater export of resources from fields, particularly when used for back-to-back cotton production.
Cover crops are common in many farming systems as they can provide a number of soil health and moisture benefits. This coming season the use of short-term cover crops immediately after picking to take advantage of mid-summer rainfall will be explored. Species such as millet which can achieve rapid post-harvest ground cover may reduce nutrient loss between crops while providing a boost to soil organic matter when incorporated. Some novel approaches will be examined along with their impact on subsequent cotton crops. The inclusion of short-term cover crops may offset some of the potential yield decline issues observed in longer term back-to-back irrigated cotton in CQ.
 

Helicoverpa survival within grown-on Bollgard® 3 crops  


Several growers who attended recent meetings about Bollgard® 3 stewardship and resistance management in CQ asked about the potential impact that natural enemies might have on Helicoverpa larvae survival in grown-on cotton crops.  In an attempt to answer this question, a trial has been set up at Theodore with Andrew French where small, single row patches of conventional cotton have been interspersed during sowing within a field of Bollgard® 3 cotton that is a possible candidate crop for growing on. These patches would enable Helicoverpa spp. larvae to survive (or larvae could be introduced), allowing assessment of parasitism or predation by natural enemies within a ‘sea’ of Bollgard® 3. Many growers have noted that natural enemies become abundant in longer season crops, so this experiment aims to assess the contribution to Helicoverpa mortality and whether it could be an important consideration for resistance management.     
 
For more information about any of this work contact Department of Agriculture’s Paul Grundy 0427 929 172 or Gail Spargo 0409 499 691.
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Header image courtesy Renee Anderson, Emerald.

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