Welcome to the December edition of the Gwydir newsletter. In this issue, we explore lessons from some of the top-performing fields in last season’s crop competition, insights designed to help you get the most from your crop. If the pictures linked to this article don’t display straight away, be sure to click download so you don’t miss the story they tell. 

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Current cotton varieties continue to prove themselves as reliable performers in our region. With strong disease packages and the ability to accumulate carbohydrates steadily through the season, they offer growers confidence in both resilience and productivity. But the real horsepower of these varieties is unlocked when we manage the crop to retain early fruit and maximize boll factors number, size, and retention while balancing canopy growth. 

Early retention: The engine of yield 

Modern varieties can compensate for late-season fruit loss, but this comes at a cost of extra irrigation demand and the risk of fibre downgrades if rain arrives late season during boll opening. By retaining fruit early, we lean into the power of the variety, allowing it to carry increasing boll loads without relying on late compensation. This strategy not only secures yield potential, but reduces exposure to late-season risks. Every boll retained early is a building block of yield, and protecting those first fruiting sites is an efficient path to high productivity. 

Canopy Management and VGR Contro

Early boll retention plays a role in canopy management. When the plant is setting and holding fruit consistently, it naturally moderates its vegetative growth rate (VGR). This prevents the canopy from expanding beyond desirable levels, ensuring light penetration to lower fruiting sites and maintaining airflow to reduce disease pressure. A balanced canopy is more efficient at intercepting sunlight, supporting boll filling across the whole plant. 

However, we also see cotton with large canopies (26+ nodes) shading early fruiting sites. In these situations, the key drivers of yield, such as boll number, size, and retention, do not reach their potential. Shaded fruit often fails to fill properly, increasing the risk of tight lock or fungal blooms when late-season rainfall arrives. This highlights the importance of canopy balance: too much vegetative growth not only wastes resources, but also undermines the very boll factors that determine yield. 

Boll factors: Number, size and retention 

Yield is ultimately determined by three interlinked boll factors: 

• Boll number per square metre - the foundation of yield potential.
• Boll size (weight per boll) - the measure of fibre-packed efficiency.
• Retention (fruit carried through to maturity) - the critical factor that converts potential into reality.

Local benchmarks show that even our best crops rarely exceed 170 bolls/m², yet they can still deliver 18+ bales/ha. The difference lies in retention and boll size. A crop that holds its fruit early and protects it through to maturity ensures that each boll contributes fully to yield. Retention is the hinge point: without it, boll number and size cannot translate into bale weight.

Practical steps to strengthen boll retention and size 

• Nutrition and irrigation alignment: Ensure steady carbohydrate supply by matching water and nutrient inputs to crop demand, supporting boll filling.
• Pest vigilance: Protect early squares and bolls from heliothis, mirids, and other threats that erode retention.
• Light interception: Manage internode length and canopy density to maximize boll filling and prevent shading losses.
• Stress avoidance: Minimize water deficits, nutrient imbalances, and overuse of growth regulators that can trigger fruit shed. This also extends to irrigation management: while intervals of 7–12 days have been common practice, the best-performing fields are often those where growers are willing to return as early as 5 days during peak flower. These fields are typically well drained re-lasered every few years and managed with careful attention to irrigation head height in supply ditches. Correct head height ensures optimal flows through furrows, reducing the risk of uneven infiltration and sudden soil temperature drops. By moderating soil cooling, growers not only avoid plant stress, but also limit conditions that can favour vascular disease. In short, tighter irrigation schedules, good drainage, and balanced head heights are practical tools to sustain canopy efficiency.

A great tool to visualise these dynamics is CottonTracka®. Its graphing capability allows growers to track canopy development in real time, comparing current field progress against an ‘ideal’ benchmark from previous seasons. This helps identify whether the crop is sailing too close to the wind in terms of canopy expansion or boll load. Importantly, CottonTracka® integrates seasonal weather information, giving growers context for how environmental conditions are influencing boll retention and canopy balance. By logging and visualising these trends, growers can make proactive decisions to protect early fruit, sustain boll size, and maintain canopy efficiency. 

So if you want to keep an eye on your crop as it develops, why not run a CottonTracka® on it and adjust your management if it looks warranted?  

Wishing you a Merry Christmas and Happy New Year,

Stuart

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