The adage rings true, especially in cotton farming: “Well sown is half grown”. As CSD’s Extension & Development Manager for QLD, NT & WA, Sam Lee aptly stated that planting the cotton crop is paramount, setting the stage for the entire season. Achieving optimal field establishment is not just about putting seeds in the ground; it’s a multifaceted process hinging on seed quality, seedling vigour, and astute environmental management. This article delves into the best practices for cotton establishment, drawing insights from recent CSD research to highlight the crucial role of seed and seedling vigour in shaping your crop’s journey.

The Foundation: Seed and Seedling Vigour

Before even thinking about tractors and planters, understanding the fundamentals of seed and seedling vigour is essential. Seedling vigour is defined as the ability of normally germinated seedlings to progress to successful establishment in the field, even when faced with a range of challenging conditions. This inherent capacity is influenced by physiological seed quality and genotypic seedling vigour. High-quality seeds with strong genetic potential are the bedrock of a robust and uniform stand.

Decoding the “Green Light”: Optimal Planting Conditions

CSD’s extensive field trials between 2016 and 2019, encompassing 11 replicated trials over three seasons, varied planting depths, and timings across five varieties and 20 seedlots, have provided invaluable insights into what constitutes ideal planting conditions. These trials have defined the criteria for a “GREEN LIGHT/GO!” for planting, ensuring your crop gets the best possible start….

For a successful planting, aim for the following optimal conditions:

• Soil Temperature:Ensure the soil temperature at a 10cm depth is above 14°C at 8 am for three consecutive days. This sustained warmth is crucial for germination and early seedling growth.
• Weather Forecast:Look for a 7-day temperature forecast that is on a rising plane. This indicates favourable conditions for emergence and establishment in the immediate future.

Planting Depth: Maintain a planting depth of around 25mm. This shallow depth facilitates quicker emergence, a key factor in seedling vigour.

Conversely, the trials also identified “RED LIGHT/STOP!” conditions that significantly hinder field establishment. Planting when the soil temperature at 10cm is below 14°C for three consecutive mornings, or when the 7-day forecast suggests cooling temperatures, significantly increases the risk of poor establishment. Planting too deep (greater than 40mm) and severe soil crusting are also detrimental.

Fine-Tuning Establishment: Insights from Recent Research

Building upon these foundational principles, more recent CSD field establishment trials in 2021-22, conducted across diverse regions using the same variety and seed lot (Sicot 746B3F), aimed to pinpoint the drivers of establishment differences even when genetic factors were controlled. This research delved into the impact of various factors at a more granular level.

Correlation analysis of this data revealed several statistically significant factors influencing the percentage of plants established:

• Timing is Everything: Planting date significantly affects establishment (R=0.76), with later plantings in the trial period showing better establishment. This is likely linked to more consistently favourable soil temperatures and weather patterns later in the planting window, aligning with the “GREEN LIGHT” conditions.
• Forecast Foresight:A higher 7-day forecast score is associated with better plant establishment (R=0.52) and faster establishment (R=0.56), and less population variability (R=-0.54). This reinforces the importance of utilising weather forecasts as a key decision-making tool.
• Depth is Critical:Planting depth has a strong negative correlation with establishment (R=-0.85). Shallower planting consistently resulted in better establishment rates, likely due to faster emergence and reduced energy expenditure for the seedling to reach the surface. Deeper sowing also leads to slower establishment (R=-0.63) and increased population variability (R=-0.59).
• Emergence Speed Matters:Faster established plants exhibit significantly better overall establishment (R=0.61). This highlights the importance of conditions that promote rapid and uniform emergence. Late and mid-established plants, conversely, show a negative correlation with overall establishment.
• Strength in Numbers (and Individuals):Strong and healthy seedlings are more likely to establish successfully (R=0.53). This underscores the intrinsic value of vigorous seed and favourable germination conditions. Weak plants, as expected, show a negative correlation with establishment.
• Surprisingly, soil temperature and planting speed did not show a statistically significant effect on establishment in this specific study. However, this should be considered within the context of the trial design, and the earlier findings emphasising the crucial role of sustained soil warmth should still be prioritised.

These findings further illuminate the nuanced factors beyond just meeting the basic “GREEN LIGHT” criteria. Emphasising conditions that promote rapid, uniform emergence and strong early crop growth are key to maximising field establishment.

The Harvest Question: Does Early Vigour Translate to Final Yield?

One of the pivotal research questions explored was whether differences in plant health and speed at establishment translate to tangible differences at harvest. Surprisingly, analysis of final yield data from the plots revealed that final yield at harvest did not show a statistically significant correlation with any of the measured variables at establishment. This included final plant spacing and the percentage of dead plants, which was remarkably low at just 1.7%.

While this might seem counterintuitive, it suggests that cotton plants possess a remarkable ability to compensate for differences in vigour and establishment, provided a reasonable stand is achieved. Factors influencing yield later in the season, such as environmental conditions during flowering and boll development, pest and disease pressure, and nutrient management, likely play a more dominant role in determining final output.

Implications for Crop Management: Setting the Stage for Success

Despite the lack of direct correlation with final yield in this specific analysis, prioritising optimal cotton establishment remains critical for efficient and effective crop management. A uniform and vigorous stand provides several key advantages:

• Improved Resource Utilisation:A consistent plant population allows for more efficient uptake of water, nutrients, and sunlight throughout the growing season.
• Enhanced Weed Control:A dense and uniform canopy can help suppress weed growth, reducing the reliance on herbicides.
• Optimised Spray Applications:A consistent plant structure ensures better penetration and coverage of pesticides and other foliar applications.
• Timely Maturity and Harvest:Uniform establishment contributes to more even crop maturity, streamlining harvest operations.
• Reduced Variability:Lower population variability, linked to faster and strong establishment, can lead to more predictable yields and easier management decisions.

Practical Recommendations for Growers: Giving Your Cotton the Best Start

Based on the wealth of information from CSD’s research, here are some key recommendations to optimise cotton establishment:

• Prioritise Planting into Optimal Conditions:Always aim to plant when soil temperatures are consistently above 14°C at 8 am for three consecutive days and the 7-day forecast indicates a warming trend. Utilise reliable weather forecasts to inform your planting decisions.
• Monitor Soil Temperature Diligently:Invest in accurate soil thermometers and monitor temperatures at the recommended depth (10cm).
• Target the Ideal Planting Depth:Ensure your planter is calibrated to achieve a planting depth of around 25mm for most conditions. Avoid planting too deep, especially when conditions are less than ideal.
• Consider Variety and Seed Type:When facing less-than-optimal planting conditions, consider the specific characteristics of your chosen variety and the quality of your seed lot. Consult germination test results for valuable insights.
• Adjust Planting Rate if Necessary:If planting into marginal conditions, you may consider slightly increasing your planting rate to compensate for potentially lower establishment percentages.
• Focus on Early Vigour:Strive for conditions that promote rapid and uniform emergence, as early establishment is strongly linked to overall establishment success and reduced variability.
• Be Mindful of Planting Date:Later plantings under optimal conditions in the trial period showed better establishment. Carefully consider your planting window based on historical weather patterns and forecasts.

In conclusion, while the intricate relationship between faster establishment and final yield may involve complex compensatory mechanisms within the cotton plant, the benefits of a uniform, vigorous stand for overall crop management are undeniable. By diligently focusing on best planting practices, understanding the critical factors influencing seed and seedling vigour, and leveraging the insights from CSD’s research, cotton growers can lay a solid foundation for a successful and productive season. Remember, well sown is indeed half grown, setting your crop on the right trajectory from the very beginning.