To maximise cotton crop yield, there are some key characteristics to look for at first flower.  

First flower is a critical milestone in the development of a cotton plant because this is when the plant starts to generate yield.  

The goal at first flower should be to have a healthy, actively growing plant with the right architecture and leaf area to develop a good boll load. 

 

Assessing crop progress at first flower

Here are some key metrics that can be used to assess crop progress at first flower and to promote high yield potential. 

• Total Nodes: The goal is to have the plant growing healthily up to and through first flower, aiming for more than 15-16 nodes at first flower (6-7 vegetative nodes, 8-10 fruiting branches). It is also important to make sure that the plant is not growing excessively, so monitoring growth rates and using growth regulators if needed is important. 

• Plant Height: While less important than overall plant health, plant height should be about 50-60 cm at first flower. This height creates a frame that will support a heavy fruit load during the flowering period. New node vegetative growth rate should not exceed 6-7 cm per node at this time. 

• Fruit per metre: At first flower, cotton crops should have 60 to 80 squares per metre, depending on plant stand. A higher fruit load might burden the plant, so growers should be prepared to respond with water and nutrients if this occurs. 

• Nodes Above White Flower (NAWF): A healthy crop should have a NAWF above 8 at first flower. This measurement is a function of the rate of growth from first square to first flower. A high NAWF value is desirable for a few reasons. It indicates that the plant is actively growing and has the potential to retain fruit on the upper and outer fruiting branches. It also enables the plant to better cope with minor stresses, such as a few days of hot temperatures. If the NAWF is lower than 8, the crop will need to be carefully managed to extend its reproductive life. NAWF should be monitored throughout the flowering period to assess crop performance. 

• First Position Retention: At first flower, whole of plant first position retention should be above 80% in the central and northern and above 90% in the southern regions. 

The concept of FastStart™ Cotton, which focusses establishing a healthy and vigorous crop early in the season, underscores this proactive approach. By setting the crop up for success from the start, growers can minimise the risks associated with poor establishment and maximise yield potential. FastStart Cotton is an initiative of CSD and Syngenta for Australian cotton growers. 

 

Yield potential

Growers should also keep in mind that achieving high yields in a shorter flowering window is possible.  

Yield is a function of both boll number and weight, and encouraging healthy growth of heavier bolls can help achieve high yield outcomes. 

The period between first flower and cut out in cotton crops is a critical period for yield generation because this is when 95% of the harvestable fruit is set. This period is also referred to as the flowering period.  

It is well understood that extending the flowering period for as long as seasonal and climatic conditions allow is important for maximising yield potential.

By focusing on extending the flowering period and ensuring optimal plant health during this critical stage, cotton growers can significantly enhance yield potential. 

Here’s why the flowering period is so important for yield. 

• Boll Development: The flowering period is when cotton bolls develop and mature. The longer the flowering period, the more bolls can be produced. 

• Yield Potential: Extending the flowering period allows for more squaring nodes, which leads to an increase in the number of bolls per meter. Boll number is a key factor in overall yield. 

• Improving Efficiencies: A longer flowering period allows the plant to efficiently use water and nutrients for boll development. 

CSD recommends that high-yielding cotton crops typically have a flowering period of 40 to 50 days. While high yields can still be achieved with shorter flowering periods, there is a positive relationship between the length of the flowering period and boll numbers. 

Importantly, the health of the cotton plant at first flower is crucial for maximising the benefits of the flowering period. A healthy plant at first flower with a high NAWF (Nodes Above White Flower) value is better equipped to produce and retain fruit and withstand stress during the flowering period. 

 

What if the crop is not set up at first flower?

If a cotton crop is not adequately set up at first flower, there are strategies to help it recover and potentially reach its yield potential during the flowering period. However, years of data highlight that having the crop in optimal condition at first flower is the most effective way to maximise yield. The period between first flower and cut-out is critical because 95% of the harvestable fruit is set during this time. 

CSD provides some specific guidance for recovering a crop that is not well-positioned at first flower: 

• Identify the Cause of the Problem: The first step is to determine why the crop is not set up well. Common causes include delayed planting, cold shock events, seedling diseases, insect damage, herbicide damage, and insufficient irrigation or nutrition. 

• Address Stress Factors: Once the cause is identified, steps should be taken to alleviate the stress factors impacting the crop. This might involve adjusting irrigation schedules to ensure adequate moisture, applying necessary nutrients, or implementing pest management strategies to control insect pressure. 

• Monitor NAWF Closely: Nodes Above White Flower (NAWF) is an important indicator of plant growth and vigour. If NAWF is low at first flower, it suggests the plant is not growing as actively as it should be. Monitor NAWF closely throughout the flowering period and adjust management practices to promote growth and avoid premature cut-out. CottonTracka is a perfect tool to assist in monitoring your crop 

• Optimise Irrigation and Nutrition: The demand for water and nutrients increases rapidly after first flower. Ensure the crop has access to sufficient water and nutrients to support boll development. Use irrigation tools and techniques to optimise water use efficiency and avoid water stress. Regularly monitor nutrition levels in crop leaf and petiole analysis to ascertain requirements. 

• Consider Growth Regulation: If the crop exhibits excessive vegetative growth at the expense of fruit development, consider applying plant growth regulators to redirect resources toward boll production. However, avoid applying growth regulators when the plant is already under stress. 

It is important to note that recovering a poorly-set-up crop can be challenging and might not fully compensate for the lost potential. Early setbacks often result in a delay in crop maturity, even if yield is not significantly affected.  

CSD highlights the importance of proactive management to minimise stress and maximise growth in the early stages of crop development to avoid the need for recovery efforts.