Prepared by the CSD Extension and Development Team

Key takeaways

• Excessive vegetative growth in cotton can be detrimental to yield and fibre quality, as it diverts resources away from fruit development and can lead to difficulties in pest management and harvest.
• Several factors contribute to a cotton crop’s susceptibility to vigorous growth, and understanding these factors is crucial for implementing effective management strategies.

Factors Contributing to Excessive Vegetative Growth

Environmental Conditions: Warm temperatures and high humidity levels stimulate vegetative growth, making crops in these conditions more prone to becoming excessively vigorous. Additionally, waterlogged soils can inhibit root growth, making plants more susceptible to rank growth. Fields with a history of heavy clay or compaction zones, long cropping history, or fallow periods may also be more prone to excessive growth.

Nutrient Availability: High nitrogen levels, particularly during the early growth stages, can fuel excessive vegetative growth. This is because nitrogen is a key component of chlorophyll and other plant tissues involved in photosynthesis and growth processes.

Variety: Some cotton varieties inherently exhibit more vigorous growth habits than others. These varieties may require more proactive management to control vegetative growth. For example, Sicot 748 B3F is a known vigorous variety that needs careful monitoring and timely PGR application as opposed to Sicot 606B3F.

Planting Date: Early planted cotton may experience a longer growing season, increasing the likelihood of excessive vegetative growth. Late-planted cotton, on the other hand, may face challenges in controlling height if PGR application is delayed.

Strategies for Managing a Vigorous Crop

Plant Growth Regulators (PGRs): PGRs, such as mepiquat chloride, are a valuable tool for controlling vegetative growth and promoting reproductive development. They work by reducing internode elongation and promoting fruit retention. Careful monitoring of the crop’s Vegetative Growth Rate (VGR) is crucial for determining the need for and timing of PGR applications.

VGR Measurement: Measure plant height and node number weekly, starting prior to first flower. A VGR greater than 5.5 cm/node generally indicates the need for a PGR application. The exact rate will depend on factors like variety, fruit load, moisture status, and field history.

Application Timing: Early PGR applications, starting at the matchhead square or early squaring stage, are generally more effective in controlling height and promoting earliness.

Nutrient Management: Balancing nitrogen fertilization is key to managing vegetative growth. Avoid excessive nitrogen applications, especially during early growth stages. Consider split applications or late-season nitrogen applications to meet the crop’s needs without promoting excessive vegetative growth.

Irrigation Management: Avoid overwatering, which can lead to waterlogged soils and promote rank growth. Monitor soil moisture levels and irrigate only when necessary to maintain adequate moisture for optimal growth.

Variety Selection: When selecting cotton varieties, consider their growth habits and potential for vigorous growth. If planting a vigorous variety, be prepared to implement proactive management strategies, including early PGR applications. Choosing varieties well-suited to the growing environment and planting window can help mitigate excessive growth potential.

By understanding the factors that contribute to excessive vegetative growth and implementing appropriate management strategies, growers can optimize cotton yields and fibre quality while minimizing negative impacts associated with overly vigorous crops.