Monitoring Nodes-Above-White-Flower in Cotton to Improve End-of-Season Management Decisions

Tuesday, July 25, 2017

Early planted cotton in Mississippi County has been flowering for the past few weeks and will soon be approaching cutout. As the crop continues to develop, producers should start thinking about end-of-season management practices. Understanding a little about the physiology of the crop can help producers make better production decisions and avoid expensive mistakes associated with end-of-season crop inputs.

Early in the season, cotton develops main-stem nodes at a rate of approximately one new node every 2.7 days. As cotton transitions from vegetative to reproductive growth, the plant allocates more resources to the developing fruit. Once flowering is initiated, developing bolls become the primary sinks for photosynthates and plant nutrients. Assuming good fruit retention, progressive boll development represents a great demand on the plant (boll load can be thought of as a good stress on the crop). As a greater proportion of plant nutrients and photosynthates are partitioned to developing bolls, main-stem nodal development slows down and 1st position white flowers develop closer and closer to the plant’s terminal.

There comes a point when the developing boll load becomes such a demand that the crop can no longer support additional fruit/boll development. Monitoring the average number of nodes above 1st position white flowers (NAWF) can give producers an indication of this occurrence. Research from multiple states, over several years has indicated that white flowers developing five nodes below the plants terminal (i.e. NAWF = 5) represents the last flower population that the plant can adequately support with nutrients.

According to Dr. Bill Robertson with the University of Arkansas Division of Agriculture, “NAWF = 5 represents the youngest population of bolls that contribute significantly to yield and profit. We make end-of-season decisions based on this group of bolls.” Flowers set closer to the plant terminal may be retained and develop to maturity, but there is insufficient plant assimilates to allow those flowers to develop into bolls that contribute significantly to the crop’s total yield. Increasing irrigation, fertilizer (including foliar), and insecticide application above current recommendations does not change this process. NAWF = 5 (i.e. Cutout) represents a combination of the plants physiological processes and signifies that the stresses associated with boll development have reached the plants supply capacity. Investing in flowers set after NAWF = 5 will likely result in unnecessary crop expenses.

Once the date a crop reaches NAWF = 5 has been identified, heat unit accumulations can help producers determine when certain crop inputs can be safely terminated. For example, white flowers that have accumulated 250 heat units are safe from plant bug feeding. Therefore insecticide applications to control plant bugs will likely not result in economic benefits after a crop has developed 250 heat units after NAWF = 5. Additionally, control of more aggressive fruit feeding pests like bollworms/budworms are not necessary after the crop as accumulated 350 heat units after NAWF = 5 (assuming the crop is pest free at NAWF = 5 + 350 heat units).

Nodes Above White Flower (NAWF) is the cotton plant’s physiological indicator of stress/boll load. Tracking its progression can provide valuable insight and help improve end-of-season management decisions. Be sure to check the NAWF status of your crop and let the cotton plant “tell you when you can stop spending money.”

For additional information on cotton development, or for other end-of-season management decisions that can be keyed to NAWF and heat unit accumulation, please feel free to contact our local county extension office at (870) 762-2075. We can also be reached at rbenson@uaex.edu or online at www.uaex.edu/Mississippi.

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