Ray Benson with the University of Arkansas Division of Agriculture's Mississippi County Extension Service, encourages growers of the importance of making economical end of season management decisions for this year's cotton crop.
Benson said a good way to know when the crop is mature is to monitor Nodes Above White Flower (NAWF) in their fields. Each week the first position white flowers in the crop should progress up the plant and get closer to the terminal. University of Arkansas research has shown that first position white flowers 5 nodes below the plants terminal (ie. NAWF = 5) represents the last population of flowers producers should base their end-of-season management decisions on. Based on our research, we have defined crop cutout as having occurred when the average NAWF value for a field is 5, not when the crop "has bloomed out the top". According to Benson, "our goal is to identify the date of the last effective flower population in the field and protect those flowers until they developed into bolls which are safe from fruit feeding insects, have matured to a point that they no longer require irrigation and have developed enough to be defoliated." Benson says that University of Arkansas researchers have shown that once flowers accumulate 350 heat units they are safe from fruit feeding insects. Additionally, bolls are mature enough to defoliate once they have obtained 850 heat units. Therefore, once we know the date of cutout, we can safely terminate insecticide after 350 heat units and schedule fields for defoliation after 850 heat units.
Growers should not let the flowering in the top of the cotton misguide their end of season management decisions. NAWF = 5 has very little to do with the calendar date, it is based on the physiology of cotton.
When NAWF = 5, the plant is saying it is finished. Measure the heat units and when the cotton is mature enough it is safe to stop spraying for insects, stop irrigation and it is time to defoliate. Managing the cotton at the end of the season can be a major savings to the grower.
Benson said the only time growers should consider a calendar date for identifying cutout is in situations where the crop is late. "We know there comes a time in the season where our temperatures drop and we don't accumulate any additional heat units so we can't wait for the crop to reach NAWF = 5". Historical weather data suggests that for Northeast Arkansas, August 10 is about the last flowering date where enough heat units can be accumulated to mature out the crop. Benson says that in situations where a field has not reached NAWF = 5 by around the 10th of August, the cutout date will need to be set for that date and heat units tracked from that point.
Benson announced the extension service is planning a cotton/corn field day on Aug. 8 starting at the Jeff Lammers Demonstration field on Highway 18 next to Farmers First Gin. He will be sending out news letters with more information to area growers. One of the topics of the day will focus on irrigation and new irrigation practices, along with other information being shared by several experts who will be joining local farmers for the day.