Nodes above white flower and heat units as indicators of harvest aid timing

The timing of harvest aid application on cotton (Gossypium hirsutum L.) is critical, and poses potential problems when mistimed. The consequences of premature harvest aid application could result in reduced profit to the grower through the need for additional applications, reduced lint yield, poor fiber quality, and/or delayed harvest. A delayed application of harvest aid materials may also reduce lint yield and fiber quality if late season inclement weather patterns are established. Currently, there are many methods utilized for determining application of harvest aid materials. One method utilizes accumulated heat units, or growing degree days (HU or DD60??s), following plant physiological maturity. Physiological maturity (cutout) is identified as nodes above white flower equals 5 (NAWF=5). This method triggers the application of harvest aid chemicals when 850 HU have been accumulated beyond cutout. Due to differing environmental and edaphic characteristics across the Cotton Belt, application of harvest aid chemicals at this time may be premature in terms of optimizing lint yield and fiber quality. A two-year study was established to determine the proper timing of harvest aid application for picker harvested cotton in south central Texas. The design utilized a split-plot with four replications. The main plots consisted of three nodal positions(NAWF=3, 4, and 5), and the subplots were five HU accumulations (650, 750, 850, 950, and 1050) that corresponded to each of the nodal positions. In both years, lint yields increased with an increase in HU accumulation. Greater yields were achieved when HU accumulation was initiated after NAWF = 4. This two-year study indicates that harvest aid applications made at NAWF = 4 plus 1050 HU would optimize yield potential for picker harvested cotton in south central Texas.