Evaluating Cotton (Gossypium hirsutum L.) Maturity Patterns in the Northern Texas High Plains

The Texas High Plains Region contributes to the majority of Texas cotton production, the leading state in United States production. Over the last two decades, cotton has migrated north of the well-known cotton region of the Southern High Plains, providing a unique opportunity for farmers to produce a drought tolerant crop as irrigation capacities from the Ogallala Aquifer dwindle. Compared to the Southern High Plains, the Texas Northern High Plains (NHP) is regarded as a more stressful production area in terms of reduced thermal units. Advancements over the last century such as boll weevil eradication, development of transgenic Bt traits, herbicide tolerance, and early maturing cotton varieties have made production in the area possible. The industry standard for monitoring cotton growth to maturity was developed in the early 1990’s in traditional cotton production regions prior to these advancements. Developmental target values for the timing of the appearance of the first square, the first flower, and physiological cutout were presented in the COTMAN manual developed by the University of Arkansas (Oosterhuis & Kerby, 2008). While these benchmarks have remained the standard for many years, the accuracy of such target values for current production systems in the Texas Panhandle is questionable. This study monitored modern, commercially available cotton cultivars commonly grown in the Texas Panhandle and presents cultivar specific developmental stage benchmarks that are representative of the region. The primary objectives of this study were to investigate (1) early season vegetative growth from planting to first square, (2) vertical flowering interval, (3) timing of physiological cutout and (4) yield contribution of the last effective boll population. Production has been proven to be successful in the area (Gowda et al., 2007 & Leng et al., 2018), certifying the need to investigate whether developmental target values differ from the industry standard, and if so, to present optimized values. Results from two trial in 2022 and 2023 growing seasons indicated a stark contrast in development when compared to the industry standard Target Development Curve (TDC). Specific developmental curves were generated by segmented regression for each trial from main-stem nodal development measurements and corresponding nodes above white flower (NAWF) values recovered from tagged white flowers. Main-stem node lint contributions were analyzed from lint weights captured after box picking and ginning. Nonlinear regression was used to recover parameters for the estimated maximum yield, mid-node where accumulation changed slope, and rate of accumulation. These parameters were then used to calculate accumulated lint yields by main-stem node which were then used to determine the percentage of the total yield to identify the effective fruiting zone (Kerby & Hake, 1996). Compared to the industry standard TDC, data from both trials illustrate decreased vegetative growth from emergence to first flower, as well as a delay in timing to first square, first flower, and physiological cutout. The trial at Bushland, Texas in 2023 was the exception to observed developmental delays, presumably due to a late planting date. Heat unit accumulations were inconsistent with published values. However, it should be noted that the appropriate heat unit targets are not well defined in the literature. The data suggests current methods of assessing cotton maturity are not optimized for production in the Texas Panhandle.