Indicators of Last Effective Boll Population and Harvest Aid Timing in Cotton

Abstract

Maintaining profi table and sustainable production of cotton (Gossypium hirsutum L.) relies on improvements in management. Th e objective of this study was to determine the proper defoliation timing to optimize lint yield and fi ber quality through calculating heat unit (HU; DD15.5) accumulation beyond cutout, defi ned as fi ve nodes above white fl ower (NAWF = 5). Experiments were conducted in Burleson County, Texas, in 2003 and 2004, on a Weswood silt loam soil (fi ne-silty, mixed, superactive, thermic, Udifl uventic Halplustepts). Treatments were applied in a split-plot arrangement using a randomized complete block design with four replications. Th e main plots consisted of three nodal positions (NAWF = 3, 4, and 5) and the fi ve subplots were HUs (361, 417, 472, 528, and 583) accumulated beyond the corresponding nodal positions (NAWF), at which time a tank-mix of harvest aids was applied. Immediately before defoliation, 10 plants plot -1 were evaluated for percent open boll (POB) and nodes above cracked boll (NACB). Lint yield was detrimentally impacted in south central Texas when defoliation was initiated at 472 HUs beyond NAWF = 5. Defoliation at 60 POB resulted in as much as 29% more lint yield than defoliation based on the current benchmark of NAWF = 5 plus 472 HUs. Th is fi nding suggests NAWF = 5 is neither an indicator of the last eff ective fl ower population in all production locations, nor a proper guide for timing cutout on which end-of-season management decisions should be based in south central Texas. Abbreviations: DAT, days aft er treatment; HU, heat unit [(maximum temperature + minimum temperature)/2-15.5 in °C]; HVI, high volume instrument; NACB, nodes above cracked boll; NAWF, nodes above white fl ower; POB, percent open boll; POBD, percent open boll at defoliation; POBH, percent open boll at harvest.

Planting Geometry Effects on the Growth and Yield of Dryland Cotton

“…That is, if cotton blooming after 20 August has less than a 50% chance of maturing near Lubbock, Texas [4] then this date likely advances when moving north to Kansas. Potential incomplete boll and lint development that requires 472 growing degree days (GDD15.5) after bloom may resemble premature harvest-aid defoliation for terminated photosynthesis and depressed yield [5]. Although the possibility of crop failure during any given year was significant, [6] used the mean long term energy for this region to estimate cotton yields from up to six open and the nearly, 85%, mature bolls that ranged from <500 kg·ha −1 to 1000 kg·ha −1 .…”

Predicting the effects of environment and management on cotton fibre growth and quality: a functional-structural plant modelling approach

“…For optimizing topping time, farmers in China usually use the number of fruit branches as an indicator while the number of nodes above the first white flower is used in the USA ( Bynum and Cothren 2008 ). Our simulation of delaying main shoot topping, which results in a greater number of fruit branches and fruits on the plant, predicted a substantially reduced cotton fibre quality due to the increase of late-formed bolls.…”

A Prominent Role for Leaf Calcium as a Yield and Quality Determinant in Upland Cotton (Gossypium hirsutum L.) Varieties Grown Under Irrigated Mediterranean Conditions

“…Leaf physiological assessments and sampling for cation and isotope determinations were conducted on 19 August 2007 and 20 August 2008 at stage 80 according to BBCH system of coding growth stages (BBCH 80). This time point was defined taking into account two factors: the last effective boll (Bynum and Cothren ) of cotton in Greece is formed about mid‐August to 20 August (Galanopoulou‐Sendouka ) and that boll‐ripening is the most suitable stage for leaf carbon isotope discrimination (Δ) measurements (Saranga et al. ).…”