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Final lint yield in cotton (Gossypium hirsutum L.) is relatively stable across a wide range of population densities. This study was conducted to determine (i) which components of final lint yield impart this yield stability across plant populations and (ii) how yield distribution is influenced by population density. Studies were conducted in 1997 and 1998 on a Tifton loamy sand (Fine‐loamy, kaolinitic, thermic Plinthic Kandiudults). Cotton was planted in each study on 91‐cm row widths at seeding rates ranging from 3.5 to 25.1 seeds m−2. At harvest, each plot was hand picked and boll numbers and weights were recorded at each monopodial branch and sympodial branch fruiting position. Lower population densities led to plants with more mainstem nodes and monopodial branches with increased fruit retention, resulting in greater fruit production per plant. Boll size was inversely related to population density. Mean net assimilation rate from first flower to peak bloom also was related inversely to population density. The mainstem node of peak boll set increased with population density. Fruit production on a ground area basis was greater in the first sympodial position as population density increased, while fruit production on a ground area basis in third positions and monopodial branches was greater as population density decreased. Accumulative seedcotton from sympodial branches also increased with population density. Total fruit number and seedcotton yield per area were not influenced by population density in these studies. Yield stability across population densities was achieved through manipulation of boll occurrence and weight.

Potassium (K) fertility recommendations based on cotton petiole diagnostic analysis results have been inconsistent in the past, partly because the lowest acceptable petiole K concentration is unknown. Therefore, cotton was grown in sand filled 8-L pots under two K treatments in a growth chamber at the Altheimer Laboratory in Fayetteville, AR to determine the petiole K concentration that will impact leaf physiology. Chamber-grown plants were watered every second day with nutrient solution and with deionized water on alternate days. At 14 days after planting two treatments were established consisting of (1) continued complete nutrient solution, and (2) nutrient solution containing no K. Measurements were taken 13, 19, and 26 days after treatment establishment (DATE). Organ K concentrations, leaf chlorophyll, photosynthesis, adenosine triphosphate (ATP), and nonstructural carbohydrate concentrations were monitored as plant K deficiencies developed. All organ K concentrations were much lower in the no-K treatment on each analysis date. Visual K deficiencies were first observed at 19 DATE along with reductions 303 304 BEDNARZ AND OOSTERHUIS reductions in leaf chlorophyll concentration. Leaf photosynthesis was greatly reduced in the no-K treatment beginning at 19 DATE. However, leaf ATP and nonstructural carbohydrate concentrations were higher at 19 and 26 DATE in the no-K treatment, which may have been the result of reduced utilization and translocation of these metabolites. Our studies show that reductions in leaf physiological processes and plant growth did not occur until the petiole K concentration fell below 0.88% on a dry weight basis. Therefore, reductions in lint yield and quality should not develop until this critical petiole level is attained.

absence of late season insect pressure, however, poorly drained soils and a history of inclement weather patterns Full season cotton (Gossypium hirsutum L.) cultivars may be better during the fall months continue to necessitate manageadapted to the lower southeastern USA because early maturing cultivars may not recover from the many episodic drought events that ment for early crop maturity in some regions of the U.S. annually plague the region. The objective of this investigation was to Cotton Belt. In the lower southeastern USA, however, determine if cotton maturity may be defined on the basis of flowering more favorable fall weather conditions and well drained interval, boll maturation period, or whole plant yield distribution. soils may not necessitate management for early crop Studies were conducted at the University of Georgia Coastal Plain maturity. In fact, management for full season crop matu-Experiment Station in 2001, 2002, and 2003. Nine commercially availrity may be the more suitable approach. able cotton cultivars were over seeded and hand thinned to 10.8 plants Water availability is frequently the most limiting facm Ϫ2 . Areas within each plot were reserved for daily white flower and tor to profitable cotton production in the southeastern open boll tagging and hand harvest. Mean vertical flowering intervals USA. Because of the shallow, coarse textured soils of were 2.1 (2001), 2.7 (2002), and 2.6 (2003) d. Mean vertical flowering intervals increased from main stem node 5 to about main stem node the Coastal Plain and the unreliable rainfall patterns 11 and then began to decline. Mean horizontal flowering intervals