Browsing by Author "Keith Edmisten, Committee Chair"

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    Defining Optimal Defoliation and Harvest Timing for Various Fruiting Patterns of Cotton in North Carolina
    (2006-05-26) Collins, Guy David; Keith Edmisten, Committee Chair; David Jordan, Committee Member; Randy Wells, Committee Member
    Upland Cotton (Gossypium hirsutum L.) is a perennial plant produced as an annual crop in North Carolina. Due to high variability in net returns, and narrow profit margins, growers must focus attention not only on lint yield but also on lint quality. Implementing sound agronomic practices, such as proper defoliation timing and harvest timing, may help maximize lint yield and fiber quality. Cotton is normally defoliated when 60 percent of the total harvestable bolls are open. It is hypothesized that defoliation could be initiated before 60 OBPD (% open bolls) if fruiting is compact, and in contrast, defoliation could be delayed beyond 60 OBPD if fruiting is extended. Two experiments were conducted in 2004 and 2005 at Upper Coastal Plains Research Station near Rocky Mount, North Carolina, to observe the effects of defoliation and harvest timings on crops of various levels of maturity or fruiting habits. One study involved plant growth regulator strategies to mimic compact, normal, and extended fruiting habits, respectively. The other study included three variety maturity groups to accomplish the various fruiting habits. The targeted defoliation timings in each study were 50, 70 and 90 OBPD and the targeted harvest timings were 14 days after defoliation and 28 days after defoliation. According to lint yield data in 2005 from the study involving plant growth regulator strategies, a crop with compact fruiting could be defoliated earlier than 60 OBPD without sacrificing yields. Delaying harvest for a crop defoliated early may help maximize yield and fiber length, whereas an early harvest may be more appropriate for a crop defoliated late, especially if significant amounts of rainfall are experienced. In 2005, micronaire values decreased 4% by delaying harvest, regardless of defoliation timing. Data also suggests that NACB (nodes above cracked boll) ~ 3 corresponded to maximum yields, especially in cases where mepiquat chloride was used. Data from the study involving various cultivars suggests that cultivar differences may be largely responsible for quality variations in micronaire, fiber length, length uniformity, and fiber strength. Defoliation before 60 OBPD was proven to be acceptable in some cases, however, harvest may need to be delayed to achieve maximum yields. In contrast, optimal yields were reached when a crop defoliated beyond 60 OBPD was harvested early. These effects were largely a result of variations in the amount of rainfall occurring during the harvest period. Data also suggests that defoliation initiated at NACB ~ 3 corresponded to maximum yields and fiber quality. Data indicated that delaying defoliation may increase yields, regardless of varieties. Plant mapping data suggests that fruiting habits were different, however, all three cultivars seemed to possess an extended fruiting habit, therefore assumptions regarding fruiting compactness can not made based on a particular cultivar maturity group.
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    Fertilization Strategies of Cotton in North Carolina
    (2009-06-01) Hunt, Andrew David; David Jordan, Committee Member; Randy Wells, Committee Member; Keith Edmisten, Committee Chair
    Upland cotton (Gossypium hirsutum L.) can be a difficult crop to manage due to the intermediate growth habits, tropical origins, and perennial nature. Because cotton is produced as an annual in North Carolina, it is highly important to promote maximum early season growth, stimulate early flowering, and at the same time prevent excessive vegetative growth, all which are important to harvest quality cotton. The use of several management practices may be applied to promote earliness, and achieve high yields. While environmental conditions can generally not be controlled, they can be altered thorough tillage methods, plant growth regulator use, and desirable fertilization programs, to manipulate cotton vegetative and reproductive growth to promote high yields. Three studies were conducted to observe fertilization strategies for cotton production in North Carolina. One study was conducted in North Carolina and Virginia during 2005 and 2006 to determine effects of increased N fertilization rates and increased plant growth regulator rates on a modern cultivar. The second study were conducted in North Carolina in 2006 and 2007 to observe the effects of effects of starter fertilizer in conventional, strip†till (ST) and no†till (NT) systems on growth, quality and yield of cotton. The third study was conducted in North Carolina in 2006 and 2007 to determine optimal N placement methods in strip†till (ST) and no†till (NT) systems based on growth, fiber quality, and yield of cotton. Data from the first study showed that N rate affected yield in Virginia in both years and in North Carolina during 2006. However, in 2005 N did not affect yield. In North Carolina 2006 the response to N was quadratic, while in the Virginia locations the response to N was linear, however, further increase in N above 112 kg N ha†1 was not significant. Overall the use of a plant growth regulator did not alter the optimum N rate. For the second starter fertilizer did not have an effect on yield in either year. Starter fertilizers did have an effect on early season vigor and plant heights in 2006 with the 11†37†0 fertilizers having greater vigor and heights. In 2006 and 2007 11†37†0 fertilizers had the highest dry weights. Data from both years suggest that tillage has an influence on early season growth such as vigor, stand counts, and early season heights. Data from 2007 indicates that more bolls may be produced in NT systems, however, the number of bolls did not correspond to an increase in lint yield. Little agronomic advantage was found in starter fertilizer, with no positive or negative effect on yield when compared to an untreated control. There is no conclusive evidence from the data that starter fertilizer responses are more likely for any tillage system. For the third study data from 2006 found that under reduced tillage systems broadcasting N was sufficient, while injecting N did not improve final yield. Data from 2007 indicates that the placement of fertilizer N at first square had no significant effect on final yield. Due to the lack of sufficient tillage by N method interactions, it is likely that all N application methods would perform similarly in both tillage systems. Based on these data an optimal N placement strategy could not be determined based on the data, due to the inconclusive results regarding application method effects on growth and yield.
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    Physiological Studies in Cotton (Gossypium hirsutum L.).
    (2010-12-06) Riar, Ranjit; Randy Wells, Committee Chair; Keith Edmisten, Committee Chair; David Jordan, Committee Member; Jack Bacheler, Committee Member; Deyu Xie, Committee Member
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    Reducing Costs and Optimizing the Timing of Agronomic Inputs for Cotton (Gossypium hirsutum L.) in North Carolina.
    (2009-10-01) Collins, Guy David; Alan York, Committee Member; Jack Bacheler, Committee Member; Keith Edmisten, Committee Chair; Randy Wells, Committee Member
    Cotton (Gossypium hirsutum L.) grown in North Carolina requires intensive management for achieving optimal yields in an early-season environment. Recent increases in production costs require cotton producers to adopt practices that allow yield potential to be reached, while reducing input costs or optimizing the timing of agronomic inputs. Six experiments were conducted in North Carolina from 2006 to 2008 to investigate various production practices that could potentially reduce production costs and to define optimal timings of agronomic inputs. The first experiment investigated precision application of in-furrow insecticides for cotton planted in a hill-dropped configuration. The second experiment investigated application rates and timings of mepiquat chloride (MC) for cotton grown in conditions that promote excessive vegetative growth. The third experiment investigated the effects of MC applied at various rates and timings on the correlation (regression) between two techniques for measuring light interception and canopy coverage: the light quantum sensor method and the overhead digital imagery method. The fourth experiment investigated the effects of MC applied at physiological cutout, in terms of defoliation, regrowth, maturity, and yield. The fifth experiment investigated the effects of preconditioning defoliation treatments for tall cotton portraying dense canopies which improve standard defoliation practices and the timeliness of harvest. The sixth experiment investigated the effects of ethephon rate in defoliant mixtures on harvest date, with regard to defoliation timing and prior MC treatment.