Browsing by Author "David Jordan, Committee Member"

Filter results by typing the first few letters
Now showing 1 - 9 of 9
  • No Thumbnail Available
    Applying Crop and Weed Competitive Dynamics For Weed Management in Soybean and Peanut
    (2009-11-16) Place, George Thomas II; Nancy Creamer, Committee Member; Chris Reberg-Horton, Committee Chair; Tommy Carter, Committee Co-Chair; David Jordan, Committee Member
    Demand for organic food products has consistently increased for more than 20 years. Demand for organic grain has been particularly high, leading to price premiums of over double the conventional price. The largest obstacle to organic soybean production is weed management. The first investigation aimed at improving weed management in organic soybean tested the effectiveness of pre-plant rotary hoeing to reduce the need for multiple post-plant rotary hoeing. Pre-plant rotary hoe treatments included a weekly rotary hoeing four weeks before planting, two weeks before planting and none. Post-plant rotary hoe treatments consisted of zero, one, two, three, and four post-plant rotary hoe uses. Weed control was increased with pre-plant rotary hoeing at Plymouth in 2006 and 2007 but this effect disappeared with the first post-plant rotary hoeing. Multiple post-plant rotary hoe uses decreased soybean plant populations, decreased soybean canopy height, lowered soybean pod position and decreased soybean yield. In another experiment, the effect of soybean population on weed control was investigated. This research was conducted in 2006 and 2007 to investigate seeding rates of 185,000; 309,000; 432,000; and 556,000 live seeds/ha. All rates were planted on 76 cm row spacing in organic and conventional weed management systems. Increased soybean seeding rates reduced weed ratings at 3 of the 5 sites. Increased soybean seeding rates also resulted in higher yield at 3 of the 4 sites. Maximum economic returns for organic treatments were achieved with the highest seeding rate in all sites. In a separate experiment, the effect of soybean genotype on weed suppression was investigated. Twenty seven genotypes were chosen based on varying seed sizes, leaf shape, and height. Genotypes were compared in weedy and weed free conditions. Canopy traits and percent ground cover estimates were measured in weed free plots. Soybean and weed biomass has harvested at 7 weeks after emergence. Differences in weed biomass were detected between genotypes in both years. Optimum models from multiple regression showed seed size to be the most significant trait measured in overall genotype competitive ability in both years. In an additional experiment, the influence of soybean seed size within a genotype was investigated. Three popular soybean varieties: Hutcheson, NC-Roy, and NC-Raleigh were separated into four or five seed size classes. Seed sizes ranged from 10 to 20 g/100 seed. Each seed size class was grown in weedy and weed free conditions at Kinston, NC in 2007 and 2008 and at Plymouth, NC in 2008. The effect of soybean seed size on increased soybean biomass was detected in all environments when grown in competition with weeds. In the two environments with higher weed population densities, planting larger soybean seed reduced weed biomass at 7 weeks after emergence (R2=0.42 and R2=0.54 in Kinston 2007 and Kinston 2008 respectively). A study in peanut production systems was conducted to define interactions of three levels of weed management (clethodim applied postemergence, cultivation and hand removal of weeds, clethodim and appropriate broadleaf herbicides applied postemergence), three levels of planting pattern (single rows spaced 91 cm apart, standard twin rows spaced 20 cm apart on 91-cm centers, narrow twin rows consisting of twin rows spaced 20 cm apart on 46-cm centers), and two levels of cultivar (NC 12C and VA 98R) on weed control, peanut yield, and estimated economic return. Cultivar and planting pattern had only minor effects on weed control and interactions of these treatment factors seldom occurred. Weed control with cultivation and hand removal was similar to weed management with grass and broadleaf herbicides. Pod yield did not differ among treatments when these broadleaf weeds were dominant, but did differ when Texas panicum was dominant.
  • No Thumbnail Available
    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.
  • No Thumbnail Available
    Evaluation of Cultural Practices to Reduce the Incidence of Tomato Spotted Wilt Virus (TSWV) in North Carolina Peanut (Arachis hypogaea)
    (2003-09-02) Hurt, Christie Anne; Rick Brandenburg, Committee Chair; David Jordan, Committee Member; George Kennedy, Committee Member
    Tomato Spotted Wilt virus (TSWV), a thrips-vectored virus, has recently become one of the most devastating pathogens of peanut (Arachis hypogaea) in North Carolina. North Carolina peanut growers saw a dramatic increase in infestations of TSWV in 2000. Certain cultural techniques in Georgia have shown to lessen the amount of virus, and these were evaluated to determine their effect on TSWV incidence. The production systems are discrete between the runner-type peanuts grown in GA and the virginia-type peanuts in NC, thereby requiring that these practices be evaluated in the NC. Treatments included plant populations, varieties, twin and single row plantings, reduced tillage, planting dates, and in-furrow insecticides. During the growing seasons of 2001 and 2002, treatments compared were plant populations of 7, 13, and 17 plants per meter of row; varieties Gregory, NC V-11, and Perry; twin and single rows; conventional tillage and strip tillage; early and late planting dates; and phorate and aldicarb. Research plots were scouted for visual symptoms of TSWV monthly in 2001, and weekly in 2002. In 2001, symptomatic plants were tested for presence of the virus using the ImmunoStrip test system (Agdia, Elkhart, IN). High plant populations had less virus than lower plant populations, Gregory was infected with less virus than either NC V-11 or Perry, twin rows had a lower amount of virus compared to single rows, preliminarily strip tillage has had less virus than conventional tillage, and peanut treated with in-furrow phorate had less incidence of virus than those treated in-furrow with aldicarb.
  • No Thumbnail Available
    Evaluation of Weed Scouting Methods and the Effects of Glyphosate Drift in North Carolina Peanut (Arachis hypogaea) Production.
    (2005-11-29) Robinson, Bridget Lynn; Gary Moore, Committee Member; David Jordan, Committee Member; John Wilcut, Committee Co-Chair; Jim Flowers, Committee Co-Chair; Gail Wilkerson, Committee Member
    Research was conducted to evaluate weed scouting methods in peanut, and the effects of glyphosate drift in peanut. Weeds were scouted on-farm in eight North Carolina counties in 2003 and 2004. A total of 16 unique fields were scouted, and weed species and density data were collected using four different scouting methods. HADSS was used to determine expected net return, yield loss ($ and %), and total treatment costs for each field. Net returns were averaged for optimal treatments in each field to determine the whole-field expected net return. Values of theoretical net return for the optimal treatment in each field ranged from $244 to $1,444 per ha, and averaged $867 per ha for all sixteen fields. The windshield method, while quickest, was also the least accurate at making herbicide recommendations. The range method was more accurate at estimating broadleaf weed densities than grass or sedge weed densities. Herbicide recommendations using the count method were more. The count method required the most time for completion (30 min). The maximum theoretical loss for fields scouted with the windshield method was as high as $528/ha. The windshield method resulted in accurate (top 10%) herbicide recommendations at least 82 and 77% of the time in 2003 and 2004, respectively. To evaluate peanut injury and pod yield when exposed to glyphosate, five experiments were conducted during 2001 and 2002 in North Carolina. Glyphosate was applied to 10 to15 cm diameter peanut plants at rates ranging from 9 to 1,120 g ai/ha. Visual injury was noted 7 DAT when glyphosate was applied at 70 g/ha and higher. Glyphosate at 280 g/ha or higher significantly injured the peanut plant and reduced pod yield. Shikimic acid accumulation was negatively correlated with visual injury and pod yield. Shikimic acid presence can be detected using plant samples, and accumulation can be an effective diagnostic tool for determining exposure to glyphosate in peanut 7 DAT, but not at 14, 21 and 31 DAT.
  • No Thumbnail Available
    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.
  • No Thumbnail Available
    Improving Cotton Production Margins through Management Decisions and Use of New and Standard commercial Products to Improve Quality and Profits
    (2005-09-09) Nuti, Russell C; Randy Wells, Committee Co-Chair; David Jordan, Committee Member; Alan York, Committee Member; Art Wollum, Committee Member; Keith Edmisten, Committee Co-Chair
    Cotton (Gossypium hirsutum L.) is a perennial plant managed as an annual crop to optimize yield and fiber quality while managing inputs to maximize profit. Transgenic improvements have simplified cotton production. Resistance to the non-selective herbicide glyphosate and in-plant production of Bacillus thuringiensis (Bt) endotoxin are two such advances. Cultural practices including use of mepiquat chloride (MC), and optimizing planting date contribute to crop uniformity and decrease risk involved with environmental stresses. Comparisons between conventional and transgenic weed and insect management systems, optimal and late planting dates, overhead sprinkle irrigation and drip irrigation, and use of MC were evaluated. Optimal-planted cotton had better yield than cotton planted late. Mepiquat chloride did not always provide an advantage, however never caused an undesirable response. At times, cotton plants treated with MC showed improved micronaire, compensation for boll loss, and earlier maturity. Broadcast glyphosate at the eight-leaf stage reduced yield of optimal-planted cotton in 1 of 3 years and 2 of 3 years in late-planted cotton. Glyphosate contact after the four-leaf stage in 2 of 3 years shifted the majority of bolls above node 10. Lint yield results were variable between overhead sprinkle and drip irrigation systems. Mepiquat chloride did not affect yield in irrigated cotton, however did control plant height, and improve fruit retention and cotton maturity. Non-labeled glyphosate applications reduced maturity in each irrigation system in 1 of 3 years. Cotton injury caused by conventional herbicides resulted in yield loss and poor returns compared to glyphosate systems. Early-season weed competition from low input herbicide programs caused cotton biomass reduction. High costs of conventional herbicide programs offset the available profit margin compared to glyphosate systems when yields were similar. Glyphosate systems provided excellent control of all weed species, while conventional herbicides gave acceptable control in most cases. Glyphosate resistant cotton cultivars with had better yield and returned more profit than the same cultivars treated with conventional herbicides.
  • No Thumbnail Available
    Investigation of Cotton Growth: Temperature and Carbohydrate Dynamics
    (2003-09-23) Viator, Ryan Patrick; Keith Edmisten, Committee Co-Chair; Randy Wells, Committee Co-Chair; David Jordan, Committee Member; Judith Thomas, Committee Member; John Wilcut, Committee Member
    Research involving NAWF monitoring determined the last effective boll population for ultra-narrow row cotton (UNRC) compared to conventional cotton (CONC) grown in the northern rain-fed production region. The UNRC produced the majority of seedcotton plant-1 on the upper portion of the plant, NAWF 3-5, while CONC produced the most seedcotton plant-1 at NAWF 3-7. Boll numbers showed a similar pattern. The UNRC produced more seedcotton on an area basis at NAWF 2, 3, 4, and 6. Research on heat unit accumulation revealed that single variable models were somewhat related to boll fill period in terms of regression fits, with degree-days 30/13°C providing the best adjusted R2 of 0.9399; the degree day 15.5°C model had an adjusted R2 of 0.9268. Modifying the DD15.5 model by adding either minimum air temperature or maximum and average air temperature increased the adjusted R2 to 0.9632 and 0.9934, respectively, while also reducing mean square error and coefficient of variation. The root and stem carbohydrates study revealed cultivar differences for starch concentration at both sample times, but starch content was only significant at first bloom in 2002. These differences, though, did not show a strong relationship with year of cultivar release, indicating that a century of breeding efforts has not altered stem and root starch dynamics.
  • No Thumbnail Available
    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
  • No Thumbnail Available
    Seed Quality Issues Associated with High-oleate Peanut (Arachis hypogaea L.)
    (2006-12-02) Sun, Minghui; David Jordan, Committee Member; Janet Spears, Committee Chair; Thomas G. Isleib, Committee Member
    The high-oleate trait of peanut is of great interest to the peanut processing industry because it produces greater oxidative stability of the oil without adversely affecting flavor. Most US peanut breeding programs have incorporation of the high-oleate trait into existing cultivars and future releases as an objective. While much of the peanut industry is concerned about peanut dietary oil quality, seed technologists are concern that altering peanut seed fatty acid or total lipid composition could influence germination rate, seed and seeding vigor, and seedling survival, especially if the seed are planted in stressful soil conditions. An experiment was designed to evaluate temperature effect on seed oil quality of high-oleate and normal peanut cultivars in controlled greenhouse environment. Two cultivars, NC-V 11 and Gregory, along with their paired backcross-derived high-oleate lines were planted in greenhouses maintained at 22⁄18oC, 26⁄22oC and 30⁄26oC day⁄night temperature. A split-plot experimental design with two replications was used. Peanut kernels were analyzed for fatty acid composition of the whole seed and axis lipids. The whole seed oleic to linoleic acid (O⁄L) ratio of normal peanuts grown in 30⁄26oC, 26/22oC, and 22⁄18oC, measured 1.9, 1.5, and 1.3, respectively. The O⁄L for their high-oleate pairs decreased from 24.7 when grown in 30⁄26oC to 15.9 in 26⁄22oC and to 13.7 in 22⁄18oC. Temperature did not affect the fatty acid composition of axis total lipid or phospholipid fractions. The high-oleate trait was however, expressed in the axis lipids. The average O⁄L of axis from normal peanut was 1.1 while that of high-oleate lines was 4.6. Likewise, axis phospholipids for normal and high-oleate lines were 1.0 and 5.9. Decreased production environment temperature in this study decreased the O⁄L ratio of seed oil of high-oleic peanut lines, and the high-oleate trait expressed in peanut seed storage lipids is also expressed in axis membrane lipids to a lesser degree. The second experiment was designed to determine if the production methods applicable to traditional peanuts will hold for high-oleate cultivars. Six Virginia-type peanut cultivars and their paired backcross-derived high-oleate lines were grown at the Peanut Belt Research Station near Lewiston, NC in 2003 and 2004. A split-plot experimental design was used with 2 x 2 factorial combinations of planting and harvest date as whole plot treatments, and 2 x 6 factorial combinations oleic acid and cultivars as subplot treatments. Seed quality evaluation included standard germination (SG), cool germination (CG), and electrical conductivity (EC). Oleic acid level had no influence on SG but did significantly alter CG and EC of high-oleate lines. Averaged across background genotypes, high-oleate lines had lower seed vigor than their paired lines with normal oleic content. The high-oleate lines of three of the six pairs had significantly lower CG and higher EC. Planting and harvest date affected all the seed quality traits measured. SG of both normal and high-oleate lines was reduced in 2004 when harvest was delayed, but was not affected in 2003. In 2003, CG of the high-oleate lines was significantly lower than that of normal lines in three of the four production environments; EC was significantly higher in the high-oleate lines in all planting date and harvest date combinations. In 2004, there was no statistical difference between the CG of normal and high-oleate lines, but EC was significantly higher in the high-oleate lines for three of the four environments.