Charles L. Webber

Chemical composition of kenaf (Hibiscus cannabinus L.) seed oil

Abstract Seeds from nine kenaf genotypes (Cubano, Everglades 41, Everglades 71, GR2563, Guatemala 48, Indian, 178-18RS-10, Tainung #1, and Tainung #2) were evaluated for oil, fatty acid, phospholipid, and sterol content. Oil content ranged from 21.4 to 26.4% with a mean of 23.7%. Total phospholipids ranged from 3.9 to 10.3% of the oil, with a mean of 6.0%. Mean sterol percent was 0.9 and ranged from 0.6% of the total oil for 178-18RS-10 accession to 1.2% for Everglades 71. Palmitic (20.1% of the total fatty acids), oleic (29.2%), and linoleic (45.9%) were the major fatty acids, and palmitoleic (1.6%), linolenic (0.7%), and stearic (3.5%) were the minor components. Medium (C 12 C 14 ) and long (C 22 C 24 ) chain fatty acids were less than 1%. Sphingomyelin (4.42% of the total phospholipids), phosphatidyl ethanolamine (12.8%), phosphatidyl choline (21.9%), phosphatidyl serine (2.9%), phosphatidyl inositol (2.7%), lysophosphatidyl choline (5.3%), phosphatidyl glycerol (8.9%), phosphatidic acid (4.9%), and cardiolipin (3.6%) were identified in the nine genotypes. Phosphatidyl choline, phosphatidyl ethanolamine, and phosphatidyl glycerol were the dominant phospholipids. In addition, eight unidentified phospholipids were also found, β-sitosterol (72.3% of the total sterols), campsterol (9.9%), and stigmasterol (6.07%) were prevalent among kenaf genotypes. Kenafs relatively high oil content and its similarity to cottonseed oil suggest that the seed oil may be used as a source of edible oil. The variation among genotypes indicates potential for genetic improvement in oil yield and quality.

Crude protein and yield components of six kenaf cultivars as affected by crop maturity

Abstract Information concerning the influence of plant maturity on kenaf ( Hibiscus cannabinus L. Malvaceae) as a livestock feed is limited. Research was conducted during 1989 and 1990 to determine the effect of plant maturity on crude protein and yield components of kenaf. Crude protein and yield data were collected on six kenaf cultivars (‘Guatemala 4’, ‘Guatemala 45’, ‘Guatemala 48’, ‘Guatemala 51’, ‘Cuba 2032’ and ‘Everglades 41’) harvested at 76 and 99 days after planting (DAP) at Ladonia, TX, on a Tinn clay, 0–2% slope. Cultivars, harvest dates and years each significantly affected yield components. Crude protein percentages in the leaves, stalks and whole plants were significantly greater at 76 DAP than 99 DAP, while the reverse was true for total crude protein production. Guatemala 48 produced the greatest crude protein (558 kg/ha) of the tested cultivars. The effects of harvest maturity were consistent across cultivars and years, even though differences existed among cultivars for yield components and crude protein. The selections of harvest maturity and cultivar are important variables in producing maximum protein and dry-matter production.

Plant maturity and kenaf yield components

Abstract Kenaf (Hibiscus cannabinus L.), an alternative fiber crop for paper pulp production, is normally grown during the entire summer growing season (150 days and longer) to maximize fiber production. However, it may be advantageous to harvest the kenaf crop earlier than 150 days after planting (DAP) depending on the harvesting conditions (e.g. soil moisture or equipment availability) or marketing opportunities (price fluctuations or alternative uses). In addition to affecting the final stalk yield, harvesting kenaf at an earlier maturity may significantly alter the composition of the kenaf plant. The objective of this field study was to determine the effect of kenaf plant maturity on kenaf yield components. Kenaf cultivar ‘Everglades 41’ was planted at Lane, Oklahoma, USA, in the spring of 1996, 1997, and 1998 on 76 cm row spacing at 250 000 plants per hecatre. Kenaf plots were harvested at four harvest dates, 60, 90, 120, and 150 DAP. At each harvest date, plants from a 3 m length of row were cut at ground level and used to determine plant population, plant height, stalk, leaf and whole plant yields, stalk and leaf percentage by weight, and the rate of plant growth during the selected growing season. The experiment was a randomized complete block design with five replications. Harvest age (60, 90, 120, and 150 DAP) did not significantly affect plant populations, but significantly affected all other yield parameters. Kenaf plant height, stalk yield, stalk percentage, and total plant biomass yields were consistently significantly greater at 150 DAP than at 60, 90, and 120 DAP for the 3 year study. Although the growth rates per day did level off or even decreased after 120 DAP, the significant increases in stalk yields after 120 DAP justify the additional 30 day growth. This research provides information that can be applied to both kenaf fiber and forage production, especially in gaining a greater understanding of the relative response of the kenaf yield components and partitioning of dry matter during the growing season. The research procedures can also be used for evaluating kenaf cultivars that may be more suitable for forage production, by identifying cultivars that have greater leaf biomass yields and leaf percentages earlier in the season and increasing values throughout the growing season.

Kenaf (Hibiscus cannabinus L.) core as a containerized growth medium component

Kenaf (Hibiscus cannabinus L.) stems contain two distinct fiber types, bast and core. The absorbent, low density core (xylem) is a possible potting mix component. Two greenhouse studies were conducted during 1993 and 1995 to determine the feasibility of substituting kenaf core for vermiculite and bark. In Study 1, fine-grade kenaf was substituted for vermiculite in three volume ratios (1, 2 or 3) with sphagnum peat moss and perlite (1:1) and compared to a 1:1:1 ratio of vermiculite:sphagnum peat moss:perlite. In Study 2, coarse-grade kenaf was substituted in three volume ratios (1, 2 or 3) with sphagnum peat moss and compared to a 1:1 ratio of pine bark:sphagnum peat moss. Plant height, canopy diameter, shoot weight, and root weight of periwinkle (Vinca minor) seedlings were determined 10 weeks after transplanting into the media contained in 12.5-cm diameter pots. The substitution of fine-grade kenaf for vermiculite at a 1:1 ratio reduced to some extent all periwinkle yield parameters except root dry weight. As the volume of fine-grade kenaf increased, all yield parameters decreased compared to the vermiculite media. Substitution of coarse-grade kenaf for pine bark in a 1:1 ratio produced equivalent or greater yield components. This research indicates that kenaf core can be a suitable containerized growth medium component, depending on the size and percentage of kenaf used, the plant growth requirements, and the specific physical characteristics desired in the containerized growth media.

Effects of Halosulfuron on Weed Control in Commercial Honeydew Crops1

Studies were conducted at four sites during a 2-yr period in Oklahoma, Texas, and Arkansas to determine effectiveness and safety of halosulfuron in honeydew crops. Halosulfuron applied postemergence at 26.3 to 78.8 g ai/ha controlled yellow nutsedge 85 to 97%, golden crownbeard 100%, and tumble pigweed 83 to 95%. Control of yellow nutsedge continued to increase for 3 to 6 wk after treatment. Golden crownbeard and tumble pigweed efficacy increased to its highest levels after 4 and 3 wk, respectively. Reduced crop growth and yellowing of foliage did not exceed 13%. No differences were recorded for yield, earliness, or percentage of marketable fruit. Nomenclature: Halosulfuron; golden crownbeard, Verbesina encelioides (Cav.) Benth. & Hook. f. ex Gray #3 VEEEN; tumble pigweed, Amaranthus albus L. # AMAAL; yellow nutsedge, Cyperus esculentus L. # CYPES; honeydew, Cucumus melo L. Inodorus group ‘Honeybrew’. Additional index words: Melon crops, mulch, plasticulture, plastic mulch. Abbreviations: POST, postemergence; PRE, preemergence; WAT, weeks after treatment.

POST Weed Control Using Halosulfuron in Direct-Seeded Watermelon

Watermelon growers rotate crops to prevent problems, but weed populations in new fields may hold unexpected control challenges. Having effective POST herbicides would provide growers an opportunity to respond to emerging weeds on an as-needed basis. To address this need, field studies were conducted over 4 yr in Oklahoma to determine efficacy and crop response of POST halosulfuron applications to direct-seeded watermelon that received PRE application of ethalfluralin at 840 g/ha. At 5 wk after crop emergence (WAE) halosulfuron was applied at 18, 27, 36, and 54 g/ha. The 27 g/ha rate was also applied at 1, 2, 3 and 7 WAE. Halosulfuron applications made 5 WAE did not provide acceptable (> 80%) control of pigweeds and cutleaf groundcherry regardless of rate. Applications made 1 WAE provided significantly better control of pigweeds and cutleaf groundcherry than did later applications. Halosulfuron treatments of 36 and 54 g/ha made 5 WAE and of 27 g/ha made 1, 2 and 3 WAE did not result in significant yield increases compared with the hand-weeded check. These studies show that POST halosulfuron application may be a useful treatment for direct-seeded watermelon. This option would enable more judicious use of herbicides and possible reduction in production costs. Nomenclature: Halosulfuron; Palmer amaranth, Amaranthus palmeri S. Wats. AMAPA; tumble pigweed, Amaranthus albus L. AMAAL; cutleaf groundcherry, Physalis angulata L. PHYAN; eclipta, Eclipta prostrata L. ECLAL; watermelon, Citrullus lanatus (Thunb.) Matsumura & Nakai var. lanatus ‘Jubilee’, ‘XIT 101’.

Injury Potential from Carryover of Watermelon Herbicide Residues

Studies were conducted to determine injury potential to rotational crops from carryover of herbicides used in watermelon production. Treatments included halosulfuron, ethalfluralin, and sulfentrazone alone; halosulfuron in tank mixtures with bensulide, clomazone, ethalfluralin, and naptalam; and a tank mixture of naptalam and bensulide. Sulfentrazone applied at 224 g ai/ha to watermelon severely reduced spinach emergence, but did not reduce emergence of broccoli, cabbage, or wheat. Residues of sulfentrazone applied to watermelon at 450 g/ha stunted growth of broccoli and cabbage and was the only treatment that reduced wheat stand. Injury to broccoli, cabbage, and spinach increased as the halosulfuron rate increased. Ethalfluralin did not reduce stand or cause injury to any of the four rotational crops. Naptalam plus bensulide did not reduce stand of the four crops and caused either slight or no injury. Residues of sulfentrazone and halosulfuron can injure vegetables following crops in which these herbicides are used, and caution should be taken particularly with spinach, broccoli, and cabbage in this respect. Nomenclature: Bensulide; clomazone; ethalfluralin; halosulfuron; naptalam; sulfentrazone; broccoli, Brassica oleracea var. botrytis (L.) ‘Everest’, ‘Green Sprouting Calabrese’; cabbage, Brassica oleracea var. capitata (L.) ‘Early Jersey Wakefield’; spinach, Spinacia oleracea (L.) ‘Cypress’, ‘F-380’; watermelon, Citrullus lanatus (Thunb.) ‘Jubilee’, ‘XIT 101’; hard red winter wheat, Triticum aestivum (L.) ‘Jagger’.

Preemergence Weed Control in Direct-Seeded Watermelon1

Studies were conducted at eight sites during a 3-yr period in Oklahoma and Arkansas to determine the effectiveness and safety of preemergence applications of halosulfuron both alone and in tank mixtures with bensulide, clomazone, ethalfluralin, and naptalam. Ethalfluralin, naptalam plus bensulide, and sulfentrazone also were applied alone. Although halosulfuron caused up to 20% seedling stunting, watermelon plants recovered by 5 to 7 wk after planting, and yield was similar to that of hand-weeded plots. Halosulfuron treatments controlled hophornbeam copperleaf, Palmer amaranth, carpetweed, and cutleaf groundcherry 80 to 100%. Control of goosegrass was at least 97% with clomazone plus ethalfluralin plus halosulfuron. Injury to watermelon treated with sulfentrazone ranged from 76 to 98% at 2 to 4 wk after treatment. This was reflected by yields that were lower than any other herbicide treatment in the studies. Nomenclature: Bensulide; clomazone; ethalfluralin; halosulfuron; naptalam; sulfentrazone; hophornbeam copperleaf, Acalypha ostryifolia Riddell #3 ACCOS; Palmer amaranth, Amaranthus palmeri S. Wats. # AMAPA; goosegrass, Eleusine indica (L.) Gaertn. # ELEIN; carpetweed, Mollugo verticillata L. # MOLVE; cutleaf groundcherry, Physalis angulata L. # PHYAN; watermelon, Citrullus lanatus ‘Jubilee’, ‘XIT 101’, ‘Crimson Sweet’. Additional index words: Broadleaf weed control, watermelon injury. Abbreviations: PRE, preemergence; WAT, weeks after treatment.

Weed Control Efficacy With Ammonium Nonanoate for Organic Vegetable Production

Organic Producers Rank Weed Management Research as their top priority. Organic vegetable producers have many challenges because their weed control tools are mostly limited to cultural methods, with a strong dependence on excessive tillage, cultivation, and hand-hoeing for weed control. Very few chemical weed control options have been approved for organic use. Racer®, ammonium nonanoate, is a new contact herbicide labeled for non-food use and under evaluation for registration as a bioherbicide for organically grown food crops. Prior to actual use in crops, new herbicides need thorough evaluations to determine the spectrum of weeds controlled at multiple growth stages as influenced by application methods. The objective of this study was to investigate the weed control efficacy of ammonium nonanoate applied at different rates and application volumes on endemic weed populations. The factorial experiment included two herbicide rates (7.2 and 10.8 kg·ha−1 a.i.) applied at four application volumes (164, 327, 654, and 981 L·ha−1). In general, application of ammonium nonanoate produced greater weed control for broadleaf weeds tumble pigweed (Amaranthus albus L.), spiny pigweed (A. spinosus L.), and carpetweed (Mollugo verticillata L.) than the monocoty weeds goosegrass (Eleusine indica L. Gaertn.) and smooth crabgrass [Digitaria ischaemum (Schreb. ex Schweig Schreb.)]. The best weed control for both pigweed species occurred at the 10.8 kg·ha−1 rate applied at 654 L·ha−1. Carpetweed was very sensitive to ammonium nonanoate, with 66% control at the lowest application rate and volume, and most application rates and volumes produced at least 88% control. Grass weed control ranged from 31% to 54% for goosegrass and 24% to 54% for smooth crabgrass. The lowest ammonium nonanoate rate provided unsatisfactory control for all weed species. Ammonium nonanoate provided consistent control across a large range of application volumes. The results indicate that ammonium nonanoate has excellent potential as an organic herbicide.

Fungicide treatment effects on kenaf seed germination and stand establishment

Uniform, healthy plant stand establishment is important to kenaf (Hibiscus cannabinus L.) fiber yield production and harvest efficiency. Since no chemical seed protectants are currently registered for use on kenaf seeds in the United States, research was conducted to evaluate the effects of single and multiple fungicide seed treatments on kenaf germination and stand establishment in field and laboratory experiments. Field studies were conducted at Weslaco and Beaumont, Texas, and Lane, Oklahoma in 1990–1991; and at Monte Alto, Texas in 1990. At three of the four locations, the metalaxyl+carboxin+captan treatment consistently resulted in greater stands than the untreated control. Combined over the Weslaco, Lane, and Monte Alto locations, five of the seven treatments showed improved plant stands compared to the control. Laboratory studies indicated that the fungicides did not effect seed germination. Several treatments reduced seedcoat susceptibility to mold growth by over 50% compared to the control and could result in improved seed shelf life. These results suggest that chemical seed treatments have the potential to reduce kenaf seed deterioration and improve field stand establishment. The use of the fungicides evaluated in this study should be registered for kenaf to enhance stand uniformity, reduce lodging, and improve fiber yield and harvest efficiency.