|dc.description.abstract||Oenothera elata Kunth, Hooker’s evening primrose, is a biennial to short-lived perennial found in a variety of habitats ranging from xeric to mesic. Currently it has limited use in landscapes. A similar species, Oenothera biennis L. or common evening primrose, is currently grown as a nutraceutical crop. The seed oil contains gamma linolenic acid (GLA), which has been used to treat ailments including eczema, arthritis, auto-immune disorders, and high cholesterol. Most primrose production is in China, because of the cooler climates which allow for increased GLA in the seed. Hooker’s evening primrose is found in warmer climates and has a similar oil profile to that of common evening primrose when grown in Lubbock, TX. This may mean there is potential for Hooker’s evening primrose production as a niche crop in this area. Best management practices must be established and cost of production must be determined before production can increase. Therefore, objectives of this research were 1) to determine spacing, irrigation, and fertility requirements for this species, 2) to evaluate several pre- and postemergence herbicides for use in O. elata production, 3) to determine most efficient harvest practices by evaluating different harvest methods and defoliants, and 4) to determine cost of production.
Research was conducted at the Texas Tech University Greenhouse complex and the Texas Tech University Plant and Soil Science Research Farm in Lubbock, TX. All experiments were replicated twice throughout the 2009-2011 growing seasons. To determine irrigation, spacing, and fertility needs an experiment was set up as a split-split plot design with irrigation (33%, 66% or 100% ET) as the main plot, spacing (0.3 m, 0.6 m, or 0.9 m) as the sub-plot, and fertility (133.79 kg N ha-1, 89.19 kg N ha-1, 44.60 kg N ha-1, and 0 kg of N ha-1) as the sub-sub plot. This experiment had six blocks and every combination was represented once in each block. Data taken included: yield, visual appearance on a criterion reference scale of 1-10, number of flowers, plant growth index (PGI), and percent floral density. Pre- and postemergence herbicide trials were set up as a randomized complete block design with five replications. These experiments were conducted in the greenhouse. Data were recorded for O. elata phytotoxicity, plant biomass, and PGI. For the postemergence herbicide experiment 4 month old seedlings were placed in containers and acclimatized for 28 days before treatment with one of the following herbicides: glyphosate, glufosinate, fenoxaprop, fluazifop, sulfosulfuron + non-ionic surfactant, quinclorac + methylated seed oil, mesotrione, and quinclorac + mecoprop + dicamba + methylated seed soil. For preemergence herbicide studies applications of oxadiazon, isoxaben, oryzalin, prodiamine, dithiopyr, metolachlor, pendimethalin, and isoxaben + trifluralin were applied two days prior to the transplanting of four month old O. elata seedling. To determine harvest practices, two different experiments were set up as a randomized complete block design. Both experiments had 4 blocks and each treatment was represented once within a block. One experiment compared yield after the use of three defoliants [Paraquat, (Ethephon + Cyclanilide) + (Thidiazuron + Diuron), and Ethephon] to a non-treated control. The other compared yield of two different harvest methods (hand and Hege combine). Cost of production was determined using best management practices investigated in the previous trials.
Data suggest Hooker’s evening primrose planted at 0.9 m spacings will increase appearance, flower number, PGI, and floral density. This spacing will not decrease yield. Irrigation equivalent to 66% reference evapotranspiration (ETo) increased appearance, PGI, and number of flowers in times of drought, but will not influence yield. Fenoxaprop and fluazifop may be used as postemergence herbicides without excessive phytotoxicity or reduction in growth. All preemergence treatments except trifluralin + isoxaben exhibited low phytotoxicity and will not reduce growth. Machine harvesting does not decrease yield and should reduce the cost of production. Defoliants can be used to harvest this species without a loss in yield. Paraquat and (Ethephon + Cyclanilide) + (Thidiazuron + Diuron) may be preferred over Ethephon alone. Cost of production is estimated at $1906.89 per acre. Growers will need to receive approximately $0.48 per pound in order to break even.||