Interest in capturing and reusing runoff from irrigation and rainfall in container nurseries is increasing due to water scarcity and water use regulations. However, grower concerns related to contaminants in runoff water and other issues related to water safety are potential barriers to the adoption of water capture and reuse technologies. In this review, we discuss some of the key concerns associated with potential phytotoxicity from irrigating container nursery crops with recycled runoff. The concentration of pesticides in runoff water and retention ponds is orders of magnitude lower than that of typical crop application rates; therefore, the risk of pesticide phytotoxicity from irrigation with runoff water is relatively low. Nonetheless, some pesticides, particularly certain herbicides and insecticides, can potentially affect crops due to prolonged chronic exposure. Pesticides with high solubility, low organic adsorption coefficients, and long persistence have the greatest potential for crop impact because they are the most likely to be transported with runoff from container pads. The potential impact on plant growth or disruption of physiological processes differs among pesticides and sensitivity of individual crop plants. Growers can reduce risks associated with residual pesticides in recycled irrigation water by adopting best management practices (e.g., managing irrigation to reduce pesticide runoff, reducing pots spacing during pesticide application, use of vegetative filter strips) that reduce the contaminant load reaching containment basins as well as adopting remediation strategies that can reduce pesticide concentrations in recycled water.
Shital Poudyal and Bert M. Cregg
Valtcho D. Zheljazkov, Tess Astatkie, Santosh Shiwakoti, Shital Poudyal, Thomas Horgan, Natasha Kovatcheva, and Anna Dobreva
Garden sage (Salvia officinalis L.) is a medicinal, culinary, ornamental, and essential oil plant with a wide range of ecological adaptation. Garden sage essential oil traditionally is extracted by steam distillation from the above-ground biomass and has widespread applications as an aromatic agent in the food and pharmaceutical industries as well as in perfumery and cosmetics. The hypothesis of this study was that the steam distillation time (DT) may significantly affect essential oil yield and composition of garden sage and, therefore, DT could be used as a tool to obtain oil with different composition. Therefore, the objective was to evaluate the effect of various steam DTs (1.25, 2.5, 5, 10, 20, 40, 80, and 160 minutes) on garden sage oil yield and composition. Most of the oil in the garden sage dry herbage was extracted in 10-minute DT; extending DT up to 160 minutes did not significantly increase oil yields. Overall, 39 oil constituents were identified in the garden sage essential oil. Fourteen oil constituents with the highest concentration in the oil were selected for statistical analyses. Monoterpenes represented the major percentage (58.2% to 84.1%) of oil composition followed by sesquiterpenes (4.0% to 16.1%) and diterpenes (0.3% to 7.6%). Overall, the monoterpene hydrocarbons (α-pinene, camphene, β-pinene, myrcene, and limonene) were eluted early in the steam distillation process, which resulted in their high concentration in the oil at 5- to 10-minute DT and relatively low concentrations in the oil obtained at 160-minute DT. In general, the concentration of sesquiterpenes (β-caryophyllene, α-humulene, and verdifloral) increased with increasing duration of the DT and reached their respective maximum concentrations in the oil at 160-minute DT. The relative concentrations of major constituents, camphor and cis-thujone, in the oil obtained at 2.5-minute DT were higher than in the oils obtained at longer DT. Therefore, if oil with high concentrations of camphor and cis-thujone is desirable, garden sage dried biomass ought to be steam distilled for 2.5 to 5 minutes and the oil collected. If oil with a high concentration of monoterpene hydrocarbons and a high concentration of oxygenated monoterpenes is desirable, then garden sage should be distilled for 20 minutes. If oil with a high concentration of the diterpene manool is desirable, then garden sage should be steam-distilled for 80 minutes. If oil with a high concentration of sesquiterpenes is desirable, then garden sage should be steam-distilled for 160 minutes. The duration of steam distillation can be used as an economical method to obtain garden sage oil with a different chemical composition. The regression models developed in this study can be used to predict garden sage oil yield and composition distilled for various amounts of time and to compare literature reports in which different durations of DT were used.
Santosh Shiwakoti, Henry Y. Sintim, Shital Poudyal, Jennifer Bufalo, Charles L. Cantrell, Tess Astatkie, Ekaterina Jeliazkova, Lyn Ciampa, and Valtcho D. Zheljazkov
Japanese cornmint, also known as menthol mint (Mentha canadensis L. syn M. arvensis L.), is an essential oil crop cultivated in several countries in Asia and South America. The plant is currently the only commercially viable source for natural menthol as a result of the high concentration of menthol in the oil compared with other crops. The hypothesis of this study was that harvesting at regular intervals within a 24-hour period would have an effect on essential oil concentration and composition of Japanese cornmint grown at high altitude in northern Wyoming. Flowering plants were harvested every 2 hours on 7 to 8 Aug. and on 14 to 15 Aug. and the essential oil was extracted by steam distillation and analyzed by gas chromatography–mass spectroscopy (GC-MS). The effects of harvest date (Harvest 1 and Harvest 2) and harvest time (12 times within a 24-hour period) were significant on oil concentration and yield of menthol, but only harvest date was significant on the concentration of menthol in the oil. The interaction effect of harvest date and harvest time was significant on water content and on the concentrations of menthol and menthofuran in the oil and on the yield of limonene, menthol, and menthofuran. Overall, the oil concentration in grams per 100 g dried material for the two harvests (1.26 and 1.45, respectively), the concentration of menthol in the oil (67.2% and 72.9%, respectively), and menthol yield (1066 to 849 mg/100 g dried biomass) were higher in plants at Harvest 2 as compared with plants at Harvest 1. The oil concentration was higher in plants harvested at 1100 hr or at 1300 hr and lowest in the plants harvested at 1500 hr. Menthol yield was the highest in plants harvested at 1300 hr and lowest in the plants harvested at 0700 hr, 1900 hr, or at 0300 hr. This study demonstrated that harvesting time within a 24-hour period and harvest date (maturity of the crop) may affect essential oil concentration and composition of Japanese cornmint grown at high altitude in northern Wyoming.