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  • Author or Editor: Robert L. Greene x
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The location of the Columbia and Yakima valleys present vineyard managers in eastern Washington with significant concerns, particularly low rainfall and wind erosion. Cover crops, as part of a complete management system, can reduce the effects of wind erosion in vineyards by stabilizing soil particles and reducing runoff. Cover crops also reduce weed biomass. During research conducted at Prosser, Wash., 175 foreign and domestic species were assessed for performance as cover crops. Using a screening process, nine species were chosen for evaluation in large commercial plots. Grass species included cereal rye, crested wheatgrass, Sherman Big Blue wheatgrass, perennial rye, pubescent wheatgrass, and three fescues. Legume species included two annual clovers (Trifolium spp.) and two reseeding annual medics (Medicago spp.). Unseeded, resident vegetation served as a control. Vine and soil water statuses were monitored regularly. Initial establishment of all species was delayed because of low rainfall throughout the growing season; thus performance varied for each species. Drought-tolerant grass species had better germination and establishment than legumes, due to planting method. In-row water status and vine water potentials remained constant throughout the main portion of the growing season. A mix of crested wheatgrass, perennial rye, and pubescent wheatgrass (Canada mix) gave especially good cover without affecting vine or soil water status. Weed biomass was reduced in most cases, with legumes having least effect; cereal rye, crested wheatgrass and the Canada mix had the greatest effect. Season-long suppression was best achieved with the Canada mix because of the nature of establishment. In this study, most drought-tolerant grasses performed better than legumes; however, with proper establishment, legumes can be a beneficial part of a sustainable agriculture system.

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A 1992 article by Nonomura and Benson (Proc. Natl. Acad. Sci. 89:9794-979X) reported increased yield and drought tolerance in a wide range of C3 species following foliar applications of methanol. The article was widely reported in the trade and popular press, which created a huge grower demand for information on the use and efficacy of methanol. To test the validity of the reports, we applied methanol with and without nutrients to a wide range of crops across California following Nonomura and Benson's (1992) protocol. Crops included watermelon, creeping bentgrass, lemons, savoy cabbage, carrots, romaine lettuce, radish, wheat, corn and peas. Environments included the greenhouse and field tests in coastal, inland valley, and desert locations. To test whether methanol improved drought tolerance, the savoy cabbage and watermelon experiments included both reduced and full irrigation. In no case was yield increased or drought tolerance attributable to methanol treatment. In some cases, methanol caused significant injury and decreased yield.

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