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  • Author or Editor: Clint C Shock x
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Eight winter squash varieties (Table Ace Acorn, Sweet Dumpling, Waltham Butternut, Honey Boat, Sugar Loaf, Spaghetti, Gold Keeper, and Kabocha) were placed in storage 3 weeks after harvested and were stored for 6, 12, or 16 weeks at 5, 10, or 15°C and 50, 60, or 70 percent relative humidity. Before storage Spaghetti squash had low dry weight and low sugars while Kabocha, Sugar Loaf, and Honey Boat had high dry weight and high sugars. Squash of all varieties suffered high spoilage when stored at 5°C. Water losses increased with temperature or with storage at 50 percent relative humidity. Considering both spoilage and water loss, marketable fruit was highest when squash was stored at 10°C or 15°C and 60 or 70 percent relative humidity. Squash sugars were maintained with storage at 5°C and 10%. Squash can be stored for several months at 10°C and 60 to 70 percent relative humidity with little fruit loss or loss of sugar.

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Sweet worm wood is a source of the anti-malarial plant secondary compound artemisinin. The effects of water stress, nitrogen rates, plant growth regulators, and harvest timing on vegetative growth and yield of artemisinin were tested in separate experiments. In the harvest timing trial, total biomass, leaf yield, leaf artemisinin content and total artemisinin yield increased during the season. The wettest treatment tested decreased the total plant dry to fresh weight ratio, but had no effect on height, total biomass, leaf yield, leaf artemisinin content and artemisinin yield. Nitrogen fertilization increased plant height, but had no effect on total biomass, leaf yield, leaf artemisinin content and artemisinin yield. The plant growth regulators decreased plant height, increased total biomass, but had no effect on leaf yield, leaf artemisinin content and artemisinin yield. The effects of chemical weed control and post-harvest leaf drying will also be discussed.

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Seven potato cultivars were grown in an adequately irrigated check (100% of crop evapotranspiration replaced at -60 kPa) and three deficit irrigation regimes in order to evaluate varietal response to water stress and to evaluate nitrate leaching below the crop root zone in relation to the irrigation management. Potatoes were grown with sprinkler irrigation on silt loam in 1882 and 1993. Water stress treatments were achieved by partial or complete crop evapotranspiration replacement when soil water potential reached -60 or -80 kPa. In 1992, over all varieties, tuber yield and grade were significantly reduced by the two higher levels of water stress. In 1993, a relatively cool year, yield was reduced by water stress, but grade was not. Tuber internal quality was affected more by variety than by deficit irrigation both years. A comparison of pre-plant and post-harvest soil nitrate and ammonium shows that a small amount of nitrate moved from the top two feet of soil to the third and fourth foot in the check plots. Soil nitrogen accounting for the season showed large surpluses, indicating the importance of natural sources of available nitrogen.

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Onions were grown with different soil water potentials as irrigation criteria to determine the soil water potential at which optimum onion yield and quality occurs. Furrow irrigation treatments in 1992 and 1993 consisted of six soil water potential thresholds (-12.5 to -100 kPa). Soil water potential in the first foot of soil was measured by granular matrix sensors (Watermark Model 200SS, Irrometer Co., Riverside, CA) that had been previously calibrated to tensiometers on the same silt loam series. Both years, yield and market grade based on bulb size (more jumbo and colossal onions) increased with wetter treatments. In 1993, a relatively cool year, onion grade peaked at -37.5 kPa due to a significant increase in rot during storage following the wetter treatments. These results suggest the importance of using moisture criteria to schedule irrigations for onions.

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