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Leafy Greens as a Winter Crop in Washington State

Leafy Greens as a Winter Crop in Washington State. BIOAg. Kristy Ott, Rich Koenig, Carol Miles, John Reganold, Joe Powers, Brad Jaeckel Department of Crop and Soil Sciences Department of Horticulture and Landscape Architecture Department of Food Science and Human Nutrition.

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Leafy Greens as a Winter Crop in Washington State

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  1. Leafy Greens as a Winter Crop in Washington State BIOAg Kristy Ott, Rich Koenig, Carol Miles, John Reganold, Joe Powers, Brad Jaeckel Department of Crop and Soil Sciences Department of Horticulture and Landscape Architecture Department of Food Science and Human Nutrition

  2. Winter vegetable production • Possible with adequate day length, protection, and cold tolerant varieties • Leafy greens accumulate NO3-N in winter • Fresh and processed vegetables are the major source of dietary nitrate • European standards for NO3-N in greens but none for US

  3. Environment can impact NO3 content • Type and amount of Fertilizer applied • Synthetic fertilizer use results in higher NO3 than organics • Light • NO3 concentration is inversely related to light intensity • Time of planting and harvest • Variety/cultivars

  4. Primary Objectives • Examine the possibility of growing leafy greens in winter in Washington State • Examine the effects of variety, location, and time of harvest on nitrate and yield in winter greens

  5. Materials and Methods

  6. Planting Dates 12/14/05-01/18/06 11/15/06-12/12/06 Harvest Dates 2/28/06-3/30/06 1/25/07-3/01/07 • Asian greens, lettuce, and spinach • Managed organically • Vancouver and Pullman, Washington • Winter 2005-2006 and 2006-2007 • Harvested for gourmet salad mix

  7. Yield Results

  8. Crop Type Lettuce and Spinach Yield Asian Green Yield Tukey’s Minimum Significant Difference = 27.8

  9. Harvest Date Harvest Date 3 Yield Harvest Date 1 Yield Tukey’s Minimum Significant Difference = 5.0

  10. Nitrate Results

  11. Crop Type Lettuce and Spinach FW NO3-N Asian Greens FW NO3-N Tukey’s Minimum Significant Difference = 537.2

  12. Location Winter 2005-2006 Winter 2006-2007 Tukey’s Minimum Significant Difference = 50.5

  13. Soil NO3-N 2005-2006 Pullman = 129 kg ha-1 Vancouver = 177 kg ha-1 Soil NO3-N 2006-2007 Pullman = 122 kg ha-1 Vancouver = 323 kg ha-1 Light Pullman > Vancouver 69 µmol m-2 sec-1 (30% higher in Pullman) Temperature Vancouver > Pullman 2005-2006 4.5° C air 3.2° C soil 2006-2007 5.0° C air 4.2° C soil Light, Soil, and Temperature

  14. European Standards • Allowed Daily Intake (ADI) Value set by the European Union Scientific Committee and Joint Expert Committee on Food Additives 0.82 mg NO3-N kg-1 body wt day-1 • A 150 lb (68 kg) person could have 56 mg NO3-N day-1

  15. Conclusions on Yield • It is possible to grow leafy greens at both locations in WA in the wintertime • Asian Greens > Spinach > Lettuce • Increased light and temperature later in the season tends to increase yield • Average 11 weeks for varieties to mature in winter • Earlier planting dates resulted in higher yields and earlier harvest • More research on varieties of lettuce

  16. Conclusions on NO3-N • Nitrate concentration was variable • Variety and Location impacted it the most • Asian Greens > Lettuce > Spinach • variability within each crop type • Genetic * Environmental Factors • soil, light, temperature, site conditions • Lettuce and Spinach always had some varieties and Asian Greens sometimes had varieties below EU maximum levels • Asian Greens give bulk to the salad mix but have high nitrate

  17. Acknowledgements Committee Members Dr. Rich Koenig Dr. Carol Miles Dr. John Reganold Dr. Joe Powers BIOAg Brad Jaeckel Lab Technicians Megan Alcott, Katie Davidson, Emily Rude, Tracy Smith, Erin Klinger, Jenn Reed, Lydia Garth and Liz Nelson Lab 172 Ron Bolton John Rumph Margaret Davies Others CSS Faculty, Staff and Graduate Students Family & Friends

  18. Questions?

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