Thesis
The effect of environment and management on yield and NO₃-N concentrations in organically managed leafy greens
Washington State University
Master of Science (MS), Washington State University
2010
Handle:
https://hdl.handle.net/2376/102371
Abstract
In leafy green crops, plant tissue nitrate concentration (TNC) is influenced by environment and management factors. Although evidence is inconclusive, excessive dietary nitrate has been implicated in digestive tract cancers and the European Commission (EC) has set limits on TNC in leafy greens. A series of field studies evaluated the effect of environment and management on yield and TNC in organic leafy greens. To compare the effect of photoperiod on TNC, a study was conducted in Pullman, WA, and Fairbanks, AK. Two lettuce (Lactuca sativa) and 2 spinach (Spinacia oleracea) cultivars were sampled and analyzed for TNC over 3, 24-hour periods. Light intensity and duration were measured for all sampling periods. There was no evidence that photoperiod influenced TNC in field growing conditions. A second study evaluated the effect of planting and harvest dates on yield and TNC in Asian greens grown in winter. A commercial Asian greens mix was direct seeded in a hoop house on 3 different dates. Initial and subsequent regrowth was harvested, and each crop type evaluated for TNC and yield. TNC for the same crop type was significantly different between planting dates with no clear trends. Some crop types yielded better in early harvest dates while others did not recover from repeat harvesting. All TNC was well below EC regulations. In a third study, 2 lettuce and 2 spinach cultivars were seeded into plots fertilized with dry fish meal (8-3-0) applied at 168 kg N ha-1 . An unfertilized control was used for comparison. Crops were grown in 2008 and 2009. At harvest, plants were separated into 3 whorls (outer, inner, center), petioles, and leaf blades. In 2008, there were significant 2-way interactions between fertility and cultivar, cultivar and plant part, and fertility and plant part. Within the fertilized treatment, lettuce had higher fresh weight TNC than spinach. Petioles had higher TNC than leaf blades. In 2009, there was a significant 3- way interaction. There were complex interactions between experimental variables, suggesting an opportunity to select cultivars and/or fertility regimes to reduce TNC.
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Details
- Title
- The effect of environment and management on yield and NO₃-N concentrations in organically managed leafy greens
- Creators
- Haly Lury Ingle
- Contributors
- Richard T. Koenig (Degree Supervisor)
- Awarding Institution
- Washington State University
- Academic Unit
- Crop and Soil Sciences, Department of
- Theses and Dissertations
- Master of Science (MS), Washington State University
- Publisher
- Washington State University; Pullman, Wash. :
- Identifiers
- 99900525151201842
- Language
- English
- Resource Type
- Thesis