Controlled Environment Agriculture (CEA) is an expanding industry in the United States. Lettuce (Lactuca sativa) possesses considerable economic importance as one of the foremost leafy vegetables worldwide in terms of financial value for production in CEA. Rapid growth rate, high yield, and potential return further enhance its suitability for cultivation within CEA. Pursuing optimal and sustainable nutrient concentrations for crops in CEA is a continuous requirement for an expanding industry. This study is set to investigate the impact of different potassium (K) sources and concentrations on 'Green Oakleaf' lettuce growth. The K concentration within the Virginia Tech base hydroponic lettuce fertilizer was increased,1x, 2x, and 3x the normal rates of K ppm, through the addition of potassium chloride (KCl) or potassium sulfate (K2SO4). To account for rising electrical conductivity (EC), due to the increase of K, KCl treatments were recreated with standardized EC through the addition of Sodium Chloride (NaCl). The Spatially and Mechanically Accurate Robotic Table (SMART) in an indoor space was utilized to cultivate and image plant growth over time through pixel count. Growth index and chlorophyll content were recorded weekly, while the fresh weight and dry weight of shoots were recorded at harvest. The KCl treatment with the highest concentration,4x K ppm, as well as those with standardized EC, led to reduced yield when compared to other treatments. All K2SO4 treatments showed no difference in growth when compared to the base solution. K source and concentration, as well as fertilizer EC, were all identified as factors influencing the impact of fertilizers on the optimization of lettuce yield. / Master of Science in Life Sciences / Controlled Environment Agriculture (CEA) is a growing industry in the U.S., and lettuce is one of the most important leafy vegetables globally in terms of economic value. As the industry expands, finding the best and most sustainable nutrient levels for crops is essential. This study explored how different types and amounts of potassium (K) in fertilizers affect the growth of 'Green Oakleaf' lettuce. Potassium levels in the base fertilizer were increased to 1x, 2x, and 3x the normal amount using either potassium chloride (KCl) or potassium sulfate (K₂SO₄). The study measured various growth factors like chlorophyll content, plant weight, and plant image pixel counts. It found that higher levels of potassium chloride (KCl) negatively impacted plant growth, while potassium sulfate (K₂SO₄) did not have the same effect. The research also showed that adding sodium chloride (NaCl) increased the salt content, measured by electrical conductivity (EC), in the fertilizer, which reduced lettuce growth. The findings suggest that high fertilizer ECs, not potassium itself, were the main cause of poor plant growth. Overall, the study identified potassium source and concentration, as well as fertilizer EC levels, as important factors in optimizing fertilizer for lettuce growth.
| Identifer | oai:union.ndltd.org:VTETD/oai:vtechworks.lib.vt.edu:10919/121346 |
| Date | 15 October 2024 |
| Creators | Doss, Mitchell C. |
| Contributors | Horticulture, Evans, Michael Robert, Lowman, James Scott, South, Kaylee Anne |
| Publisher | Virginia Tech |
| Source Sets | Virginia Tech Theses and Dissertation |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Format | ETD, application/pdf, application/pdf |
| Rights | In Copyright, http://rightsstatements.org/vocab/InC/1.0/ |
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