Date of Award:

5-2024

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Plants, Soils, and Climate

Committee Chair(s)

Shital Poudyal

Committee

Shital Poudyal

Committee

Kelly Kopp

Committee

Lance Stott

Abstract

Growing nursery plants in containers requires a timely supply of mineral nutrients for optimum growth. However, there is a misconception among growers that the application of higher doses of fertilizers hastens plant growth; instead, it can lead to runoff and leaching loss of nutrients. Reducing fertilizer application while sustaining healthy plants can not only negate environmental consequences but also save fertilizer costs. For example, two ground covers, Lysimachia nummularia (creeping jenny, moneywort) and Vinca minor 'Bowles' (periwinkle), can be grown for three months by applying 6 mg/L of phosphorus (P) as reduction of P to single application of 6 mg/L once from 6 mg/L twice or with 6 mg/L witheach irrigation did not negatively impact their morphology or physiology.

Fertilizers in leachate or runoff may also be reduced by employing a phytoremediation strategy such as floating treatment wetlands (FTW). Two wetland plants, Helianthus maximiliani (maximilian sunflower) and Asclepias speciosa (showy milkweed), were cultivated under varying concentrations of nitrate nitrogen (10, 20, and 30 mg/L) and subjected to two different water temperatures of 75°F and 85°F. The results indicated that these plants effectively absorb nitrate from the water, demonstrating their potential suitability for growth in FTW systems and remediation of nutrient impaired waters. The use of different types of container substrate combinations has seen to effect leachate nutrient concentrations. However, in our research employing a mixture of coconut coir and pine bark as a substrate did not result in a reduction of nutrient leaching. Furthermore, incorporating 10% biochar by volume into substrate mixtures showed no impact on the leaching of nitrate and phosphorus. Interestingly, plant growth and morphology remained consistent across all substrate combinations, indicating that coconut coir could be a more sustainable alternative to sphagnum moss.

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