Date of Award:

8-2025

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

Youping Sun

Abstract

When early pioneers settled in Utah, they faced challenges living in a dry region with limited water. They built dams, canals, and irrigation systems by working together as a community to manage their water needs. However, adoption of European landscaping methods, farming and rapidly growing population increased water need while climate change and frequent drought reduced water supply.

Today, Utah is one of the driest states and uses more water per person than most other states in the nation. If things don't change, the state could run out of water by 2060. To address Utah's growing water challenges, this research explored several strategies to reduce landscape water use and enhance sustainability in ornamental plant production. Specifically, we evaluated the effectiveness of commercial soil amendments under limited irrigation, investigated the use of laundry graywater as an alternative irrigation source, and assessed how fertilizer rates interact with reduced watering. We also examined the potential of spent mushroom compost as a sustainable alternative to peat moss in container plant production.

Our findings indicated that most of the commercial soil amendments we tested did not improve plant performance under water-limited conditions. Laundry graywater showed potential for landscape irrigation; however, plant response varied based on the type of detergent used. No significant effects or interactions were observed between fertilizer and irrigation rates. Although unusually high rainfall during the summer of 2023 may have confounded the results. Spent mushroom compost emerged as a promising sustainable substrate for ornamental plants.

These findings suggest that most commercial soil amendment products may offer limited benefits under drought conditions, but laundry graywater can serve as an alternative resource for landscape irrigation, and spent mushroom compost can be an alternative to peat-based production media. However, further study is needed to clearly understand the interaction between fertilizer dose and irrigation rates for landscape plants.

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