Date of Award:

8-2025

Document Type:

Dissertation

Degree Name:

Doctor of Philosophy (PhD)

Department:

Plants, Soils, and Climate

Committee Chair(s)

Bruce Bugbee

Committee

Bruce Bugbee

Committee

Scott Jones

Committee

Shuyang Zhen

Committee

Raymond Wheeler

Committee

Lawrence Hipps

Abstract

Controlled environment agriculture (CEA) helps grow plants in spaces where resources like water and nutrients are limited, such as deserts or spacecraft. Effective management of water in the root zone, the area where plant roots grow, is vital to keeping plants healthy, especially in closed-loop systems where water cannot be wasted, as will be necessary for long-duration space missions.

An improved automated watering system designed for use in space-like environments was developed over several trials. Early designs using suction to draw water through tubes faced problems with uneven watering and roots blocking the tubes. Switching to a system that pushed water through the tubes improved the consistency of water delivery. Additional improvements included using stronger, thicker tubes and special materials to prevent clogging from microorganisms. These upgrades made the system more reliable and long-lasting.

In this research, we also looked at ways to improve the growth in peat-based growing media by carefully controlling how much water was available to the roots. Peas, mizuna, and lettuce were grown using a special irrigation system with ceramic tubes placed below the surface. The tubes provided water and nutrients directly to plant roots at different moisture levels. Plants grew well across a wide range of moisture conditions with better performance observed at 50% of the maximum water content, but very wet conditions reduced root growth. This shows that carefully balancing water and air in the root zone is crucial for plant health.

Finally, we tested whether it was possible to grow multiple crops in the same peat-based media without changing it, mimicking a no-till farming approach. The results showed that when carefully managed, the same peat media could support repeated crop growth with little decrease in productivity. This method significantly reduces waste and the need for fresh supplies.

Overall, this research demonstrates practical root zone management approaches for more sustainable plant cultivation in controlled environments, highlighting strategies useful for both agriculture on earth and future agricultural practices for space.

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