Date of Award:

8-2024

Document Type:

Dissertation

Degree Name:

Doctor of Philosophy (PhD)

Department:

Plants, Soils, and Climate

Committee Chair(s)

Scott B. Jones

Committee

Scott B. Jones

Committee

Bruce Bugbee

Committee

Lawrence Hipps

Committee

Wenyi Sheng

Committee

Pin Shuai

Abstract

Space exploration stands as one of humanity's most profound endeavors, and plant growth in space is essential for sustaining astronauts during long-duration missions. However, operating plant growth systems under reduced gravity conditions presents challenges, particularly in ensuring uniform water distribution in the root zone. Non-uniform water distribution such as excess water and/or insufficient water in the root zone can significantly impact plant yield, necessitating the need to accurately estimate water status in the root zone and understand the dynamics of water flow in plant growth media under reduced gravity conditions. The objectives of this research were to enhance the accuracy of thermal property sensors using innovative techniques such as Heat Pulse Probes (HPPs), which were used in previous space missions to monitor water content in the root zone. We also wanted to advance our understanding of managing optimal water status in containerized plant growth media, particularly how water is retained and released from synthetic and natural fibers. Calibrating HPPs using air-free ice provided sharper temperature rise curves compared to traditional calibration media, leading to improved thermal property estimation. Various granular media with reproducible bulk density were utilized to establish thermal property calibration standards across different water content levels. The development of an automated water retention system enabled efficient characterization of water retention in coarse-textured media. This research clarified the suitability of lightweight fabrics as candidate plant growth media by comparing them with the water retention characteristics of traditional plant growth media (i.e., peat moss). Furthermore, an optimized irrigation system requiring no automated controls was presented. That system included a Mariotte bottle connected to a check valve and porous membrane used to maintain the target water status during plant growth, offering potential simplification of plant growth systems used in past space missions. Overall, this research contributes to advancing plant growth systems for microgravity conditions, with implications for both space exploration and agriculture on Earth. By ensuring efficient water distribution in plant growth media, we pave the way for sustainable food production in space and on Earth.

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