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Physical and hydraulic properties of baked ceramic aggregates used for plant growth mediumBaked ceramic aggregates (fritted clay, arcillite) have been used for plant research both on the ground and in microgravity. Optimal control of water and air within the root zone in any gravity environment depends on physical and hydraulic properties of the aggregate, which were evaluated for 0.25-1-mm and 1-2-mm particle size distributions. The maximum bulk densities obtained by any packing technique were 0.68 and 0.64 g cm-3 for 0.25-1-mm and 1-2-mm particles, respectively. Wettable porosity obtained by infiltration with water was approximately 65%, substantially lower than total porosity of approximately 74%. Aggregate of both particle sizes exhibited a bimodal pore size distribution consisting of inter-aggregate macropores and intra-aggregate micropores, with the transition from macro- to microporosity beginning at volumetric water content of approximately 36% to 39%. For inter-aggregate water contents that support optimal plant growth there is 45% change in water content that occurs over a relatively small matric suction range of 0-20 cm H2O for 0.25-1-mm and 0 to -10 cm H2O for 1-2-mm aggregate. Hysteresis is substantial between draining and wetting aggregate, which results in as much as a approximately 10% to 20% difference in volumetric water content for a given matric potential. Hydraulic conductivity was approximately an order of magnitude higher for 1-2-mm than for 0.25-1-mm aggregate until significant drainage of the inter-aggregate pore space occurred. The large change in water content for a relatively small change in matric potential suggests that significant differences in water retention may be observed in microgravity as compared to earth.
Document ID
20050231784
Acquisition Source
Johnson Space Center
Document Type
Reprint (Version printed in journal)
Authors
Steinberg, Susan L.
(NASA Johnson Space Center Houston, TX United States)
Kluitenberg, Gerard J.
Jones, Scott B.
Daidzic, Nihad E.
Reddi, Lakshmi N.
Xiao, Ming
Tuller, Markus
Newman, Rebecca M.
Or, Dani
Alexander, J. Iwan. D.
Date Acquired
August 23, 2013
Publication Date
September 1, 2005
Publication Information
Publication: Journal of the American Society for Horticultural Science. American Society for Horticultural Science
Volume: 130
Issue: 5
ISSN: 0003-1062
Subject Category
Man/System Technology And Life Support
Funding Number(s)
CONTRACT_GRANT: NAG9-1399
Distribution Limits
Public
Copyright
Other
Keywords
NASA Center JSC
NASA Discipline Life Support Systems

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