Ground Based Verification Tests and Equipment for Selection of Root-Zone Media for Higher Plant Cultivation in Space

Paper number

IAC-06-A2.P.06

Author

Mr. Plamen Kostov, Space Research Institute, Bulgarian Academy of Sciences, Bulgaria

Coauthor

Dr. Tania Ivanova, Space Research Institute, Bulgarian Academy of Sciences, Bulgaria

Coauthor

Mrs. Svetlana Sapunova, Space Research Institute, Bulgarian Academy of Sciences, Bulgaria

Coauthor

Ms. Iliana Ilieva, Space Research Institute, Bulgarian Academy of Sciences, Bulgaria

Coauthor

Dr. Snejana Doncheva, Bulgaria

Coauthor

Dr. Nikolina Tzvetkova, Bulgaria

Year

2006

Abstract

Continuous improvement of the root-zone media is an important research area motivated by the need to provide suitable root environment for higher plant cultivation in microgravity. Substrates of solid particles are considered to be the most appropriate medium for plant growth in long term space experiments. Systems for maintaining suitable environment in the root media are required to provide moistening, nutrients transfer and gas exchange. The specific conditions in space habitats impose additional requirements to the substrates. Microgravity affects heat transfer, mass exchange processes, fluid behavior, and gradients of nutritive concentration and capillary properties of the artificial soils. The “free” movement of small substrate particles between the larger ones in the root medium volume changes the aerating - water-carrying pore ratio and geometry and disturbs the medium homogeneity and density. In addition the substrate particle shrinkage and swelling caused by changes in their water content and the vigorously developed root systems in small root modules also leads to variable pore geometry.
The objective of this study is to propose an approach for early evaluation of the substrate properties. This includes a course of measurements for preliminary evaluation of a part of substrate physical, hydro-dynamical, and biological characteristics. In case some parameter exceeds the bounds of admissibility the substrate is not subjected to accurate study in specialized laboratories.
Three kinds of substrates of different trade-marks and similar particle size range (1-2 mm) were tested in laboratory experiments. A number of measurements were carried out using standard methods to make analysis of some agro-physical properties:
 1)The bulk density of substrate layers of three different thicknesses was measured to study the possibility to achieve repetitive density for the needs of mathematical modeling.
 2)The capillary water capacity and the capillary water suction dynamics of a 10 cm substrate layer were measured.
Seed germination and plant growth-testing apparatus was developed. It allows evaluating substrate agro-properties in different constant moisture, light intensity and temperature levels. The equipment applicability for agro-physical measurements of substrates was tested in a preliminary experiment. The photosynthetic and transpiration rate as well as the stomatal conductivity of the grown experimental samples were analyzed by the infrared gas-analyzer LICOR 6400. The experimental results are reported.

Abstract document

IAC-06-A2.P.06.pdf

Manuscript document

IAC-06-A2.P.06.pdf (🔒 authorized access only).

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