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  • 1
    Language: English
    In: Journal of Hydrology, Oct 10, 2013, Vol.502, p.120(8)
    Description: To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.jhydrol.2013.08.031 Byline: T.K.K. Chamindu Deepagoda, Jose Choc Chen Lopez, Per Moldrup, Lis Wollesen de Jonge, Markus Tuller Abstract: acents Water and oxygen availability for soilless plant growth substrates were determined. acents Integral water storage and energy concepts were expanded to dual-porosity media. acents An analog integral oxygen diffusivity parameter was introduced. Article History: Received 28 June 2013; Revised 13 August 2013; Accepted 21 August 2013 Article Note: (miscellaneous) This manuscript was handled by Peter K. Kitanidis, Editor-in-Chief, with the assistance of J. A imA[macron]nek, Associate Editor
    ISSN: 0022-1694
    Source: Cengage Learning, Inc.
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  • 2
    Language: English
    In: Journal of Hydrology, 10 October 2013, Vol.502, pp.120-127
    Description: Over the last decade there has been a significant shift in global agricultural practice. Because the rapid increase of human population poses unprecedented challenges to production of an adequate and economically feasible food supply for undernourished populations, soilless greenhouse production systems are regaining increased worldwide attention. The optimal control of water availability and aeration is an essential prerequisite to successfully operate plant growth systems with soilless substrates such as aggregated foamed glass, perlite, rockwool, coconut coir, or mixtures thereof. While there are considerable empirical and theoretical efforts devoted to characterize water retention and aeration substrate properties, a holistic, physically-based approach considering water retention and aeration concurrently is lacking. In this study, the previously developed concept of integral water storage and energy was expanded to dual-porosity substrates and an analog integral oxygen diffusivity parameter was introduced to simultaneously characterize aeration properties of four common soilless greenhouse growth media. Integral parameters were derived for greenhouse crops in general, as well as for tomatoes. The integral approach provided important insights for irrigation management and for potential optimization of substrate properties. Furthermore, an observed relationship between the integral parameters for water availability and oxygen diffusivity can be potentially applied for the design of advanced irrigation and management strategies to ensure stress-free growth conditions, while conserving water resources.
    Keywords: Soilless Plant Growth Substrates ; Plant Available Water ; Substrate Water Characteristic ; Integral Water Storage ; Integral Energy ; Integral Oxygen Diffusivity ; Geography
    ISSN: 0022-1694
    E-ISSN: 1879-2707
    Source: ScienceDirect Journals (Elsevier)
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  • 3
    Language: English
    In: Vadose Zone Journal, 2013, Vol.12(3), p.0
    Description: Growing plants in containerized substrates has long been common practice in horticulture. Containerized plants (e.g., greenhouse tomatoes) have restricted access to essential growth resources such as oxygen, water, and nutrients. Since a wide range of inorganic and organic materials, and different combinations thereof, are commonly used as growth media, detailed and comparable physical characterization is key to identify the best performing media. In this study, five potential growth media and two mixtures thereof were characterized based on soil gas diffusivity (D (sub p) /D (sub o) , where D (sub p) and D (sub o) are gas diffusion coefficients in soil air and free air, respectively) and an operationally defined critical window of diffusivity (CWD) representing the interval of air-filled porosity between critical air filled porosity where D (sub p) /D (sub o) nearly equal 0.02 and interaggregate porosity. The D (sub p) measurements were conducted with 100-cm (super 3) samples from wet to complete dry conditions achieved by stepwise air drying and equilibration of initially water-saturated samples. A previously developed inactive pore and density-corrected (IPDC) model was able to describe gas diffusivities for media with distinct inactive pore space in the interaggregate pore region reasonably well. An extended IPDC model was introduced for media exhibiting a second percolation threshold in the intra-aggregate pore region. The analysis revealed comparable CWD values for the majority of the investigated media. The results further highlighted the importance of other major aspects (physical, chemical, and biological) of growth media characterization for optimal growth media design. A simple approach toward designing a gas diffusivity mixing model is presented to assist with selection of optimal mixing ratios of growth media with markedly different D (sub p) /D (sub o) behavior.
    Keywords: Environmental Geology ; Aeration ; Characterization ; Design ; Diffusivity ; Equations ; Experimental Studies ; Foamed Glass Aggregate ; Gaseous Phase ; Glasses ; Growth Media ; Igneous Rocks ; Mixtures ; Oxygen ; Perlite ; Porous Materials ; Pumice ; Pyroclastics ; Recycled Glass ; Rockwool ; Roots ; Size Distribution ; Soil Gases ; Soils ; Substrates ; Unsaturated Zone ; Volcanic Rocks ; Water Characteristic;
    ISSN: Vadose Zone Journal
    E-ISSN: 1539-1663
    Source: CrossRef
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  • 4
    Language: English
    Description: The greenhouse industry is facing significant challenges such as the demand for more efficient use of energy and natural resources and prevention of detrimental environmental impacts. Reducing negative environmental impacts can be achieved by utilizing recycled and environmentally friendly products and by optimizing the use of water and root zone substrates. New and advanced root zone substrates are currently tested as substitute for natural soils in greenhouse agriculture. They can be inert non-organic materials such as rockwool and perlite. These are mined products from the earth, and are difficult to dispose after use. Natural substrates such as peat are being consumed faster than being regenerated. A new potential substrate that consists of recycled foamed glass aggregates is considered an alternative, as it is environmentally friendly, non-toxic and disposable. Experiments with foamed glass aggregates and with foamed glass aggregate/coconut coir mixtures indicated that the yield of greenhouse tomatoes was not statistically significant different (α=0.05) when compared to rockwool. To investigate the potential application of recycled glass as a root zone substrate, physical and hydraulic properties were measured. For comparison, the same measurements were completed for rockwool, coconut coir, perlite, and PET/PE fibers as well as for a mixture of coconut coir and recycled glass. The water characteristics (WC) determined for each substrate exhibited distinct air entry potentials, which provided information for irrigation scheduling, water storage and aeration for optimum plant growth conditions. Coconut coir and rockwool exhibited a unimodal shaped water retention curve, while foamed glass aggregates and perlite exhibited bimodal shaped curves. The obtained substrate properties were used as input paramaters for HYDRUS- 2D/3D model to simulate water mass balance and matric potential distributions within a typical growth container of foamed glass aggregates. The simulated matric potential and water content distributions were compared to tensiometer measurements of matric potential in the foamed glass aggregates. The simulations compared favorably with laboratory experiments measured under controlled environmental conditions.
    Keywords: Numerical Simulation ; Physical Properties ; Substrates ; Tomatoes ; Agricultural & Biosystems Engineering ; Foamed Glass ; Greenhouse
    Source: Networked Digital Library of Theses and Dissertations
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