Air-filled Porosity, Gas Relative Diffusivity, and Tortuosity: Indices of Prunus ×cistena sp. Growth in Peat Substrates

Allaire, Suzanne; Caron, Jean; Duchesne, Isabelle; Parent, Léon‐Étienne; Rioux, Jacques-André

doi:10.21273/jashs.121.2.236

Cited by 70 publications

(55 citation statements)

References 18 publications

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“…However, Madsen (1976) observed that -50 cm H^O (or pF 1.7) would be a better approximate to mimic field capacity in coarse-textured media. This is also in agreement with the study by Allaire et al (1996) who used-50 cm H2O as the limiting potential of "easily available water (EAW)" for containerized media. In reduced gravity conditions, for example at Martian gravity (0.37 g), the corresponding matric potential may occur at -19 cm HjO or pF 1.3 (i.e., in equilibrium with free water held 19 cm below the gravity vector), assuming the equilibrium matric potential scales linearly with the gravitational force (Jones et al, 2011).…”

Section: Field Capacity and Critical Water Storage Windowssupporting

confidence: 92%

“…For the limiting Earth criterion for gas diffusivity we used the value D /D^ = 0.02 reported in many studies as the threshold (minimum) value for adequate soil aeration in uncontrolled (field) conditions (Stepniewski, 1980;Schjonning et al, 2003). Jones et al (2011) used the same threshold value to discuss gas diffusivity in containerized media while Nkongolo and Caron (2006) and Allaire et al (1996) also observed a threshold nearZ) /Z)^ ~0.015 in containerized peat substrates. There is no analogous well-documented criterion for solute diffusivity/relative permittivity (E/E^, we therefore evaluated and compared die media for critical nutrient supply based on a value oíE/ £^ = 0.01, at which there is assumed to be sufficient media connectivity to fecüitate movement of solutes in root zone environments.…”

Section: Oxygen and Nutrient Diffusivities And Plant Limiting Criteriamentioning

confidence: 99%

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Diffusion Aspects of Designing Porous Growth Media for Earth and Space

Deepagoda

Møldrup

Jensen³

et al. 2012

Soil Science Society of America Journal

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Growing plants in extraterrestrial environments, for example on a space station or in a future lunar or Martian outpost, is a challenge that has attracted increasing interest over the last few decades. Most of the essential plant needs for optimal growth (air, water, and nutrient supply, and mechanical support) are closely linked with the basic physical properties of the growth media. Diffusion is the main process whereby oxygen and nutrients are supplied to plant roots, and gas and solute diffusivity are the key parameters controlling the diffusive movement of oxygen and nutrients in the root zone. As one among several essential aspects of optimal porous media design for plant growth, this study presents a diffusionbased characterization of four commercial, aggregated growth media. To account for the observed large percolation threshold for gas diffusivity in the selected media, an inactive pore and density corrected (IPDC) model was developed and excellently described measured gas diffusivity in both inter-and intraaggregate pore regions. A strong relation (r^ = 0.98) between percolation threshold for gas diffusivity and mean particle (aggregate) diameter was found and suggested to be used in future design models. Also, critical windows of diffusivity (CWD) was defined identifying the air content range where gas diffusivity (hence, oxygen supply) and solute diffusivity or the analogous electrical conductivity (hence, nutrient supply) are above pre-defined, critical minimum values. Assuming different critical values for gas diffusivity under terrestrial and Martian conditions, the four growth media were compared and it was found that one medium did not fulfill the pre-set criteria. Overall, the analyses suggested that particle (aggregate) sizes below 0.25 and above 5 mm should likely be avoided when designing safe plant growth media for space. The CWD concept was also applied to a natural volcanic ash soil (Nishi-Tokyo, Japan), and the natural soil was found competitive or better than the tested commercial growth media. This could bear large perspectives for Martian outpost missions, since NASA has found that Martian dust/soil mostly resembles volcanic ash soil among terrestrial materials.

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Section: Field Capacity and Critical Water Storage Windowssupporting

confidence: 92%

Section: Oxygen and Nutrient Diffusivities And Plant Limiting Criteriamentioning

confidence: 99%

Diffusion Aspects of Designing Porous Growth Media for Earth and Space

Deepagoda

Møldrup

Jensen³

et al. 2012

Soil Science Society of America Journal

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“…According to Ghislerod (1982) and Allaire et al (1996a;1996b), the physical growth potential of a medium is not only restricted by bulk density, air-filled porosity, and water-holding capacity but also by gas exchange characteristics. According to Ghislerod (1982) and Allaire et al (1996a;1996b), the physical growth potential of a medium is not only restricted by bulk density, air-filled porosity, and water-holding capacity but also by gas exchange characteristics.…”

Section: Soil Gas Storage and Exchangementioning

confidence: 99%

Direct and Indirect Short-term Effects of Biochar on Physical Characteristics of an Arable Sandy Loam

et al. 2013

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Biochar addition to agricultural soil is reported in several studies to reduce climate gas emissions, boost carbon storage, and improve soil fertility and crop productivity. These effects may be partly related to soil physical changes resulting from biochar amendment, but knowledge of how biochar application mechanistically affects soil physical characteristics is limited. This study investigated the effect of biochar application on soil structural and functional properties, including specific surface area, water retention, and gas transport parameters. Intact soil cores were taken from a field experiment on an arable sandy loam that included four reference plots without biochar and four plots with 20 tons ha −1 biochar incorporated into the upper 20 cm 7 months before sampling. Water retention was measured at matric potentials ranging from wet (pF 1.0) to extremely dry conditions (pF ∼6.8), whereas gas transport parameters (air permeability, k a , and gas diffusivity, D p /D o , where D p is the gas diffusion coefficient in soil and D o is the gas diffusion coefficient in free air) were measured between pF 2.0 and 3.0. Water retention under dry conditions and measured specific surface area were not significantly greater in the biochar-amended soil than the reference soil probably because of the relatively low biochar application rate. Yet, the biochar-amended soil showed a significant decrease in soil bulk density and an accompanying increase in total porosity. Water retention and air-filled porosity (ε) were both markedly greater in the biocharamended soil than in the reference soil between pF 1.0 and 3.0. Soil macroporosity (equivalent to >0.1 mm pore diameter) and the ratio of macroporosity to total porosity were also significantly greater in the biochar-amended soil. As a result, the level of the pore organization (PO, k a /ε) was greater in the biochar-amended soil. Across the tested matric potentials, biochar amendment caused average increases of 28 to 34% in ε, 53 to 161% in D p /D o , and 69 to 223% in k a , with the most significant increases occurring around natural field capacity (pF 2.0). Overall, the results suggest that biochar application even at a relatively low rate can alter soil functional characteristics, especially under normal field moisture conditions. Mean ± SE of three samples analyzed by the EGME technique. Sun et al.Different letters indicate statistically significant differences (Mann-Whitney U test; P < 0.05) between treatments (n = 20 each; n = 4 for specific surface area).† Macroporosity (Φ mac ) was derived from total porosity and the volumetric water content at pF 1.5.

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“…This can be interpreted as the effect of a limited diffusivity of CO 2 and other gases at a high relative water content in the growing media. It is generally accepted that the ratio between gas diffusivity in a particular substrate and in open air is proportional to the air-filled porosity (King and Smith 1987;Bunt 1988;Allaire et al 1996). Hence, variations in the volumetric water content have a direct effect on the mobility of gases in the substrate.…”

Section: Discussionmentioning

confidence: 99%

“…In horticultural growing media, the empirical relationship between volumetric water content and the SWP often shows a plateau near water saturation (Orozco and Marfà 1995;Allaire et al 1996). The SWP at which water release begins in a saturated medium is the air-entry potential and corresponds to the SWP at which the bigger pores begin to drain (Campbell 1988).…”

Section: Discussionmentioning

confidence: 99%

Dynamics of CO2 efflux from the substrate root system of container-grown plants associated with irrigation cycles

2007

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In intensive horticultural crops, the choice of growing media and the adequate management of irrigation must ensure an optimal trade-off between aeration and water supply to roots. The proportion of gas-filled pores and their composition can be strongly affected by the water status and hence by irrigation. In this context, continuous measurement of gas exchange and water status of the growing medium could bring out some insights into how irrigation events affect root activity and aeration in a time scale of minutes to several hours. For this purpose, a measuring system was developed that measured the CO 2 efflux rate from the entire substrate root system of pot plants while their shoots were kept outside, undisturbed. It was able to monitor four plants at a time for several weeks at a rate of one measurement per plant every 10 min, thus tracing the dynamics of CO 2 efflux through a great many irrigation cycles. The results showed a marked pattern of CO 2 efflux around each irrigation event, consisting mainly of a sharp, conspicuous peak followed by a depression until a threshold in substrate water potential was reached. Analysis of these data suggests that the pattern is imposed mainly by the effects of irrigation and water content on the mobility of gases in the growing medium. The peak can be explained by the CO 2 -enriched air being displaced by the water added to the growing medium in the pot, and the following depression can be the result of the reduced mobility of gases when substrate water content is high. In spite of the great variation in the instantaneous efflux rate of CO 2 , the integration of these CO 2 values for the entire day provides a rather predictable value given the root biomass and does not seem to be affected by the number of irrigation events that occur in a given day.

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Air-filled Porosity, Gas Relative Diffusivity, and Tortuosity: Indices of Prunus ×cistena sp. Growth in Peat Substrates

Cited by 70 publications

References 18 publications

Diffusion Aspects of Designing Porous Growth Media for Earth and Space

Diffusion Aspects of Designing Porous Growth Media for Earth and Space

Direct and Indirect Short-term Effects of Biochar on Physical Characteristics of an Arable Sandy Loam

Dynamics of CO2 efflux from the substrate root system of container-grown plants associated with irrigation cycles

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