Determining Air Entry Value in Peat Substrates

Nemati, M. R.; Caron, Joanie; Banton, Olivier; Tardif, Pier‐Alexandre

doi:10.2136/sssaj2002.0367

Cited by 7 publications

(4 citation statements)

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“…The air‐entry point was defined as the point at which the first important drop in water content occurred as the water potential decreased. The determination procedure was detailed by Nemati et al (2002).…”

Section: Methodsmentioning

confidence: 99%

Pore Tortuosity and Wettability as Main Characteristics of the Evolution of Hydraulic Properties of Organic Growing Media during Cultivation

Kerloch

Michel

2015

Vadose Zone Journal

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Irrigation in soilless culture is generally managed by taking into account the air-illed porosity and water availability of the growing medium for plants, which are determined before culture from the water retention curve. However, many factors can affect the physical properties during the growth period and then lead to poor irrigation. This study aimed to analyze the combined effects of root development and irrigation management on the hydraulic properties of organic media and their consequences for water and air availability for the root system with time. A culture of Radrazz Rosa ´hybrida was performed with four different materials (peat, pine bark, coir, and wood iber) during 6 mo in a greenhouse, with the most common irrigation management between −1 and −10 kPa. Root volume, total volume, air and water retention properties, saturated hydraulic conductivity, relative gas diffusivity, and wettability of each growing medium were measured at the beginning and the end of the experiment. The study showed different physical behaviors for the growing media in terms of air and water retention but mainly highlighted decreases in total volume, pore tortuosity, and wettability and an increase in gas diffusion as the common and most relevant parameters inluencing their evolution with time.Abbreviations: AFP, air-illed porosity; EAW, easily available water.Investments in the horticultural industry (greenhouse, growing media, fertilizer, recycling system, heating, etc.) are generally expensive, and crop failures can lead to severe inancial losses for growers. he main reason for such failure, as noted by experts and producers, is faulty irrigation management of the growing medium, which can lead to ʶ root asphyxia, nutrient leaching (and then pollution), and risks for plant health with the development of pathogens due to excessive irrigation ʶ poor rewetting of the growing medium (with risks of hydrophobicity) and plant physiological stress (nutrient deiciency) under the driest conditions and then a deterioration of plant yield and quality. Knowing these risks, producers generally use coarse growing media with excessive fertigation to avoid water and nutrient stress for the plant (Raviv and Lieth, 2008).

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Section: Methodsmentioning

confidence: 99%

Pore Tortuosity and Wettability as Main Characteristics of the Evolution of Hydraulic Properties of Organic Growing Media during Cultivation

Kerloch

Michel

2015

Vadose Zone Journal

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“…[32] The SSA-OBS site has some soil layers with very high organic fractions, reaching volumetric organic carbon fractions of 0.45. To run the biosphere model at the site, SPA's soil routines for calculating soil field capacity [Saxton et al, 1986] were modified for organic soils with equations from Nemati et al [2002] The routine for calculating the thermal conductivity of the soil layers was also changed to use [van Wijk, 1963]. The stand alone SPA model is driven by meteorological drivers and verified with eddy covariance measurements and stand-based observations.…”

Section: Ecosystem Submodelmentioning

confidence: 99%

Modeling feedbacks between a boreal forest and the planetary boundary layer

2008

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[1] The atmosphere and biosphere interact strongly in the planetary boundary layer. Understanding the mechanisms controlling the coupled atmosphere-biosphere system allows improved scaling between observations at the stand scale (e.g., flux towers) and those at larger scales, e.g., airborne or satellite measurements. Simulation of the joint atmosphere-biosphere system permits the study of feedbacks occurring within the coupled system. In this paper, two well-tested models, one a process-based biosphere model (SPA) and the other a planetary boundary layer model (CAPS), were coupled to allow simulation of atmosphere-biosphere feedbacks and interactions with a focus on ecological controls. As part of the validation process, the biosphere model was tested using eddy covariance, surface meteorology, and soil data collected during a 120 day period at a boreal black spruce site during the 1994 BOREAS field campaign. The coupled atmosphere-biosphere model was also validated with radiosonde data above the black spruce site, demonstrating that atmosphere and biosphere models can be coherently combined. We show that negative feedbacks at the black spruce site have strong moderating effects. The feedbacks reduce the mean impact of LAI changes on the atmospheric surface layer by 21% for latent energy, 64% for air temperature, and 44% for water mixing ratio. We show that both radiative and hydraulic limitations imposed by the vegetation structure strongly affected the interactions within the atmosphere-biosphere system, while the impact of the canopy roughness length was weak.

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“…Subsequently, the point of air entry (y a ) was determined by the procedure described by Nemati et al (2002). he point of air entry is the matric potential at which air irst enters the substrate when going from a saturated toward an unsaturated state.…”

Section: Physical Propertiesmentioning

confidence: 99%

Substrate Aeration Properties and Growth of Containerized White Spruce: A Case Study

Boudreault

Pépin

Caron

et al. 2014

Vadose Zone Journal

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Seedlings are rejected every year in forest nurseries because of insufficient root development and root plug cohesion. Adequate substrate bulk density and aeration properties are of critical importance for root growth and water and nutrient uptake. The quality norms for nursery substrates, based in part on the ratio of coarse to fine particle sizes, have recently been questioned with respect to substrate performance. We conducted experiments in 2008 and 2009 under commercial nursery conditions to determine the effects of substrate physicochemical properties on seedling growth and nutrition. Seedlings were grown in 13 different substrates composed of coarse and fine peat particles (threshold size: 0.5 mm), perlite, and vermiculite, covering a broad range of physical properties with adequate available water and various coarse/fine particle ratios and aeration properties. Substrate properties had significant effects on growth parameters in both years. Seedling growth was affected by water stress in 2008 and low gas diffusivity in 2009. This study emphasizes the importance of management on substrate performance, indicating that short periods of moderate water stress (matric potential lower than −10 kPa) may hinder seedling growth. It also suggests that when irrigated substrates are maintained within the 0 to −5 kPa matric potential range, gas diffusivity should not be lower than 0.003 to 0.005 cm2 s cm−2 s−1, in agreement with the modeled O2 profiles in root plugs. Hence, when designing and using substrates at the nursery scale, more attention should be paid to aeration properties after potting and to the management rather than to the coarse/fine particle ratio.

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Determining Air Entry Value in Peat Substrates

Cited by 7 publications

References 0 publications

Pore Tortuosity and Wettability as Main Characteristics of the Evolution of Hydraulic Properties of Organic Growing Media during Cultivation

Pore Tortuosity and Wettability as Main Characteristics of the Evolution of Hydraulic Properties of Organic Growing Media during Cultivation

Modeling feedbacks between a boreal forest and the planetary boundary layer

Substrate Aeration Properties and Growth of Containerized White Spruce: A Case Study

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