Physical Properties of Organic Soil: Adapting Mineral Soil Concepts to Horticultural Growing Media and Histosol Characterization

Abstract

Growing media are used in a broad range of applications, for which special consideration must be given to their physical and hydraulic character. Because they are relatively fragile, dominantly consisting of dried plant remnants, their preparation, processing, and handling before potting affect their properties. This is complicated by their subsidence and decomposition during use, which leads to a reduction of their initial bulk volume. Organic growing media show many similarities to Histosols because of the common botanical origin of some of their components. For both growing media and Histosols, classical concepts and values related to physical properties like air‐filled porosity, bulk density, available water, hydraulic conductivity, gas diffusivity, and field capacity need to be adapted to reflect distinct differences in their composition, structure, and stability compared with mineral soils. Their use in containers with a variety of shapes and sizes influences water and air storage and exchange as well. They can subside extensively as they undergo decomposition. They shrink. Hence, the range of values observed for the physical properties of organic media differs from those of mineral soils. The methods to be used for measuring such properties must be adapted to that specific context of use and to account for their fragile and dynamic nature. Finally, specific norms to guide substrate manufacturing and for diagnosis of plant growth problems have been derived specifically and should be used in such a situation.

Hydrological Behavior of Peat- and Coir-Based Substrates and Their Effect on Begonia Growth

“…The abovementioned variation of the substrate particle sizes led to differences in various physical properties of the substrates. Large differences in particle size can result in the migration of fine particles into the spaces between larger fragments, resulting in reduced air-filled porosity, increased volumetric water content at specified pressures, and increased bulk density [28]. With regard to particle size distribution (Figure 3), in the case of the peat-perlite mixtures (Ps, Ps 75 :P 25 , Ps 50 :P 50 ), the addition of perlite decreased the percentage of particle sizes greater than 4 mm and less than 1 mm and increased the percentage of particle sizes between 4 and 1 mm.…”

“…The abovementioned variation of the substrate particle sizes led to differences in various physical properties of the substrates. Large differences in particle size can result in the migration of fine particles into the spaces between larger fragments, resulting in reduced air-filled porosity, increased volumetric water content at specified pressures, and increased bulk density [28].…”

Irrigation and drainage management strategies to enhance cranberry production and optimize water use in North America

“…The second factor that will obviously affect the crop growth is the soil texture itself. From sawdust to peat, hydraulic properties of histosols greatly differ from those mineral soils and deserves special consideration (Caron et al 2015) too important to be addressed herein, because of their fibric nature and the layered arrangement of fibers within a given layer. Sand remains the most popular material to be used in the top layer and Périard et al (2016Périard et al ( , 2017 investigated profile evolution for such layers.…”

Organic Materials Used in Agriculture, Horticulture, Reconstructed Soils, and Filtering Applications

“…In addition, unlike soils, the properties of growing media with high organic contents are dynamic. Physical and chemical properties of growing media change as organic matter oxidizes, media consolidate, nutrients and fine particles leach, salts accumulate, and root growth and expansion reduce macropores to a much larger extent than in mineral soils over a short time course, as outlined by Caron et al (2015). Still, much of the media selection and management is based on initial properties at the time of planting.…”

“…In particular, the concept of available water differs from mineral soils because drying results in irreversible shrinkage leading to decreased porosity and changes in pore size distribution (Giskin and Levin, 1978) and water transfers are affected by poor interconnection between fibers (Örlander and Due, 1986). In addition, the soil structure is strongly affected by the position of the water table, where it affects the overburden pressure and subsequent compaction of the top horizons in Histosols (Caron et al, 2015). Also, evolution of the soil profile is linked to decomposition of the organic and debris fibers dominating the Histosols horizons.…”