Abstract
The physical–hydraulic properties of eight substrate mixtures based on sphagnum peat and coir were determined and their effect on the growth of Begonia xelatior was studied. The particle size distribution, water retention curve, saturated hydraulic conductivity, and pore size distribution of the substrates were determined. All substrates exhibited high total porosity, satisfactory water retention capacity, and high saturated hydraulic conductivity. Increasing the percentage of perlite in the mixtures contributed to the reduction of water retention capacity and the increase of large pores. Unsaturated hydraulic conductivity estimated by the Mualem–van Genuchten model showed a sharp decrease within a range of water pressure heads (0 to −50 cm) observed between two successive irrigations. To assess aeration and water retention capacity, total porosity; airspace; and easily, and nonavailable water, as well as the bulk density of the substrates, were determined and concomitantly compared with the “ideal substrates” determined by De Boodt and Verdonck. The comparative results showed that substrate porosity alone is not efficient to create ideal plant growth conditions, but dynamic parameters are also needed. Plants grown in a substrate classified as “nonideal” showed significantly greater growth than the plants grown in most of the other substrates studied.
Highlights
Soilless growing substrates used in greenhouse, container, and green-roof production systems consist of either organic materials or mixtures of organic and inorganic materials
This paper presents a study of the physical–hydraulic characteristics of eight substrate mixes based on peat and coir and assessment of their effect on the growth of Begonia xelatior
The addition of perlite into peat and coir decreases the total porosity and water retention capacity of the peat–perlite (Figure 1a) and coir–perlite (Figure 1b) mixtures compared to the pure substrates
Summary
Soilless growing substrates used in greenhouse, container, and green-roof production systems consist of either organic materials or mixtures of organic and inorganic materials. Suitable attributes of the materials used in these substrates for horticultural use are low cost and physical properties supporting adequate aeration and water retention for optimal plant growth. Research has been heavily focused on the use of industrial, municipal, or agricultural wastes (e.g., [6,7]), but some of these either are not produced in sufficient quantities and/or may contain undesirable materials or properties (chemical and physical). There are other products that are considered alternative substrates to peat, such as different mixtures based on biochar or by-products of the agri-food industry [9]
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