In an effort to improve the physical–hydraulic properties of substrates, either pure organic materials such as peat, coir, etc., or mixes at various proportions with other organic or inorganic materials (e.g., perlite) are used to compose a substrate. In recent years, soilless substrates have been more widely used for growing pot plants because of several advantages that include facilitated root penetration, reduced levels of pathogenic microorganisms, absence of weeds, light weight, high water capacity, and high water retention capacity.
Among organic materials used as substrates, peat is the most widely distributed worldwide (Bunt, 1988; Heiskanen, 1993; Puustjärvi, 1977) with many desirable characteristics such as both high cation exchange capacity and water retention capacity and resistance to decomposition (Nelson, 2011). However, coir (coconut coir dust) is reported to have many characteristics that make it equal or superior to peat as a component in substrates (Arenas and Vavrina, 1998; Cresswell, 1992; Evans et al., 1996; Meerow, 1994; Stamps and Evans, 1997).
During irrigation of organic substrates (i.e., peat, coir), as the amount of water increases, root aeration decreases as a result of the large water retention capacity of these substrates, which render them extremely difficult in retaining a sufficient water–air balance (De Boodt and Verdonck, 1972; Heiskanen, 1993; Puustjärvi, 1977). As a result, organic substrates are mixed with inorganic materials such as coarse sand, perlite, etc., with an aim to improve substrate aeration and physical properties (Bunt, 1988; Heiskanen, 1995a, 1995b; Nektarios et al., 2011a, 2011b).
Begonia is a species sensitive to soil moisture and demanding to soil oxygen concentration (Johnson, 1968). The root system is easily damaged by irregular moisture levels of substrates. Substrates suitable for the root growth of begonias require at least 10% to 20% air-filled porosity (Johnson, 1968). Drip irrigation and capillary mat sub-irrigation are the most common irrigation methods for begonia production.
In this article, the water–air balance of four soilless substrates on the growth of Begonia ×elatior ‘The President’ was investigated under two different irrigation methods used widely in begonia production.
ArgoW.R.BiernbaumJ.A.FontenoW.C.1996Root medium carbon dioxide and oxygen partial pressures for container-grown chrysanthemumsHortScience31385388
BuntA.C.1988Media and mixes for container-grown plants. Unwin Hyman London UK
CresswellG.C.1992Coir dust—A viable alternative to peat? Proc. Austral. Potting Mix Manufacturers Conf. Sydney Australia. p. 1–5
HainesW.B.1930Studies in the physical properties of soils. V. The hysteresis effect in capillary properties and the modes of moisture distribution associated therewithJ. Agric. Sci.2097116
HandreckK.A.BlackN.D.1994Growing media for ornamental plant and turf. UNSW Press Randwick Australia
HeiskanenJ.1993Favourable water and aeration conditions for growth media used in containerized tree seedling production: A reviewScand. J. For. Res.8337358
HeiskanenJ.1995aPhysical properties of two-component growth media based on Sphagnum peat and their implications for plant-available water and aerationPlant Soil1724554
HeiskanenJ.1995bWater status of sphagnum peat and a peat–perlite mixture in containers subjected to different irrigation regimesHortScience30281284
HildingA.1982Produktion av Begonia ×elatior. Trädgård 220. Swedish University of Agricultural Sciences Research Information Centre Alnarp Sweden
JohnsonP.1968Horticultural and agricultural uses of sawdust and soil amendments. Paul Johnson National City CA
NaaszR.MichelJ.C.CharpentierS.2008Water repellency of organic growing media related to hysteretic water retention propertiesEur. J. Soil Sci.59156165
NektariosP.A.AmountziasI.KokkinouI.NtoulasN.2011aGreen roof substrate type and depth affect the growth of the native species dianthus fruticosus under reduced irrigation regimensHortScience4612081216
NektariosP.A.KastritsisS.NtoulasN.TsiotsiopoulouP.2011bSubstrate amendment effects on potted plant production and dry weight partition of lantana camaraHortScience46864869
NelsonP.V.2011Greenhouse operation and management. 7th Ed. Prentice Hall Englewood Cliffs NJ
PuustjärviV.1977Peat and its use in horticulture Turveteollisuuslitto r.y. Publication 3. Liikekirjapaino Helsinki Finland. p. 160
StampsR.H.EvansM.R.1997Growth of Dieffenbachia maculata ‘Camille’ in growing media containing sphagnum peat or coconut coir dustHortScience32844847