Eur.J.Hortic.Sci. 80 (4) 190-195 | DOI: 10.17660/eJHS.2015/80.4.7|
ISSN 1611-4426 print and 1611-4434 online | © ISHS 2015 | European Journal of Horticultural Science | Original article
Effects of freezing on the physical properties and wettability of highly decomposed peats used as growing media
Agrocampus Ouest, Centre d’Angers, UP EPHor, France
The influence of freezing on Sphagnum highly decomposed peats was estimated from their physical properties and their wettability measured in relation to the degree of desiccation. The results showed that the physical properties of peats were drastically affected by freezing, particularly improving their water availability and resulting in less, and more reversible, shrinkage after air-drying. However, contact angles measured for frozen or unfrozen peats are very similar. These results seem to indicate that the changes in physical properties are only due to a change in peat structure during freezing and are not a consequence of a change in water affinity. Nevertheless, even if freezing does not affect the wettability of materials, its influence on peat structure contributes to an improvement in their hydric properties.
contact angle, peat substrate, shrinkage, water repellency, water retention
Significance of this study
What is already known on this subject?
What are the new findings?
The extraction of highly decomposed peat by freezing temperatures during winter is commonly performed by substrate manufacturers. Except for an improvement of agronomic properties, there is no information available on the effect of freezing on the affinity of peat to water.
What is the expected impact on horticulture?
This paper showed that freezing modified physical properties of highly decomposed peats by improving air capacity and water availability, however, it had no effect on wettability.
Since peats began to show a hydrophobic character at water potentials close to those commonly used for irrigation scheduling, the end-users have to be careful in order to avoid poor wettability of both unfrozen and frozen peat.
- Bauters, T.W.J., Di Carlo, D.A., Steenhuis, T.S., and Parlange, J.Y. (1998). Preferential flow in water-repellent sands. Soil Sci. Soc. Am. J. 62, 1185–1190. https://doi.org/10.2136/sssaj1998.03615995006200050005x.
- Beardsell, D.V., and Nichols, D.G. (1982). Wetting properties of dried-out nursery container media. Sci. Hort. 17, 49–59. https://doi.org/10.1016/0304-4238(82)90061-9.
- Brandyk, T., Szatylowicz, J., Oleszczuk, R., and Gnatowski, T. (2000). Hydro-physical properties of histic soils. In Proceedings of the 11th International Peat Congress 2, L. Rochefort and J.Y. Daigle, eds., p. 1063 (abstract only).
- Busscher, H.J., Van Pelt, A.W.J., De Boer, P., De Jong, H.P., and Arends, J. (1984). The effect of surface roughening of polymers on measured contact angles of liquids. Colloid Surface 9, 319–331. https://doi.org/10.1016/0166-6622(84)80175-4.
- De Boodt, M., Verdonck, O., and Cappaert, I. (1974). Method for measuring the water release curve of organic substrates. Acta Hortic. 37, 2054–2062. https://doi.org/10.17660/ActaHortic.1974.37.20.
- De Jonge, L.W., Jacobsen, O.H., and Moldrup, P. (1999). Soil water repellency: effects of water content, temperature, and particle size. Soil Sci. Soc. Am. J. 63, 437–442. https://doi.org/10.2136/sssaj1999.03615995006300030003x.
- Dekker, L.W., and Ritsema, C.J. (1996). Variation in water content and wetting patterns in Dutch water-repellent peaty clay and clayey peat soils. Catena 28, 89–105. https://doi.org/10.1016/S0341-8162(96)00047-1.
- Dekker, L.W., and Ritsema, C.J. (2000). Wetting patterns and moisture variability in water repellent Dutch soils. J. Hydrol. 231–232, 148–164. https://doi.org/10.1016/S0022-1694(00)00191-8.
- Dekker, L.W., Ritsema, C.J., and Oostindie, K. (2000). Wettability and wetting rate of Sphagnum peat and turf on dune sand affected by surfactant treatments. In Proceedings of the 11th International Peat Congress 2, L. Rochefort and J.Y. Daigle, eds., pp. 566–574.
- EN 13041. (2000). Amendements du sol et supports de culture – Détermination des propriétés physiques – Masse volumique apparente sèche, volume d’air, volume d’eau, valeur de rétraction et porosité totale (Paris, France: Association Française de Normalisation).
- Farnham, R.S. (1979). The classification of peat, peatlands and organic soils in the US. In International Symposium on Classification of Peat and Peatlands, pp. 194–199.
- Galvin, L.F. (1976). Physical properties of Irish peats. Irish J. Agr. Res. 15, 207–221.
- Holden, N.M., and Ward, S.M. (1998). Rewetting of milled peat: laboratory investigation of water movement and storage. Soil Use Mgt. 14, 149–154. https://doi.org/10.1111/j.1475-2743.1998.tb00141.x.
- Holden, N.M. (1998). By-pass of water through laboratory columns of milled peat. Int. Peat J. 8, 13–22.
- Jouany, C., Chenu, C., and Chassin, P. (1992). Détermination de la mouillabilité des constituants du sol à partir des mesures d’angles de contact: revue bibliographique. Sci. Sol 30, 33–47.
- Kaila, A. (1956). Determination of the degree of humification of peat samples. J. Agr. Sci. Finland 28, 18–35.
- Kerloch, E., and Michel, J.C. (2015). Pore tortuosity and wettability as main characteristics of the evolution of hydraulic properties of organic growing media during cultivation. Vadose Zone J. https://doi.org/10.2136/vzj2014.11.0162.
- King, P.M. (1981). Comparison of methods for measuring severity of water repellence of sandy soils and assessment of some factors that affect its measurement. Aust. J. Soil Res. 19, 275–285. https://doi.org/10.1071/SR9810275.
- Letey, J. (1969). Measurement of contact angle, water drop penetration time, and critical surface tension. In Water-Repellent Soils. Proceedings of the Symposium on Water-Repellent Soils, L.F. DeBano and J. Letey, eds., pp. 43–47.
- Levesque, M.P., and Dinel, H. (1977). Fiber content, particle size distribution and some related properties of four materials in Eastern Canada. Can. J. Soil Sci. 57, 187–195. https://doi.org/10.4141/cjss77-023.
- Ma’shum, M., and Farmer, V.C. (1985). Origin and assessment of water repellency of a sandy south Australian soil. Aust. J. Soil Res. 23, 623–626. https://doi.org/10.1071/SR9850623.
- McGhie, D.A., and Posner, A.M. (1980). Water repellence of a heavy textured western Australian surface soil. Aust. J. Soil Res. 18, 309–323. https://doi.org/10.1071/SR9800309.
- Michel, J.C. (2015). Wettability of Organic Growing Media used in Horticulture: A Review. Vadose Zone J. https://doi.org/10.2136/vzj2014.09.0124.
- Michel, J.C., Rivière, L.M., and Bellon-Fontaine, M.N. (2001). Measurement of the wettability of organic materials in relation to water content by capillary rise method. Eur. J. Soil Sci. 52, 459–467. https://doi.org/10.1046/j.1365-2389.2001.00392.x.
- Michel, J.C. (1998). Etude de la mouillabilité de matériaux organiques utilisés comme support de culture. Ph.D. diss., Ecole Nationale Supérieure Agronomique, Rennes, France.
- Morita, H. (1976). Linuron absorption and the degree of decomposition of peats as measured by rubbed fiber content and pyrophosphate index. Can. J. Soil Sci. 56, 105–109. https://doi.org/10.4141/cjss76-015.
- Naasz, R., Michel, J.C., and Charpentier, S. (2008). Water repellency of organic growing media and its influence on hysteretic water retention properties. Eur. J. Soil Sci. 59, 156–165. https://doi.org/10.1111/j.1365-2389.2007.00966.x.
- Niggemann, J. (1971). Influences on the wettability of peats. Torfnachrichten 21, 13–15.
- Oliver, J.F., Huh, C., and Mason, S.G. (1980). An experimental study of some effects of solid surface roughness on wetting. Colloid Surface 1, 79–104. https://doi.org/10.1016/0166-6622(80)80039-4.
- Qi, G. (2011). Hydrophobie des matières organiques et ses consequences sur l’hystérèse et l’évolution de leurs propriétés hydriques. Ph.D. diss., Agrocampus Ouest, Angers, France.
- Ritsema, C.J., and Dekker, L.W. (1996). Water repellency and its role in forming preferred flow paths in soils. Aust. J. Soil Res. 34, 475–487. https://doi.org/10.1071/SR9960475.
- Rivière, L.M., and Nicolas, H. (1987). Conduite de l’irrigation des cultures hors sol sur substrats: contraintes liées au choix des substrats. Bull. GFHN 22, 47–70.
- Valat, B., Jouany, C., and Rivière, L.M. (1991). Characterization of the wetting properties of air dried peats and composts. Soil Sci. 152, 100–107. https://doi.org/10.1097/00010694-199108000-00006.
- Van Dijk, H., and Boekel, P. (1965). Effect of drying and freezing on certain physical properties of peat. Neth. J. Agri. Sci. 13, 248–260.
- Verdure, M. (1982). Improvement of physical properties of black peat. Acta Hortic. 126, 131–142. https://doi.org/10.17660/ActaHortic.1982.126.16.
- Von Post, L. (1922). Sveriges Geologiska Undersöknings torvinventering och några av dess hittills vunna resultat. Sven. Mosskulturfoeren. Tidskr. 1, 1–27.
- Washburn, E.W. (1921). The dynamics of capillary flow. Phys. Rev. 17, 273–283. https://doi.org/10.1103/PhysRev.17.273.
- Young, T. (1805). An essay on the cohesion of fluids. Phil. Trans. R. Soc. London 95, 65–87. https://doi.org/10.1098/rstl.1805.0005.
Received: 10 October 2014 | Revised: 12 June 2014 | Accepted: 23 June 2015 | Published: 23 August 2015 | Available online: 23 August 2015