Hydrological characteristics of some volcanic materials as affected by particle size distribution and internal porosity
Volterrani, M.; Magni, S.
Acta Agriculturae Scandinavica Section B-Soil and Plant Science 62: 150-154
ISSN/ISBN: 0906-4710 DOI: 10.1080/09064710.2012.682161
A number of internally porous inorganic amendments have been recently introduced to replace peat in rootzone mixes used for golf greens and sports fields. In Italy, volcanic rocks provide a large availability of internally porous materials such as pumice, lapillus and zeolite. Volcanic sands are currently used as substitutes of silica sand. In order to assess the suitability of these volcanic materials for sand amelioration and/or as construction materials, the present research was aimed at studying the water retention and release of these materials considering different particle size distributions and a non-porous silica sand as a reference. Water retention curves were constructed for the internally porous sands as: (a) raw material, (b) graded material with the same particle size distribution of a non-internally porous silica sand. Additionally, available water was determined on specific sand fractions namely coarse sand (0.5-1.0 mm) and medium sand (0.25-0.5 mm) of all the materials. The available water content of raw volcanic materials was higher than of graded sands made of the same materials, thus showing the expected effect of texture on water retention. The comparison of water retention properties of the internally porous materials and non-internally porous silica sand with the same particle size distribution, showed a significant contribution given by internal porosity to water retention. Volcanic coarse sand fraction showed higher water availability than volcanic medium sand fraction. Volcanic materials used as amendments could enhance the water availability of sand-based rootzones, but if used as raw materials the possibility exists for the final mix not to meet the specifications for sports use. The use of sole volcanic sands as rootzone material could have a major impact on water-holding capacity, and hence on management, although investigation on their particle stability is still needed.