PHYSICAL AND MICROMORPHOLOGICAL PROPERTIES OF ORGANIC AND INORGANIC MATERIALS FOR PREPARING GROWING MEDIA

The production of crops in containers is related to the selection of growing media which is based upon water retention capacity and drainage. However lack of knowledge of the type, form and arrangement of the particles makes it difficult to predict its structural behavior in the container. Within this context, the objective of this study was to evaluate physical and micromorphological properties of organic material such as Sphagnum peat, coconut fiber, compost and vermicompost and inorganic materials such as pumice, perlite, zeolite and volcanic scoria. The particle size distribution of the materials was 3.36 mm, 2.00, 1.00 mm, 0.50 mm, 0.25 mm and <0.25 mm. The description of pores and particles was conducted though thin sections with resin impregnation. The parameters evaluated were size, abundance, shape, surface roughness, orientation and distribution patron. The micromorphological analysis showed that organic materials pores exhibiting compound packing voids that the storage and percolation function while inorganic materials had pores of simple packing. The total porosity varied depending on the nature of material and its particle size distribution. In materials with 1 at 2 mm particle size, the total porosity values were 94.3% (coconut fiber), 94.2% (Sphagnum peat) and 85% (perlite); while those for 2 at 3.36 mm particle size were 71.9% (compost), 67.7% (vermicompost) and 67.5% in volcanic scoria, and 0.25 at 0.50 mm particle size were 72.2% (pumice) and 70.18% in zeolite. The total porosity values for other particle sizes were lower. In case of volcanic scoria and perlite, then internal pores are disconnected vessels and only the external pores contributed to the percolation. Coconut fiber, Sphagnum peat, vermicompost, compost and pumice and are characterized by internally connected porosity due to which they have a higher water retention capacity. It concluded that particle size distribution, the type and number of pores determine the physical and micromorphological properties of the studied materials as growing media.