Influence of firing on the properties of clays: a substrate for soilless cultivation

Material science

Faced with global population growth requiring increased food production, urban agriculture is one of the innovative solutions. The article focuses on the production and use of calcined clay balls, a growing medium made from clay sourced from rice fields in the Urban Commune of Antananarivo, Madagascar. The manufacturing stages, such as mixing, extrusion, shaping and firing, influence the physical and chemical characteristics of the balls, in particular their porosity, water retention capacity, pH and cation exchange capacity. Firing improves intragranular and intergranular porosity by removing organic matter and reducing bound water. Agronomic trials carried out on the soilless cultivation of Mentha spicata show that the use of calcined clay balls substrate is more effective than that on arable land. Although the study focused on potassium, it is suggested that its interaction with phosphorus should also be explored and that the water retention capacity of the substrate should be improved by adding water retainers.

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