Effects of mixtures made of alperujo (solid by-product of olive oil extraction) and soil, on bioindicators development (Eisenia andrei and Medicago sativa)

Abstract

Solid wastes resulted from olive oil extraction represent an important environmental problem in Catamarca where they are generated in huge quantities, within short periods of time. These wastes are phytotoxic materials, but they contain valuable resources such as large proportions of organic matter that could improve soil productivity of these regions. The aim of this study was to determine the impact on soils, caused by the addition of alperujo to soils in different proportions, by using Medicago sativa and Eisenia Andrei as bioindicators. Mixtures were typical soil of the Central Valley of Catamarca with the addition of fresh alperujo in different proportions (0-30%). The assays were performed under controlled conditions of temperature and humidity for 10 days. Adult worm survival and the presence and number of other stages were analyzed. Additionally, Medicago sativa germination percentage and plant growth parameters were also recorded. Results revealed the survival of around 100% of the adult worms at 5 and 10% of alperujo/soil mixtures. Cocoons were found in soil without alperujo and alperujo/soil mixture 5%. The germination of M. sativa reached the 40 and 10% in alperujo/soil mixtures of 20 and 30% respectively; whereas the 5 and 10% mixtures showed no inhibition of the germination. The emergence was affected from 10% alperujo/soil mixture. The plant height decreased with the concentration of alperujo, the plants being exposed to 30% the most affected. We conclude that 5% of alperujo in these soils does not produce substantial changes on bioindicators, however, other studies would be needed to assess environmental waste.