Abstract

LUGO, Jorge et al. ORGANIC FERTILIZER MADE OF SEWAGE SLUDGE AND MANURE EQUINE TROUGH VERMICOMPOSTING: A PROPOSAL FOR SOIL IMPROVEMENT. Rev. Int. Contam. Ambient [online]. 2017, vol.33, n.3, pp.475-484. ISSN 0188-4999.  https://doi.org/10.20937/rica.2017.33.03.10.

Human activities produce tons of organic solid waste causing problems to the environment, polluting soil, water and groundwater. In view of this, strategies such as vermicomposting -a process of organic solid waste stabilization- has been developed. This study aims to use the process of vermicomposting to test mixtures of sewage sludge and horse manure in different percentages in order to know its stability and to propose it as a soil improver. Four percentages for processing equine manure and sewage sludge were used: E100, E85-LR15, E70-LR30 and E55-LR45, followed by a 90 day-period under greenhouse conditions. The product showed gradual decrease in the percentage of organic C, C: N ratio and pH. It increased in the total content of N after 30 days and electric conductivity after 75 days. The P increased in E70-LR30 (57.3 ± 8.3 mg/kg a 1369.8 ± 114.8 mg/kg) towards the end. After a 45 days of vermicomposting, the stability in the C:N ratio, E100 (11.4); E85-LR15 (10.8); E70-LR30 (12.6) y E55-LR45 (11.2) was reached. The best relationship is E70-LR30, as it presents a balance in the supply of N and C and the concentration of heavy metals decreased for Cu, Zn, Ni and Cd. Furthermore, the pH (7.24 ± 0.1) was neutral, the P concentration increased significantly and the number of worms was higher (1790) in comparison to other treatments. Thus, this relationship is suitable as organic fertilizer.

Keywords : earthworm; C:N ratio; residues; vermistabilization.