Biological indicators for evaluating soil quality improvement in a soil degraded by erosion processes

Purpose: Erosion is one of the main soil degradation problems. It diminishes soil biological activity and therefore its quality. The aim of the study was to evaluate if the application of two biostimulation processes could significantly increase biological activity, and therefore productivity, in soils deteriorated by erosion. This was done without synthetic fertilizers but with treatments accessible for farmers, in line with the 2030 Agenda for Sustainable Development. In particular, the addition of a soil microorganism suspension or Macrocystis pyrifera algae concentrate was evaluated. Materials and methods: Soil samples were taken from a field area (Bihor County, Romania) affected by surface erosion processes. In particular, microbial mass, dehydrogenase activity (DHA), and the bacteria and fungi presence were analyzed for three soil uses (corn, black locust and uncultivated field with terracing) and in different locations (above a slope, at the midpoint and below it). A bio-stimulation process (addition of a microbial suspension or seaweed concentrate based on the Macrocystis pyrifera algae; incubation for 24 h) was used in order to improve the activity of the soil with the lowest values of activity. Results and discussion: Statistical differences in DHA, bacterial numbers, and microbial biomass were found depending on field use and the areas from which the soil samples were gathered. Higher values of the biological parameters were in general recorded in the middle part of the slope, because they favor bioaccumulation processes (e.g., actual and potential dehydrogenase activity values of about 3 mg TPF/10 g dry soil). The use of microbial suspensions did not significantly stimulate DHA for the soils with a low biological potential. This activity was stimulated by adding the seaweed concentrate to the soil. Conclusions: The use of the seaweed concentrate can be a good practice for improving activity in eroded soil. The study provides useful indications for better soil fertility management, in line with many of the goals of the 2030 Agenda For Sustainable Development.