Conventional versus organic management: application of simple and complex indexes to assess soil quality

Organic management aims to maintain and/or enhance the soil quality by adopting crop rotation, reduced tillage, and application of organic fertilizers. Several studies highlight the advantages of organic management in terms of soil quality and soil fertility, the key themes in sustainable agronomy. The aim of this study was to understand whether there were differences in soil quality between two different approaches of organic management. Soil quality was assessed using a set of biochemical parameters individually or in combination, in simple and complex indexes, respectively. Soil samples were procured from a long-term field experiment area located in Monsanpolo del Tronto (Central Italy) in which conventional (Conv), and two different organic managements (Org1, organic traditional; Org2, organic agroecological) were followed, and were assessed for soil quality. Results from individual soil properties, simple and complex indexes highlighted that Conv and Org1 were similar in terms of acquisition activity indicating that both mineral and organic fertilizers supply C, N, and P equally to agro-ecosystems. However, in Org2, despite theoretical imbalances in terms of C:N:P, microbial activity efficiently filled this imbalance without affecting soil organic carbon content. The indexes showed a positive metabolic response and a higher soil quality in both the organically managed plots, indicating that organic management, independent of the agronomic approach, maintains the soil quality despite the differences in biochemical processes. Moreover, simple and complex soil quality indexes were sensitive enough to discriminate the two organic management strategies.