In the ongoing work, environmentally sound technologies for converting organic wastes into fertilizers, to improve soil sustainability and crop yield have been identified and assessed. Wet wastes were combined with 50% wood sawdust and 50% 50% wet wastes (Compost 1) or (10% Straw + 90% wet wastes) (Compost 2) to produce soil improvers with a balanced level of nutrients and their effectiveness on soil ecosystem functioning have been tested and compared to horse manure (HM) and nitrogen:phosphorous:potassium (NPK) fertilizers. Unfertilized soil was used as control. Soil chemical and biological properties, have been detected after the harvesting of broccoli and red cabbage (90 days from the initial treatments). Three independent experiments have been conducted in open field in a randomized complete block design with three replications (n=9). Results showed that Compost 1 had the highest C/N ratio and CSC, indicating a better humification of wet material. Compost 1 even if contained a minor amount of organic carbon, as well as a less activity of FDA and DHA than Compost 2, was the most effective in improving soil quality, significantly increasing the labile fraction of organic matter, the oxidative enzyme (DHA), microbial biomass and crop yield. Both composts increased crop productivity.