Soil Biological Activity under Heat-Treated Organic Management: A Comparative Study with Red and White Cabbage in a Mediterranean Climate

Heat-treated organic amendments offer a sustainable approach to improving soil biological quality while reducing the sanitary risks associated with organic fertilizers. This study evaluated the effects of plant species, growing season, and heat-treated organic amendments on soil biological properties during two successive cultivation seasons of white cabbage (Brassica oleracea var. capitata f. alba) and red cabbage (Brassica oleracea var. capitata f. rubra). The experiment was arranged in a randomized complete block design with three replications, and the data were analyzed using a three-way factorial ANOVA. Significant interactions among plant species, growing season, and amendment type were observed for all measured biological parameters, indicating that soil microbial responses depended on the combined effects of these factors. Overall, heat-treated organic amendments increased urease, alkaline phosphatase, β-glucosidase, dehydrogenase, microbial biomass carbon, and soil respiration by up to 135.7%, 43.7%, 45.8%, 235.2%, 185.7%, and 275.0%, respectively. Growing season was the dominant factor affecting most biological properties, with enzyme activities and microbial biomass generally increasing during the second cultivation season, whereas dehydrogenase activity declined. The results indicate that the evaluated heat-treated amendments maintain a high potential to stimulate soil biological processes, highlighting a promising alternative despite the lack of direct raw counterparts. Furthermore, considering the literature-supported hygienic benefits of thermal processing, these findings substantiate the overall agronomic viability and efficacy of heat-treated organic management in sustainable cabbage production systems.