Soil disinfection with steam alone or combined with CaO in a greenhouse radish crop

Soil steaming has become an important practice in commercial greenhouse production as an alternative to chemicals to control soil-borne pathogens. In addition to their effect on pests, due to soil temperature increase, steaming methods may also have an impact on soil chemical properties, on plant nutrient regime and, consequently, on crop yield. The aim of this work was to investigate the effect of two steam disinfection methods (deep or shallow steam injection) with or without the addition of an exothermic reacting compound (1000 kg CO ha-1) on two consecutive greenhouse radish crops. The steam disinfection methods had a significant impact in soil thermal dynamics, on soil chemical properties and on radish crop production (with similar but more marked effects in the first than in the second crop cycle). The best results, in terms of both yield and quality, were obtained with shallow steam injection, while deep steam injection without CaO addition, resulted in a similar or lower yield than that obtained in the control soil. The main changes observed in soil chemical parameters were a temporary increase of pH following the incorporation of CaO and an increase of exchangeable K in the case of shallow steam injection.