EFFECT OF STEAM AND EXOTHERMIC SUBSTANCES (KOH AND CAO) ON LETTUCE AND STRAWBERRY: TWO YEARS OF EXPERIMENTATION

Addition to the soil of substances causing an exothermic reaction in order to make disinfection by means of steam more efficient may have effects on crops due to the resulting changes of soil chemical characteristics. The present paperdescribes effects on lettuce and strawberry of soil disinfection by means of steam combined with increasing doses of KOH or CaO (0, 1000, 2000, 4000 and 8000 kg ha-1) performed for two consecutive years in the same soil. The results indicate that KOH and CaO can be used in association with steam for soil disinfection in vegetable crops without production risks, provided that the applied dose does not exceed 4000 kg ha-1, with regard to soils comparable to that used in the trials (sandy loam texture, alkaline pH, sufficient amount of organic matter and nutrients). In fact, relevant reductions of yield were observed only with the 8000 kg ha-1 dose, that caused more evident increases in soil pH and electric conductivity. In order to exclude problems due to repeated applications and to reduce the cost of the treatment, doses of 1000-2000 kg ha-1 are recommended.