Chemical changes occurring in the soil after the heat treatment may represent a further mechanism for the solarization effects (Chen and Katan 1980; Chen et al. 1991). An increased concentration of soluble mineral nutrients was generally found in solarized soil (Katan 1987; Stapleton and DeVay 1995; Stapleton 2000), prevalently due to the death and degradation of soil microbiota killed by the heat treatment. Accumulation of toxic ammoniacal nitrogen was found to result from the microaer-obic conditions originated by the thermal death of nitrifying microorganisms in soils with high moisture and organic matter content (Hasson et al. 1987), whereas a minimal release of rapidly nitrified nitrogenous compounds was reported in soil with poor organic material when low temperatures raised by an uneffective soil solarization and/or a low moisture content increased survival of soil biota and promoted aerobic conditions (Stapleton et al. 1985). Heat-induced breakdown of organic matter may also generate volatile compounds toxic to soil biota in solarized soils (Gamliel et al. 2000).
Was this article helpful?