Use of soil solarization to improve growth of eucalyptus forest nursery seedlings in Argentina

Damping-off and root rot are major diseases affecting seedlings of Eucalypt us species in forest nurseries in temperate regions in Argentina. The most common fungi associated with these diseases and affecting the vigor of the root system are Fusarium and Pythium species. Two forest nursery experiment s were conducted in the province of Buenos Aires, Argentina, to determine t he effect of soil solarization on growth of Eucalyptus viminalis seedlings and relate this effect to the presence of pathogenic and native ectomycorrh izae populations in roots and nutrient availability in soil. Changes in pop ulations of soilborne pathogens were determined by a bioassay that relates their potential to induce disease. Changes in native ectomycorrhizae were a ssesed by measuring colonization levels in roots. Nutrient availability was determined by the amount of nitrates released by solarization. Solar heati ng decreased pathogenic and ectomycorrhizal inoculum potential and increase d soil nitrates. Seedling growth in solarized seedbeds may be related to a low initial pathogenic population and/or to increases in nitrate availabili ty. Solarization may induce soil suppressiveness against re-establishment o f major seedling pathogens in treated soils.