Saprophytic growth in soil of a strain of Trichoderma koningii

A soil-sandwich bioassay was used to determine the influence of temperature , moisture, form of nitrogen, and the soil microflora on the saprophytic gr owth through soil of an isolate of Trichodel ma koningii. Incubation temper ature affected the saprophytic growth of the fungus in soil over the range tested. Saprophytic growth of the isolate in sterile soil increased with in cubation temperature from 5 degrees C to the optimum temperature 25 degrees C; there was no saprophytic growth at 30 degrees C. Saprophytic growth als o increased with soil moisture content in sterile soil, with a growth optim um at 70% soil water holding capacity (WHC). There was little saprophytic g rowth at soil moisture contents below 20% WHC. Nitrogen added as ammonium s ulphate (NH4+-N) increased the saprophytic growth of T. koningii in sterile soil whereas nitrogen added as nitrate (NO3--N) suppressed growth of T. ko ningii. Saprophytic growth of T. koningii was markedly reduced in the prese nce of a natural soil microflora, and enhanced in soil sterilised with ethy lene oxide and, to a lesser extent, in soil pasteurised by microwave treatm ent. The soil sandwich technique could be used as a screen to identify soil s and soil factors conducive to Trichoderma establishment and growth.