| Abstract: | The effect of a granular formulation of sodium azide, applied annually to pine nursery beds at rates of 0, 67.2, and 134.5 kg a. i. ha?1 under water seal or plastic seal, on soil fungal populations was determined over a 3-year period. Populations of fungi in the soil decreased following application of the sodium azide each year; the greatest decrease occurred at the highest rate of application. Populations of fungi in soil treated with the azide generally remained lower than in the controls throughout each of the 3 years; however, the population disparity between treated and control plots decreased in magnitude with each succeeding year. Populations of Trichoderma spp., in plots treated with 134.5 kg sodium azide ha?1, increased 2 weeks after treatment each year, and the population peaks increased in magnitude each year. In addition the effect of sodium azide (technical grade > 99%) at concentrations of 0, 2, 5, 10, 20 and 50 μg ml?1 in potato dextrose agar and blackstrap molasses agar media was determined in vitro for 14 isolates of Trichoderma harzianum. Growth and sporulation differed among the isolates and between the two media tested. Generally, the azide temporarily inhibited growth of the fungi, but the majority of the isolates were able to grow on either medium containing 50 μg sodium azide ml?1, although sporulation was more profuse on the molasses than on the potato dextrose agar medium. |
