Prior to the placement of the greenhouses and planting of vegetable seeds, soil samples were taken from the 0-3, 3-6, and 6-9 cm segments of the vertical trench profile. Similarly, soil samples were col- lected during the harvest of mature plants from within the greenhouses at the same depth intervals. Forty-eight soil samples were collected. Previous experiments in NTS soils had shown that no major changes in the microbial population could be expected to occur during the time period of these experiments (Au, 1972). Accordingly, no further soil samples were collected from outside of the greenhouse structures. Soil moisture of the collected soil samples was determined in separate experiments according to standard procedures (Pramer and Schmidt, 1964). Dilution plate counts were made of the collected soil samples to quantify and differentiate the fungal and bacterial populations. From each soil sample, an amount corresponding to 20 g of oven-dried soil was added to 100 ml of sterile distilled water and shaken for 10 min. Coarser particles were allowed to settle, and 1-ml samples of the soil suspension were used to prepare dilutions for plate counts according to standard procedures (Clark, 1965). The dilutions used were 5 x 1077 and 5 x 107? for molds, and 5 x 107* and 5 x 107° for bacteria and Streptomyces counts. dilution. Five plates were poured of each Cooke's Rose Bengal agar with antibiotic added was used for fungal determinations, and sodium albuminate agar was used for bacteria and Streptomyces determinations. The plates were incubated at room temperatures; fungal and bacterial counts were made after 2 and 14 days, respectively. In addition to the microbial plate counts, the classification and the relative abundance (in percent of the total fungal and bacterial numbers) were determined for the fungi Muecors, Aspergttllus, Pentcilltum, and Demattaceae as well as for the bacterial genus Streptomyces. RESULTS AND DISCUSSION In this discussion, only the overall changes of microbial population caused by the agricultural use of the soil will be highlighted. More 70 it