Greenhouse study of fertilizer applied to one-year-old Eucalyptus camaldulensis was carried out at the Faculty of Forestry, Kasetsart University in Bangkok. Soil from 7 infertile sites of 4 provinces in the Northeast were used as planting material. Kinds of Fertilizer applied were considered as treatment consisted of manure (12.5 g/l kg soil), urea (0.3 g/l kg soil), and control. Total height, diameter at root collar, and total biomass of eucalypt seedlings did not respond to soil types, but all variables concerned responded to fertilizer treatments. Maximum growth in terms of total biomass was recorded from manure application, about 23 percent and 38 percent higher than urea application and control, respectively.

In four forest ecosystems Cognettia sphagnetorum accounted for 68-98% of the total density and for 71-98% of the total biomass of Enchytraeidae. In general, C. sphagnetorum produced biomass of an energy content ranging from 17.3 to 94.4 kJ m-2. year-1, depending on the season and plant community. The production: biomass ratio for this species varied from 2.4 to 3.8

Soil enzyme activities are often used as indices of microbial growth and activity in soils. Quantitative information concerning which soil enzymes most accurately reflect microbial growth and activity is lacking. Relationships between the activities of 11 soil enzymes and microbial respiration, biomass, viable plate counts, and soil properties were determined in surface samples of 10 diverse soils. Correlation analyses showed that alkaline phosphatase, amidase, α-glucosidase, and dehydrogenase activities were significantly (P < 0.01) related to microbial respiration as measured by CO₂ evolution in soils which had received glucose amendments. Phosphodiesterase, arylsulfatase, invertase, α-galactosidase, and catalase activities were correlated at the 5% level while acid phosphatase and urease activities were not significantly correlated to microbial respiration. There was no significant correlation between the 11 soil enzymes assayed and CO₂ evolution in the 10 unamended soils. Only phosphodiesterase and α-galactosidase activities were significantly (P < 0.05) related to microbial numbers obtained on some selective culture media. Alkaline phosphatase, amidase, and catalase were highly correlated (P < 0.01) with microbial biomass as determined by CO₂ evolution after chloroform fumigation pretreatment. The organic C content in the 10 surface soils was correlated (P < 0.05) with acid and alkaline phosphatase, phosphodiesterase, arylsulfatase, amidase, urease, and invertase activities. Urease activity was also positively correlated with total N and cation exchange capacity and negatively correlated with the percentage of sand. These relationships suggest that urease can exist in soil as an extracellular enzyme in a three-dimensional network of organo-mineral complexes. Of the 11 enzymes evaluated, alkaline phosphatase, amidase, and catalase were concluded to be the most satisfactory choices in determining the relative activity and mass of the microbial population in soils. The activities of these enzymes were highly correlated with both microbial respiration and total biomass in soils.