Biodynamics of microbial biomass nitrogen and sulfur in glucose and cellulose amended soil

Abstract

Soil samples were amended with 2ml aliquots of nutrient solution containing 3000 μg or 3333 μg C, 15 μg S and 250 μg N/g soil in the form of D-glucose or cellulose, MgSO₄7H₂O and NH₄NO₃ and incubated at 26 ± 4^°C for 30 days to assess biodynamics of microbial biomass nitrogen and sulfur. A basal dressing of 200 μg P and 250 μg K/g soil in the form of KH₂PO₄ was applied for each treatment except control. The highest rate of CO₂-C evolution was recorded in glucose plus N plus S amended soil which was significantly higher than that obtained from glucose plus N, glucose plus S, glucose and control soil. A similar pattern of CO₂-C formation was observed in the cellulose amended soil treated with N and S. The respiration rate in the glucose amended soil was higher than that of the cellulose amended soil. In glucose and cellulose amended soil treated with N and S, the amounts of biomass-C, -N and -S were increased following an increase in the rate of CO₂-C evolution. The concentrations of inorganic N and SO₄-S were higher in those soils that received N and S than the soils where no N and S were added. The critical N concentrations were ca. 122.5 and 44 mg N/g biomass in cellulose and glucose amended soil, respectively. The critical S concentrations were ca. 12.0 and 8 mg S/g soil in cellulose and glucose amended soil, respectively.