APPLICATION OF ECOPHYSIOLOGICAL QUOTIENTS (QCO2 AND QD) ON MICROBIAL BIOMASSES FROM SOILS OF DIFFERENT CROPPING HISTORIES

Metabolic quotients for CO2C (qCO2C) and microbial-C-loss (qD) were studied on soil microbial communities under long-term monoculture (M) or continuous crop rotations (CR). Under defined laboratory conditions the mean qCO2C (unit CO2C unit-1 Cmic h-1) of different microbial biomasses from 17 M systems amounted to 1.097 μg CO2qCO2CC as compared to 0.645 μg CO2C of microbial biomasses from 19 CR systems. The 1.7 times higher CO2C release per unit biomass and time of microbial biomasses from M systems was significantly different at the P =0.001 level. In addition, microbial C-loss in samples from M or CR plots was followed for 5 weeks. Again, mean qD per unit microbial biomass and time was 1.6 times higher (P = 0.01) for microbial biomasses from M systems (0.301 μg C, 14 soils) when compared with CR systems (0.188μg C, 14 soils). These differences were not related to soil texture, Corg or pH of these soils. The effects of environmental influences (soil management) on the microbial pool in terms of a changing energy demand are discussed. © 1990.