Vergleichende Untersuchung von Methoden zur Bestimmung der mikrobiellen Aktivität im Boden

Six existing methods for the determination of the total microbial activity (heat output with and without addition of glucose. ATP-content, arginine ammonification, hydrolysis of fluorescein diacetate, Fe(III)-reduction) were compared over a period of 7 to 8 weeks with respect to their sensitivity to indicate modifications of the soil microflora. An agricultural soil was amended with two pesticides and HgCl 2(Ioxynil 2 mg/kg and 20 mg/kg; Thiram 5 mg/kg and 50 mg/kg; HgCl2 2mg/kg and 20mg/kg). The results show that all methods at least slightly differ from each other, indicating that each one reflects only a part of the microbial life in the soil. Due to limited nutrient supply the main part of the soil microflora is dormant, but can be activated by addition of an anergy source. While heat output after addition of glucose (potential heat output) determines the whole microflora in the active state, heat output without glucose (actual heat output) seems to indicate mainly the active micro organisms. The ATP-determinatiom seems to indicate as well as at least a part of the dormant microorganisms. The arginine ammonification proved to be very sentitive. As the mineralization of arginine is widespread, the arginine degrading enzymes seem to be more sensitive to the addition of pesticides than the microorganism itself. In contrast to these above methods the hydrolysis of fluorescein diacetate and the Fe(III)-reduction method had different sensitivies for the pesticides used. By the fluorescein diacentate method mainly fungi whereas mainly anaerobic bacteria obviously respond to the Fe(III)-reduction method