Effects of Microwave Radiation on the Microbial Biomass, Phosphatase Activity and Levels of Extractable N and P in a Low Fertility Soil under Pasture

Amsterdam

1986

S. 377-382

3 Abb., 1 Tab., 29 Lit. Ang.

Bandaufführung

145326

Microwave irradiation was investigated as a controlles soil biological treatment which could selectively kill microbial biomass. Plate counts indicated that fungi were more susceptible to irradiation than were bacteria, but selective-inhibition of substrate-induced respiration (SIR) indicated that eukaryotes and prokaryotes were generally susceptible. Under the experimental conditions chosen, irradiation of the soil sample for 90 s gave a kill of microbial biomass equal to that achieved by CHCl3 fumigation. Extractable mineral N was increased after incubation of irradiated soil, and after 90 s irradiation was only slightly lower than that of fumigated soil. At intermediate irradiation times, the increase in extractable mineral N was closely related to the decrease of SIR biomass C, indicating that the N was largely of microbial origin. It was not possible to determine microbial P content of irradiated soil because heat denaturation of intracellular enzymes resulted in releases of extractable inorganic and total P considerably lower than would be expected. Soil phosphatase activity was more resistant to microwave irradiation than was the microbial biomass. The heat stability of soil extracellular enzymes may make it possible to use the controlled heating of microwave irradiation to apportion activity into intra- and extracellular components.