EFFECT OF STORAGE OF SOIL AT 4-DEGREES-C ON THE MICROBIAL ACTIVITY STUDIED BY MICROCALORIMETRY

The effect of the storage of soils on their microbial activity has bee n studied using a microcalorimetric method. Soil samples were kept in closed polyethene bags at 4-degrees-C during 3-6 months. Results show changes in the slope of the different P-t curves recorded from the sam ples stored at 4-degrees-C. This fact strongly suggest the existence o f changes of the microbial activity of soil as the heat evolution is a direct measurement of the cells metabolic activity. The value of the Peak-time (time in which the microcalorimetric signal reaches the maxi mum value) is related with the microbial density of soil samples. This parameter was affected by the time of storage increasing with time. T he total heat evolution Q(t), of the soil samples amended with glucose calculated from the area limited by the Power-Time curves, also decre ases with the time of storage. The soil that had been stored for 6 mon ths before experiments, showed the lowest value of Q(t).