BIOLOGICAL ACTIVITY AND MINERALIZATION OF NITROGEN IN THREE SOILS AS INDUCED BY FREEZING AND DRYING

Abstract

Rapid freezing and short-term drying effected marked changes in the biological activity of a Calcareous Black and a Brown Forest soil and only minor changes in a Solodized Solonetz soil which had a lower organic carbon and total nitrogen content. Freezing increased the initial rate of organic matter decomposition but further studies, with the Brown Forest soil only, showed that freezing did not affect the total amount decomposed over an extended incubation period; drying, however, increased the total amount decomposed throughout the incubation period. Freezing all soils decreased the number of viable fungi, whereas drying had no marked effect on the number of either fungi or bacteria. Freezing markedly increased the mineralization of nitrogen in the two higher organic matter soils whereas short-time drying did not. The influence of freezing on mineralization was reflected by a greater uptake of nitrogen by millet in one of the soils.