Nouvelles informations relatives aux variations temporaires de l'activite nitrifiante d'un sol evaluee au laboratoire. incidences d'un apport de matieres organiques
Abstract The results reported in this paper confirm the seasonal influence on soil nitrifying activity estimated in the laboratory. The variations of this activity depend on different factors: climatic conditions, soil nature, occurence of plants, characteristics of the organic matter added to the soil. A fresh organic matter (straw, for example) leads to reduced nitrifying activity immediately after its incorporation; its depressive action disappears after a month under laboratory condi‐tions. A decomposed organic matter, as a manure, produces no effect. This work also shows the seasonal variations of the mineral nitrogen immobilization after addition of a fresh organic matter.