[Studies on survival of Salmonella typhimurium in different types of soils under outdoor climatic conditions (author's transl)].

Subsequent to experimental contamination of the surface of different soils--sand, loam and clay types--persistence of S. typhimurium had been investigated under outdoor climatic conditions over the period June 1977 to Dec. 1978 to judge public health problems resulting from land application of animal manures. The studies showed the following results:--in general survival time of Salmonellae reduced with decreasing temperature both at the soil surface and in deeper soil layers of the correspondent soil-type. Relative to average soil temperatures of 14.1, 3.2 and -0.6 degrees C the Salmonellae showed average survival times of 46.8 d, 32.1 d and 3.3 d respectively (p < 0.01).--by means of infiltration Salmonellae penetrated into the soils. Below soil surface the pathogens exhibited mean survival times approximative twice as long as pathogens remaining at the soil surface. At the soil surface the Salmonellae persisted over an average period of 26 d (3-69 d as a function of soil type), while out of deeper soil layers the pathogens could be reisolated over an average period of 44.7 d (7- > 120 d as a function of soil type), (p < 0.05).--with increasing depth of soil (5-50 cm) frequency of isolation of Salmonellae reduced (p < 0.01). In this connection rate of infiltration seemed to be restricted mostly within the first 15 cm.--the heavier soil types gave better chances for survival of S. typhimurium than the sandy soil types (p < 0.01). This could be shown by the higher isolation rate of Salmonellae from the loam- and clay-type soils (15.9%), compared with the isolation rate of 7.8% from the sandy soil-types.--genuine soil microorgnisms took part in elimination of Salmonellae. The degree of self-decontamination however was not related to the biomass contents of the investigated soils. From the viewpoint of environmental hygiene, the results point to distinct organic loading capacities of soils. This leads to the conclusion that the degree of manuring should be devoted to the capability of self-decontamination of the corresponding soil-type. Relative to heavier soils, this results in longer intervalls of manuring. Related to the spreading of liquid manures, methods have been developed to avoid odor emission by injecting the liquid manures into the soil. These methods seem to be critical from the viewpoint of hygiene, because beneath soil surface pathogenic bacteria, as it could be shown, exhibited survival times for much longer periods than at the surface of the soils. The presented data point to the urgency of decontaminative pretreatments of animal manures (esp. to regions with high density of livestock) before spreading on land.