LAUSR

Abstract Best soil management practices can be achieved by evaluating the spatial cross-correlation variability of soil microbiological and physicochemical indicators, in order to comprehend the underlying relations between these mutually dependent properties, being valuable indicators for prospective evaluation of soil resources. The purposes of this study were to measure microbiological and physicochemical variables in superficial soil, spatially cross-correlate and determine spatial causalities between these two families of variables. The spatial variability of pH, gravimetric soil water content, 238U, 232Th, 40K, 137Cs, acid phosphatase, dehydrogenase activity, microbial biomass carbon, mesophilic aerobic bacteria and filamentous fungi was studied at a 13 ha field located in Uruguay. 238U and 232Th were both negatively lineally correlated with gravimetric soil water content (−0.42), 137Cs (-0.45 and −0.48 respectively) and dehydrogenase activity (-0.44 and −0.48 respectively). A semivariogram analysis revealed that the best fit model for soil variables was spherical, with moderate to strong spatial dependence. Cross-correlation results suggest that there is an influence factor from spatial interaction. In this sense, gravimetric soil water content connects physicochemical variables with soil biodiversity. Spatially, soil water content is inversely influenced by 232Th and 238U (as indicators of sub-superficial soil), and directly influenced by dehydrogenase activity (indicator of soil microbial activity), revealing soil microbial activity as a possible indicator of water retention in drying soils. The combination of spatial patterns of environmental radionuclides with microbiological indicators of soil quality could represent a valuable integrated approach to assess soil conservation status and further explain the impact of anthropogenic disturbance.