TEMPORAL PERSISTENCE OF SPATIAL PATTERNS FOR MINERALIZABLE NITROGEN AND SELECTED SOIL PROPERTIES

To assist N-fertilization planning and to avoid N-pollution problems, an evaluation of soil N-mineralization ability is imperative. In addition to the accuracy of that evaluation under laboratory conditions, knowledge of its spatial and temporal variation is helpful for further data analyses. This study aimed to characterize the spatial variation of soil mineralizable N, to investigate its spatial relation with rive basic soil properties (oxidizable C, pH, electrical conductivity, exchangeable NH4+, and gravimetric water content), and to examine the changes in the spatial patterns and correlation structures during the winter. In October and April 1989, 73 samples were collected from spots 1 to 57 m apart in a long-term fallow plot. Nitrogen-mineralization ability was measured through an anaerobic incubation experiment. The study of scale-dependent correlation structures and spatial patterns was carried out through a multivariate geostatistical analysis. The mean and standard deviation of most properties studied changed slightly during the winter. Nitrogen-mineralization ability was mainly explained by the amount of oxidizable C, which appeared to be well correlated with gravimetric water content. The spatial structure of all soil properties measured was characterized by large variation at small distances (< 1 m) and by the independence of the observations beyond 12 m. In addition, most of the spatial patterns showed a temporal persistence, i.e., high and low values generally occurred at the same locations before and after winter.