Variabilidad espacial de atributos químicos y físicos en un suelo de La Pampa llana Santafesina Spatial variability of soil chemical and physical attributes in a flat Pampa Santa Fe field

Los procesos y atributos que influyen sobre el desempeño de los cultivos varían en el espacio y tiempo. Su magnitud y estructura espacial es específica para cada lote y su cuantificación es necesaria para la aplicación del manejo sitio-específico de cultivos (MSEC). Nuestro objetivo fue examinar la variabilidad espacial intra-lote de atributos químicos y físicos del horizonte superficial de un Argiudol típico del centro de Santa Fe para la implementación del MSEC. En una parcela de 475 x 100 m se tomaron 60 muestras distribuidas en 3 transectas de 20 puntos separados cada 25 m y 50 m entre transecta. En cada muestra perturbada (0-20 cm) se determinó N de nitratos (N-NO3), C orgánico total (COT), N total (Nt); P extractable (P), arena, arcilla, reacción del suelo (pH). La densidad aparente del suelo (Ds) se determinó a partir de muestras no perturbadas de las profundidades 0-10 y 10-20 cm. Se calcularon estadísticas descriptivas y se analizó la dependencia espacial de los atributos mediante variogramas empíricos y sus límites obtenidos por permutación (envelopes). Los coeficientes de variación (CV) para COT, Nt, Arena, Arcilla, Ds 0-10, Ds 10-20 y pH fueron bajos (CV The processes and properties that regulate crop performance and yield vary in space and time. The assessment of the magnitude and spatial structure of their variation is required in order to apply site-specific crop management (SSCM). Our aim was to assess the intra-field spatial variability of some chemical and physical topsoil properties of a typic Argiudoll of the center of Santa Fe for the use of the SSCM. Sixty soil samples of the top layer (0-20 cm depth) were taken in a 475 x 100 m plot. Sampling was distributed in three transects separated by 50 m with 20 points every 25 m. Disturbed soil samples were used to analyze N of nitrates (NNO 3), total organic C (COT), total N (Nt); available P (P), sand (Arena), clay (Arcilla) and soil reaction (pH). Soil bulk density (Ds) was determined on non-disturbed soil samples taken at 0-10 and 10-20 cm depths. Summary statistics were calculated and the spatial dependence was determined with sample variograms and envelopes obtained by permutations. Coefficients of variation (CV) for COT, Nt, Arena, Arcilla, Ds 0-10, Ds 10-20, and pH were low (CV < 15%) while they were moderate for P and N-NO3 (15 < CV < 35%). Moderate spatial dependence with a range of 96 m was only observed for N-NO3. The other soil properties had no autocorrelation because their variation occured at distances shorter than 25 m. In this study, the low variability and lack of spatial dependence of the soil properties did not allow modeling their spatial distribution as well as the development of reliable soil maps that would allow the use of the SSCM