Abstract

FROLLA, F.D; ZILIO, J.P  and  KRUGER, H. Variabilidad espacial de la profundidad del suelo: Métodos de interpolación para el sudoeste bonaerense. RIA. Rev. investig. agropecu. [online]. 2015, vol.41, n.3, pp.309-316. ISSN 1669-2314.

Petrocalcic horizons are among the main soil constraints to agricultural production in the south-west of Buenos Aires province. They decrease effective soil depth and water holding capacity. This paper deals with the mapping of soil depth. The objectives were: to compare predictive ability of two interpolation methods (ordinary Kriging and Inverse Distance Weighted, IDW), and establish the minimum observation density requirements to define management units. In a 60-ha production farm located near San Germán town (Puán district, Bs. As. province), 199 soil depth observations were performed using a mechanical probe. Data were grouped into 5 observation densities (0.5-0.75-1-1.5-2 observation ha^-1). Resulting maps were checked against a set of data reserved for this purpose. Statistics like Mean Square Error (PCE), goodness of Prediction estimator (E), and coefficient of determination (R2), for linear and quadratic regressions were used to estimate their precision. Maps representing the Interpolation Error (EI) were made to identify prediction variability. Interpolation methods showed no great differences in precision, but the increase in observation density improved mapping precision. Based on its relative simplicity and a slight trend to better statistics values, IDW is proposed as a possible standard method, with a minimum density of 1 observation ha^-1 for this specific soil management maps. A higher observation densities (1.5 - 2 ha^-1), can be used to increase accuracy in more complex areas of this field related to shallow soils.

Keywords : Soil depth; Interpolation methods; Observation density; Kriging.