Comparing Ordinary Kriging and Cokriging to Estimate Infiltration Rate

Measuring infiltration within a landscape is important because it is one of the key processes controlling water budgets for the agricultural production and transport processes in the soil profile. Estimation of this process at an acceptable level of accuracy is important, especially in the case when it exhibits high variability, since its measurement is a time‐ and labor‐consuming procedure. This study was conducted to evaluate and compare kriging and cokriging to estimate infiltration rate (IR) using limited available data on an 8.5‐ha alluvial field (loamy mixed mesic Ustifluvent). Infiltration tests were conducted using double‐ring infiltrometers until steady‐state IRs were obtained at nodes of an irregular grid consisting of 24 columns and four rows. Values of field‐measured IR ranged from 1.92 to 8.88 cm h−1, with a mean of 5.11 cm h−1 Bulk density of subsoil was significantly related to IR and, therefore, helped estimation of IR values at unobserved locations. Both kriging and cokriging adequately estimated IR when 50 observed IR values were used with both estimators (mean reduced error was 4.15 × 10−3 for kriging and 4.10 × 10−3 for cokriging). To determine the minimum number of observed IR values needed to estimate IR without losing significant spatial information, kriging and cokriging were repeated with 45, 40, 35, and 30 observed IR values. Forty‐five measured IR values with kriging, and 40 values with cokriging were adequate to estimate IR. Therefore, cokriging was found superior to kriging in estimating IR in the case of limited available data.