Spatial variability of soil color parameters and soil properties in an alluvial soil

Understanding of spatial variability of soil properties provides the factors and processes controlling their potential in agricultural production. The objectives of this study were to analyze spatial structure of soil properties and soil color parameters (L*, a*, b*) in an alluvial field (45 ha) under different crop patterns, and to map soil properties using geostatistical methods. A geostatistical sampling scheme was adopted, and 188 soil samples were taken from topsoil (0-20 cm) and subsoil (20-40 cm). Soil color value b* showed the lowest variation (CV = 6.4% for topsoil and CV = 6.1% for subsoil) between soil color parameters. Available Phosphorus showed the highest variation (CV = 64.6% for topsoil and CV = 52.4% for subsoil). Geostatistical range varied from 114 m (available phosphorus) to 633 m (EC) in topsoil. Soil pH had the shortest (72 m), and CaCO3 had the longest range value (612 m) in subsoil. Map of CaCO3 content visually correlation with lightness (L*) map in both depths but maps of the organic matter did not show visual correlation with maps of L* in both depths. Organic matter maps can be used for site specific N application because OM to some extent characterizing potential N-supplying capacity could be used as reference for N fertilizer recommendation.   Key words: Geostatistics, semivariogram, kriging, soil color.