Spatial Variability of Soil Properties in a Dry Zone Soil Catena of Sri Lanka

Abstract

Detailed information on spatial variability of soil properties is important for the decision making in site specific soil management and land use planning. Available coarse scale classical soil maps are insufficient to provide information for such requirements. Therefore, the soil variability needs to be investigated to provide detail soil information. The objectives of this study were to spatially characterize soil properties in a dry zone soil catena and to determine the impact of present land uses on the variability of soil properties. A dry zone catena consists of uncultivated lands and cultivated with paddy and vegetable lands was selected as a study area. Latin hypercube sampling technique was used to collect 58 soil samples. Soil samples were analyzed for pH, electrical conductivity (EC), cation exchange capacity (CEC) and texture. Summery statistics were calculated and statistical tests were performed to determine the land use impacts on soil properties. Semivariograms for each property were calculated and theoretical models were fitted using Variowin software. Continuous maps were constructed using ordinary point kriging interpolation technique. Normality test indicated that all the properties were normally distributed. Large coefficient of variation values indicated a considerable heterogeneity o f soil properties within the catena. The relative nugget effect (RNE) values of pH (8.25 % ), EC (7.41 % ), sand (1 2 % ), CEC (50.9 % ), silt (50.5 % ) and clay (29 % ) revealed a high to moderate spatially structured variability for soil properties. Range of spatial dependencies of soil properties ranged from 193 to 650 m. Kriged maps further explained the variation of soil pH, EC and CEC in uncultivated and cultivated land uses and clay and silt enrichments were observed in vegetable lands and paddy lands, respectively.