Geospatial Assessment and Mapping of Selected Soil Physical and Chemical Properties of CTCRI Farm

Abstract

Analysis and interpretation of spatial variability of soil properties is important in site specific nutrient management, precision farming and sustainable land management. The study assessed the spatial variation of soil physical and chemical properties of the agricultural farm of Central Tuber Crops Research Institute (CTCRI), Thiruvananthapuram, Kerala. Georeferenced surface (0-15 cm) and subsurface (15-30 cm) soil samples were collected from 130 locations, 50-60 m apart, in an irregular grid. Spatial variability analysis was done for selected soil physical and chemical properties like bulk density, water holding capacity, porosity, soil texture, organic carbon, available nitrogen, available phosphorus and exchangeable potassium. Descriptive statistical analysis was carried out to study the variability of different soil properties. The spatial analysis was done using geostatistical analyst extension of ArcGIS 10.0 software. Results showed that majority of the farm area are sandy clay in texture. Among the soil physical properties studied, bulk density and porosity showed low spatial variations (CV <10.00) in both soil layers. Among the soil chemical properties studied, very high spatial variability was observed for available phosphorus followed by exchangeable potassium. Gaussian and exponential models fitted well with the experimental semivariograms of most of the soil physico-chemical properties. The nugget to sill ratios, which gives the degree of spatial dependence, was observed to be weak to strong for the soil properties. Spatial distributions of soil physico-chemical properties in the farm were estimated using kriging interpolation. The semivariogram parameters were used for kriging that produced interpolation maps of the soil properties which can be used as very good tools for farm planning at regional scale.