Spatial Variability Analysis of Soil Field Capacity at Lalgudi Block in Tamil Nadu using Geostatistical Models

Background: Knowledge about the spatial variability of soil field capacity is important to understand the nuances of soil water holding capacity and how to manage it so that the farm does not need to irrigate or suffer from a drought. Methods: A study was conducted in order to evaluate the spatial variability of filed capacity of Lalgudi block of Tiruchirapalli district located in Tamil Nadu, India. The soil samples were collected from different locations in Lalgudi block and the field capacity of the soil samples was estimated by using pressure plate apparatus for the soil samples. Geostatistics was applied for identifying the best interpolation method to acquire the spatial map of field capacity. Ordinary kriging and Disjunctive kriging fitted with six models via circular, spherical, exponential, Gaussian, pentaspherical and sine-hole effect model were used for spatial prediction of field capacity. Result: Initial data exploration resulted in non-normal distribution of field capacity and hence log-transformation was done before kriging was used. The semivariograms showed that the field capacity dataset had moderate spatial dependency in case of both kriging methods and with six models except Sine-Hole effect model in disjunctive kriging. A maximum range of 10709 m was observed in Exponential and Sine-Hole Effect model in ordinary kriging. The cross validation statistics indicated that the circular model in disjunctive kriging gave lesser root mean square value. The significant variability of field capacity should be taken into account in soil management practices.