Spatial variability of soil properties using geostatistical approach: a case study in alluvial soils of Samastipur district of Bihar, India

In a developing country like India, the research on precision agriculture is concentrated on precision nutrient management. However, in intensive agriculture, crop production is hugely affected by micronutrient deficiency. In the intensively cultivated regions of India, the spatial variability of key micronutrients has not been adequately captured, and there is a dearth of such information. Since the availability of micronutrients is directly connected to plant uptake, it is. crucial to develop an understanding of the variations of soil micronutrients across the fields of any region to establish management zones. The present study is an attempt to evaluate the spatial variability of major soil fertility parameters, namely, pH, electrical conductivity (EC), organic carbon (OC), soil available zinc (Zn), and soil available copper (Cu) in Samastipur district of Bihar, India. The spatial variability of micronutrient availability is expected to be high in the district due to small farms and varied management. The coefficient of variation value was highest for EC (77.7%) and lowest for soil pH (6.3%). The use of geostatistical analyses has been made to determine the spatial variation structure of all the parameters, followed by the generation of surface maps through kriging. The nugget/sill ratio obtained from the experimental semivariogram indicated a moderate degree of spatial dependence (25–75%) for all the studied soil fertility parameters. The maps developed by kriging were observed to be superior to assuming the mean of the observed value for any unsampled location. These maps may help farmers to adopt need-based variable rates of fertilizer application, thus optimizing resource utilization.