SPATIAL VARIABILITY AND MAPPING OF SELECTED SOIL QUALITY INDICATORS FOR PRECISION FARMING AT A SMALLHOLDING LEVEL IN MINNA, NIGERIA

Abstract

Smallholding farmers in Nigeria still practice blanket application of fertilizers, without giving consideration to spatial variations in soil properties across their fields. Understanding of spatial variability in soil properties is essential for precision farming, especially in this era of resource scarcity and high cost of fertilizers. This study was carried out to assess and map the spatial variability in selected soil quality indicators in a smallholder farm in Minna, North-central Nigeria, for site-specific management. Four hectare field was selected for the study. The field was divided into subplots of 25 m x 25 m and serially numbered from 1 to 64. Each subplot was geo-referenced and soil samples were collected from 0-15 cm depth in 10 randomly selected subplots and sent to the laboratory for analysis. Field and laboratory data were analyzed using descriptive statistics. The data were then transferred into GIS software, SURFER 11, for interpolation and production of spatial maps of the selected soil quality indicators. Results indicated that the texture of the soils was sandy loam, pH was neutral; soil organic carbon and total nitrogen were low while phosphorus and potassium were medium. Spatial variability was low in sand, clay, bulk density and pH with their coefficient of variation (CV) ≤ 10 %. The CV for silt (28 %) and nitrogen (25 %) were moderate, while soil organic carbon (40 %), phosphorus (38 %) and potassium (36 %) were high. Correlation analysis indicated a non-significant (> 0.05) relationship between the micro-relief and spatial distribution of the soil properties within the farm. Based on the results, management practices related to soil organic carbon, nitrogen, phosphorus and potassium will require dividing the farm into relatively smaller homogenous units. This would help the farmers significantly in managing the spatial variability through application of the right quantity of fertilizers appropriate for each unit.