Spatial Variability and Fertility Mapping for Site Specific Management of a Smallholder Farm in Minna, Nigeria

Abstract

Farmers’ practice of blanket application of fertilizers negates the inherent variation of nutrients in the soil. This work assessed and mapped the spatial variability of some soil properties in a smallholder maize farm in Minna, north-central Nigeria, for site-specific soil nutrients management. The study was conducted on a 1.13 ha farm. The farm was divided into 9 subplots of 35 m x 35 m dimension. In each subplot, geo-referenced soil sample was collected at 0-20 cm depth for purpose of interpolation and mapping. The samples were analysed in the laboratory for particle size distribution, soil reaction (pH), soil organic carbon (SOC), total nitrogen (N), available phosphorus (P) and potassium (K). Data from laboratory analysis was subjected to descriptive statistics to describe the spatial variability of the nutrients in the soil. Mapping of spatial distribution of the measured parameters was based on point krigging interpolation techniques using Surfer 11 GIS software. Texture of the soils varied from sandy loam to sandy clay loam. Soil reaction was slightly acid to neutral. Nitrogen was high in all the soil, while K ranged from high to low. Phosphorus was low in all the soils. Soil organic carbon (CV = 51.17%), N (CV = 36.11%) and K (CV = 47.62%) all had a high spatial variability, while silt (CV = 27.72%) and P (CV = 27.50%) had moderate spatial. Spatial variability was low in land configuration (CV = 9.37%), sand (CV = 5.18%), clay (CV = 13.66%) and pH (CV = 1.64%). Micro-relief had non-significant (P = .05) effect on distribution of soil separates. Mapping could be helpful in partitioning of the farm into relatively uniform units to allow site-specific management of SOC, N and K with high spatial variability.