Geostatistical Analysis of Soil Fertility Status in Part of Nigeria’s Dryland
Mohammed Ahmed, Juliana Aduku Nekeche and Amatullah Sadiq Yahaya
Keywords: Geostatistics, Semi-variogram, soil fertility, GIS
Majority of the farmers in the drylands of Northern Nigeria cultivates small pieces of land that are < 2ha, with different soil management practices coupled with low distribution of soil fertility has not been documented at global scale. The main objective of this study is to assess the spatial distribution soil fertility using geostatistical approach. Soil samples were taken for pH, organic carbon, nitrogen, phosphorous and potassium at 11 random locations at the depth of 0 – 20cm with the help of a GPS. The soil was analyzed in the soil lab and the result were imputed into GIS environment for the spatial distribution using semivariogram and co-kriging. The result shows that there are low concentration of N, P, and K at the northern part while OC at the southeastern part of the area, however the distribution of pH indicated an opposite or negative distribution compared with the other parameters. The result of the semi-variogram, for Nitrogen, Phosphorus, Potassium, Organic carbon and pH indicated that Gaussian, Circular, Exponential, Tetrasphericals and Stable respectively. The spatial dependency for N, P, OC and Soil pH are showing weak dependency but K indicating a strong spatial dependency. This implies that N, P, OC and pH are all affected with management practices such as tilling, harrowing, nature of cropping which includes mixed cropping and fertilizer application. The study concluded that the use of geostatistics can be applied within the larger scale which can give a guide for fertilizer application and recommended for site specific nutrient analysis.