Fertility Status of Selected Soils in the Sudan Savanna Biome of Northern Nigeria

Sustainable crop production in the Nigerian Sudan Savanna biome requires a good understanding of the fertility status of the soil in order to impose appropriate nutrient management strategies. Field surveys were conducted to assess the fertility status of selected soils from Shanono and Bunkure Local Government Areas (LGAs) of Kano State in the Northern Nigerian Sudan Savanna. All the surveyed fields had soil organic C, total N and ECEC within very low and low fertility classes. Very low and low available P was also found in the majority of fields with only 25.0 and 8.7% of the fields falling in the moderate P fertility range in Shanono and Bunkure LGA respectively. About 75.0% of fields in Shanono LGA and 39.1% in Bunkure LGA fell within the low exchangeable K class, with the rest of the fields having moderate level. Despite moderate to high content of exchangeable Ca and Mg in most of the fields, 4.3-8.7% of the fields had depleted status of the two basic cations. Micronutrients (Zn, Cu, Mn and Fe) levels in all the fields were in the moderate and high classes, except the subsurface soil of Shanono LGA where 4.2% of the fields had low Cu contents. Correlation analysis between northerly latitude and soil properties showed a northward increase in sand, pH and Zn levels and a decrease in silt and available Fe levels. The low status of Ca, Mg and Cu in some of the fields indicates the insufficiency of the current fertilizer recommendations which focus mainly on primary macronutrients (N, P and K). Therefore, apart from recommending all strategies that will enhance and stabilize organic matter, current fertilizer recommendations need to be reviewed and should contain other nutrients in addition to primary macronutrients.