Mapping the essential soil nutrients status of smallholder farmers fields in the Wolaita area, southern Ethiopia

Abstract

Soil properties can vary significantly within farmland or across landscapes due to a combination of physical, chemical, and biological processes. It is essential to understand this spatial variation to effectively manage soil nutrients and enhance crop yield sustainably. Thus, the purpose of this study was to investigate the spatial variability of essential plant nutrients in agricultural lands in Wolaita Zone, southern Ethiopia. A total of 789 soil samples were collected and analysed for macro- and micronutrients. Soil samples were analysed to determine the content of macronutrients [total nitrogen (TN), available phosphorous (P), sulphur (S), and calcium (Ca)] and micronutrients [boron (B), copper (Cu), iron (Fe), zinc (Zn), and manganese (Mn)]. The measured data were first subjected to descriptive statistics, and the digital soil map (DSM) that shows spatial variability was generated after geostatistical analysis. The result showed that there was low [S, Mn], moderate [TN], and high [P] variability in the nutrient concentrations among fields. The nutrient concentration varied between 0.02-0.47% (TN), 0.78-26.22 mg kg-1 (P), 6.45-17.50 mg kg-1 (S), 0.05-1.83 mg kg-1 (B), and 0.05-2.64 mg kg-1 (Cu). The contents of TN, P, S, B, and Cu were low. The DSM further exhibited the wide-ranging spatial variability structures in which, from the total area, 64.8% (TN), 100% (P), 100% (S), and 98% (both B and Cu) have indicated low status. In addition, Mg-induced K deficiency on 68% of studied area was suspected. Based on these findings, it is recommended that site-specific nutrient management practices be implemented on smallholder farms, and the nutrient requirements of major crops should be calibrated accordingly.