Exploring the variability of soil properties as influenced by land use and management practices: A case study in the Upper Blue Nile basin, Ethiopia

The knowledge of how soil properties vary over space and time is essential to better understand the potential of soils and their sensitivity to management interventions under different local conditions. The objective of this study was to analyze the variation in key soil properties as influenced by different land use types (cropland, grazing land, and bushland) and sustainable land management (SLM) practices (soil bund reinforced with grass, and fanya juu for croplands, and exclosures with and without trenches for grazing and bushlands) in the three contrasting agro-ecological zones of the drought-prone Upper Blue Nile basin, Ethiopia. Nine soil properties-texture, bulk density (BD), pH, electrical conductivity (EC), cation exchange capacity (CEC), total nitrogen (TN), soil organic carbon (SOC), available phosphorus (P-av), and available potassium (K-av)-were measured for topsoil (0-20 cm) samples collected from experimental plots established for monitoring runoff and soil loss rates. The results showed that seven of the nine studied soil properties significantly differed among the three land use types in the three agro-ecological zones (P< 0.05 to P< 0.001); pH, CEC, SOC, and TN values were generally lower in croplands than in others. These results imply that soil quality under crop production has been greatly deteriorated by unsustainable cropping systems practiced over centuries. Three years after the implementation of SLM practices, however, most soil parameters become within optimal ranges for supporting plant production. More particularly, sensitive soil properties (BD, SOC, TN, P-av, and K-av) showed remarkable improvement in plots where soil bunds reinforced with grass and exclosures were implemented. This improvement was primarily associated with the development of well-established vegetation cover owing to the favorable natural conditions maintained by fencing of plots and minimum tillage. These results therefore indicate that soil degradation can best be controlled through enhancing vegetation growth and reducing soil disturbance by tillage operations. We conclude that integrating land uses with suitable SLM practices is the most effective way to maintain and restore soil quality and sustain ecosystem functioning.