Phosphorus Fractionation and Soil Properties across Smallholder Land Uses in the South Ethiopia Regional State

Soil fertility decline and land degradation pose significant challenges to agricultural production and food security for smallholder farmers in South Ethiopia. The widespread deficiency and limited plant availability of phosphorus (P), often locked in less available forms despite its presence. This study aimed to examine P fractionation characteristics across different land uses, encompassing home gardens, forage land, grazing land, cropland, and woodlot in Wolaita Zone, South Ethiopia regional state. Soil samples were collected from two depths (0-20 cm and 20-40 cm) and analyzed for physicochemical properties and P fractions using the modified Hedley sequential method. The result indicated that the home gardens exhibited the highest pH, soil organic carbon (SOC), total nitrogen (TN), available phosphorus (AP), exchangeable bases (Ca, K, Na), and cation exchange capacity (CEC) across both soil depths. These higher values are attributed to intensive management, continuous organic amendment application, and diverse plant species. The analysis of soil P fractions revealed that home gardens had the highest labile P, while cropland showed higher NaOH-Pi and residual P. The Corg:Po ratio indicated the highest values in grazing lands, suggesting potential P immobilization, and the lowest in croplands, potentially favouring mineralization. Total inorganic P (TPi) was highest in home gardens, supporting enhanced mineralization, whereas total organic P (TPo) showed significant variation influenced by management. The soil pH, SOC, TN, AP, Ca⁺², and K⁺ were positively significant with the various P fractions, while exchangeable acidity showed an inverse relationship. Thus, home gardens demonstrated enhanced P availability and better soil fertility. The findings indicate the critical need for site-specific nutrient management strategies to optimize phosphorus use efficiency, improve soil health, and enhance agricultural sustainability in South Ethiopia.