Acacia decurrens-based rotational agroforestry improves soil properties and promotes sustainable land management in Northwestern Ethiopia

Soil degradation from erosion and nutrient depletion threatens agricultural sustainability in the Northwestern Ethiopian highlands, undermining global efforts toward sustainable development. Agroforestry systems, particularly those integrating Acacia decurrens under rotational and long-term management, offer a promising strategy for restoring soil fertility. Although A. decurrens–cereal rotational agroforestry is expanding rapidly, its effects on soil properties across depths and its legacy on cereal crops remain poorly quantified. This study, conducted in Ethiopia’s Ankesha District, evaluated soil changes under A. decurrens rotations to provide context-specific evidence for sustainable land management. A blocked mensurative design compared three land-use systems: cropland without A. decurrens; cropland two years post-A. decurrens harvest (rotational agroforestry with legacy effects); and farmland under A. decurrens cultivation for ≥ 10 years, across two soil depths (0–20 cm and 20–40 cm). A total of 18 composite samples were collected from the three treatments and two soil depths, replicated three times. Soils under A. decurrens cultivation exhibited markedly improved physical and chemical properties compared to cropland without A. decurrens. Acacia decurrens–based rotational agroforestry significantly improved overall soil physical and chemical quality compared to conventional cropland. Bulk density decreased (1.10 vs. 1.57 g cm− 3), while porosity (58.6% vs. 40.8%) and moisture (25.5% vs. 11.2%) increased (all p = 0.001). Soil fertility was also markedly enhanced, with higher soil organic carbon (4.05% vs. 0.94%), total nitrogen (0.39% vs. 0.10%), cation exchange capacity (20.5 vs. 13.7 cmol(+) kg− 1), and pH (6.18 vs. 4.25) (p = 0.001). Crop land two years post-harvest retained intermediate values, indicating a positive legacy effect. Soil organic carbon was strongly positively correlated with soil moisture (r = 0.89), pH (r = 0.80), and cation exchange capacity (r = 0.81), and negatively correlated with bulk density (r = − 0.92). This study showed that A. decurrens–based rotational agroforestry restores soil health and delivers lasting benefits for sustainable cereal production in the northwestern Ethiopian highlands. Its integration into soil conservation strategies can help reduce land degradation and improve food security.