Long-term effects of soil and water conservation practices on soil fertility and crop productivity in the Ethiopian Highlands

Abstract

Land degradation and declining soil fertility remain major constraints to agricultural productivity in the Ethiopian Highlands. Yet, evidence on the long-term effectiveness of soil and water conservation (SWC) interventions across contrasting farming systems remains limited. This study integrated two decades of land restoration records, multi-temporal NDVI data (2003–2024), and field measurements from 56 watersheds to assess the long-term effects of SWC interventions on soil properties, vegetation recovery, and crop productivity across four major farming systems in the Ethiopian Highlands. A paired watershed matched-control design compared SWC-treated and adjacent untreated watersheds using 672 composite soil samples. Results show that land restoration interventions significantly improved soil quality − increasing soil moisture content from 16.65% to 20.92%, soil organic carbon from 1.71% to 3.08%, total nitrogen from 0.13% to 0.27%, and cation exchange capacity from 11.83 to 33.51 cmol(+) kg⁻¹, while reducing bulk density from 1.26 to 1.17 g cm⁻³. Average grain yields increased by approximately 56% for maize and 50% for wheat, with soil bunds producing the strongest maize response and fanya juu terraces generating the largest wheat gains. NDVI increased by 22.6%, from 2003 to 2024, indicating substantial landscape-scale vegetation recovery consistent with field-based evidence of improved soil fertility and crop productivity. Overall, the results provide robust highland-scale evidence that long-term SWC interventions can simultaneously restore soil functions, enhance vegetation recovery, and sustain crop productivity across diverse farming systems of the Ethiopian Highlands, although the magnitude of soil, vegetation, and yield responses varied across farming systems.