The agricultural system that incorporates eucalyptus is used by 75% of the agricultural producers in the east of DR Congo (Walungu and Kabare). However, the latter’s perception and results from some studies on the effect of eucalyptus exploitation on soil quality bring out a negative balance. This study characterized the state of soils by determining the soil quality index (SQI) in three land-use types to guide soil fertility management policies. A survey was conducted to collect preliminary data on the historical effect of eucalyptus on the soil from 300 producers. Subsequently, the soils were sampled in the three land-use types and analyzed to assess SQI through a statistical approach based on principal component analysis (PCA). Using R 4.05 package software and crop exploitation as the baseline, the three land-use types were compared using analysis of variance. Out of the 13 considered crucial for SQI assessment, findings highlighted nine soil quality indicators (Al3+, pH, silt, SOC, CEC, H2O, sand, clay, and BD). Soils with eucalyptus (SQI = 0.486 0.07) and crops (0.539 ± 0.034) alone had low SQIs, suggesting unfavorable soils for better production, whereas soils with crop-eucalyptus association had SQI equals to 0.655 ± 0.034, indicating moderate soils. The calculated SQI highlighted soils’ acidity, their ability to maintain plants’ chemical nutrients equilibrium, and clay and sand content as soil quality determinants. To further improve soil conditions, we raised the need to understand the long-term effects of eucalyptus on soils and the appropriate soil management as a result of the aforesaid results.

Background: Soil fertility provides the basis for agricultural productivity and food security, but conventional laboratory analyses remain inaccessible to smallholder farmers in sub-Saharan Africa. In the eastern Democratic Republic of the Congo, farmers rely on locally derived indicators such as weed communities, soil color, crops productivity, and erosion, but their validity remains underexplored. Objective: This study assessed the reliability of farmer-identified soil fertility indicators and examined how they align with laboratory-based measurements, with the goal of integrating local knowledge into practical fertility assessments in Lurhala and Kamisimbi, during Season A 2019 and Season A 2023, corresponding to the main cropping period (September–January) in South Kivu. Methods: On 148 plots, we combined farmer surveys, weed inventories and soil analyses including pH, nitrogen (N), phosphorus (P), potassium (K), and organic matter (OM). We constructed a composite Soil Fertility Index (SFI), computed Bray–Curtis (BC) similarities and trained decision-tree classifiers (0.7:0.3 split). Results: Twenty-eight weed species were recorded; Bidens pilosa , Conyza sumantrensis , and Galinsoga ciliata associated with higher fertility, while Imperata cylindrica and Hyparrhenia rufa marked degraded plots. Laboratory means for high-fertility soils were pH = 6.1 ± 0.6, OM = 3.9 ± 1.5% and K = 1.9 ± 0.5 cmol kg ⁻¹ ; low-fertility soils averaged pH = 4.8 ± 0.2, OM = 3.0 ± 1.2% and K = 0.8 ± 0.3 cmol kg ⁻¹ . Overall SFI = 0.514 ± 0.097 (low = 0.341 ± 0.073; medium = 0.537 ± 0.10; high = 0.526 ± 0.086), clearly indicating general degradation and limited separation of farmers’ medium and high classes. Decision trees ranked soil color (53.8%) and weed species (51.6%) highest indicators; model accuracies ranged from 79.7 to 93.2% (overall 82.4%), area under the ROC curve (AUC): 0.96–0.99, indicating reliable relationships between standard and local knowledge. Phosphorus content was unexpectedly higher in farmer-classified low-fertility plots, highlighting complex nutrient dynamics incorporated into farmers’ holistic assessments. Conclusion: Farmer-derived indicators offer cost-effective, context-specific diagnostics but struggle to resolve subtle fertility gradients. We argue that the way forward lies not in choosing one knowledge system over the other, but in forging a synergistic partnership between them.

Cassava mosaic disease (CMD) and cassava brown streak disease (CBSD) are the two main viral diseases threatening cassava production in the Democratic Republic of the Congo (DRC). CMD can be effectively controlled using resistant varieties; however, currently, there are no cassava varieties that exhibit durable resistance to CBSD. As the deleterious effects of CBSD become more pronounced with the maturity of the cassava, we assessed the potential benefits of early harvesting on mitigating the impact of CBSD on the performance of two improved CMD-resistant cassava varieties, Nabana (MM 96/4653) and Sawasawa (MM 96/3920). The percentage yield reduction was calculated by comparing the yield of infected treatments to that of uninfected treatments. At 9 months after planting (MAP) and 12 MAP, overall fresh root yield from farmer-selected healthy planting material of varieties Nabana and Sawasawa was significantly higher than the yield of crops established using CBSD-infected cuttings of the same varieties. Fresh root yield losses due to CBSD for Nabana were 44% at 9 MAP and 86% at 12 MAP, while for Sawasawa, they were 40% at 9 MAP and 72% at 12 MAP. Healthy planting material of the two varieties yielded 5% more at 12 MAP than at 9 MAP, while infected planting material yielded 52.5% less at 12 MAP than at 9 MAP. These results highlight the benefits of using healthy planting material in conjunction with early harvesting to minimize losses among CBSD-susceptible cassava varieties. These results suggest the need for a robust seed system that can deliver disease-free planting material of market-preferred varieties to farmers, thereby promoting food security.