Agro-economic Evaluation of Lime and Tithonia diversifolia Biomass for Reducing Empty Pods in Groundnut on Acidic Ferralsols of Kenge, DRC

This study investigated the effects of lime and Tithonia diversifolia leaf biomass on the reduction of empty pods in groundnut (Arachis hypogaea L.) grown on acidic sandy soils in the grassland savanna of Kenge, Democratic Republic of Congo. A 2 × 3 factorial split-plot design with three replicates was used. Factor 1 consisted of two groundnut varieties (Local and G17), and factor 2 included soil amendments: lime, T. diversifolia leaves, and an untreated control. The experiment was conducted at the Faculty of Agronomic and Environmental Sciences, University of Kwango (4°50’10.4’’ S, 17°01’23.8’’ E; 532 m a.s.l.). Results showed significant differences among treatments for dry pod yield, number of empty pods, 1000-seed weight, and dry seed yield. Dry pod yields were 4.0 t·ha⁻¹ with lime, 3.8 t·ha⁻¹ in the control, and 3.6 t·ha⁻¹ with Tithonia amendment (LSD₀.₀₅ = 0.66 t·ha⁻¹, P = 0.01, CV = 15.7%). Dry seed yields ranged from 2.4 t·ha⁻¹ to 2.5 t·ha⁻¹, with 2.5 t·ha⁻¹ for lime, and 2.4 t·ha⁻¹ for both control and Tithonia (LSD₀.₀₅ = 0.67 t·ha⁻¹, P = 0.05, CV = 23.9%). Empty pod formation averaged 5 pods per plant in the control, 0.5 with lime, and 3 with Tithonia (LSD₀.₀₅ = 0.33, P = 0.01, CV = 0.78). Economic analysis based on the marginal rate of return (MRR) and cost–benefit ratio (CBR) confirmed the advantage of lime application, with MRR values of 2.31 for the Local variety and 0.61 for G17, both exceeding the conventional adoption threshold of 0.5. Likewise, the cost–benefit ratio was most favorable for agricultural lime application in the Local variety, with a CBR equal to or greater than 1, demonstrating its economic viability. These findings clearly indicate that lime application not only reduces empty pod formation and increases groundnut yield but also provides a profitable return on investment, thereby supporting its recommendation for farmers cultivating groundnuts on acidic sandy soils.