Effect of Green Biomass from Tithonia diversifolia and Chromolaena odorata on the Growth and Yield of Broccoli in the Haut-Sassandra Region, Côte d’Ivoire

Abstract

Soil degradation and declining fertility are major constraints to vegetable production, particularly in the Haut-Sassandra region. This study evaluated the effects of green biomasses of Tithonia diversiflora and Chromolaena odorata on the growth of broccoli (Brassica oleracea var. italica). The experiment was conducted using a randomised complete block design with four replications and four treatments: Tithonia diversiflora alone, Chromolaena odorata alone, their combination, and an unfertilised control. Observations focused on plant height, stem circumference, leaf number, leaf length and width, and soil chemical properties. Results showed that the application of green biomasses enhanced vegetative growth and improved soil organic matter, cation exchange capacity, and exchangeable bases. Plants fertilised with Tithonia diversiflora or Chromolaena odorata individually performed better than the control, while their combination did not exhibit a marked synergistic effect. Fertilised treatments exhibited significantly greater growth than the control (p < 0.05), with no notable differences between T1, T2, and T3. This trend intensified until the eighth week, when the control remained significantly lower (p = 0.001). These findings indicate that the use of these biomasses is a promising organic fertilisation strategy for sustaining soil productivity and promoting sustainable agriculture. It can help to reduce production costs, limit dependency on chemical inputs, and preserve long-term soil fertility.