Efficacy of Tithonia diversifolia and NPK fertilizers on papaya seedling growth in marginal soils

The utilization of marginal soils, particularly peat (Histosol) and Ultisol, presents challenges due to low fertility and unfavorable physical and chemical characteristics. This study evaluates the efficacy of liquid organic fertilizer derived from Tithonia diversifolia (wild sunflower) and compound NPK fertilizer (with a ratio 16:16:16) in stimulating the growth of papaya (Carica papaya L.) seedlings in tropical marginal soils. The soil samples were collected from agricultural lands in Riau Province, Indonesia, where both peat and Ultisol soils are dominant and commonly used for farming. A factorial experiment was conducted using a split-split plot design with two factors: T. diversifolia liquid fertilizer (0, 100, and 200 mL L-1) and NPK fertilizer (0, 1.5, and 3 g per polybag), applied to both peat and Ultisol soils. Each treatment combination was replicated three times in an open-field setting, with three seedlings grown in individual polybags per replicate. Significant interaction effects between T. diversifolia liquid fertilizer and NPK were observed on growth parameters, including plant height, stem diameter, leaf number, and leaf length. The combination of 200 mL L-1 T. diversifolia liquid fertilizer and 3 g per polybag of NPK resulted in the highest growth across both soil types. Peat soil showed comparatively better growth performance, attributed to higher water retention and organic matter content. These findings provide empirical evidence supporting the use of integrated organic and chemical fertilizers to enhance papaya seedling growth in low-fertility tropical soils.