Comparative Advantage of Mucuna and Tithonia Residue Mulches for Improving Tropical Soil Fertility and Tomato Productivity

Aims: To evaluate the suitability of Mucuna cochinchinensis and Tithonia diversifolia residue mulches for improving tropical soil fertility and tomato productivity, by determining the residue quality and their effect on specific soil properties and crop yield. Methodology: Experimental plots were treated with inorganic and organic inputs (i.e. comprised a control with no input, mineral NPK fertilizer, residues of Mucuna and Tithonia, and mixture of Mucuna and Tithonia). Results: Soil available P increased from 81.3 to 148.3 mg/kg across treatments, with the highest for mineral fertilizer that differed from the plant residues and control, followed by the plant residuesthat differed from control (Tukey’s HSD, P = .05). Soil exchangeable K increased from 1.3 to 1.9 cmol/kg across treatments, with the highest recorded for plant residues and mineral fertilizer compared to the control (Tukey’s HSD, P = .05), and correlated with treatments (r = 0.51, P = .05). Soil organic C increased from 2.3 to 2.7% across treatments, with the highest recorded for plant residues compared to mineral fertilizer and control (Tukey’s HSD, P = .05), and positively correlated with treatments (r = 0.75, P = .05). Soil pH increased from 4.7 to 5.8, with the highest for mineral fertilizer that differed from the control (Tukey’s HSD, P = .05), and correlated with the soil available P (r = 0.72, P = .05). Tomato yield increased from 9.5 to 13.5 t ha-1 with the highest recorded for sole Tithonia and Mucuna+Tithonia, followed by sole Mucuna and mineral fertilizer as compared to the control, and correlated with soil organic C (r = 0.71, P = .05) and exchangeable K (r = 0.67, P = .05). Conclusion:Mucuna and Tithonia residue mulches are sustainable organic alternatives to improve tropical soil fertility, either singly or in combination, but Tithonia residue has a better impact on tomato productivity due to the higher content of exchangeable K.