Combining Charcoal Application and Tithonia diversifolia-Based Agroforestry to Achieve Sustainable Maize Production on Smallholder Farms in Kinshasa, DR Congo

Improving soil fertility in the context of climate change is of paramount importance. This study addresses this challenge in Kinshasa (DR Congo) where the combined effect of charcoal waste and Tithonia diversifolia biomass was evaluated in an alley cropping trial, with two successive maize crops. The objective was to sustain optimum maize yields, and to derive insights into sub-Saharan Africa (SSA). Three treatments were applied: a control (T0) plots; and two other plots receiving 5 t ha-1 of charcoal prior to cultivation combined with alley cropping using T. diversifolia pruned in situ at 50 cm (T1) or at 100 cm (T2)) and applied as mulch. The results showed that Tithonia biomass production reached approximately 100 t DM ha-1 year-1. Maize grain yields in the first season were higher in the amended plots (2.7 to 2.9 t ha-1) compared to the control (1.6 t ha-1). The yields obtained in the second season were similar for all plots, but they declined significantly for T0 compared to the first season. While yields stabilized with amendments, they stayed below SSA self-sufficiency targets (4.45 t ha-1). Improving crop N absorption and use efficiency, which were low in this study, is key to closing the yield gap.