Waterleaf (Talinum triangulare), like many other leafy vegetable is cultivated in home gardens to improve nutritional quality for the family and may provide additional income for female farmers. However, the role of Talinum cultivation is often counteracted by declining soil fertility. In recent years, biochar (pyrolysed biomass) has gained importance as a soil amendment tool. However, not much attention has been focused on the influence of biochar on soil quality and plant growth in the humid tropics. This study was conducted to assess different locally available crop waste residues as possible sources of biochar for home garden or small-scale production units of leafy vegetable using Talinum as proxy on highly weathered acid soils in the humid tropics. The experimental set-up was a pot experiment in a complete randomized design in five replicates using biochar sources from cassava stems, rice husk, corncob and sawdust. The results obtained showed that biochar samples had a high cation exchange capacity (CEC), total nitrogen, total carbon and pH (7.8 to 10.8), as compared to the no-input soil (pH 5.7). It is evident that adding biochar to poor and acidic soils could possibly increase the pH and reduce lime requirements. Positive and significant response of biochar (P<0.05) application were also observed with the growth, nutrient uptake, and yield of waterleaf. Biochar produced from rice husks obtained the best response followed by sawdust, cassava and corncob. Similarly, the C and N uptake of waterleaf was generally higher with rice husk biochar use as compared to the other treatments. This study has demonstrated that biochar production could be useful in valorizing crop waste residues and biochar use is likely to enhance the productivity of leafy vegetables. More research on possible combination of biochar and other farming strategies such as the application of animal manure and mineral fertilizer to maximize Talinum production should be encouraged.
Key words: Biochar, cassava stems, crop waste, residues, nitrogen, soil pH, Talinum.
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