The influence of rice husk biochar, compost, and their mixture on maize yields and soil organic carbon content in southern Togo

Abstract

Soil fertility decline is the basis of crop yield reduction, especially in sub-Saharan Africa where ensuring food security is one of the greatest challenges. Biochar application could be an option to alleviate this decline, also improving soil organic carbon content (SOC) which is a major goal for resilient agricultural systems under changing climate. This study aimed to understand the effect of biochar applied alone or in combination with compost and mineral fertilizers in synergistic way on SOC and maize productivity. From 2022 to 2024, a two-year field experiment over three growing seasons was conducted in a coastal agroecological zone of southern Togo. The experimental design was arranged in a split-split plot design with three factors: (1) Application of compost (no compost = C0 and 10 t ha⁻¹ = C1), (2) Application of mineral fertilizer (no mineral fertilizer = F0 and half of the recommended rate in the country = F1), (3) Application rates of biochar (0 t ha⁻¹ = B0, 10 t ha⁻¹ = B10, and 20 t ha⁻¹ = B20). A linear mixed-effects model was applied for statistical data analysis. A correlation analysis between, on the one hand, maize yield and yield components and SOC and total nitrogen, on the other hand, was carried out for the second and third growing seasons to understand the interrelation between maize yield and soil properties. The application of 20 t ha⁻¹ of biochar (B20) significantly increased SOC concentration by 2.20 g kg⁻¹. Meanwhile, B10 and C1 did not significantly influence SOC. The effect on soil total nitrogen from different treatments was not significant. Grain yield increased significantly with biochar application at a rate of 20 t ha⁻¹ during the second season, while the positive effect was marginal in the third growing season. The mineral fertilizers showed a significant effect for all three seasons thanks to their immediate response. Our study concluded that applying biochar at a rate of 20 t ha⁻¹, with re-application after one year, can significantly enhance maize yield. This approach may also contribute to mitigating the impact of climate change on agriculture. Biochar can be crucial in building the resilience of maize production to effectively address the decline in soil quality. Although biochar alone in a reasonable rate improved soil carbon and yield in later seasons, its combination with compost and mineral fertilizers did not lead to significant interactive effects under the conditions of this study, suggesting that further research is needed to assess the context-dependent benefits of integrated soil amendments.