Sewage Sludge Biochar Improves Water Use Efficiency and Bean Yield in a Small-Scale Field Experiment with Different Doses on Sandy Soil Under Semiarid Conditions
2025
Raví Emanoel de Melo | Vanilson Pedro da Silva | Diogo Paes da Costa | Maria Fernanda de A. Tenório Alves | Márcio Henrique Leal Lopes | Eline Dias Barbosa | José Henrique de Souza Júnior | Argemiro Pereira Martins Filho | Gustavo Pereira Duda | Antonio Celso Dantas Antonino | Maria Camila de Barros Silva | Claude Hammecker | José Romualdo de Sousa Lima | Érika Valente de Medeiros
Soil degradation and water scarcity pose major challenges to sustainable agriculture in semiarid regions, requiring innovative strategies to enhance water use efficiency (WUE) and soil fertility. This study assessed the effects of sewage sludge biochar (SSB) on soil properties, WUE, and common bean yield through a small-scale controlled field experiment under rainfed conditions in Northeast Brazil. Four SSB application rates (5, 10, 20, and 40 t ha<sup>−1</sup>) were compared with conventional NPK fertilization, treated sewage sludge (SS), and chicken manure (CM). The application of 20 t ha<sup>−1</sup> (B20) significantly improved soil organic carbon, nitrogen content, water retention, and microbial biomass. B20 also increased WUE by 148% and grain yield by 146% relative to NPK, while maintaining safe levels of potentially toxic elements (PTE) in bean grains. Although 40 t ha<sup>−1</sup> (B40) enhanced soil fertility further, it posed a risk of PTE accumulation, reinforcing the advantage of B20 as an optimal and safe dose. These results highlight the potential of SSB to replace or complement conventional fertilizers, especially in sandy soils with limited water retention. The study supports SSB application as a sustainable soil management practice that aligns with circular economy principles, offering a viable solution for improving productivity and environmental resilience in semiarid agriculture.
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