Horizon 1 1 17 ACL : Articles dans des revues avec comité de lecture répertoriées par l'AERES Journal of Soil Science and Plant Nutrition [12 p.] Biocarbon Phaseolus vulgaris Soil microbiome Organic amendments Co-occurrence networks Microbial diversity BRESIL 2026 fdi:010096330 ENG Journal of Soil Science and Plant Nutrition 0718-9508 ISI:001682315700001 10.1007/s42729-026-03005-1 https://www.documentation.ird.fr/hor/fdi:010096330 https://www.documentation.ird.fr/intranet/publi/2026-03/010096330.pdf [Early access] Horizon (IRD) Purpose This study evaluated how poultry manure-derived biochar influences the structure, diversity, and co-occurrence networks of soil bacterial communities in nutrient-poor tropical sandy soils. We examined the trade-off between improved soil fertility and potential simplification of microbial networks, testing the hypothesis that high biochar rates would enhance nutrient availability but reduce microbial complexity and diversity. Methods A field experiment was conducted over two years in sandy soils of northeastern Brazil, applying poultry biochar. We used six treatments: (a) control (no amendments), (b) low-rate biochar (Bio_10t = 10 t ha(-1)), (c) high-rate biochar (Bio_40t = 40 t ha(-1)), (d) chicken manure (E.Av = 5 t ha(-1)), (e) synthetic mineral fertilizer (Mineral = NPK), and (f) poultry manure (C.Av = 10 t ha(-1)). Soil chemical properties were assessed, and bacterial communities were analyzed using 16 S rRNA gene sequencing. Network analyses were performed using SparCC and NetCoMi, and multivariate statistics determined key environmental drivers. Results High biochar inputs increased organic C, P, and K levels, leading to a distinct shift in microbial community structure. However, this nutrient enrichment reduced amplicon sequence variants richness by 22.4% (from 3,250 to 2,521) and Shannon diversity by 3.6% (from 7.16 to 6.90) relative to the control. Network analysis showed substantial simplification of microbial interactions: the control treatment had 3,116 co-occurrence edges, which fell to 1,423 under low biochar (Bio_10t) and 1,849 under high biochar (Bio_40t)-reductions of 54% and 40%, respectively. Conclusions Our findings underscore a trade-off: while poultry biochar effectively enhances soil fertility, excessive application may disrupt microbial diversity and interaction networks, potentially compromising long-term soil resilience. These results highlight the need to optimize biochar rates to balance immediate fertility gains with preservation of microbial ecological stability in fragile sandy soils. [GRAPHICS] . 076 ; 068 ; 074 UR144 Brésil