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Changes in soil characteristics due to varying farming practices can modify the structure of bacterial communities. However, it remains uncertain whether bacterial groups that break down organic material are similarly impacted. We examined changes in the bacterial community by pyrosequencing the 16S rRNA gene when young maize plants, their neutral detergent fibre fraction, or urea were applied to an Australian Vertisol. This soil was managed with either conventional tillage with continuous cotton, minimum tillage with continuous cotton, or a wheat-cotton rotation. The soil organic carbon content was 1.4 times higher in the wheat-cotton rotation than in the conventional tillage with continuous cotton treatment. Approximately 41.6% of the organic carbon was added with maize plants, and 13.1% of the neutral detergent fibre fraction was mineralized after 28 days. The application of young maize plants and the neutral detergent fibre fraction significantly altered the bacterial community and the presumed metabolic functional structure, but urea did not. Many bacterial groups, such as Streptomyces, Nocardioides, and Kribbella, and presumed metabolic functions were enriched by the application of organic material, but less so by urea. We found that a limited number of bacterial groups and presumed metabolic functions were affected in an irrigated Vertisol by the different cotton farming systems, but many were strongly affected by the application of maize plants or its neutral detergent fibre.

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Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional (Cinvestav) Consejo Nacional de Humanidades, Ciencia y Tecnología (CONAHCyT) Centro Internacional de Mejoramiento de Maíz y Trigo (CIMMYT)