Mechanisms of tobacco yield enhancement in winter crop-tobacco rotations: Enhancing soil aggregate stability, organic carbon content, and microbial diversity

Winter crop-tobacco ( Nicotiana tabacum L.) rotation (WCTR) is vital for sustainable mountain agriculture, promoting carbon (C) nutrient cycling, enhancing soil structural stability, and increasing microbial diversity. However, the effects of winter barley ( Hordeum vulgare L.) and pea ( Pisum sativum L.) rotations with tobacco on soil physicochemical properties, soil microbial community structure, and their synergistic impact on soil quality and tobacco yield are not well understood. Therefore, this study examined winter fallow field and continuous cropping tobacco (T), barley-tobacco rotation (BT), and pea-tobacco rotation (PT) over two consecutive years in a mid-term (more than 5 years) field experiment in mountain agriculture. Water-stable aggregate stability, chemical and biological properties, tobacco root structure development, and economic characteristics were measured. WCTR significantly reduced soil bulk density, increased water holding capacity of a field, enhanced aggregate stability, and boost soil C nutrient accumulation. Over a two-year period, it increased the macroscopic aggregate content (R 0.25 ) by 7.82–24.06 %, geometric mean diameter by 9.66–32.42 %, and mean weight diameter by 49.76–120.36 %. Furthermore, the content of soil organic carbon (SOC) increased by 24.16–53.93 %, and the activity of C-acquiring enzyme increased by 3.11–10.47 %. Simultaneously, the soil bulk density decreased by 7.94–26.06 %. WCTR stimulated the development of microbial communities dominated by Actinobacteria and Basidiomycota , creating a more complex microbial molecular ecological network. Chloroflexi microbial communities were more prevalent in PT. WCTR notably increased carbohydrate metabolism, glycan biosynthesis and metabolism, metabolism of terpenoids and polyketides. Concurrently, WCTR facilitated the development of tobacco root structures, resulting in increased tobacco yield (21.24–24.48 %) and economic value (28.65–29.40 %). Comparatively, PT outperformed BT in maintaining tobacco yield and economic value during mid-term rotational cycles. The redundancy analysis and Mantel test revealed that the abundances of Actinobacteria and Basidiomycota drive R 0.25 , SOC, as well as tobacco root biomass and yield, with R 0.25 and SOC mediating these effects. Additionally, partial least squares path modeling revealed that soil microbial diversity enhanced tobacco root structure development and tobacco productivity. Additionally, PT improved soil aggregate stability, SOC content, and microbial diversity compared to BT. In summary, PT emerges as a sustainable agroecological practice in mountain agroecosystems, and highlights the crucial role of soil aggregate stability, SOC content, and soil microbial diversity in enhancing tobacco productivity. • Winter crops-tobacco rotation (WCTR) enhances the water stability of soil aggregates. • WCTR boosts soil fertility and tobacco productivity by facilitating carbon cycling. • Actinobacteria and Basidiomycota are crucial for effective carbon cycling. • Peas are a more effective rotation crop for tobacco than beer barley.