Abstract
The shortage of land resources restricts the sustainable development of agricultural production. Multiple cropping has been widely used in Southern China, but whether the continuous planting will cause a decline in soil quality and crop yield is unclear. To test whether multiple cropping could increase grain yield, we investigated the farmlands with different cultivation years (10–20 years, 20–40 years, and >40 years). Results showed that tobacco-rice multiple cropping rotation significantly increased soil pH, nitrogen nutrient content, and grain yield, and it increased the richness of the bacterial community. The farmland with 20–40 years of cultivation has the highest soil organic carbon (SOC), ammonium nitrogen, and grain yield, but there is no significant difference in the diversity and structure of the bacterial community in farmlands with different cultivation years. The molecular ecological network indicated that the stability of the bacterial community decreased across the cultivation years, which may result in a decline of farmland yields in multiple cropping system> 40 years. The Acidobacteria members as the keystone taxa (Zi ≥ 2.5 or Pi ≥ 0.62) appeared in the tobacco-rice multiple cropping rotation farmlands, and the highest abundance of Acidobacteria was found in the farmland with the highest SOC and ammonium nitrogen content, suggesting Acidobacteria Gp4, GP7, GP12, and GP17 are important taxa involved in the soil carbon and nitrogen cycle. Therefore, in this study, the multiple cropping systems for 20 years will not reduce the crop production potential, but they cannot last for more than 40 years. This study provides insights for ensuring soil quality and enhancing sustainable agricultural production capacity.
Highlights
The multiple cropping system increases crop diversity, makes full use of limited soil resources, to a certain extent alleviates the shortage of cultivated land resources in agricultural production, and guarantees food security (Yang et al, 2015; Xu et al, 2019b)
Compared with rice monoculture farmland, a higher abundance of the soil bacterial community was observed in tobacco-rice multiple cropping rotation farmlands, but there is no significant difference in the alpha diversity of soil bacterial community in tobacco-rice multiple cropping rotation farmlands with different cultivation years
The two main axes of principal component analysis (PCA) explained 72.08% of the variation, indicating that it can better represent the characteristics of microbial community composition, of which 61.61% of the variation is explained by PC1, and 10.47% of the variation is explained by PC2
Summary
The multiple cropping system increases crop diversity, makes full use of limited soil resources, to a certain extent alleviates the shortage of cultivated land resources in agricultural production, and guarantees food security (Yang et al, 2015; Xu et al, 2019b). Tobacco-rice multiple cropping rotation, that is, planting tobacco in spring and rice in autumn on the same farmland, is one of the main double-cropping systems in southern China (Hu et al, 2021). It ensures crop security production and improves the income of farmers and effectively alleviates the social problems of rural laborers moving to cities and no production activities in cultivated land due to insufficient income (Xu et al, 2019a). Increasing cultivation years changed the structure and diversity of soil bacterial and fungal communities in farmland, and the longterm fertilization increased soil organic carbon (SOC) storage and macroaggregate content (Zhang et al, 2019; Li et al, 2020), but these studies focused on farmland whose cultivation years generally spanned about 20 years, and there were fewer studies on the changing trends of soil bacterial community in multiple cropping farmlands with more than 40 years of cultivation
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