Flue-cured tobacco (Nicotiana tabacum L.) is a major cash crop in Yunnan, China, and the yield, chemical components, and their proportions decide the quality of tobacco leaves. To understand the effects of environmental factors (soil and climatic factors) on the yield and quality of flue-cured tobacco and determine the main regulating factors, we selected three flue-cured tobacco cultivars [K326, Yunyan87 (Yun87), and Honghuadajinyuan (Hongda)] grown in the Honghe Tobacco Zone. Indices related to yield and economic traits, chemical component properties, soil physical and chemical properties, and climatic factors at different planting sites, were evaluated. We used variance analysis, correlation analysis, and redundancy analysis (RDA) in this study. The results showed that the yield and chemical component properties of flue-cured tobacco, except for the number of left leaves and plant total sugar (PTS) content, were significantly correlated with climatic factors. Particularly, the yield increased in drier and sunnier weather. In terms of the carbon supply capacity, PTS, petroleum ether (PPE), and starch contents (PS) were higher under high-altitude and high-latitude climatic conditions, whereas for the nitrogen supply capacity, plant nitrogen (PTN) and nicotine (PN) contents improved under low-altitude and low-latitude climatic conditions. PTS, reducing sugar (PRS), potassium (PTK), chlorine (PCL), and PPE contents were negatively related to soil clay content, soil pH, and soil organic matter, whereas PRS and PTK contents were positively correlated with alkali-hydrolyzed nitrogen (AN). According to RDA, the soil clay, AN, available phosphorus (AP), and soil chlorine content (SCL) strongly affected the quality of flue-cured tobacco. The quality of the K326 and Yun87 cultivars was mostly influenced by moisture, whereas the quality of the Hongda cultivar was mostly affected by temperature. In conclusion, compared with soil properties, climatic factors more significantly affect the yield and quality of Honghe flue-cured tobacco leaves.

Fertilization can be optimized and managed during the flue-cured tobacco growing period by studying the response of soil and microbial biomass stoichiometric characteristics to fertilization. In this study, we investigated the effect of compound fertilizers combined with microbial fertilizer treatments on the stoichiometric characteristics of the rhizosphere soil and the limitations of microbial resources during the flue-cured tobacco growing period. The results indicated that soil and microbial C:N:P varied greatly with the growing period. The effect of sampling time was usually greater than that of fertilization treatment, and microbial C:N:P did not vary with the soil resource stoichiometric ratio. The microbial metabolism of the tobacco-growing soil was limited by phosphorus after extending the growing period, and phosphorus limitation gradually increased from the root extension to the maturation periods but decreased at harvest. The rhizosphere soil microbial nitrogen and phosphorus limitations were mainly affected by soil water content, soil pH, microbial biomass carbon, and the ratio of microbial biomass carbon to microbial biomass phosphorus. Applying microbial fertilizer reduced phosphorus limitation. Therefore, applying microbial fertilizer regulated the limitation of microbial resources by affecting the soil and microbial biomass C:N:P in flue-cured tobacco rhizosphere soils.

A good soil environment helps to ensure the healthy growth of flue-cured tobacco plants, and the nutrients therein profoundly affect the sustainable development of planted tobacco resources. In exploring the spatial variability characteristics of soil nutrients, visualization methods and the construction of a comprehensive soil fertility evaluation system can provide a scientific reference for determining the nutrient content of tobacco planting soil. Using a bibliometric approach, we collected 90 published papers from 2008 to 2022 from the Web of Science and CNKI databases on the spatial variation in soil nutrient characteristics of flue-cured tobacco planting soil, with a focus on the conditions found in China. The current situation and potential issues were analyzed according to the indicator selection frequency, spatial variation visualization method, and influencing factors. There were 20 indicators reflecting the soil nutrients of flue-cured tobacco planting soil. The frequency of available zinc was the highest at 42.86%, followed by phosphorus, organic matter, pH, alkali-hydrolyzable nitrogen, and available potassium. Among the visualization methods, Kriging interpolation was the most widely used, with an application frequency of 68.80%. The influencing factors were divided into natural and human ones. Principal component analysis was commonly used to screen indicators and determine weights, and the soil fertility suitability index was used to evaluate the spatially integrated fertility of soil nutrients for flue-cured tobacco planting. Available zinc, available phosphorus, soil organic matter, soil pH, soil alkali-hydrolyzable nitrogen, and available potassium are important evaluation indices for determining the spatial variability of soil nutrients in flue-cured tobacco planting soil. The selection of indicators, the determination of their weights, and method selection all significantly affect the accuracy of soil nutrient evaluation; thus, future work should focus on the development of a comprehensive evaluation system for tobacco planting soil that also considers trends associated with natural and human factors and their effects on spatial variability.

Soil-borne diseases of tobacco roots and stems, caused by pathogens including Ralstonia solanacearum (bacterial wilt), Phytophthora parasitica var. nicotianae (black shank), and root-knot nematodes ( Meloidogyne spp.), represent critical threats to tobacco cultivation. However, information regarding alterations in rhizosphere soil properties and microbial communities following co-infection by multiple soil-borne pathogens remains limited for tobacco-growing regions in Luxi County, Honghe Prefecture, Yunnan Province, China. This study therefore investigated rhizosphere soils collected from healthy and diseased tobacco plants in Baishui Town. Eighteen soil physicochemical parameters and six enzyme activities were measured. Bacterial and fungal community compositions were analyzed using high-throughput sequencing targeting the 16S rDNA V4 region and the ITS1 region, respectively. Relationships between environmental factors and microbial community shifts were further explored using redundancy analysis (RDA) and Spearman correlation analysis. Results demonstrated that, compared with healthy tobacco plants, various physicochemical factors and enzyme activities in the rhizosphere soils of diseased plants were significantly elevated. Bacterial community diversity and species richness in diseased tobacco rhizosphere soils were significantly altered by pathogen infection. Specifically, the relative abundance of the phylum Proteobacteria significantly decreased by 18.20%, whereas Chloroflexi and Gemmatimonadetes significantly increased by more than two-fold. The fungal phylum Chytridiomycota significantly decreased by 72.68%. At the genus level, the beneficial bacterium Sphingomonas significantly decreased by 36.13%, and the beneficial fungus Penicillium significantly decreased by 90.59% in relative abundance. Conversely, pathogenic fungi Fusarium , Phoma , and Plectosphaerella significantly increased by 3-fold, 5-fold, and 3-fold, respectively. RDA and Spearman correlation analyses revealed that variations in rhizosphere microbial communities were significantly and positively correlated with elevated soil pH, organic matter, total nitrogen, available nitrogen, total phosphorus, manganese content, and the activities of peroxidase and protease, while significantly and negatively correlated with decreased total potassium, available potassium, and boron contents. Our findings indicate that the imbalance (or alternatively: dysbiosis of microbial communities coupled with the disruption ) of soil physicochemical properties, enzyme activities, and microbial community structure constitutes a typical characteristic of tobacco rhizosphere soils subjected to multiple pathogen co-infections in this region.

Soil microbes are vital for the development of plant growth. Little is known about how the discrepancy of microbes mediate the microbial community structure of healthy (CK) and disease-susceptible soils with black root rot (BR, Thielaviopsisbasicola) and root-knot nematode (RK, Meloidogyne incognita; M. javanica) of flue-cured tobacco (Nicotianatabacum L.). In this study, we analyzed the soil and microbial properties, and showed the differences of soil microbial composition and diversity between soils. Specially, soil was more acid with lower diversity, higher nutrient content with higher abundance of Proteobacteria, Ascomycota, Basidiomycota in the disease-susceptible soils. While, compared with disease-susceptible soils, the protease and urease activities, as well as soil pH, available potassium content, and the relative abundance of beneficial bacterial and fungal genera (including Bacillus, Micromonospora, Lysobacter, Microvirga, Chaetomium and Arthrobotrys) were higher in CK soils. The variations of soil physiochemical factors and enzyme activities resulted in differences in microbial community structure and composition between healthy and disease-infected flue-cured tobacco soils. Our results bring novel insights to control the disease-susceptible of flue-cured tobacco fields through management of rhizosphere community struture.

The fate of soil carbon (C) under climatic warming predominantly depends on temperature sensitivity of soil microbial functioning, but it is poorly understood. Using temporal measurements of soil respiration in an incubation experiment with cross-inoculation of microbial communities to contrasting soils, we constrained a microbial-explicit C model to infer temperature responses of two general microbial functional groups: fast-growing r- vs slow-growing K-strategists. We found that the two groups exhibit distinct, non-monotonic temperature responses. Both historical environment, under which the microbial communities were originated, and current environment, under which the microbial communities are colonized/adapted, significantly shape the temperature responses of the two groups. Our findings highlight the importance of combined effects of historical and current environment on microbial decomposition for regulating soil C dynamics under warming. We suggest that distinct, non-monotonic temperature responses of microbial functional groups may cause pronounced feedbacks between soil C dynamics and warming depending on climate-soil-microbe interactions.