Most studies on the effects of biochar and fertilizer on soil carbon (C) and nitrogen (N) mineralization, and microbial C and N content, are restricted to a single soil type, limiting our understanding of the interactions between these factors and microbial functions. To address this paucity in knowledge, we undertook a 3-year experiment using four contrasting soils to assess the role of peanut shell biochar and fertilizer on C and N mineralization, microbial C and N, and N stoichiometry. Across all four soils, biochar significantly (P < 0.05) increased soil carbon mineralization (C) and nitrogen mineralization (N) over three years compared to fertilizer and the control. Biochar also increased total C (C) across the four soils in year 1, with the Fluvisol recording greater total C in year 2 and Phaeozem having greater total C in year 3. Biochar resulted in a higher microbial biomass C (C), total N (N) and microbial biomass N (N); the degree of change was closely related to C and N. There was a positive correlation between C:N and C:N; while C and C increased following amendment with biochar, which reduced the soil C and N stoichiometric imbalance (N) caused by the increase in the C to N ratio. However, fertilizer exacerbated the imbalance of soil C and N stoichiometry. Fertilizer also reduced the C:N and C:N ratios. Soil pH had a positive correlation with C, C, N, C, N, C:N, C:N, and biochar increases this correlation. The soil pH was negatively correlated with C:N and N. Fertilizer was positively correlated C:N and N. In contrast, fertilizer N application lowered microbial biomass C:N. We conclude that biochar reduces the imbalance of soil C and N stoichiometry, whereas fertilizer increased this imbalance. Biochar had a greater impact on C and N in soils with a lower pH.

The usage of fertilizer with high nitrogen content in many countries, as well as its enormous surplus, has a negative impact on the soil ecological environment in agricultural system. This consumption of nitrogen fertilizer can be minimized by applying biochar to maintain the sufficient supply of nitrogen as nutrient to the near-root zone. This study investigated the effects of various amounts of biochar application (450, 900, 1350, and 1800 kg/hm) and reduction of nitrogen fertilizer amount (10, 15, 20, and 25%) on the nutrients and microorganism community structure in rhizosphere growing tobacco plant. The microorganism community was found essential in improving nitrogen retention. Compared with conventional treatment, an application of biochar in rhizosphere soil increased the content of soil available phosphorus, organic matter and total nitrogen by 21.47%, 26.34%, and 9.52%, respectively. It also increased the abundance of microorganisms that are capable of degrading and utilizing organic matter and cellulose, such as Actinobacteria and Acidobacteria. The relative abundance of Chloroflexi was also increased by 49.67-78.61%, and the Acidobacteria increased by 14.79-39.13%. Overall, the application of biochar with reduced nitrogen fertilizer amount can regulate the rhizosphere microecological environment of tobacco plants and their microbial population structure, thereby promoting soil health for tobacco plant growth while reducing soil acidification and environmental pollution caused by excessive nitrogen fertilizer.

Biochar and organic fertilizer are commonly used to maintain soil health and sustainable agroecosystems, and the alternate wet-dry management of soil moisture in dry direct-seeded paddy fields can complicate the effects of biochar and organic fertilizer on soil microhabitats. Therefore, this study used chicken manure organic fertilizer to replace some of the inorganic fertilizer and applied biochar to explore the ability of biochar and organic fertilizer to regulate the functions of the soil microhabitat in dry direct-seeded paddy fields. The coupling effect of organic fertilizer and biochar increased the diversity and richness of soil bacteria but had no significant effect on soil fungi. Biochar and organic fertilizer affected the distribution and composition of soil bacteria and fungi, and the total number of soil bacteria and fungi increased by 1365 and -71 (5 t/hm biochar and no organic fertilizer), 660 and 79 (10 t/hm biochar and no organic fertilizer), 3121 and 7 (no biochar and 20 % organic fertilizer substitution), 1873 and -72 (5 t/hm biochar and 20 % organic fertilizer substitution), and -544 and -65 (10 t/hm biochar and 20 % organic fertilizer substitution), respectively, compared with that of the control treatment. Compared with the application of biochar alone, the coupling effect of biochar and organic fertilizer increased the average degree (0.95 and 0.16), links (190 and 32), and ratio of fungal positive links (1.651 %), and decreased the modularity (0.034 and 0.052) and ratio of bacterial positive links (6.482 %) of bacterial and fungal networks. In addition, the coupling effect resulted in a more complex association between soil microbial diversity and richness and microbial ecological functions. Random forest predictions indicated that, organic fertilizer as a random factor, changes in the abundance of bacterial Bacteroidetes and Nitrospirae and fungal Monoblepharomycota were the main factors driving the differences in soil microbial ecological functions.

Introduction:The continuous application of cow manure in soil for many years leads to the accumulation of heavy metals, pathogenic microorganisms, and antibiotic resistance genes. Therefore, in recent years, cow manure has often been mixed with botanical oil meal as organic fertilizer applied to farmland to improve soil and crop quality. However, the effects of various botanical oil meal and cow manure mixed organic fertilizers on soil microbial composition, community structure, and function, tobacco yield, and quality remain unclear. Methods:Therefore, we prepared organic manure via solid fermentation by mixing cow manure with different oil meals (soybean meal, rape meal, peanut bran, sesame meal). Then, we studied its effects on soil microbial community structure and function, physicochemical properties, enzyme activities, tobacco yield and quality; then we analyzed the correlations between these factors. Results and discussion:Compared with cow manure alone, the four kinds of mixed botanical oil meal and cow manure improved the yield and quality of flue-cured tobacco to different degrees. Peanut bran, which significantly improved the soil available phosphorus, available potassium, and NO-N, was the best addition. Compared with cow manure alone, soil fungal diversity was significantly decreased when rape meal or peanut bran was combined with cow manure, while soil bacterial and fungal abundance was significantly increased when rape meal was added compared with soybean meal or peanut bran. The addition of different botanical oil meals significantly enriched the and bacteria and and fungi in the soil. The relative abundances of functional genes of xenobiotics biodegradation and metabolism, soil endophytic fungi, and wood saprotroph functional groups increased. In addition, alkaline phosphatase had the greatest effect on soil microorganisms, while NO-N had the least effect on soil microorganisms. In conclusion, the mixed application of cow manure and botanical oil meal increased the available phosphorus and potassium contents in soil; enriched beneficial microorganisms; promoted the metabolic function of soil microorganisms; increased the yield and quality of tobacco; and improved the soil microecology.

We tested the hypothesis that soil texture and nitrogen (N) fertilisation are the primary factors regulating the N cycle and soil bacterial community structure. The response of soil bacterial communities to N fertilisation in different textured soils might help in identifying the specific underlying mechanism and hence management of N fertiliser application in fields. We examined how N fertiliser accumulates in flue-cured tobacco and influences soil bacterial community structure in different textured soils. We conducted plot and micro-plot experimental measurements of N content in soil and tobacco samples using the KNON isotope technique. Soil bacterial community structure was determined using high-throughput sequencing of 16S rRNA. Nitrogen absorption and utilisation by tobacco plants were highest in sandy loam soils, followed by loam soil and clay loam. The ability of clay loam to supply N was weak during the plant growth period. Absence of fertilisation could reduce bacterial abundance in soils to various degrees. Bacterial diversity was higher in sandy loam soil than in loam soil and clay loam. Soil texture and N fertilisation significantly affected soil bacterial community structure and diversity. Proteobacteria, Acidobacteria, Firmicutes, Bacteroidetes, Actinobacteria, and Chloroflexi were the dominant bacterial phyla, while Bacillus, Nitrobacter, Nitrosospira, Nitrospira, and Rhizobium were the primary N transformation bacteria at the genus level in all treatments. However, relative abundances differed with N fertiliser application, which could lead to differential N availability and N use efficiency of tobacco among soil types. We conclude that both soil texture and N fertilisation influence N accumulation and distribution in flue-cured tobacco and thus regulate soil bacterial communities. N fertiliser application in sandy loam soil should be strictly controlled for its higher N use efficiency, soil bacterial abundance, and diversity.

As the promotive/complementary mechanism of the microbe-soil-tobacco ( L.) interaction remains unclear and the contribution of this triple interaction to tobacco growth is not predictable, the effects of intercropping on soil nutrients, enzymatic activity, microbial community composition, plant growth, and plant quality were studied, and the regulatory mechanism of intercropping on plant productivity and soil microenvironment (fertility and microorganisms) were evaluated. The results showed that the soil organic matter (OM), available nitrogen (AN), available phosphorus (AP), available potassium (AK), the urease activity (UE) and sucrase activity (SC), the diversity, abundance, and total and unique operational taxonomic units (OTUs) of bacteria and fungi as well as plant biomass in T1 (intercropping onion), T2 (intercropping endive), and T3 (intercropping lettuce) treatments were significantly higher than those of the controls (monocropping tobacco). Although the dominant bacteria and fungi at the phylum level were the same for each treatment, LEfSe analysis showed that significant differences in community structure composition and the distribution proportion of each dominant community were different. Proteobacteria, Acidobacteria, and Firmicutes of bacteria and Ascomycota and Basidiomycetes of fungi in T1, T2, and T3 treatments were higher than those of the controls. Redundancy analysis (RDA) suggested a close relation between soil characteristic parameters and microbial taxa. The correlation analysis between the soil characteristic parameters and the plant showed that the plant biomass was closely related to soil characteristic parameters. In conclusion, the flue-cured tobacco intercropping not only increased plant biomass and improved chemical quality but also significantly increased rhizospheric soil nutrient and enzymatic activities, optimizing the microbial community composition and diversity of rhizosphere soil. The current study highlighted the importance of microbe-soil-tobacco interactions in maintaining plant productivity and provided the potential fertilization practices in flue-cured tobacco production to maintain ecological sustainability.

Field trails were carried to study the effects of tobacco straw incorporation and potassium (K) fertilizer on rice yield, K uptake and use efficiency, and its substitute for K fertilizer under different paddy soil K levels in tobacco-rice rotation areas. Results showed that both tobacco straw incorporation (2250 kg·hm) and K fertilizer application (75 kg KO ·hm) could increase grain yield and aboveground K uptake of rice. The treatment of tobacco straw incorporation with K fertilizer (St+NPK) got the best effect on rice yield compared with the control (NP). In this treatment (St+NPK), rice yields were increased by 13.3%, 17.1% and 13.5% for low-K soil (available potassium content < 100 mg·kg), middle-K soil (available potassium content 100-150 mg·kg) and high-K soil (available potassium content > 150 mg·kg), respectively, compared with NP. Tobacco straw incorporation (St+NP) could increase K fertilizer recovery efficiency and K fertilizer agronomic efficiency. Under the current practice of applying 75 kg KO·hm, St+NPK showed no significant effect on K fertilizer recovery efficiency and K fertilizer agronomic efficiency, demonstrating that the recommended rate of K fertilizer might be more than the actual demand of rice growth. More importantly, data of tobacco straw substitute for K fertilizer showed that tobacco straw incorporation could replace 10%-22% K fertilizer during rice growing season, i.e. K fertilizer could be reduced by 7.2-16.5 kg·hm for rice under the condition of tobacco straw incorporation. Therefore, it was suggested that straw incorporation could reduce the rate of K fertilizer for high-K soil, but the current K fertilizer inputs (75 kg KO·hm) should be supplied to get high rice yield and maintain the soil potassium balance for low-K soil and middle-K soil.

Identifying field management practices to promote crop production, while conserving soil health is essential to maintain long-term food production in a changing world. Also, providing experimental evidence to support the use of traditional agricultural practices is necessary to secure sustainable agriculture. Here, we conducted a long-term 12-year experiment to investigate the impact of different combinations of fertilization type (control, inorganic fertilizer, organic fertilizer) and cropping regimes (continuous cropping and rotation cropping) on the crop (tobacco) production and multiple soil attributes associated with soil health, including proportions of soil-borne pathogens and decomposers, soil microbial diversity, microbial network stability and biomass, nutrient pools and microbial resource limitations. Our long-term experiment supports that the combination of organic fertilizer with rotation cropping increased crop production by at least 40% compared to the other management combinations and improved soil nutrient pools (e.g. the content of soil organic matter), improved the relative proportion of soil decomposers, and promoted bacterial and fungal network stability and biodiversity. Furthermore, this combination treatment relieved microbial resource limitation and reduced the abundance of potential fungal plant pathogens by at least 20% compared to other management combinations. In summary, we provide experimental evidence to support that the combined use of organic fertilization and rotation cropping management can help maintain long-term soil health, crop production, and economic outputs.

In order to explore the effects of biochar on root system and growth characteristics of flue-tobacco, three years of field experiments were conducted to study the influence of different biochar application levels [600 (T), 1200 (T), 1800(T), 2400 (T), 3000 (T) kg/ha] and no fertilizer (CK) on the root physiological indexes and growth index of tobacco. Compared with local conventional fertilization, the application rate of N fertilizer in each treatment (except for control) was reduced by 40% to analyze the effects of different amount of biochar on the physiological indexes of tobacco roots and leaf photosynthesis during flourishing. The results showed that tobacco plants' root development status in the flourishing period was consistent with the photosynthetic physiological indexes, chlorophyll content, and leaf-area coefficient. Compared with the control, the application of biochar could increase the root vigor by 177.8%. Biochar improved the roots, increasing the total root area by 91.35% and the number of root tips by 100.9%. Meanwhile, biochar increased the net photosynthetic rate of tobacco leaves by 77.3% and the total tobacco biomass by 72.5%. Studies have shown that biochar can promote the development of tobacco roots, and then enhance the photosynthesis of leaves, so that tobacco plants can grow healthily, which is conducive to the tobacco production and the cultivation of soil.

A large amount of fresh tobacco waste with high water content are produced in farmland, and it may cause environmental pollution if it is not properly treated. The fresh tobacco waste is not easily collected and transported, resulting in its centralized treatment is expensive. This study is to clarify whether it is feasible to treat fresh tobacco wastes by co-composting of them and soil in farmland and applied the obtained compost product into the soil instead of a part of tobacco-specific fertilizer. The results showed that, compared with that in original soil, the relative abundance of Pseudomonas, Azotobacter, and Coprinus of the co-composted products increased by roughly 244%, 323%, and 675%, respectively, and effective nitrogen and available potassium increased by roughly 157% and 132%, respectively. In addition, the nicotine content in co-composted products decreased dramatically compared with the discarded tobacco leaves. The application of the co-composted products and 20% fertilizer amount (15 g/plant) (YD5) exhibited the highest relative abundance of beneficial microbial communities in the soil and the best growth of tobacco plants. The co-composting of fresh tobacco waste and soil in farmland is an effective measure to treat the fresh tobacco waste, and its products increased beneficial microorganisms and stimulate the growth of tobacco plants by replacing an amount of the fertilizer.

Southwestern China is receiving excessive chemical fertilizers to meet the challenges of continuous cropping. These practices are deteriorating the soil environment and affecting tobacco ( L.) yield and quality adversely. A novel microbially enriched biochar-based fertilizer was synthesized using effective microorganisms, tobacco stalk biochar and basal fertilizer. A field-scale study was conducted to evaluate the yield response of tobacco grown on degraded soil amended with our novel biochar-based microbial fertilizer (BF). Four treatments of BF (0%, 1.5%, 2.5% and 5%) were applied in the contaminated field to grow tobacco. The application of BF, BF and BF increased the available water contents by 9.47%, 1.18% and 2.19% compared to that with BF respectively. Maximum growth of tobacco in terms of plant height and leaf area was recorded for BF compared to BF. BF, BF and BF increased SPAD by 13.18-40.53%, net photosynthetic rate by 5.44-60.42%, stomatal conductance by 8.33-44.44%, instantaneous water use efficiency by 55.41-93.24% and intrinsic water use efficiency by 0.09-24.11%, while they decreased the intercellular CO concentration and transpiration rate by 3.85-6.84% and 0.29-47.18% relative to BF, respectively ( < 0.05). The maximum increase in tobacco yield was recorded with BF (23.81%) compared to that with BF. The present study concludes that the application of BF improves and restores the degraded soil by improving the hydraulic conductivity and by increasing the tobacco yield.

Organic fertilizer is effective in improving soil quality, and promoting crop growth. Combined organic and inorganic fertilization has been proved as a more favorable way to tobacco yield and quality. However, the mechanisms underlying tobacco yield and quality under combinations of different organic and inorganic fertilizer remain unclear. We conducted a 12-year tobacco ( L.)-maize crop rotation field experiment in Yanhe experimental station, China to examine the yields and qualities of tobacco, soil nutrients, and extracellular enzyme activities associated with carbon, nitrogen, and phosphorus cycles in response to different fertilization treatments. Five fertilization treatments (no fertilization; 75 kg N fertilizer ha; 450 kg oil cake ha + 75 kg N fertilizer ha; 15,000 kg pig dung ha + 60 kg N fertilizer ha; 3,000 kg straw ha + 75 kg N fertilizer ha) were applied to tobacco while maize was fertilized with inorganic compound fertilizers. After 12 years of tobacco-maize rotation, the results showed that organic fertilizer additions elevate tobacco yield and quality, and the soil extracellular enzymes activities. Gram-negative bacteria, actinomycetes, and total soil microbial biomass were increased by organic fertilizer additions, both plant-based (oil cake and straw) and animal-based (pig dung) organics. The levels of soil organic matter, total organic carbon, total phosphorus and available phosphorus are higher in pig dung addition treatment than oil cake and straw additions. By variance analysis with respect to fertilization treatments, organic sources differentially affected the activities of diverse soil enzymes. The redundancy analysis gave that yield and quality of tobacco leaves (upper, middle, and lower leaves) positively related to soil extracellular enzyme activities. Based on analysis of yield and quality of tobacco leaves with extracellular enzyme activities and soil nutrients, it is suggested animal-based organic fertilizer, thus pig dung, should be used in combining with chemical fertilizers to improve the quality of tobacco and soil nutrients.

To improve tobacco leaf quality, excessive KSO fertilizers were applied to soils in major tobacco-planting areas in China. However, the effects of KSO application on soil microbial community and functions are still unclear. An eight-year field experiment with three kinds of KSO amounts (low amount, KO 82.57 kg hm, LK; moderate amount, KO 165.07 kg hm, MK; high amount, KO 247.58 kg hm, HK) was established to assess the effects of KSO application on the chemical and bacterial characteristics of tobacco-planting soil using 16S rRNA gene and metagenomic sequencing approaches. Results showed that HK led to lower pH and higher nitrogen (N), potassium (K), sulfur(S) and organic matter contents of the soil than LK. The bacterial community composition of HK was significantly different from those of MK and LK, while these of MK and LK were similar. Compared to LK, HK increased the relative abundance of predicted copiotrophic groups (e.g. , families and genus) and potentially beneficial bacteria (e.g. phylum and genus) associated with pathogens and heavy metal resistance, N fixation, dissolution of phosphorus and K. While some oligotrophic taxa (e.g. phylum) related to carbon, N metabolism exhibited adverse responses to HK. Metagenomic analysis suggested that the improvement of pathways related to carbohydrate metabolism and genetic information processing by HK might be the self-protection mechanism of microorganisms against environmental stress. Besides, the redundancy analysis and variation partitioning analysis showed that soil pH, available K and S were the primary soil factors in shifting the bacterial community and KEGG pathways. This study provides a clear understanding of the responses of soil microbial communities and potential functions to excessive application of KSO in tobacco-planting soil.

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.