Haiming Tang

Introduction: Long-term organic fertilization is known to improve soil fertility, but the mechanisms by which it enhances soil nitrogen (N) availability, particularly the relative importance of direct nutrient stimulation versus diazotroph-mediated pathways, remain unclear. Methods: We examined the effects of four fertilization regimes (without fertilizer, CK; 100% chemical fertilizer, NPK; rice straw plus chemical fertilizer, RS; and 30% organic manure plus 70% chemical fertilizer, OM) on soil properties, diazotrophic community composition ( nif H gene amplicon sequencing), N ₂ fixation activity (potential BNF and nitrogenase concentration), and soil N pools (NH ₄ ⁺ –N, NO ₃ ⁻ –N, and MBN) in a 37 year double-cropping paddy rice field experiment. Results and discussion: Long‑term organic fertilization, particularly OM, significantly increased soil organic carbon, total nitrogen and microelements (Mo, Fe, V and AMo). Relative to CK, OM treatment increased soil potential BNF rates by 342% and nitrogenase concentration by 178%, and maintained the highest soil inorganic nitrogen and MBN pools. Soil diazotrophic community composition (PCoA Axis1), rather than alpha diversity or nif H gene abundance, was the strongest correlate of potential BNF rates ( r = 0.70, p < 0.001) and nitrogenase concentration ( r = 0.85, p < 0.001). Partial least squares path modeling revealed that soil nutrients influenced soil N availability through dual pathways: a dominant direct effect on soil N fixation potential (0.734, p = 0.002), and a significant indirect effect mediated by soil diazotrophic community composition and N fixation activity (0.330). The model explained 98.8% of the variance in soil N availability with a goodness of fit of 0.842. In contrast, soil microelements showed negligible direct or indirect effects. These findings demonstrate that long-term organic fertilization enhances paddy soil N availability through coupled mechanisms: a dominant direct stimulation of N fixation by increased carbon and nutrient availability, complemented by a secondary pathway involving shifts in diazotrophic community composition and their concomitant N fixation activity. This study provides mechanistic evidence that sustaining soil N fertility in intensive rice agriculture depends on both adequate organic nutrient inputs and the maintenance of functional diazotrophic communities.

Introduction: Alterations in the composition and structure of the soil microbial community exert a substantial impact on soil nutrient cycling and fertility. Implementing sustainable land use strategies involves a deeper comprehension of the dynamics of the soil microbial community under different fertilization approaches. Methods: Phospholipid fatty acid (PLFA) method was employed to characterize soil microbial community abundance and structure under four fertilization treatments (no fertilizer (CK), 100% mineral fertilizer (NPK), 30% organic fertilizer + 70% mineral fertilizer (LOM), and 60% organic fertilizer + 40% mineral fertilizer (HOM)) in a Camellia oleifera plantation area in southern China. Results: Fertilization application substantially increased the Camellia oleifera yields, with the highest increment observed under the HOM treatment. Soil organic carbon and total nitrogen levels were significantly increased in LOM and HOM treatments as compared to CK. Total PLFAs absolute abundance in LOM and HOM treatments increased by 68.45% and 85.38%, respectively, compared to CK treatment. Furthermore, the absolute abundances of bacteria, fungi, and actinomycetes, as well as total PLFAs, were markedly enhanced in HOM and LOM treatments but not in the NPK treatment relative to CK treatment. There was less distinction observed in the microbial community structure than in microbial abundance across four fertilization treatments. Soil nutrients were identified as the primary factor affecting soil microbial abundance and crop yield. These findings imply that the combined application of organic and mineral fertilization than employing solely mineral fertilization may be more effective in improving soil nutrient levels, regulating soil microbial community composition and increasing crop yield in a Camellia oleifera plantation.

The partial substitution of chemical fertilizer with organic fertilizer has been regarded as an effective strategy for enhancing crop yield and soil quality. Nevertheless, its effects on soil properties and microbes remain contentious. In this study, we examined the effects of four different fertilization strategies (including without fertilizer (CK), 100% chemical fertilizer (NPK), 30% organic fertilizer + 70% chemical fertilizer (LOM) and 60% organic fertilizer + 40% chemical fertilizer (HOM)) on soil nutrients and microbial communities through metagenomic sequencing in a Camellia oleifera field experiment. Compared to CK and NPK, HOM significantly increased SOC, TN, TP, AK and AN contents. The substitution of organic fertilizer notably increased Camellia oleifera yield, with the highest increase of 93.35% observed in HOM relative to NPK. Soil bacterial and fungal communities responded inconsistently to fertilization patterns. Bacteria predominated as the main soil microorganisms, and higher rates of organic fertilizer substitution facilitated a shift from bacterial to fungal communities. Organic fertilizer substitution significantly increased soil bacteria diversity and fungal richness, particularly in the HOM. Soil bacterial community structure was more sensitive to fertilization regimes than soil fungi. High rates of organic fertilizer substitution substantially suppressed oligotrophic and increased copiotrophic bacterial communities. Mucoromycota emerged as the dominant fungal group, with a considerable increment in HOM soils. SOC and TN were the main factors affecting Camellia oleifera yield and shaping soil bacteria and fungal diversity and composition. This study provided crucial insights into the ecological implications of organic fertilizer application and the potential of managing soil microorganisms for sustainable Camellia oleifera productivity.

Agent addition is increasingly recognized as a crucial strategy for improving soil health in tobacco cultivation. However, its impacts on soil microbial community and plant growth differ depending on soil conditions. In this study, tobacco soil was collected in Wu Ding County, Yunnan Province, under four distinct agent addition treatments, simply chemical fertilizer (T1), microbial agent + chemical fertilizer (T2), lime + chemical fertilizer (T3), and microbial agent + lime + chemical fertilizer (T4). Using the Illumina high-throughput sequencing platform and fungal ribosomal DNA internal transcribed spacer 1 to analyze the distribution characteristics of fungal communities in tobacco soil. Soil nutrient indicators (pH, SOC, TN and AP) were considerably higher in T4 than in T1. In comparison to T1, agent addition boosted the agronomic characteristics such as maximum leaf length, maximum leaf width, stem girth, and leaf number. T4 treatment facilitated the harmonization of chemical composition of tobacco leaves and greatly increased tobacco yield by 8.94% than T1. The application of T4 resulted in a reduction of fungal diversity. Ascomycota was the most dominant phylum across all soil and agent applications distinctly shifting the soil fungal community diversity. Furthermore, certain beneficial fungi were obviously accumulated, but the potentially pathogenic fungi were noticeably reduced or absent in T4. An explicit enrichment of saprotrophic fungi in T4 is predicated by the FUNGuild function. Soil nutrients were extremely significant and relevant in relation to the fungal community structure. In summary, we propose that T4 treatment could be an effective strategy to alleviate the continuous cropping barrier in tobacco cultivation since it eliminates soil acidity, improves soil nutrients, and modifies the soil microbial community structure, thereby improving the plant growth and increasing the yield of tobacco.

Summary: This study was designed to explore changes in soil bulk density (BD), soil organic carbon (SOC) content, SOC stocks, and soil labile organic carbon (C) fractions after 5 years of soil tillage management under the double-cropping rice system in southern of China. The experiment included four soil tillage treatments: rotary tillage with all crop residues removed as a control (RTO); conventional tillage with crop residues incorporation (CT); rotary tillage with crop residues incorporation (RT); and no-tillage with crop residues retention. Our results revealed that soil tillage combined with crop residue incorporation (CT and RT) significantly decreased BD at 0–20 cm soil layer compared to RTO treatment. SOC content and stocks were increased with the application of crop residues. Compared with RTO treatment, SOC content and stocks were increased by 16.8% and 9.8% in CT treatment, respectively. Soil non-labile C content and proportion of labile C were increased due to crop residue incorporation. Compared with RTO treatment, soil proportion of C mineralisation (Cmin), permanganate oxidisable C (KMnO₄), particulate organic C (POC), and microbial biomass C (MBC) was increased by 196.1%, 41.4%, 31.4%, and 17.1% under CT treatment, respectively. These results were confirmed by the carbon management index, which was significantly increased under soil tillage with crop residue incorporation. Here, we demonstrated that soil tillage and crop residue incorporation can increase the pool of stable C at surface soil layer while increasing labile C content and proportion. In conclusion, conventional or rotary tillage combined with crop residue incorporation is a soil management able to improve nutrient cycling and soil quality in paddy fields in southern China.

Ammonia oxidation plays a vital role in regulating soil nitrogen (N) cycle in agricultural soil, which is significantly influenced by different fertilizer regimes. However, there is still need to further investigate the effects of different fertilizer managements on rhizosphere soil ammonia-oxidizing archaea (AOA) and bacteria (AOB) community in the double-cropping rice field. Therefore, the effects of different long-term (37 years) fertilizer managements on rhizosphere soil potential nitrification activity (PNA), AOA and AOB community structure, and its relationship under the double-cropping rice system in southern of China were studied in the present paper. The field experiment included without fertilizer input as a control (CK), inorganic fertilizer (MF), rice straw and inorganic fertilizer (RF), 30% organic manure and 70% inorganic fertilizer (OM). This result indicated that rhizosphere soil organic carbon (SOC) (SOC), total N and ammonium N (NH₄⁺-N) contents in paddy field with RF and OM treatments were increased. Rhizosphere soil PNA, potential nitrification rate (PNR) and abundance of AOB in paddy field with MF treatment were increased, and abundance of AOA in paddy field with RF and OM treatments were increased, respectively. The result also showed that rhizosphere soil diversity index of AOA and AOB with RF and OM treatments were enhanced, compared with CK treatment. Rhizosphere soil AOB and AOA community composition was dominated by Proteobacteria, Actinobacteria and Acidobacteria with all fertilizer treatments. There had significantly positively correlation between the abundance of AOA and SOC, total N, and NH₄-N contents. However, there had significantly negatively correlation between soil pH and abundance of AOA, soil PNA, PNR. As a result, long-term application of rice straw and organic manure was benefit for increasing community structure of rhizosphere soil ammonia oxidizer under the double-cropping rice system in southern of China.

Unreasonable soil tillage measures have caused a sharp decline in the soil carbon (C) pool capacity of rice (Oryza sativa L.) paddy fields, have reduced soil fertility, and have threatened the safe production of rice. Based on long-term position–location experiments started in 2005, this paper systematically studied the effects of different soil tillage treatments (CT: no return of plowing straw to the field as control; CTS: return of plowing straw to the field; NTS: return of no-tillage straw to the field; RTS: return of rotary plowing straw to the field) on soil physical and chemical properties and soil organic carbon (SOC) accumulation characteristics in rice paddy fields, in order to clarify the impact of different long-term soil tillage measures on soil carbon cycle microecology in double-cropped rice paddy fields and provide a theoretical basis for soil SOC sequestration and the sustainable utilization of rice paddy fields in double-cropped rice paddy fields in southern China. The results were as follows: A total of 30.7–40.7% of the SOC stored in rice paddy fields was residue C derived from microorganisms, and 45.7–54.2% of SOC accumulation came from plant residue-derived C. Straw return treatments (CTS, RTS, and NTS) significantly increased soil lignin phenol content and promoted the accumulation of plant-derived SOC. Soil lignin phenol content in the RTS treatment was significantly higher than that in the CTS treatment (p < 0.05). Amino sugar content in rhizosphere soil was higher than that in non-rhizosphere soil. The measure of returning straw to the field increased amino sugar content in the rhizosphere and non-rhizosphere. C derived from plants was greater than that from microbial residues in double-cropped rice paddy fields in southern China. Hence, no-till/rotary tillage and straw return can improve the sequestration of soil SOC, which is of great significance for achieving “C neutrality” and alleviating the pressure on food security.

Soil organic carbon (SOC) plays a vital role in maintaining or enhancing soil fertility and quality of paddy field, but there is still limited information about how SOC mineralization responds to different tillage managements under the double-cropping rice (Oryza sativa L.) system in southern of China. Therefore, this study was designed to explore the changes in SOC content, soil enzyme activities (invertase, cellulose and urease), SOC mineralization at 0–10 cm and 10–20 cm layers and its relationship with 7-years tillage management under the double-cropping rice system of southern China. The experiment included four tillage managements: rotary tillage with all residues removed as a control (RTO), conventional tillage with residue incorporation (CT), rotary tillage with residue incorporation (RT), and no-tillage with residue retention (NT). The results indicated that SOC and soil labile organic carbon contents at 0–10 cm and 10–20 cm layers in paddy field with CT and RT treatments were significantly higher than the RTO treatment. Compared to the RTO treatment, SOC mineralization and accumulation at 0–10 cm and 10–20 cm layers in paddy field with CT, RT and NT treatments were increased. SOC accumulation and potential mineralization at 0–10 cm layer with NT treatment were significantly higher than the CT, RT and RTO treatments. Soil mineralization constant at 10–20 cm layer with CT treatment was significantly higher than those of RT, NT and RTO treatments. This result indicated SOC mineralization rate and accumulation at 10–20 cm layer of CT, RT, NT and RTO treatments were lower than those of treatments at 0–10 cm layer. Compared to RTO treatment, soil invertase, cellulose and urease activities with CT and RT treatments were significantly increased. Compared to RTO treatment, soil invertase, cellulose and urease activities at 0–20 cm layer of CT treatment increased by 22.6%, 46.2% and 89.0%, respectively. There was significantly positive correlation between SOC accumulation and SOC content, soil invertase, cellulose, urease activities, but SOC accumulation was significantly negative correlated with soil pH, bulk density. Therefore, CT and RT treatments were beneficial managements to improve SOC content and SOC mineralization in the double-cropping rice field of southern China.

Haiming Tang, Li Wen, Kaikai Cheng, Chao Li, Lihong Shi, Weiyan Li, Yong Guo, and Xiaoping Xiao. J. Microbiol. Biotechnol. 2024;34:1464-74. https://doi.org/10.4014/jmb.2401.01032