Jianfu Wu

Soil acidification and nutrient imbalances threaten mountain tea plantation sustainability, while nutrient-driven acidification mechanisms along elevation gradients in deep soil profiles remain poorly understood. This study examined three tea plantations at different elevations (107, 400, and 711 m) on Mount Lu, Jiangxi Province, sampling soils at five depths to 100 cm. Objectives were to quantify vertical differentiation of acidity, base ions, and nutrients, reveal altitudinal conversion patterns of acidification drivers, and guide fertilizer management. Soils exhibited strongly acidic conditions (pH 3.86–5.46), with the most severe acidification at the mountain foot and surface layer (0–20 cm). Potential acid accumulation in deep soils exceeded 75% (exchangeable aluminum/exchangeable acidity: 80.61%, 77.42%, 80.10% at mountain foot, mountainside, and mountaintop, respectively), and acidification spread was most pronounced at the mountain foot. The mountaintop and surface layer showed strongest acid–base resistance. Cation exchange capacity and base cations decreased with depth; base saturation in surface soil was 47.12% higher than in deeper layers. Organic matter, nitrogen, phosphorus, and available potassium were surface-enriched, whereas total potassium accumulated in deeper layers. Correlation analysis showed that pH was significantly negatively correlated with exchangeable acidity, exchangeable aluminum, organic matter, total nitrogen, and alkaline-hydrolyzable nitrogen, and significantly positively correlated with exchangeable calcium, exchangeable magnesium, and total potassium. Structural equation modeling revealed that nitrogen accumulation was the primary acidification driver, with total effect sizes ranking as total nitrogen (0.549) > organic matter (0.319) > total potassium (0.247) > alkaline-hydrolyzable nitrogen (0.156). Nitrogen drove soil acidification via direct and indirect pathways by increasing exchangeable acidity and depleting base cations dominated by Ca²⁺. Organic matter exerted bidirectional regulation on soil pH, while total potassium indirectly alleviated soil acidification. These findings underscored the need to adjust the N:K₂O ratio from 2:1 to approximately 1.5:1; Organic fertilizers and soil amendments should be applied as base fertilizers, with the mountainside (400 m) being the most suitable elevation for tea cultivation.

Soil C, N, and P, along with their stoichiometric ratios, are important indicators for evaluating soil fertility. However, the dynamics of C:N:P stoichiometry in soils under citrus cultivation of varying durations remain unclear. This study investigated soil C:N:P stoichiometry and extracellular enzyme activities (βG, NAG, and AP) across different soil depths (0–10, 10–20, and 20–40 cm) in navel orange orchards with different ages (3-, 5-, 10-, and 15-year-old). Soils cultivated for 10 years exhibited significantly higher DOC, available N, and P contents compared to other durations. The TC:TN and TC:TP ratios at 0–10 cm were significantly 0.17–4.78 and 3.94–16.1 higher than those at 10–40 cm, respectively (p < 0.05). Notably, the TC:TP and TN:TP ratios observed in the 5-, 10-, and 15-year-old orchards were lower than in the 3-year-old orchard, suggesting an alleviation of P limitation in older orchards. The MBC:MBN ratio remained largely stable with orchard age at 0–20 cm (p > 0.05), whereas younger orchards (3- and 5-year-old) exhibited significantly 18.2–168 and 2.17–17.4 higher MBC:MBP and MBN:MBP ratios than older ones (10- and 15-year-old) at 10–40 cm (p < 0.05). At 0–10 cm, the 15-year-old orchard exhibited higher βG:NAG and βG:AP ratios than the younger orchards. Soil total C:P and microbial C:P ratios explained 29.7% and 20.1% of the variation in enzyme activity composition among abiotic and biotic factors, respectively (p < 0.01). These findings highlight the importance of monitoring P availability in mature orchards to maintain sustainable soil fertility. Future research should focus on long-term field experiments to validate optimal P fertilization thresholds and investigate the specific microbial community shifts driving these stoichiometric changes across different soil depths.

Microorganisms respond to changes in habitat resources by regulating their community structure. However, the variation in characteristics of microbial communities in soils with citrus cultivating for different durations remains unclear. We investigated the effects of the duration (3–5, 5–10, 10–15 and >15 years) of continuous citrus cultivation on the diversity and composition of bacterial and fungal communities, and the co-occurrence patterns of generalists and specialists in the orchard soils. The cultivation duration had no significant effect on fungal alpha diversity, but it increased the dissimilarity levels in both bacterial and fungal communities between the minimal 3–5-year duration and each subsequent duration. The top three most abundant generalists identified in the soils were Gammaproteobacteria, Subgroup_2 and Bradyrhizobium, for the bacteria, and Tremellales, Fusarium and Kernia, for the fungi. In total, 17–21% of generalists (e.g., Subgroup_2 and Candidatus_Nitrosotalea) and none of the specialists were found in bacterial networks, and 12–14% of generalists (e.g., Fusarium and Kernia) and 1.1–2.9% of specialists (e.g., Mortierella and Trechispora) were observed in fungal networks. The results highlighted that resource availability and environmental factors played a crucial role in shaping microbial communities. Our results provide insights into the roles of specific microbes in maintaining the stability of microbial co-occurrence networks and contribute to the exploration of microbial resources for the management of citrus orchard soils.

The synergistic effects of soil acidification and heavy metal pollution present major challenges for global agroecosystems. To systematically trace the evolution of research and identify key topics in this field, this study employed CiteSpace to visualize and analyze 691 records from the China National Knowledge Infrastructure (CNKI) and 6747 highly relevant articles or reviews from the Web of Science (WOS) Core Collection database from 2005 to 2025. The results indicate a steady to rapid rise in global publications, with China contributing the largest share, at 2468 publications. This has produced a research cluster centered around the Chinese Academy of Sciences (CAS); however, the centrality of its international cooperation remains limited. Studies in the CNKI database are driven by agricultural needs, focusing on national food security, rice yield stability, improvement of arable land, and heavy metal passivation and remediation, with a concentration on basic agricultural science. By contrast, research in the WOS database emphasizes fundamental mechanisms and interdisciplinary integration, addressing aluminum toxicity, microbial communities, the nitrogen cycle, and global climate change, intersecting fields such as environmental science, soil science, ecology, and microbiology. The evolution of research hotspots shows a clear trajectory: from acidity regulation and chemical speciation analysis of heavy metals (2005–2013), to heavy metal passivation, remediation, and phytoremediation (2014–2018), and then to biochar materials, microbiome analysis, and the synergistic role of carbon sequestration (2019–2025). This study argues that future research should move beyond single remediation measures and adopt integrated strategic management to jointly improve bioremediation efficiency, promote soil carbon sequestration and soil health, and enhance microbial adaptation to global climate change.

Potassium (K) is crucial for rice yield and quality, but continuous yield increase reduces protein content, challenging the balance between high yield and quality. This study analysed 3 178 case studies (1994–2024) on K management impact...

Microbial necromass carbon (MNC) is the dominant contributor to soil organic carbon (SOC). However, the contribution of MNC in different soil compartments to SOC sequestration has not been comprehensively studied, especially under the organic fertilizers input. To address this gap, we conducted a rice root box experiment by adding organic fertilizer (straw and straw biochar) and chemical fertilizer alone to red loamy paddy soil, respectively. We found that although SOC accumulation was stimulated by both biochar and straw in the rhizosphere, more substantial SOC was sequestered in the rhizosphere due to biochar addition (increased by 25.82% compared to straw addition). Additionally, the input of organic fertilizers resulted in varying degrees of MNC retention in the different soil compartments. Compared with that in bulk soil, fungal necromass carbon (FNC) content was reduced by 1.37% and 7.06%, and bacterial necromass carbon (BNC) content was reduced by 5.53% and 9.49% in the rhizosphere and hyphosphere, respectively, following straw addition. Conversely, the addition of biochar leads to a significant increase of FNC (increased by 2.92%) and BNC (increased by 2.00%) in the rhizosphere compared with bulk soil. However, straw addition also significantly enhanced SOC thermal stability within the rhizosphere and hyphosphere soils. Based on partial least squares path modeling, we found that SOC thermal stability was significantly and positively influenced by FNC, which was strongly associated with carbon degradation gene abundance. These results emphasize the critical role of soil compartments in SOC sequestration under organic fertilizer application and underscore the importance of FNC in enhancing SOC stability in the rhizosphere.

This study investigated the effects of long-term method of fertilization on growth and yield formation in early-season rice. Based on a 42-year field experiment initiated in 1981, three treatments: chemical N, P, and K (NPK), a double dose of chemical NPK (HNPK), and a combination of chemical and organic fertilizers (NPKM) were selected for comparison. Measurements included rice yield, yield components, tiller dynamic, dry matter accumulation, chlorophyll content (SPAD values), and transcriptome analysis of leaves at full heading stage in 2022. Results showed that rice yield followed the order NPKM > HNPK > NPK. The HNPK and NPKM treatments increased by 56.64% and 90.33%, respectively (p < 0.05). Spikelet density and 1000-grain weight increased by 9.16–22.89% and 3.74–4.28%, respectively. Both HNPK and NPKM enhanced the tillering rate by 43.84–72.73%, leading to an 18.95–57.54% increase in effective panicles. Dry matter accumulation from heading to filling stages was highest in NPKM-treated rice, with an increase of 3.31–4.25 g/plant in dry matter transport from leaves and stems to spikes during the filling to maturity stages. The SPAD values of NPKM-treated plants were consistently higher than those of HNPK and NPK treatments, with a smaller decline (6.94%) from heading to filling stages compared to 18.23% and 26.29% for HNPK and NPK, respectively. Correlation analysis indicated a positive relationship between yield and SPAD values or dry matter accumulation and a negative correlation with the decline in SPAD values from full heading to filling stage. Transcriptome analysis revealed significant enrichment of photosynthesis and plant senescence pathways among treatments. Overall, long-term combined application of chemical and organic fertilizers (NPKM) improved yield components, delayed chlorophyll degradation, promoted dry matter accumulation and transport, and regulated the expression of photosynthesis-related and senescence-related genes, ultimately optimizing growth and yield in early-season rice.

Background and Aims Silicon (Si) -accumulating plants alleviate the problem of low soil Si availability due to high weathering by absorbing labile Si from phytoliths in the soil. However, the efficient release of Si from Si-rich plant residues has not been well studied. Methods Rice husk and bamboo leaves were prepared and transformed into rice husk biochar (RHB), bamboo leaf biochar (BLB) and their alkali-modified biochar (ARHB, ABLB), which were then applied to highly weathered soils (high-available Si soil (HASi) and low-available Si soil (LASi)). Explore efficient Si release pathways and evaluate their potentials as efficient Si fertilizers. Results The first-order model demonstrated that the biochar Si pools were divided into rapidly-released Si pool C1 and slowly-released Si pool C2, and that alkali-modified biochar had higher Si solubilization capacity. A soil incubation experiment showed that available Si of the soils treated with alkali-modified biochar were significantly increased compared to those treated with original biochar, and this effect was more significant in LASi. In a rice growth pot experiment, biochar addition increased the grain, straw, and root Si concentration in LASi, with the effect being independent of amount added. However, for HASi, Si-rich biochar had no effect on straw Si concentration. Conclusions The alkaline pre-treatment of Si-rich biomass can improve its Si release efficiency, leading to increased labile Si content in the soil and improved soil Si availability. Therefore, alkali-modified Si-rich biochar can better sustain Si availability in soils characterized by high weathering and severe desilication.

In recent years, frequent occurrences of low temperature disasters due to global climate change have significantly impacted the normal growth of crops. Research has indicated that inorganic selenium (which is more toxic) can not only enhance the effects of low temperature stress but also increase selenium content on plants; however, there is a scarcity of studies investigating the impacts of organic selenium and nano-selenium on crops. In order to investigate whether organic selenium and nano-selenium can enhance low-temperature tolerance and increase selenium content in pak choi (Brassica chinensis var. pekinensis. cv. ‘Suzhouqing’), different concentrations (0, 5, 10, 20 mg L-1) of exogenous selenium were applied in this experiment to assess their effects on plant growth, nutritional quality and antioxidant properties. RNA-Seq technology was used to sequence the transcriptome of the leaves. Based on the transcriptome data, a Weighted Gene Co-expression Network Analysis (WGCNA) was employed to construct a network that associates with physiological traits related to stress resistance. Two highly correlated gene co-expression modules were identified, and within them, nine hub genes associated with endocytosis, antioxidant stress, absorption, transport, and metabolism of selenium were discovered. The results indicated that the beneficial effects on yield and total selenium content under low temperature were attributed to (1) protection of photosynthetic pigments for enhancing photosynthetic capacity by the up-regulation of LHca2, LHcb1, LHca1, LHcb4 in KEGG pathway: photosynthesis-antenna proteins; (2) activation of antioxidant system for efficient ROS homeostasis such as SOD, POD and CAT by the genes such as Superoxide dismutase, Monodehydroascorbate and (3) selenium absorption by endocytosis, seleninum transportation by ABC transporter gene family and selenium metabolism related genes such as Cysteine synthase, Glutaredoxin. These findings provide a foundation for further investigation into the molecular mechanisms underlying the effects of organic selenium and nano-selenium on cyanochloride production at low temperatures.