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Existing agricultural nitrogen datasets in China are mostly developed using coarse national or provincial statistics. A crop‐specific nitrogen rate dataset based on the finest‐scale agricultural nitrogen statistics at the county level remains lacking. Here, we constructed a new dataset (CN‐N), which provides annual nitrogen rates for rice, wheat and maize in China at a 1‐km spatial resolution from 2004 to 2016. This dataset was developed by harmonizing county‐level and provincial agricultural nitrogen statistics with gridded crop distribution maps, resulting in 13 years of nitrogen rate maps for each crop covering 2004–2016. Validation against farmers' surveys by crop indicates CN‐N reliably quantifies average nitrogen rates and trends for each crop over 2004–2016, demonstrating improved spatial heterogeneity compared to previous datasets rasterized using only provincial statistics. Our study provides a crop‐specific, temporally consistent, gridded nitrogen rate dataset based on the finest‐scale county‐level agricultural nitrogen statistics. This can support future process‐based modelling for sustainable agricultural nitrogen management strategies. [ABSTRACT FROM AUTHOR]

Nitrogen (N) and phosphorus (P) fertilizers change the morphological structure and effectiveness of P in the soil, which in turn affects crop growth, yield, and quality. However, the effects and mechanism of combined N and P application on the content of P fractions and the transformation of effective forms in alfalfa (Medicago sativa L.) production is unclear. This experiment was conducted with four levels of N: 0 (N0), 60 (N1), 120 (N2) and 180 kg·ha-1 (N3); and two levels of P (P2O5): 0 (P0) and 100 kg·ha-1 (P1). The results indicated that, under the same N level, P application significantly increased soil total N, and total P, available P, and content of various forms of inorganic P when compared to no P application, while decreasing the content of various forms of organic P and pH value. In general, under P0 conditions, soil total N content tended to increase with increasing N application, while total P, available P content, pH, inorganic P content in all forms, and organic P content in all forms showed a decreasing trend. When compared to no N application, insoluble P (Fe-P, O-P, Ca10-P) of the N application treatments was reduced 2.80 - 22.72, 2.96 - 20.42, and 5.54 - 20.11%, respectively. Under P1 conditions, soil total N and O-P tended to increase with increasing N application, while, pH, Ca2-P, Al-P, Fe-P, Ca10-P, and organic P content of each form tended to decrease. Total P, available P, and labile organic P (LOP) of N application reduced 0.34 - 8.58, 4.76 - 19.38, and 6.27 - 14.93%, respectively, when compared to no application. Nitrogen fertilization reduced the soil Ca2-P ratio, while P fertilization reduced soil Fe-P, moderately resistant organic P (MROP), and highly resistant P (HROP) ratios, and combined N and P elevated the Ca8-P to LOP ratio. The results of redundancy analysis showed that soil total N content, available P content, and pH were the key factors affecting the conversion of P fractions in the soil. Nitrogen and P reduced the proportion of soil insoluble P, promoted the activation of soil organic P, resulting in accumulation of slow-acting P in the soil, thereby improving the efficiency of soil P in alfalfa production. [ABSTRACT FROM AUTHOR]

This study was designed to determine the optimal nitrogen application rate for strong-gluten wheat cultivation in the North China Plain. Employing Zhongmai 578, a strong-gluten wheat variety, a field experiment was conducted with the following four nitrogen levels: 0 kg/ha (N0), 150 kg/ha (N1), 210 kg/ha (N2), and 270 kg/ha (N3). The research focused on examining the impact of nitrogen application on the photosynthesis, yield, and quality of strong-gluten wheat. The findings revealed that the N2 treatment (210 kg/ha) yielded the highest results compared to the N0 treatment. Photosynthetic parameters, including chlorophyll content in wheat flag leaves, generally exhibited an increase followed by a decrease, peaking at 7 days after anthesis (except for the transpiration rate, which peaked at 14 days post-anthesis). In the first year, quality indices such as water absorption, capacity, sedimentation value, ductility, protein, and wet gluten initially increased and then decreased with rising nitrogen levels. Conversely, in the second year, these quality indices, including hardness, showed a progressive increase with elevated nitrogen application. These results indicate that enhanced nitrogen application can significantly improve the photosynthetic characteristics of strong-gluten wheat, thereby augmenting both yield and quality. Within the parameters of this experiment, an application of 210 kg/ha of nitrogen emerged as the optimal rate, promoting the superior yield and quality of strong-gluten wheat in the North China Plain. [ABSTRACT FROM AUTHOR]

The nitrogen application rate (NAR) has a significant effect on the contents of wheat grain protein and its composition. There is still no consensus regarding the appropriate NAR, given the differences in studied conditions and influence of factors such as geographical location, climate, and soil nutrient contents. In this study, 66 papers related to wheat grain protein and its composition published from 1984 to 2021 were selected for meta-analysis in comprehensively evaluating the response of wheat grain protein content and composition to NAR in China. The results reveal that NAR significantly increased total protein content by 9.49–28.6%, gliadin by 9.13–30.5%, glutenin by 12.9–45.4%, albumin by 5.06–15.8%, and globulin by 8.52–24.0% of wheat grain in China, respectively, compared to no nitrogen application. The optimal NAR is 240–300 kg ha−1 when specific planting conditions are not being considered. Under different growing conditions, the NAR that provided the greatest increase in wheat grain protein and its composition varied as follows: 180–240 kg ha−1 in Northwest China and at >100 m altitudes; >300 kg ha−1 in North China and at <100 m altitudes and lower soil base nutrient levels; 240–300 kg ha−1 in Southeast China, with higher soil nutrients levels and for all average annual temperatures and precipitation ranges. In conclusion, the results of the present study reveal that it is feasible to systematically enhance the contents of wheat grain protein and its related fractions by appropriate NAR under different cropping conditions. [ABSTRACT FROM AUTHOR]

Nitrogen is one of the significant pollutants emitted from coal combustion, and the study of its distribution and occurrence is very important for the efficient and clean utilization of coal resources. Four kinds of coal with different metamorphic ranks from major coal-producing provinces of China were studied. A gravity float-and-sink experiment was applied to obtain coal samples with different densities from Shanxi Province. The microscope optical method, Kjeldahl method, and X-ray photoelectron spectroscopy (XPS) were used to assess the occurrence, form, and distribution of nitrogen in the coal. The results show that the nitrogen content was about 0.47%–1.85%, and the maximum nitrogen content was positively correlated with the rank of coal, but the difference was not obvious. In the low-rank coal, the nitrogen content was mainly related to vitrinite and inertinite, while in the middle–high-rank coal, the nitrogen content was mainly related to inertinite and minerals. Pyrrolic (N-5) and pyridinic (N-6) were the main forms of nitrogen in the low-rank coal. The contents of N-6 and N-5 decreased with increases in the coal density, but the contents of quaternary N-Q1 and quaternary N-Q2 increased. N-Q2 mainly comes from fixed ammonia nitrogen in minerals, and vitrinite and liptinite contain more N-6 and less N-Q1 than inertinite. This research provides valuable evaluation guidance for the efficient utilization of coal. [ABSTRACT FROM AUTHOR]

Davidia involucrata is a woody perennial and the only living species in the Genus Davidia. It is native to southern China where it holds cultural and scientific importance. However, D. involucrata is now an endangered species and its natural range includes low pH soils which are increasingly impacted by acid rain, nitrogen deposition and imbalanced nutrient cycling. The combination of these stresses also poses the additional risk of aluminum (Al) toxicity. Since the responses of D. involucrata to low pH and aluminum toxicity have not been investigated previously, a hydroponic experiment was conducted to examine the growth of one year old D. involucrata saplings after 50 d growth in a range of pH and Al conditions. Plant biomass, morphology, antioxidant enzyme activity, mineral concentrations and plant ecological strategy were compared at pH 5.8 and pH 4.0 without added Al (AlCl3) and in 0.1, 0.2 and 0.5 mM Al at pH 4.0. Our results showed that compared with pH 5.8, pH 4.0 (without added Al) not only inhibited root and shoot growth but also limited accumulation of nitrogen (N) and phosphorus (P) in leaves of D. involucrate. However, low Al concentrations (0.1 and 0.2 mM Al) at pH 4.0 partially restored the aboveground growth and leaf N concentrations, suggesting an alleviation of H+ toxicity by low Al concentrations. Compared with low Al concentrations, 0.5 mM Al treatment decreased plant growth and concentrations of N, P, and magnesium (Mg) in the leaves, which demonstrated the toxicity of high Al concentration. The results based on plant ecological strategy showed that D. involucrate decreased the competitiveness and favored its stress tolerance as pH changed from 5.8 to 4.0. Meanwhile, the competitiveness and stress tolerance of D. involucrata increased and decreased at low Al concentrations, respectively, and decreased and increased at high Al concentration, respectively. These trade-offs in ecological strategy were consistent with the responses of growth and antioxidant enzyme activity, reflecting a sensitive adaptation of D. involucrata to acid and Al stresses, which may aid in sustaining population dynamics. These findings are meaningful for understanding the population dynamics of D. involucrata in response to aluminum toxicity in acid soils. [ABSTRACT FROM AUTHOR]

With the development of rice varieties and mechanized planting technology, reliable and efficient nitrogen and planting density status diagnosis and recommendation methods have become critical to the success of precise nitrogen and planting density management in crops. In this study, we combined population structure, plant shape characteristics, environmental weather conditions, and management information data using a machine learning model to simulate the responses of the yield and nitrogen nutrition index and developed an ensemble learning model-based nitrogen and planting density recommendation strategy for different varieties of rice types. In the third stage, the NNI and yield prediction effect of the ensemble learning model was more significantly improved than that of the other two stages. The scenario analysis results show that the optimal yields and nitrogen nutrition indices were obtained with a density and nitrogen amount of 100.1 × 104 plant/ha and 161.05 kg·ha−1 for the large-spike type variety of rice, 75.08 × 104 plant/ha and 159.52 kg·ha−1 for the intermediate type variety of rice, and 75.08 × 104 plant/ha and 133.47 kg·ha−1 for the panicle number type variety of rice, respectively. These results provide a scientific basis for the nitrogen application and planting density for a high yield and nitrogen nutrition index of rice in northeast China. [ABSTRACT FROM AUTHOR]

Leaf senescence have shed light on its contribution to the recovery of nutrients and signaling of the transition from the active to the dormant stage in winter. The manner by which climatic and edaphic factors and plant phylogeny affect the senescent leaf economics spectrum (more mineral elements included) of different growth habits along elevational gradients in mountain ecosystems is highly uncertain. To fill this knowledge gap, we examined 15 representative subalpine forest species' senescent leaf functional traits (i.e., specific leaf area [SLA], leaf dry matter content [DMC], pH, carbon [C], nitrogen [N], phosphorus [P], potassium [K], calcium [Ca], sodium [Na], magnesium [Mg], manganese [Mn], aluminum [Al], iron [Fe], C:N, N:P, and C:P ratios) to determine the senescent leaf economics spectrum along elevational gradients in the Hengduan Mountains, China. Our results demonstrate that all the functional traits of senescent leaf showed strong correlations with one another, and K was observed as the hub for the leaf economics spectrum. Irrespective of the difference among growth habits (arbor vs. shrub), leaf habits (deciduous vs. evergreen), and leaf types (broad vs. needle), the variations in the two‐dimensional spectrum of the senescent leaf trait exhibited uniformly positive associations with elevation, primarily attributed to climatic drivers. However, the modulation of the senescent leaf economics spectrum by soil properties and plant phylogeny was surprisingly modest. Collectively, our results revealed that the resource trade‐off of senescent leaf showed a trend from acquisition to conservation along elevational gradients, which could broaden the plant economics spectrum to include senescent leaf. [ABSTRACT FROM AUTHOR]

Purpose: Dam construction can impact nitrogen accumulation in reservoir sediments and may potentially lead to internal release due to intricate nitrogen cycling at the sediment–water interface (SWI), exacerbating nitrogen loading in the water body. This study aims to clarify the transformation and transportation processes and key influencing factors of nitrogen species at the SWI in deep reservoirs. Methods: Two consecutive sediment cores were collected from Baihua Reservoir (BHR) and Hongjiadu Reservoir (HJD) in July 2019 and were stratified on-site. Pore water was extracted via centrifugation for water-soluble inorganic nitrogen measurement. Adsorbed inorganic nitrogen was extracted using 2 mol L−1 KCl. Inorganic nitrogen forms were measured by an analytical continuous flow analyzer (SEAL Analytical Limited, Germany). Particulate organic nitrogen (PON) samples were obtained after the removal of inorganic carbon and inorganic nitrogen with 2 mol L−1 KCl and 0.5 mol L−1 HCl. Stable isotopes (δ15N-PON) and the ratios of C/N were measured via a stable isotopic mass spectrometer (MAT-253) and an elemental analyzer (Elementar, Rhine main, Germany). Fick's First Law and Grey correlation analysis (GCA) were employed to estimate the diffusion fluxes and controlling factors. Results: The sediment nitrogen concentrations in BHR were influenced by higher-level anthropogenic activities, as indicated by the comparison of nitrogen concentrations and δ15N-PON values (averaging 9.13‰ and 5.39‰ in BHR and HJD, respectively). Dissolved oxygen (DO) was the key factor affecting nitrogen transformation processes at the SWI. Mineralization and nitrification were dominant in HJD, while BHR exhibited mineralization, denitrification, and potential anaerobic ammonia oxidation (anammox). Livestock waste and soil organic matter were common sources of PON in both reservoirs. Moreover, the contribution of phytoplankton in BHR was also significant due to high-level eutrophication. Evaluations of diffusion fluxes revealed that both sediments in BHR and HJD acted as sources of water-soluble ammoniacal nitrogen (NH4+-N) for internal release (0.97 and 0.27 mg m−2 day−1 in BHR and HJD, respectively). Additionally, adsorbed NH4+-N exhibited high-level diffusion fluxes in both BHR (15.81 m−2 day−1) and HJD (3.37 m−2 day−1). Furthermore, GCA revealed that pH, T, and DO trigger the desorption of adsorbed nitrogen, leading to an increase in the nitrogen load in the overlying water. Conclusion: Sediments in eutrophic reservoirs experience high-level nitrogen inputs. Complex nitrogen cycling processes at the SWI and environmental factors (pH, DO, and T) may lead to significant internal releases. Further studies on the fate of nitrogen at the SWI in different eutrophic-level reservoirs are still necessary. [ABSTRACT FROM AUTHOR]

Estimation of energy partitioning at leaf scale, such as fluorescence yield (ΦF) and photochemical yield (ΦP), is crucial to tracking vegetation gross primary productivity (GPP) at global scale. Nitrogen is an important participant in the process of light capture, electron transfer, and carboxylation in vegetation photosynthesis. However, the quantitative relationship between leaf nitrogen allocation and leaf energy partitioning remains unexplored. Here, a field experiment was established to explore growth stage variations in energy partitioning and nitrogen allocation at leaf scale using active fluorescence detection and photosynthetic gas exchange method in rice in the subtropical region of China. We observed a strongly positive correlation between the investment proportion of leaf nitrogen in photosynthetic system and ΦF during the vegetative growth stage. There were significant differences in leaf energy partitioning, leaf nitrogen allocation, and the relationship between ΦF and ΦP before and after flowering. Furthermore, flowering weakened the correlation between the investment proportion of leaf nitrogen in photosynthetic system and ΦF. These findings highlight the crucial role of phenological factors in exploring seasonal photosynthetic dynamics and carbon fixation of ecosystems. [ABSTRACT FROM AUTHOR]

The nitrogen deposition process, as an important phenomenon of global climate change and an important link in the nitrogen cycle, has had serious and far-reaching impacts on grassland ecosystems. This study aimed to investigate the survival adaptation strategies of plants of different functional groups under nitrogen deposition, and the study identified the following outcomes of differences in biomass changes by conducting in situ simulated nitrogen deposition experiments while integrating plant nutrient contents and soil physicochemical properties: (1) nitrogen addition enhanced the aboveground biomass of grassland communities, in which Poaceae were significantly affected by nitrogen addition. Additionally, nitrogen addition significantly influenced plant total nitrogen and total phosphorus; (2) nitrogen addition improved the plant growth environment, alleviated plant nitrogen limitation, and promoted plant phosphorus uptake; and (3) there was variability in the biomass responses of different functional groups to nitrogen addition. The level of nitrogen addition was the primary factor affecting differences in biomass changes, while nitrogen addition frequency was an important factor affecting changes in plant community structure. [ABSTRACT FROM AUTHOR]

Forest productivity usually declines with the increase in the age of stand, which may be associated with the disturbance in the balance of nitrogen (N) and phosphorus (P) nutrients. However, the effects of stand age on plantation nutrient balance and productivity in plantation is still unclear. Therefore, an experiment was conducted in this study to investigate the influence of the increase in the age of stand (6‐, 10‐, 15‐, 25‐, 30‐, and 34‐year‐old stands) on plant growth and the dynamics of N and P in Castanopsis hystrix plantations of Southern China. The increase in the age of stand reduced plantation productivity and leaf N:P. Moreover, productivity was found to be positively correlated with leaf N:P, reflecting that the decrease in productivity was related to changes in N and P contents in leaves. Reduction in leaf N:P was associated with declining N content and stable P content in leaves. The decrease in leaf N content may be due to the declining NO3−–N and microbial biomass N contents in soil, although activities of N‐acetylglucosaminidase, cellobiohydrolase, and polyphenol oxidase decreased with the increase in stand age. The stability of leaf P content may be associated with the increase in soil total P and microbial biomass P, boosting P supply to plants. In contrast, decreased soil phosphatase activity with the increase in the age of stand likely suggests that no additional P was needed through P mineralization. The findings indicate that increasing stand age would improve N consumption but alleviate relative P limitations. Thus, more attention needs to be paid to N fertilizer management (e.g., 10–15‐year stages) to sustain C. hystrix productivity with stand age. [ABSTRACT FROM AUTHOR]

Premise: Previous work searching for sexual dimorphism has largely relied on the comparison of trait mean vectors between sexes in dioecious plants. Whether trait scaling (i.e., the ratio of proportional changes in covarying traits) differs between sexes, along with its functional significance, remains unclear. Methods: We measured 10 vegetative traits pertaining to carbon, water, and nutrient economics across 337 individuals (157 males and 180 females) of the diocious species Eurya japonica during the fruiting season in eastern China. Piecewise structural equation modeling was employed to reveal the scaling relationships of multiple interacting traits, and multivariate analysis of (co)variance was conducted to test for intersexual differences. Results: There was no sexual dimorphism in terms of trait mean vectors across the 10 vegetative traits in E. japonica. Moreover, most relationships for covarying trait pairs (17 out of 19) exhibited common scaling slopes between sexes. However, the scaling slopes for leaf phosphorus (P) vs. nitrogen (N) differed between sexes, with 5.6‐ and 3.0‐fold increases of P coinciding with a 10‐fold increase of N in male and female plants, respectively. Conclusions: The lower ratio of proportional changes in P vs. N for females likely reflects stronger P limitation for their vegetative growth, as they require greater P investments in fruiting. Therefore, P vs. N scaling can be a key avenue allowing for sex‐specific strategic optimization under unequal reproductive requirements. This study uncovers a hidden aspect of secondary sex character in dioecious plants, and highlights the use of trait scaling to understand sex‐defined economic strategies. [ABSTRACT FROM AUTHOR]

Leaf nutrient content (nitrogen, phosphorus) and their stoichiometric ratio (N/P) as key functional traits can reflect plant survival strategies and predict ecosystem productivity responses to environmental changes. Previous research on leaf nutrient traits has primarily focused on the species level with limited spatial scale, making it challenging to quantify the variability and influencing factors of forest leaf nutrient traits on a macro scale. This study, based on field surveys and literature collected from 2005 to 2020 on 384 planted forests and 541 natural forests in China, investigates the differences in leaf nutrient traits between forest types (planted forests, natural forests) and their driving factors. Results show that leaf nutrient traits (leaf nitrogen content (LN), leaf phosphorus content (LP), and leaf N/P ratio) of planted forests are significantly higher than those of natural forests (P< 0.05). The impact of climatic and soil factors on the variability of leaf nutrient traits in planted forests is greater than that in natural forests. With increasing forest age, natural forests significantly increase in leaf nitrogen and phosphorus content, with a significant decrease in N/P ratio (P< 0.05). Climatic factors are key environmental factors dominating the spatial variability of leaf nutrient traits. They not only directly affect leaf nutrient traits of planted and natural forest communities but also indirectly through regulation of soil nutrients and stand factors, with their direct effects being more significant than their indirect effects. [ABSTRACT FROM AUTHOR]

Introduction: Variation in plant nitrogen uptake rate and substrate preference is complicated due to the combined influence of abiotic and biotic factors. For the same species of tree across different ages, the interactions between root structural traits, nitrogen uptake rate, and soil environment have not been fully characterized, a situation that constrains our understanding of underground resource strategies employed by trees at different ages. Methods: In the present study, we examined the nitrogen uptake rate, mycorrhiza, morphology, architecture, and chemistry of the roots of Larix principis-rupprechtii in a chronosequence (aged 18, 27, 37, 46, and 57 years) in the Saihanba Mechanical Forest Farm in Northern China. Results: L. principis-rupprechtii preferred to absorb ammonium, followed in order by glycine and nitrate. The ammonium uptake rate of L. principisrupprechtii significantly decreased (aged 18-37 years) and then increased (aged 46-57 years) with tree age. The glycine, nitrate, and total nitrogen uptake rates decreased with tree age. The root resource acquisition strategy appeared to shift from an acquisitive strategy to a conservative strategy associated with increasing tree age. Discussion: Along the root-mycorrhizal collaboration gradient, the younger L. principis-rupprechtii relied more on their own root morphology and physiology to acquire resources, adopting a "do it yourself" strategy comprising increasing the specific root length, the specific root area, and the N uptake rate (nitrate and glycine). Conversely, older trees depended more on mycorrhizal partners to acquire nitrogen resources, an "outsourcing" strategy. The results contribute to our understanding of underground resource-use strategies of plants and the nitrogen cycle in forest ecosystems according to stand age. [ABSTRACT FROM AUTHOR]

The brief history of monitoring nutrient levels in Chinese lake waters limits our understanding of the causes and the long-term trends of their eutrophication and constrains effective lake management. We therefore synthesize nutrient data from lakes in China to reveal the historical changes and project their future trends to 2100 using models. Here we show that the average concentrations of nitrogen and phosphorus in lake sediments have increased by 267% and 202%, respectively since 1850. In the model projections, 2030–2100, the nitrogen concentrations in the studied lakes in China may decrease, for example, by 87% in the southern districts and by 19% in the northern districts. However, the phosphorus concentrations will continue to increase by an average of 25% in the Eastern Plain, Yunnan–Guizhou Plateau, and Xinjiang. Based on this differentiation, we suggest that nitrogen and phosphorus management in Chinese lakes should be carried out at the district level to help develop rational and sustainable environmental management strategies. Nutrient levels in Chinese lakes have rapidly increased since 1950 but future trends in lacustrine nitrogen and phosphorus across China will differentiate, according to projections up to 2100. [ABSTRACT FROM AUTHOR]

Reducing nitrogen fertilizer application, selecting a reasonable planting density, and adding silicon fertilizer can be used together to decrease excessive nitrogen fertilizer inputs in rice fields, reduce production costs, and ensure stable rice yield. However, the dynamics of the stem and internodes, as well as the changes in the physical and physiological characteristics of rice under a combination of these three strategies, are still unclear. In this study, we aimed to clarify these effects to improve the efficiency of rice production in northeastern China. A 2-year field experiment was conducted using five treatments: a conventional densification treatment (DM), a densification combined with reduced N input (−20%) treatment (DLM), and three densifications combined with reduced N input (−20%) and basal silicon fertilizer treatments (low fertilizer: DLMS1; medium fertilizer: DLMS2; and high fertilizer: DLMS3). This study revealed that the addition of silicon fertilizer improved rice yield compared to that under reduced nitrogen or increased density treatments alone, prevented excessive ineffective tillering after a density increase, and increased the number of productive panicles. Among the treatments, the DLMS3 treatment had the highest yields of 10.53 t/ha and 10.73 t/ha over the 2 years. Reducing nitrogen and increasing density reduced the weight and length of single panicles, while the addition of silicon fertilizer was beneficial for improving stem toughness, improving the physical and physiological characteristics of the plants and panicles, and enhancing plant bending resistance. Among the treatments, DLMS3 had the highest bending resistance, which increased by 440.1 g and 503.8 g compared to the lowest values in the DM treatment in 2020 and 2021, respectively. Nitrogen reduction resulted in the lowest lodging index values, with DLMS3 having the lowest values in both years, which decreased by 19.6% and 22.5% compared to the highest values in DM (2020) and DLM (2021), respectively. This study indicates that the application of 150.0 kg/ha silicon fertilizer in combination with reduced nitrogen and increased density (DLMS3) reduces the lodging index while ensuring rice yield, preventing a tradeoff between yield reduction and lodging due to a density increase or due to nitrogen reduction combined with a density increase and allowing for a reduction in nitrogen fertilizer input, which could ensure a uniform yield and an increase in lodging resistance. These results provide a scientific basis for rice cultivation measures that lead to high yield and lodging resistance while protecting the environment. [ABSTRACT FROM AUTHOR]

Nitrogen (N) is an essential nutrient for food production. The rapid increase in population requires high inputs of N to meet the growing food demand. If not managed well, the substantial loss of N from the food system has multiple impacts on grain yield, air and water pollution, and the economic benefits of agricultural. Multi-objective (food security, environmental sustainability and economic sustainability) synergistic consideration of N management in the food system is still lacking. This study employed strategies for optimizing N management in the food system, using Quzhou County as a typical example on the North China Plain. Firstly, a food chain approach was adopted to understand drivers and reasons behind N losses from the food system. Secondly, a top-down approach was used to define multi-objective N management, taking into consideration food security, environmental sustainability and economic sustainability. Multi-objective N management aims to reduce N losses to the environment and increase N use efficiencies, while simultaneously increasing yields and economic benefits. Thirdly, 3R (reduce-retain-recycle) N management strategies were identified for specific crops and animals through a bottom-up approach and then analyzed the potential of these strategies to achieve the multi-objectives. Finally, there is a discussion of how to engage different stakeholders to promote the technologies implementation. This study provides new insights into the synergistic achievement of multi-objective N management in the food system and the development of environmentally-friendly agriculture. [ABSTRACT FROM AUTHOR]

The effects of nitrogen application or earthworms on soil respiration in the Huang-Huai-Hai Plain of China have received increasing attention. However, the response of soil carbon dioxide (CO2) emission to nitrogen application and earthworm addition is still unclear. A field experiment with nitrogen application frequency and earthworm addition was conducted in the Huang-Huai-Hai Plain. Results showed nitrogen application frequency had a significant effect on soil respiration, but neither earthworms nor their interaction with nitrogen application frequency were significant. Low-frequency nitrogen application (NL) significantly increased soil respiration by 25%, while high-frequency nitrogen application (NH), earthworm addition (E), earthworm and high-frequency nitrogen application (E-NH), and earthworm and low-frequency nitrogen application (E-NL) also increased soil respiration by 21%, 21%, 12%, and 11%, respectively. The main reason for the rise in soil respiration was alterations in the bacterial richness and keystone taxa (Myxococcales). The NH resulted in higher soil nitrogen levels compared to NL, but NL had the highest bacterial richness. The abundance of Corynebacteriales and Gammaproteobacteria were positively connected with the CO2 emissions, while Myxococcales, Thermoleophilia, and Verrucomicrobia were negatively correlated. Our findings indicate the ecological importance of bacterial communities in regulating the carbon cycle in the Huang-Huai-Hai Plain. [ABSTRACT FROM AUTHOR]

In the production of small-seed peanut cultivars in South China, landraces with high plants and bred cultivars with dwarf plants were both planted. Thus a differential fertilization strategy had to be figured out according to their nitrogen requirements. In this study, the main landrace with high plants Anhua Xiaozi and improved dwarf cultivar Xianghei Xiaoguo were used as materials. Four compound fertilization rates were set including 0, 450, 600, and 750 kg/hm², representing soil background (CK), low (F30), medium (F40), and high (F50) fertilizer levels. Nitrogen content, accumulation, and distribution were recorded at 4 growth stages. Results showed that, in high landrace Anhua Xiaozi, N content were in the order of pod> leaf> root> stem, while those of dwarf cultivar Xianghei Xiaoguo were in leaf> pod> root> stem. N content in leaves and roots of Anhua Xiaozi was less than dwarf cultivar Xianghei Xiaoguo. The opposite trend was found in stems and pods. The influence degree of increasing fertilizer on N content was in the order of stem> leaf> root> pod, which was beneficial to N assimilation and absorption in vegetative organs. N accumulation in different organs of the 2 materials was leaf> pod> stem> root. Except the seedling stage, N accumulations of the whole plant, leaf and stem in other stages were larger in Anhua Xiaozi stem. N accumulations were both higher in Anhua Xiaozi pods and roots, but only in roots during seedling and podding stages. Fertilization was beneficial to N accumulation in early stages. N distribution rate of both varieties was the highest in leaves, and then in pods and stems. N distribution rate in higher variety were larger in aboveground parts, while the underground parts was the opposite. It indicated that N absorbed by dwarf variety was more conducive to transport to pods. N production efficiency was higher in dwarf Xianghei Xiaoguo. N production efficiency and N partial factor productivity of F40 and F30 treatments were both high, indicated that excessive fertilization decreased N use efficiency. In conclusion, lower response of N accumulation to fertilizer increase was found in dwarf cultivar Xianghei Xiaoguo, with less total accumulation but more distribution in pods. Therefore, in barren and acidic red soil regions in South China, peanut plant architecture should be considered during fertilizer determination. [ABSTRACT FROM AUTHOR]

Over the past decades, many forests have been converted to monoculture plantations, which might affect the soil microbial communities that are responsible for governing the soil biogeochemical processes. Understanding how reforestation efforts alter soil prokaryotic microbial communities will therefore inform forest management. In this study, the prokaryotic communities were comparatively investigated in a secondary Chinese fir forest (original) and a reforested Chinese fir plantation (reforested from a secondary Chinese fir forest) in Southern China. The results showed that reforestation changed the structure of the prokaryotic community: the relative abundances of important prokaryotic families in soil. This might be caused by the altered soil pH and organic matter content after reforestation. Soil profile layer depth was an important factor as the upper layers had a higher diversity of prokaryotes than the lower ones (p < 0.05). The composition of the prokaryotic community presented a seasonality characteristic. In addition, the results showed that the dominant phylum was Acidobacteria (58.86%) with Koribacteraceae (15.38%) as the dominant family in the secondary Chinese fir forest and the reforested plantation. Furthermore, soil organic matter, total N, hydrolyzable N, and NH+ 4 - N were positively correlated with prokaryotic diversity (p < 0.05). Also, organic matter and NO-3 -N were positively correlated to prokaryotic abundance (p < 0.05). This study demonstrated that re-forest transformation altered soil properties, which lead to the changes in microbial composition. The changes in microbial community might in turn influence biogeochemical processes and the environmental variables. The study could contribute to forest management and policy-making. [ABSTRACT FROM AUTHOR]

Wheat yield and nitrogen use efficiency (NUE) have improved simultaneously with the genetic development of wheat varieties. However, wheat selection is carried out routinely in N‐rich field conditions, with breeding progress limited under low soil available nitrogen. Thus, we performed a 2‐year field investigation using eight milestone winter wheat varieties released between 1947 and 2017 in the Huang‐Huai‐Hai region of China with two N applications—normal (CK; 220 kg N ha−1) and reduced (RN; 110 kg N ha−1)—in Shaanxi, China, to examine changes in wheat yield, NUE, water use efficiency (WUE) and root biomass. Our findings revealed average annual yield increases of 49.615 kg ha−1 and 36.905 kg ha−1 under CK and RN, respectively. Notably, the NUE trend mirrored yield, increasing with the release year of wheat varieties, with average annual increases in NUE of 0.192 and 0.336 kg kg−1 under CK and RN, respectively. In the RN treatment, N uptake efficiency (UPE) increased with year of release, while N utilization efficiency (UTE) had no significant relationship. In the CK treatment, UTE increased with year of release, while UPE had no significant relationship. Across the 2‐year experiment, surface root biomass (0–20 cm layer) increased with year of release under CK but had no relationship under RN, while deep root biomass (20–200 cm layer) decreased with year of release under CK and increased under RN. The roots of modern wheat varieties responded better to soil nitrogen levels and produced higher yields, NUE and WUE than earlier varieties by adjusting root biomass distribution in soil. [ABSTRACT FROM AUTHOR]

Free‐living N2 fixation (FNF) is an important source of bioavailable nitrogen for forests. Though increasing plant species diversity (PSD) benefits soil nitrogen accumulation, how it impacts FNF rate has not been explored.Forty‐five plots covering a PSD gradient were selected in a subtropical karst forest, southwest China. FNF rates in leaf litter and soil were measured using acetylene reduction assay calibrated with a 15N2 fixation method. Diazotrophic community, litter and soil properties were determined as well.The nifH gene abundance was not significantly altered in litter but was significantly decreased in soil by higher PSD. Diazotrophic community's Shannon diversity was significantly increased by higher PSD in both litter and soil. Increasing PSD inhibited litter FNF rate via aggravating phosphorus limitation and decreasing the relative abundance of Betaproteobacteria and Deltaproteobacteria. For the mineral soil horizon, increasing PSD suppressed FNF rate via decreasing nifH gene abundance caused by elevated N availability and lowered phosphorus and iron availability or through decreasing the relative abundance of Deltaproteobacteria but increasing that of Betaproteobacteria.Our findings, for the first time, reveal the microbial and abiotic controls on FNF in litter and soil in response to PSD, and hence benefit the prediction of nitrogen input via biological N2 fixation under changes in PSD. Read the free Plain Language Summary for this article on the Journal blog. [ABSTRACT FROM AUTHOR]

Denitrification plays a critical role in soil nitrogen (N) cycling, affecting N availability in agroecosystems. However, the challenges in direct measurement of denitrification products (NO, N2O, and N2) hinder our understanding of denitrification N losses patterns across the spatial scale. To address this gap, we constructed a data‐model fusion method to map the county‐scale denitrification N losses from China's rice fields over the past decade. The estimated denitrification N losses as a percentage of N application from 2009 to 2018 were 11.8 ± 4.0% for single rice, 12.4 ± 3.7% for early rice, and 11.6 ± 3.1% for late rice. The model results showed that the spatial heterogeneity of denitrification N losses is primarily driven by edaphic and climatic factors rather than by management practices. In particular, diffusion and production rates emerged as key contributors to the variation of denitrification N losses. These findings humanize a 38.9 ± 4.8 kg N ha−1 N loss by denitrification and challenge the common hypothesis that substrate availability drives the pattern of N losses by denitrification in rice fields. [ABSTRACT FROM AUTHOR]

Obtaining a holistic understanding of the impacts of atmospheric nitrogen deposition on multiple ecosystem services of forest is essential for developing comprehensive and sustainable strategies, particularly in heavy N deposition regions such as subtropical China. However, such impacts remain incompletely understood, with most previous studies focus on individual ecosystem function or service via understory N addition experiments. To address this knowledge gap, we quantified the effects of over-canopy and understory N additions on multiple ecosystem services based on a 7-year large-scale field experiment in a typical subtropical forest. Our results showed continued over-canopy N addition with 50 kg ha−1 year−1 over a period of 4–7 years significantly increased plant nutrient retention, but did not affect the services of soil nutrient accumulation, water yield, C sequestration (in plants and soil), or oxygen release. There were trade-offs between the soil and plant on providing the services of nutrient accumulation/retention and C sequestration under over-canopy N addition. However, without uptake and retention of tree canopy, the trade-off between soil and plant were more weaken under the understory N addition with 50 kg ha−1 year−1, and their relationships were even synergetic under the understory N addition with 25 kg ha−1 year−1. The results suggest that understory N addition cannot accurately simulate the effects of atmospheric N deposition on multiple services, along with mutual relationships. Interestingly, the services of plant N, P retention, and C sequestration exhibited a synergetic increase under the over-canopy N addition but a decrease under the understory N addition. Our results also found tree layer plays a primary role in providing plant nutrient retention service and is sensitive to atmospheric N deposition. Further studies are needed to investigate the generalized effects of forest canopy processes on alleviating the threaten of global change factors in different forest ecosystems. [ABSTRACT FROM AUTHOR]

Reabsorbing nutrients from senescent tissues before leaf falling has been recognized as a strategy to adapt to nutrient deficiency. However, how nutrient resorption modulates the nitrogen (N)–phosphorus (P) balance inside plants remains unclear, especially under increased soil N availability. We examined the impacts of N addition at varying rates (0–32 g N m−2 yr−1) on nutrient resorption and the performance of nutrient resorption on controlling the internal N–P balance in the leaf and stem of a dominant grass species, Leymus secalinus , in a saline–alkaline grassland in northern China. After 6 years of N addition, N concentration and N:P ratio in green and senesced tissues (leaf and stem) rose with increasing N addition. The P concentration in green tissues decreased, but did not significantly change in senesced tissues with increasing N addition. The N resorption efficiency (NRE), P resorption efficiency (PRE), and NRE:PRE ratio significantly decreased along the N addition gradient. Moreover, we found more sensitive responses of N:P ratio in senesced tissues than in green tissues; such exacerbation of plant internal N–P imbalances mainly resulted from a disproportionate reduction in nutrient resorption, especially NRE. Overall, our study suggested that differences in NRE and PRE further exacerbated the internal N–P imbalances in plant litters. [ABSTRACT FROM AUTHOR]

Global warming is predicted to change precipitation amount and reduce precipitation frequency, which may alter grassland primary productivity and biomass allocation, especially when interact with other global change factors, such as nitrogen deposition. The interactive effects of changes in precipitation amount and nitrogen addition on productivity and biomass allocation are extensively studied; however, how these effects may be regulated by the predicted reduction in precipitation frequency remain largely unknown. Using a mesocosm experiment, we investigated responses of primary productivity and biomass allocation to the manipulated changes in precipitation amount (PA: 150 mm, 300 mm, 450 mm), precipitation frequency (PF: medium and low), and nitrogen addition (NA: 0 and 10 g N m-2 yr-1) in a Leymus chinensis grassland. We detected significant effects of the PA, PF and NA treatments on both aboveground biomass (AGB) and belowground biomass (BGB); but the interactive effects were only significant between the PA and NA on AGB. Both AGB and BGB increased with an increment in precipitation amount and nitrogen addition; the reduction in PF decreased AGB, but increased BGB. The reduced PF treatment induced an enhancement in the variation of soil moisture, which subsequently affected photosynthesis and biomass formation. Overall, there were mismatches in the above- and belowground biomass responses to changes in precipitation regime. Our results suggest the predicted changes in precipitation regime, including precipitation amount and frequency, is likely to alter primary productivity and biomass allocation, especially when interact with nitrogen deposition. Therefore, predicting the influence of global changes on grassland structure and functions requires the consideration of interactions among multiple global change factors. [ABSTRACT FROM AUTHOR]

In large river basins, the nitrogen (N) cycle is largely regulated by complicated interactions between human and natural elements. Nevertheless, the origins, fate and driving forces of reactive nitrogen (Nr) flows in the basins are still not clear. An estimation model of N flux was established for evaluating the Nr flow and its environmental effects in the Yellow River Basin of Henan Province (HYRB) by means of material flow analysis. Total N input and output of HYRB were calculated at 4090.9 and 3948.8 Gg N yr−1, causing 142.0 Gg yr−1 of N stored in the basin. Industry, cropland and residential activities, respectively occupied for 42.2%, 23.2% and 12.3% of the whole input, as well as 43.6%, 25.1% and 12.3% of the whole output, which were central to HYRB's N cycle. Anthropogenic activities regulated above 95.0% of total inputs, and 49.5% of N outputs was emitted into the air and 4.5% into hydrosphere. High N input, energy intensive, imperfect sewage disposal facilities and low N utilization efficiency were the main reasons of contaminate. How to effectively regulate the input of high-strength N pollutant associated with insufficient N cycling and Nr elimination is the main issue in the Yellow River Basin. In present research also put forward corresponding control measures according to the evaluation of N flow and Nr release of HYRB. The research can supply science foundation for coordinating the human–environment relationship in large basins, and also has important reference significance for the formulation of Nr emission reduction strategies. [ABSTRACT FROM AUTHOR]

Introduction: Water is an important ecological factor, and non-point source pollution (NPSP) seriously affects water security. In recent years, NPSP has affected water security and human survival in China. Methods: The Luhun Lake Basin has been selected as an example region of Yellow River Basin (YRB) in China, and the trends and impacts of nitrogen (N) and phosphorus (P) has been quantitatively evaluated by using geographic information system (GIS), remote sensing (RS) and InVEST model. Results: The results show that (1) the arable land and water bodies decreased, while forest land, grass land, construction land and unutilized land increased in the 20 years. The average annual precipitation increased from the northeast to the southwest in the 20 years; (2) the N and P exports first increased in 2000-2010 and then decreased in 2010-2020, and finally increased in 2000-2020; (3) with the increase of precipitation, the N and P exports decreased in 2000-2010, 2010-2020 and 2000-2020; (4) the amount of N and P exports on arable land and construction land were more than that on the other land use types. The N and P exports on each land use type all first increased and then decreased, and the overall change trend all increased in 2000-2020. Discussion: This study demonstrates how geographic information system (GIS), remote sensing (RS) and InVEST model can be used to assess nitrogen and phosphorus pollution in data scarce regions. [ABSTRACT FROM AUTHOR]

Although straw returning to the field (SRTTF) is conducive to promoting sustainable agricultural production and protecting the environment, straw resources are still wasted due to the lack of suitable straw-returning technology in southern China. Based on the statistical yearbook and a large number of studies, different methods were used to calculate the total straw resources and SRTTF potential, and differences in these methods were compared. The results indicate that the total amount of straw resources in southern China in 2021 was 3.35×108 t. The nutrient content of K2O in the straw accounted for the highest proportion of total nutrient resources (63.66%), followed by N (26.88%) and P2O5 (9.46%). In theory, total SRTTF could replace almost all K2O and part of N and P2O5, indicating that the nutrient substitution potential of SRTTF was high. It is suggested that the SRTTF method be adopted in the middle and lower reaches of the Yangtze River, which mainly uses direct returning (DR) supplemented by indirect returning (IDR). In southeast China, straw returning is carried out by the combination of IDR and IR. In southwest China, straw returning is mainly carried out by IR and supplemented by MDR. This study will provide theoretical support for the government to formulate straw-returning policy. [ABSTRACT FROM AUTHOR]

This study investigates the decomposition process of algal blooms (ABs) in eutrophic lakes and its impact on the labile endogenous nitrogen (N) cycle. In situ techniques such as diffusive gradients in thin films (DGT) and high-resolution dialysis (HR-Peeper) were employed to decipher the vertical distribution of N fractions within the sediment–water interface (SWI) in Taihu, China. Additionally, an annular flume was used to simulate regional differences in lake conditions and understand labile nitrogen transformation during AB decomposition. This study reveals that the NH4+-N fraction exuded from algae is subsequently converted into NO3-N and NO2-N through nitrification, resulting in a significant increase in the concentrations of NO3−-N and NO2−-N at the SWI. The decomposition of algae also induces a significant increase in dissolved organic matter (DOM) concentration, referring to humic acid and humus-like components; a seven-millimeter decrease in dissolved oxygen (DO) penetration depth; as well as a significant decrease in the pH value near the SWI, which consequently promotes denitrification processes in the sediment. Moreover, the decomposition process influences nitrogen distribution patterns and the role conversion of sediments between a "source" and a "sink" of nitrogen. This investigation provides evidence on the migration and/or transformation of N fractions and offers insights into the dynamic processes across the SWI in eutrophic lakes. [ABSTRACT FROM AUTHOR]

Kam Sweet Rice (KSR) is a rice cultivar cultivated for thousands of years in China. Proper and balanced use of nitrogen sources is essential for achieving optimal growth and yield in KSR. This study was carried out to find the most effective hydroponic nutrient solution for cultivating and promoting the growth of KSR. Different nitrogen treatments were applied to KSR cultivars GouDan (GD), GouHa (GH), HongHe (HH), LeiLongGang (LG), and ZaiBianXiaoXiangHe (ZH), resulting in noticeable changes in both growth and physiological traits. Our findings revealed that D3 treatment [1.2 mM NH4Cl + 2.4 mM NaNO3+ neutral amino acids (0.1 mM Ser + 0.2 mM Thr + 0.2 mM Gly + 0.2 mM Pro +0.3 mM Ala)] had a notable positive impact on the growth of GH and ZH which showed the best performance in terms of plant height, root length and fresh weight when compared to the control (CK). Through transcriptome analysis, we discovered that these treatments altered the expression levels of genes associated with carbon metabolism, photosynthesis, and nitrogen pathways within 40 days. Interestingly, by altering the growth and tillering in rice transgenic plants, we validated the role of amino acid transporter OsAAP13 identified in transcriptome profiling, underscoring its significance. Our results are helpful for large‐scale production of KSR with the key methods for controlling the growth of KSR. It is a valuable asset for future investigations aimed at unravelling the intricate mechanisms governing plant growth in the context of different nitrogen supplies. [ABSTRACT FROM AUTHOR]

The Lijiang River Basin is a humid, subtropical, karst landform in China and is listed as a World Heritage Site. However, with the rapid development of urbanization and tourism activities in recent years, it faces increasingly severe non-point source pollution. To understand the temporal and spatial variations in nitrogen and phosphorus pollution discharge and the changes in river water quality, the Jingui Small Basin, in the upper reaches of the Lijiang River, was chosen as a representative system. Changes in nitrogen and phosphorus concentrations were continuously monitored in the main river channel and the river water quality was evaluated using the comprehensive water quality identification index method. The results indicated that there were obvious seasonal changes in nitrogen and phosphorus discharge loads in the basin. Both nitrogen and phosphorus discharge loads were higher in the crop-growing season than in the non-growing season. No significant difference in nitrogen and phosphorus discharge load between different scales was found, and the scale was not the key factor affecting the nitrogen and phosphorus discharge load of Jingui River. As the river flowed from the initial water source to the outlet of the basin, water quality was characterized by the spatial pattern of the upper reaches > the middle reaches > the lower reaches. Except for the water quality at the outlet of the basin in November and December, which reached Class V, the comprehensive water quality of each sub-basin reached the target water quality of the water function zoning from May to December. The elucidation of the nitrogen and phosphorus pollution discharge patterns in the Jingui River and the changes in water quality provide a reference for the control and management of agricultural non-point source pollution in the Lijiang River Basin. [ABSTRACT FROM AUTHOR]

In the subtropical mountainous area of Huangshan, China, 81 Torreya grandis were selected for research on growth and element distribution, with the aim of providing empirical and theoretical support for the promotion and management of T. grandis. Seven growth equations were constructed for tree height (H) and diameter at breast height (DBH) in age levels 40–2000. The most suitable Korf equation was selected by comparing the R-squared values. With R-squared values of 0.93 and 0.80, the equations H = 33.98 × Exp(−53.56/age0.84) and DBH = 158.48 × Exp(−21.41/age0.55) fit T. grandis growth best, respectively. The results show that T. grandis growth was relatively rapid before the age of 45 and then slowed. Among the carbon (C), nitrogen (N), and phosphorus (P) elements found in different T. grandis organs of the same age, the roots had the lowest C content, the leaves had the highest N content, and the branches had the lowest P content. The roots had the highest C:N and C:P, and the leaves had the highest N:P. The amount of N in the leaves and P in the branches both increased significantly with age, and the N:P ratio indicates that considering only one organ may not accurately indicate T. grandis nutrient limitations. [ABSTRACT FROM AUTHOR]

Nitrogen (N) and phosphorus (P) play crucial roles in tea planting, but information on how the long-term excessive application of chemical N fertilizer affected N and P in subtropical tea plantations remains limited. In this study, soil and leaf samples were collected along a chronosequence of tea plantations (0-, 5-, 10-, 18- and 23-year-old plantations) with excessive N input but no P application to investigate the effects of planting age on N and P availability. Diverse soil N forms and P fractions, and the concentrations of leaf N and P were measured. The results showed that (1) N O 3 − -N and dissolved organic nitrogen (DON) concentrations in both topsoil and subsoil, and the N concentration of mature leaf showed significant upward trends with tea plantation age; (2) the concentrations of available phosphorus (AP), NaHCO3-Pi in labile P pool, NaOH-Pi and D.HCl-Pi in moderately labile P pool in both layers of soil and that the P concentration of mature leaf also increased with age; (3) the N concentration of mature leaves had closely significant logarithmic relations with N O 3 − -N concentration, while the TP (total P) concentration of mature leaves had significant positive correlations with AP; and (4) the ratio of N/P in tea leaves indicated a slightly P limitation in tea plantations. We concluded that the N O 3 − -N concentration, instead of TN (total N) of N H 4 + -N, would be a good indicator to reflect N availability for tea trees, and the increasing of N O 3 − -N concentration in soil has a diminishing promoting effect on the TN concentration of mature leaves. The long-term application of chemical N fertilizer had not lead to serious P limitation in subtropical tea plantations. Generally, our study could contribute to improving our understanding of N and P availability and optimizing fertilization management in subtropical tea plantations. [ABSTRACT FROM AUTHOR]

Tobacco black shank induced by Phytophthora nicotianae causes significant yield losses in tobacco plants. MicroRNAs (miRNAs) play a pivotal role in plant biotic stress responses and have great potential in tobacco breeding for disease resistance. However, the roles of miRNAs in tobacco plants in response to P. nicotianae infection has not been well characterized. In this study, we found that Nta-miR6155, a miRNA specific to Solanaceae crops, was significantly induced in P. nicotianae infected tobacco. Some of predicted target genes of Nta-miR6155 were also observed to be involved in disease resistance. To further investigate the function of miR6155 in tobacco during P. nicotianae infection, Nta-miR6155 overexpression plants (miR6155-OE) were generated in the Honghua Dajinyuan tobacco variety (HD, the main cultivated tobacco variety in China). We found that the Nta-miR6155 overexpression enhanced the resistance in tobacco towards P. nicotianae infections. The level of reactive oxygen species (ROS) was significantly lower and antioxidant enzyme activities were significantly higher in miR6155-OE plants than those in control HD plants during P. nicotianae infection. In addition, we found that the accumulation of salicylic acid and the expression of salicylic acid biosynthesis and signal transduction-related genes is significantly higher in miR6155-OE plants in comparison to the control HD plants. Furthermore, we found that Nta-miR6155 cleaved target genes NtCIPK18 to modulate resistance towards P. nicotianae in tobacco plants. Additionally, phenotypic analysis of miR6155-OE plants showed that Nta-miR6155 could inhibit the growth of tobacco by suppressing nitrogen uptake and photosynthesis. In conclusion, our findings indicated that miR6155 plays a crucial role in the regulation of growth and resistance against P. nicotianae infections in tobacco plants. [ABSTRACT FROM AUTHOR]

Gas flooding is a key technique for increasing coalbed methane (CBM) production of declining wells in coal mining areas. Nitrogen is clean, pollution-free, low-cost, and relatively safe compared with carbon dioxide. In this study, nitrogen drive experiments were conducted under different conditions using a coal–gas–liquid relative permeability device and gas chromatography. The effects of the temperature, intermittent time, nitrogen purity, and displacement pressure on the output characteristics were investigated, and then, field tests were conducted. The results show that with increasing displacement time, the produced gas volume and flow rate are dominated by methane at the beginning and then quickly transform into nitrogen. The volumes of both methane and nitrogen are positively correlated with the displacement time via a power function. Additionally, increasing the nitrogen temperature, intermittent time, nitrogen purity, and injection pressure can effectively increase methane production. In the field test conducted in the Fanzhuang block in the Qinshui Basin, China, the methane production of 10 monitoring wells was 11,700 m3/day , which was 2,700 m3/day higher than that before nitrogen injection. This paper provides an optimized scheme for the stimulation of CBM via nitrogen displacement in coal mining areas, which has a good application prospect. [ABSTRACT FROM AUTHOR]

Determining the amount of nitrogen (N) and phosphorus (P) discharged into lakes and assessing the effectiveness of reduction measures in a basin that involve the interaction of multiple factors are still daunting challenges. In this study, the random forest (RF) model was employed to simulate the impact of controlling measures on the amount of N and P discharged in 2025 under seven specific reduction scenarios. Discharged N and P decreased in the basin by 23.38% and 31.69% from 2011 to 2020, respectively. The N and P nutrient discharge intensities were significantly higher in the western part of the basin (13.31 kg·ha−1·a−1 and 1.34 kg·ha−1·a−1) than those in the eastern region (10.24 kg·ha−1·a−1 and 0.74 kg·ha−1·a−1). Fertilizer runoff (N: 34.72%, 5934.49 t; P: 13.60%, 199.76 t), domestic sewage (N: 29.14%, 4009.27 t; P: 34.84%, 496.59 t), and livestock farming (N: 15.11%, 2657.50 t; P: 40.05%, 616.05 t) were the key sources of N and P. The RF model shows that (R2 > 0.994, p < 0.01) the multi-factor reduction effect is the best, and under this discharge reduction effect, the amount of N and P discharged in 2025 are expected to decrease by 13.79% and 19.42%, respectively, compared with those in 2020. In addition, different key sources in sub-basins might lead to regional differences in the discharge reduction effects of various measures. Ultimately, we recommend that the synergistic treatment of point and non-point sources, using treatments with multiple measures, should be implemented in different regions to reduce the amount of N and P discharged in the Chaohu Lake Basin. [ABSTRACT FROM AUTHOR]

Dry matter (DM) and nitrogen (N) transport from nutritive organs to the grain is critical for cereal crop yield and protein content. There is limited research on the effects of slow-release or controlled-release fertilizers on dry matter and nitrogen partitioning in the nutrient organs of spring corn. A field trial was conducted in the National Corn Industry Technology System Xinzhou Comprehensive Experiment Station, China. The effects of different fertilizer management on yield, photosynthetic capacity, and nutrient partitioning of spring maize were studied. We modeled local farmers' planting and management practices (T3). Based on T3, we added a slow-release compound fertilizer (T2), which does not require a follow-up fertilizer, and a controlled-release formulated fertilizer (T1), which is highly efficient and has low carbon emissions. The net photosynthetic rate (Pn), transpiration rate (E), stomatal conductance (Gs), and intercellular CO2 concentration (Ci) were 23%, 18.5%, 18%, 10.5% and 19%, 10.9%, 7%, and 5.5% higher in T1 compared to those of T3 and T2, respectively, at the ripening stage. The contribution of post-flowering DM transport to the kernel of T1 was 46% and 41.4% higher than that of T3 and T2, respectively. The nitrogen content of the kernel of T1 was 35.2% and 18.5% higher than that of T3 and T2, respectively. After a comprehensive analysis, T1 prolonged the photosynthetic effect through adequate nitrogen supply, provided nutrients to the kernel, promoted maize nitrogen uptake and utilization, and ultimately improved yield. [ABSTRACT FROM AUTHOR]

In the context of the Chinese government's policy guidance, there is black soil protection and ecological environment protection. The purpose of this paper is to solve the problem that the soil ecology of the black soil in Northeast China is changing year by year, and it is necessary to explore the sowing and fertilization strategy under the new situation; most Chinese growers rely excessively on their personal experience in the process of soybean sowing and fertilization. In this study, we used "Heihe 43" soybeans and used regression experimental design methods to analyze the effects of planting density, nitrogen, phosphorus, and potassium fertilizer application on soybean yield and to determine the optimal planting density and fertilizer ratios. The study reveals that the optimal soybean planting density in Northeast China is 45.37 × 104 plants/ha, with nitrogen at 98.4 kg/ha, phosphorus at 218.96 kg/ha, and potash at 47.62 kg/ha. Under these conditions, soybean yields can reach 3816.67 kg/ha. This study can provide a theoretical method for decision-making to obtain the optimal planting density and fertilizer ratio for different regions of the farming system. [ABSTRACT FROM AUTHOR]

Soil bacteria are crucial components of terrestrial ecosystems, playing an important role in soil biogeochemical cycles. Although bacterial community diversity and composition are regulated by many abiotic and biotic factors, how soil physiochemical properties impact the soil bacteria community diversity and composition in wetland ecosystems remains largely unknown. In this study, we used high-throughput sequencing technology to investigate the diversity and composition of a soil bacterial community, as well as used the structural equation modeling (SEM) method to investigate the relationships of the soil's physicochemical properties (i.e., soil pH, soil organic carbon (SOC), total nitrogen (TN), ammonium nitrogen (NH4+N), electrical conductivity (EC) and nitrate nitrogen (NO3−N)), and soil bacterial community structures in three typical wetland sites in the Sanjiang Plain wetland. Our results showed that the soil physicochemical properties significantly changed the α and β-diversity of the soil bacteria communities, e.g., soil TN, NH4+N, NO3−N, and SOC were the main soil factors affecting the soil bacterial α-diversity. The soil TN and pH were the key soil factors affecting the soil bacterial community. Our results suggest that changes in soil pH indirectly affect soil bacterial communities by altering the soil nitrogenous nutrient content. [ABSTRACT FROM AUTHOR]

Estuaries are key areas for terrestrial material transport and marine biogeochemical processes, particularly those of dissolved inorganic nitrogen (DIN) and dissolved organic nitrogen (DON). However, the fate of DON in estuaries with a high runoff remains poorly understood. In this study, we explored the translocation and transformation of DON in the Pearl River Estuary (PRE) and adjacent coastal areas of southern China based on DON concentrations, optical and fluorescence characteristics, and environmental parameters. The results revealed that DIN and DON exhibited dissimilar distributions. The distribution of DIN was primarily influenced by freshwater‐seawater mixing. In contrast, biological processes and freshwater‐seawater mixing shaped the distribution of DON. High levels of DON in the terrestrial‐dominated zone were predominantly anthropogenic sources through terrestrial inputs, whereas DON in the freshwater‐seawater mixing zone and seawater‐based zone were mainly influenced by biological activities, as high concentrations of Chla were observed in these two areas. DON exhibits fast dilution in low‐salinity areas and retention in moderate‐salinity areas (freshwater‐seawater mixing area) in summer and winter, while undergoes a rapid decrease in open water areas during winter. Consequently, DON in the PRE and adjacent coastal areas exhibited nonconservative mixing despite seasonal variations. These findings provide novel insights into the role of DON in nitrogen biogeochemical processes in river‐dominated estuaries and adjacent coastal areas. Plain Language Summary: Physical and biological mechanisms affect the fate of dissolved organic nitrogen (DON) in estuaries and coastal waters. The results revealed that dissolved inorganic nitrogen (DIN) and DON exhibited dissimilar distributions. Freshwater discharge governed DON in areas dominated by terrestrial inputs, whereas biological activities shaped the DON fate in less affected areas. Increasing phytoplankton‐derived autochthonous DON triggered by terrestrial inputs and seawater intrusion jointly promoted DON retention in brackish waters. This study shed light on how terrestrial inputs and biological activities shape DON dynamics in distinct areas, contributing to a deeper understanding of nitrogen cycling in high‐runoff estuaries. Key Points: Dissolved organic nitrogen (DON) and dissolved inorganic nitrogen exhibited dissimilar distributions in a subtropical river‐dominated estuaryPhysical mixing and biological activities promoted DON retention in the freshwater‐seawater mixing zoneFreshwater discharge mainly affected DON distribution in the main estuary [ABSTRACT FROM AUTHOR]

Over recent decades, there has been a severe nitrogen-deposition in alpine meadows which often leads to phosphorus limitation of plant productivity. In these high-altitude localities, Cyperaceae have an increasing biomass while other functional groups decrease. Meanwhile, Cyperaceae are known to have the ability of producing dauciform roots, which are formed under phosphorus limitation, but in China, are only described in these high-altitude places. So, is the superiority of Cyperaceae and the formation of dauciform roots in high-altitude localities related to the accumulation of nitrogen? And is there a link between them? A Carex filispica dominated community in Baima Snow Mountain was selected and quantitative fertilization with four levels of nitrogen and three levels of phosphorus was performed. After 2 weeks, Carex filispica individuals with and without dauciform roots were separated and analyzed for their regular root properties, dauciform root properties, biomass and chemical traits of above- and belowground parts. The total cover of the community declined under phosphorus limitation with increasing nitrogen supply, while the relative cover difference of Carex filispica increased with increasing nitrogen supply and decreased with increasing phosphorus supply. Dauciform roots had a more significant response to nitrogen supply than to phosphorus supply and they were formed the most at a low supply of nitrogen. The biomass and root properties of individuals with dauciform roots were enhanced by nitrogen supply and inhibited by phosphorus supply, while those of individuals without dauciform roots were often enhanced by phosphorus supply. Individuals with and without dauciform roots showed two different mechanisms, and were limited by significantly different factors, which can explain the opposite performance of Cyperaceae after nitrogen and phosphorus supply in previous studies. [ABSTRACT FROM AUTHOR]

Nitrate transporters (NRTs) actively take up and transform nitrate (N) to form a large family with many members and distinct functions in plant growth and development. However, few studies have identified them in the context of low nitrate concentrations in Chinese cabbage (Brassica rapa L. ssp. Pekinensis), an important vegetable in China. This study focuses on the identification and analysis of the nitrate transporter 1 (NRT1) gene family as well as various aspects, including its phylogenic distribution, chromosomal position, gene structure, conserved motifs, and duplication pattern. Using bioinformatics methods, we identified and analyzed 84 BrNRT1 genes distributed on ten chromosomes. Furthermore, we conducted an analysis of the expression profile of the NRT1 gene in various tissues of Chinese cabbage exposed to varying nitrate concentrations. A phylogenetic analysis revealed that BrNRT1s members are distributed in six distinct groups. Based on an analysis of gene structure and conserved motifs, it can be inferred that BrNRT1 exhibits a generally conserved structural pattern. The promoters of BrNRT1 were discovered to contain moosefs (MFS) elements, suggesting their potential role in the regulation of NO3− transport across the cell membrane in Chinese cabbage. A transcriptome study and a subsequent RT-qPCR analysis revealed that the expression patterns of some BrNRT1 genes were distinct to specific tissues. This observation implies these genes may contribute to nitrate uptake and transport in various tissues or organs. The results offer fundamental insights into investigating the NRT1 gene family in Chinese cabbage. These results provide basic information for future research on the functional characterization of NRT1 genes in Chinese cabbage and the elucidation of the molecular mechanisms underlying low nitrogen tolerance in Chinese cabbage. [ABSTRACT FROM AUTHOR]

Understanding the relative importance of climates at coarse scales and nitrogen (N) availability at fine scales in driving litter decomposition is crucial for ecosystem functioning. In this study, we explored the relative importance of coarse-scale climatic contrast (China vs. France) and local soil fertility contrast related to N availability in determining 'home-field advantage (HFA)' effects. Four tree-species litters from four forest types with contrasting chemical properties from China and France were reciprocally transplanted in a litterbag decomposition experiment. The Decomposer Ability Regression Test showed highly significant HFA effects for the Chinese litter (Castanopsis eyrei), that is, the most recalcitrant litter with low P and N contents, and marginally significant HFA effects for the French litter (Carpinus betulus), that is, the most labile litter with high P and N contents. The climatic contrast was more important in determining HFA effects than the N availability contrast. Our findings highlight the importance of climate in determining the occurrence of HFA effects that likely can be attributed to differences in soil weathering intensity driving soil P legacy, an important coarse-scale component of soil fertility. [ABSTRACT FROM AUTHOR]

Silage maize is cultivated due to its high nutritional value as a forage. China's recent agricultural policy promotes the popularization and cultivation of silage maize. The production of silage maize is affected by planting density and nitrogen application. Based on investigating the planting habits of local farmers, we adjusted the planting density and nitrogen application rate to optimize the growth of silage maize. This study was conducted to investigate the effects of planting density (65,000 plant ha−1 (D1), 80,000 plant ha−1 (D2), and 95,000 plant ha−1 (D3)) and nitrogen rate (150 kg ha−1 (N1), 230 kg ha−1 (N2), and 310 kg ha−1 (N3)) on growth, yield, and quality of silage maize using a two-factor random block design. Planting density and nitrogen fertilizer significantly affected plant height, stem diameter, leaf area index, crude protein, neutral detergent fiber, acid detergent fiber, and starch of silage maize. In summary, the combination of a planting density of 80,000 plants ha−1 and a nitrogen application rate of 310 kg ha−1 produced a higher crude protein and starch yield and better palatability and quality; this result can aid silage maize growth. [ABSTRACT FROM AUTHOR]

Camellia oleifera Abel. is a unique woody edible oil tree species in China mainly distributed in red soil areas. Nitrogen is one of the important growth-limiting factors for C. oleifera, and the nitrogen form has a vital impact on the growth and development of the plants. Ammonium and nitrate are the two nitrogen forms that are maximally absorbed and utilized by the plants. Here, we used one-year-old seedlings of the main varieties of C. oleifera ('Xianglin No. 1', 'Xianglin No. 27', and 'Xianglin No. 210') to set up six experimental groups treated with different nitrogen forms ([ N O 3 − : N H 4 + ] 0:0, 10:0, 7:3, 5:5, 3:7, and 0:10) and investigated the effects of nitrogen on the vegetative growth and photosynthetic characteristics of the seedlings. This study showed that mixed nitrogen sources could significantly increase the seedling height, ground diameter, biomass accumulation, and photosynthesis efficiency. Transcriptome sequencing analysis led to the identification of 3561 differentially expressed genes in the leaves. Preliminary screening identified several key enzyme genes from nitrogen nutrient metabolic pathways that were differentially expressed among seedlings grown with different nitrogen forms, and their expression pattern changes were further characterized. All the results demonstrate that the same proportion of ammonium nitrate ratio promoted the expression of genes encoding glutamine synthetase and glutamate synthase, thereby improving nitrogen assimilation and utilization efficiency. This study could provide a theoretical basis for scientific and rational fertilization and the improvement of nitrogen utilization efficiency in C. oleifera seedlings. [ABSTRACT FROM AUTHOR]

The rise in environmental nitrogen (N) is a worldwide concern, particularly in southern China, which contains highly N-contaminated areas. The ecological outcome of the increase in N should be paid additional consideration. Thus, this study was conducted to assess the impact of N on seed germination and seedling emergence of four timber species in subtropical southern China. We conducted a growth chamber experiment with three nitrogen fertilizers i.e., Ammonium sulfate (NH4)2SO4, Ammonium Nitrate (NH4NO3), and Potassium Nitrate (KNO3) with three concentrations (0.1%, 0.5% & 1%) along with control treatment (CK). We hypothesized that the impact of N on seed germination and seedling emergence would differ among species and N levels. Results showed that higher N concentration affected Cunninghamia lanceolata, Fokienia hodginisi and Pinus massoniana seedlings compared with Phoebe zhennan. Overall, fresh and dry weight as well as the length of broad-leaved species was better than coniferous and pine species. It was observed that 1% KNO3 solution enhanced the germination capacity, germination time, radicle, and hypocotyl elongation along with fresh and dry weights as compared to (NH4)2SO4 and NH4NO3. The outcome showed that deposition of 1% KNO3 is promising to increase the germination of seed and seedlings emergence. [ABSTRACT FROM AUTHOR]

The tillage method in farming systems is essential to develop strategies to increase fertilizer uptake by plant roots and to avoid environmental pollution. The field study aimed to investigate the characteristics of nitrogen and enzyme activities in rhizosphere soil with different tillage methods. Four treatment plots applied with fertilizers were established: continuous rotary tillage (CR), plowing-rotary tillage (PR), continuous no-till (CN) and ploughing-no-till (PN). The total content of nitrogen in chernozem was high during early stages of plant growth, and then it decreased with the maize growth. In the rhizosphere soil, the total N accounted 1314.45, 1265.96, 1120.47, 1120.47, 1204.05 mg·kg−1 of CR, PR, CN, and PN, respectively, which were markedly greater than that of non-rhizosphere soil (1237.52, 1168.40, 984.51, 1106.49 mg·kg−1 of CR, PR, CN, and PN, respectively). At first growth stages, content of NH4+-N and NO3−-N in two soil regions was low, then increased gradually, which followed the order of CR < PR < PN < CN. The rhizosphere soil showed slightly higher concentration of NH4+-N and NO3−-N than non-rhizosphere. The soil enzymes were more active in the rhizosphere soil than that of non-rhizosphere during the whole maize growth stages. Due to minimal damage to the soil environment and optimal soil moisture and temperature, the urease and catalase activities were greatest in the rhizosphere for CN treatment. Therefore, CN was recommended to be used by farmers for the improvement of macronutrient availability and soil enzyme activities in the soil. [ABSTRACT FROM AUTHOR]