Nitrogen Loss Research Articles

Augmented Renal Clearance: Prevalence, Risk Factors and Underlying Mechanism in Critically Ill Patients with Subarachnoid Hemorrhage.

Augmented renal clearance (ARC) is an increase in the measured creatinine clearance (CLCR), the cause of which remains poorly understood. ARC may be associated with drug underdosing and appears to be more frequent in patients with brain damage, such as subarachnoid hemorrhage (SaH), although the incidence of ARC remains poorly understood. The aim of this study was to investigate the prevalence of ARC in patients with SaH in a neurointensive care unit (neuro-ICU) and to identify factors associated with ARC. All consecutive patients hospitalized in the neuro-ICU of Bordeaux University Hospital between June 2018 and June 2019 for SaH treatment were retrospectively included. CLCR was measured daily via 24-h urine collection. ARC was defined as a CLCR ≥ 130mL/min/1.73 m2. The effects of different covariates on the time course of CLCR were investigated using a linear mixed model. Of the 205 included study participants, 168 developed ARC during their neuro-ICU stay; the estimated ARC prevalence was 82% (95% confidence interval 76-87) with a median of 4days (range 3-6days) after hemorrhage; ARC persisted for a median of 5days (range 2-8days). Patients with ARC were younger and had a lower BMI and lower mortality rate. In multivariate analysis, younger patients with a higher mean arterial pressure, no history of hypertension, and greater nitrogen loss were more likely to have ARC. Augmented renal clearance is very common in critically ill patients with SaH, persists over time, and seems to lack specific risk factors. Daily CLCR measurements could be essential.

Simulating Agricultural Water Recycling Using the APEX Model

Irrigation plays a vital role in many agricultural crop production regions. Drainage water recycling (DWR) is a popular irrigation water management system that collects excess water drained from cropland fields and stores it in on-site reservoirs for reuse. The efficacy of these systems varies by location, climate, irrigation frequency, and crop demands. Simulating this system would be beneficial for assessing the impact of water and land management practices on agriculture and natural resources. This study presents the development of computational algorithms for DWR simulation with the Agricultural Policy Environmental eXtender (APEX) model, along with the results for 39 testing sites where both reservoir and drainage systems are adopted. Simulating a DWR system with the revised reservoir module, the APEX model simulates irrigation water reuse ranging between 29% and 93%; sediment reduction of around 66%; nitrogen loss reduction of 23% and 73% for the mineral and organic forms, respectively; and phosphorus loss reduction of 22% and 79% for the soluble and sediment-transported forms, respectively. In conclusion, the results provided by the APEX model for sediment loss reduction align with field data, but discrepancies for nitrogen and phosphorus losses emerged from this test.

Low protein diet influences mineral absorption and utilization in medium-growing yellow-feathered broilers from 1 to 30 days of age

Reduced-protein diet can save protein ingredients and reduce nitrogen (N) losses. However, the effect of low protein diet on the mineral uptake and utilization in broilers needs to be explored. The aim of this study was to investigate the effect of low-protein diet on the growth performance, N deposition, mineral contents in serum, tissues and excreta, and the activities and gene expression of related enzymes in tissues of medium-growing yellow-feathered broilers, so as to elucidate the relationship between dietary protein level and the absorption and utilization of minerals in broilers. A total of 72 1-d-old Spotted-Brown male broilers were randomly allotted to 1 of 2 treatments with 6 replicate cages of 6 birds per cage for each treatment. The dietary crude protein (CP) levels for the two treatments were 21 % (the control treatment) and 19 % (low protein treatment), respectively. The experimental period was 30 d. The results showed that no differences (P > 0.05) were detected in average daily gain, average daily feed intake and feed: gain ratio of broilers during 1 to 30 d between the two treatments. However, low protein intake increased (P < 0.05) N retention rate, serum P, Cu and Mn, and excreta Cu, Mn and Zn, and decreased (P < 0.05) liver P and excreta P. In addition, birds fed low protein diet had higher (P < 0.05) manganese superoxide dismutase, and total superoxide dismutase activities in liver, and total antioxidant capacity and malondialdehyde content in heart, and lower (P < 0.05) copper-zinc superoxide dismutase (CuZnSOD) and succinate dehydrogenase activities in liver and CuZnSOD mRNA level in heart. In conclusion, the reduction of dietary CP content from 21 % to 19 % improved N retention, the absorption of P, Cu and Mn, as well as the antioxidant ability of liver and heart, and influenced metabolic utilization of P, Cu, Zn, Fe and Mn in medium-growing yellow-feathered broilers from 1 to 30 d of age.

Newly Established Blueberry Plants: The Role of Inorganic Nitrogen Forms in Nitrogen and Calcium Absorption

Efficient nitrogen (N) management is crucial for maximizing the growth of young blueberry plants (Vaccinium corymbosum). This study evaluates the effects of the N fertilization form (ammonium, NH4+; nitrate, or NO3−) and application timing on the blueberries’ establishment, N and Ca absorption, and N distribution. The experiment was conducted in the southern hemisphere, in Chile, from October 2023 to January 2024. Six-month-old blueberry cv. Blue Ribbon plants were cultivated in pots. NH4+ and NO3− were used as full or split-dose applications using the 15N isotopic dilution technique. Plant leaves, stems, root growth, and biomass, as well as their N and Ca contents, were measured. Our results showed that 90 days after nitrogen application, blueberry plants obtained the lowest biomass in their leaves, stems, and roots when NO3− was applied in T1 or T1T2. The same pattern was observed for N and Ca contents, hence for N recovery. During the first period (T1) of application, heavy rain (100 mm) was registered over the course of a few days and caused leaching. Therefore, applying nitrate to young blueberry plants cultivated in areas with spring rainfall and low temperatures would not be recommended because the leaching losses and lower growth conditions, such as low temperatures and high precipitation, led to reduced transpiration, resulting in lower calcium and nitrogen contents. These confirm that N fertilization management (form and timing) can ensure a better establishment for young blueberry plants, optimizing their growth and sustainable production by minimizing nitrogen losses.

Heterologous biosynthesis of betanin triggers metabolic reprogramming in tobacco

Engineering of a specialized metabolic pathway in plants is a promising approach to produce high-value bioactive compounds to address the challenges of climate change and population growth. Understanding the interaction between the heterologous pathway and the native metabolic network of the host plant is crucial for optimizing the engineered system and maximizing the yield of the target compound. In this study, we performed transcriptomic, metabolomic and metagenomic analysis of tobacco (Nicotiana tabacum) plants engineered to produce betanin, an alkaloid pigment that is found in Caryophyllaceae plants. Our data reveals that, in a dose-dependent manor, the biosynthesis of betanin promotes carbohydrate metabolism and represses nitrogen metabolism in the leaf, but enhances nitrogen assimilation and metabolism in the root. By supplying nitrate or ammonium, the accumulation of betanin increased by 1.5–3.8-fold in leaves and roots of the transgenic plants, confirming the pivotal role of nitrogen in betanin production. In addition, the rhizosphere microbial community is reshaped to reduce denitrification and increase respiration and oxidation, assistant to suppress nitrogen loss. Our analysis not only provides a framework for evaluating the pleiotropic effects of an engineered metabolic pathway on the host plant, but also facilitates the development of novel strategies to balance the heterologous process and the native metabolic network for the high-yield and nutrient-efficient production of bioactive compounds in plants.

Comprehensive effects of biochar-assisted nitrogen and phosphorus bioremediation on hydrocarbon removal and microecological improvement in petroleum-contaminated soil

Biochar is widely used in agricultural soils, but its effects with nitrogen and phosphorus amendments on petroleum-contaminated soil are unclear. This study investigated biochar-assisted biostimulation in a microcosm experiment, focusing on hydrocarbon degradation, nitrogen cycling, and soil properties. Compared to the biostimulation alone (BS), biochar combined biostimulation (BSC) significantly enhanced the abundances of petroleum hydrocarbon degraders including Lysobacter and Brevundimonas, which led to a 17% increase in total petroleum hydrocarbon (TPH) degradation, with 9% and 39% enhancements in saturated hydrocarbon degradation and aromatic hydrocarbon fraction degradation, respectively. Biochar also promoted ammonia and nitrous oxide oxidation by upregulating AOA, AOB, norB, and nosZ genes, while controlling nitrogen loss by downregulating nirK. Soil moisture, oxidation–reduction potential (ORP), dehydrogenase activity (SDHA), and microbial proliferation were significantly enhanced. Structural equation models (SEM) indicated synergistic interactions between nitrogen cycling and hydrocarbon degradation. Biochar enhances hydrocarbon degradation and nitrogen cycling, offering a promising soil remediation approach.

Feedstock optimization with low carbon to nitrogen ratio during algal sludge aerobic composting: Quality and gaseous emissions

This study investigated compost quality and gaseous emissions during the algal sludge composting. The experiment explored the feasibility of low initial carbon to nitrogen (C/N) ratio composting by using different volume ratios of algal sludge and spent mushroom substrates (1:1, 1:2, 1:3, and 1:4, corresponding to C/N ratios of 9.5, 12.3, 14.6, 16.0, respectively). The results showed that increasing the proportion of algal sludge in the initial material led to a longer maturation time and higher nitrogen losses but also enhanced the mineralization of organic nitrogen (converted to NH4+ and NO3-) and reduced carbon losses. The addition of carbon-rich bulking agents within a certain range improved the diversity and interactions of bacterial communities during algal sludge composting. In conclusion, considering the nitrogen and carbon lost, retained, and made available across the four treatments, treatment 3 (C/N = 14.6) appears to be the optimal choice for low C/N composting.

Promoting role of nitrogen-fixing bacteria and biochar on nitrogen retention and degradation of PBAT plastics during composting

Since the increasing number of polybutylene adipate terephthalate (PBAT)–based plastics entering the environment, the search for sustainable treatment methods has become a primary focus of contemporary research. Composting offers a novel approach for managing biodegradable plastics. However, a significant challenge in the composting process is how to control nitrogen loss and enhance plastic degradation. In this context, the effect of various additives on nitrogen retention, PBAT plastics degradation, and microbial community dynamics during composting was investigated. The findings revealed that the addition of nitrogen-fixing bacteria Azotobacter vinelandii and biochar (AzBC) significantly improved nitrogen retention and accelerated PBAT rupture within 40 days of composting. Specifically, the PBAT degradation rate in the AzBC group reached 29.6%, which increased by 12.14% (P < 0.05) compared to the control group. In addition, the total nitrogen (TN) content increased by 6.20% (P < 0.05), and the Nitrogen-fixing enzyme (NIT) content increased by 190 IU/L (P < 0.05). Further analysis of GC-MS confirmed the presence of low molecular weight fragmentation products, such as 6-(4-hydroxybutoxy)-6-oxohexanoic acid. The AzBC treatment promoted the proliferation of Klebsiella at the genus level that could enhance nitrogen retention and the bacteria that have the ability to degrade PBAT, such as Proteobacteria and Firmicutes at the phyla level, and Pseudoxanthomonas, Pseudomonas, and Flavobacterium genera at the genera level (P < 0.05). Correlation analysis indicated that the degradation of PBAT is positively correlated with Temperature (T), NIT, and TN, but negatively correlated with the organic matter (OM) content and germination index (GI). In conclusion, the co-application of biochar and Azotobacter vinelandii offers promising sustainable prospects for enhancing PBAT plastic degradation and reducing nitrogen loss during composting.

Unprecedented N2O production by nitrate-ammonifying Geobacteraceae with distinctive N2O isotopocule signatures.

Dissimilatory nitrate reduction to ammonium (DNRA), driven by nitrate-ammonifying bacteria, is an increasingly appreciated nitrogen-cycling pathway in terrestrial ecosystems. This process reportedly generates nitrous oxide (N2O), a strong greenhouse gas with ozone-depleting effects. However, it remains poorly understood how N2O is produced by environmental nitrate-ammonifiers and how to identify DNRA-derived N2O. In this study, we characterize two novel enzymatic pathways responsible for N2O production in Geobacteraceae strains, which are predominant nitrate-ammonifying bacteria in paddy soils. The first pathway involves a membrane-bound nitrate reductase (Nar) and a hybrid cluster protein complex (Hcp-Hcr) that catalyzes the conversion of NO2- to NO and subsequently to N2O. The second pathway is observed in Nar-deficient bacteria, where the nitrite reductase (NrfA) generates NO, which is then reduced to N2O by Hcp-Hcr. These enzyme combinations are prevalent across the domain Bacteria. Moreover, we observe distinctive isotopocule signatures of DNRA-derived N2O from other established N2O production pathways, especially through the highest 15N-site preference (SP) values (43.0‰-49.9‰) reported so far, indicating a robust means for N2O source partitioning. Our findings demonstrate two novel N2O production pathways in DNRA that can be isotopically distinguished from other pathways.IMPORTANCEStimulation of DNRA is a promising strategy to improve fertilizer efficiency and reduce N2O emission in agriculture soils. This process converts water-leachable NO3- and NO2- into soil-adsorbable NH4+, thereby alleviating nitrogen loss and N2O emission resulting from denitrification. However, several studies have noted that DNRA can also be a source of N2O, contributing to global warming. This contribution is often masked by other N2O generation processes, leading to a limited understanding of DNRA as an N2O source. Our study reveals two widespread yet overlooked N2O production pathways in Geobacteraceae, the predominant DNRA bacteria in paddy soils, along with their distinctive isotopocule signatures. These findings offer novel insights into the role of the DNRA bacteria in N2O production and underscore the significance of N2O isotopocule signatures in microbial N2O source tracking.

Impact of low crude protein diets containing animal byproducts on growth performance, nitrogen excretion, meat yield and quality in broiler chickens

This study examined the impact of a low crude protein (CP) diet incorporating meat and bone meal (MBM) as an alternative (AD) to standard diet, on broiler performance, nitrogen intake, excretion, and meat quality. A total of 846 male Ross 308 chicks were assigned to two diets in a randomized complete block design with 9 replicates of 47 birds/replicate. The diets were a plant-based control (20.4 and 19.5% CP) and an AD diet (-2.0% CP, +2.5% MBM) in the grower and finisher phases. Compared to the control, the AD diet reduced nitrogen intake (P = 0.01) and excretion (P &lt; 0.01) while improving nitrogen retention efficiency (P &lt; 0.001) without affecting body weight, feed conversion, or carcass yield. Breast yield was higher in the AD group (P &lt; 0.001). In the AD group, the ultimate pH of breast meat increased slightly (P = 0.07), cooking loss decreased (P = 0.002), sarcoplasmic protein solubility tended to increase (P = 0.09), while muscle protein emulsifying properties remained unchanged. Breast meat proximate composition was not affected by the AD diet. In conclusion, the AD diet can reduce nitrogen loss and emissions without negatively impacting broiler production, provided that amino acid requirements are met.

Assessment of nitrogen and phosphorus losses due to erosion in compost-treated and non-treated vineyard soils: effect of rainfall intensity

Vineyards in Mediterranean areas suffer from significant soil degradation through erosion, due to rainfall and soil characteristics, as well as soil management practices. Previous studies pointed out the nutrient losses produced by erosion and the benefits that some management practices could have on reducing erosion. This research tried to evaluate the effect of events of different intensities and to assess whether the beneficial effect of compost amendment may pose a potential risk of nutrient loss and environmental pollution in particular under high-intensity events. The study compared soil and nutrient losses in compost-treated and non-treated vineyard soils after rainfall events of different intensities analyzed over 2 years in two vineyards. Runoff samples were collected by triplicate in treated and non-treated soils. Sediment and nitrogen and phosphorous concentrations in the runoff samples were analyzed. The results reveal a reduction in runoff rates and an increase in soil water content in compost-treated soils, which represents a benefit for rainfed vineyards. Both nitrogen and phosphorus losses depended on rainfall characteristics. Although for low intensities there were no significant differences in the amount of nutrient lost by runoff in both treated and non-treated soils, nitrogen and phosphorus losses were higher after high-intensity rainfall events in compost-treated soils. With the expected increase in high-intensity rainfall events associated with climate change in the Mediterranean region, organic amendments should be applied in several splits or incorporated into the soil to avoid increased nutrient loss to water bodies.

The dynamic relation between fertilization, precipitation and the diffusion of agricultural non-point pollution in Hainan Island

With the increasing demand for crops, the excessive application of fertilizers has gradually become a significant factor affecting water quality. Therefore, studying the relationship between agricultural fertilizer runoff and water quality is crucial for the sustainable development of agricultural production. The present study sets up a new dynamic model of nitrogen fertilizer loss, introducing variables such as precipitation, fertilization application during dry and rainy seasons, and their lagged and interaction terms. The paper analyzed the issue of fertilizer runoff under the complex interactions of various factors, including spatial and temporal scales and climatic conditions, and explored the relationship between agricultural activities and water quality changes in the context of sustainable development. Due to Hainan Island’s independent river system, which is free from transboundary pollution, and its low level of industrial pollution, it provides an excellent sample for assessing the impact of agricultural non-point source pollution on water quality. Based on watershed monitoring data from Hainan Island, this study draws the following conclusions: 1. Precipitation exhibits a pronounced seasonal influence on total nitrogen concentration. 2. Nitrogen fertilizer enters into water bodies through precipitation, resulting in a lag effect on total nitrogen concentration. 3. The influence of grain and tropical crops on nitrogen loss is less significant, while cash crops will trigger the nitrogen overloading of rivers in scenarios where they account for a high proportion of the planting structure of the sown area.

Application of Nitrate–Ammonium Nitrogen Fertilization Reduced Nitrogen Loss in Surface Runoff and Infiltration by Improving Root Morphology of Flue-Cured Tobacco

Nitrogen loss in water from farmland has become an environmental issue. Nitrogen fertilizer is the main cause of agricultural non-point source pollution in the Lake Basin, Yunnan. However, it is unclear how different nitrogen fertilizer forms affect water loss from farmland and how the root systems of crops respond. We established five nitrogen fertilizer treatments (100–0% [T1], 75–25% [T2], 50–50% [T3], 25–75% [T4], and 0–100% [(T5)] nitrate–ammonium) and performed an investigation to determine nitrogen loss in water and root morphological parameters of tobacco in Mile County and Chengjiang County. Compared with in the T1, T4, and T5 treatments, the total nitrogen loss in surface runoff was reduced by 4.67%, 11.85% and 9.56% in the T2 treatment and 27.32%, 23.20%, and 31.43% in the T3 treatment, respectively. Similar results were observed for the nitrogen loss due to infiltration. The root biomass was negatively correlated with nitrogen loss. There was greater root biomass, root surface area, and root spatial distribution in T2 and T3 compared with in T1, T4, and T5. These results indicate that 50–50% nitrate–ammonium nitrogen fertilizer can facilitate the root growth of tobacco and reduce nitrogen loss, which provides a reference for agricultural sustainable development.

Synthesis and Evaluation of Starch-Grafted-Poly[(Acrylic Acid)-Co-Acrylamide] Based Nanoclay Polymer Composite Fertilizers for Slow Release of Nitrogen in Soil.

Nitrogen (N) losses from conventional N fertilizers contribute to environmental degradation and low N use efficiency. Highlighting the need for slow-release fertilizers (SRFs) to mitigate these problems, this study aims to develop slow-release N fertilizers using starch-grafted-poly[(acrylic acid)-co-acrylamide] based nanoclay polymer composites (NCPCs) and investigate their efficacy for slow N delivery in soil. Three types of NCPCs, NCPC(A) (poly [(acrylic acid)-co-acrylamide]), NCPC(W) (wheat starch-grafted-poly[(acrylic acid)-co-acrylamide), and NCPC(M) (maize starch-grafted-poly[(acrylic acid)-co-acrylamide) were prepared and characterized using FTIR spectroscopy and X-ray diffraction techniques. N-release behaviour of the products was assessed under two distinct soils, i.e., Assam (Typic Hapludults, pH 4.2) and Delhi (Typic Haplustepts, pH 7.9) soils. Additionally, the effects of varying soil moisture and temperature levels on N release were studied in the Assam soil. The N-release kinetics of the synthesized fertilizers were assessed using zero-order, first-order, Higuchi, and Korsmeyer-Peppas models. Degradability of the NCPCs was evaluated by measuring evolved CO2-C under various soil conditions as an indicator of microbial degradation. The results indicated that NCPC fertilizers significantly slowed down the release of N compared to urea. According to the R2 values obtained, it was evident that the first-order kinetic model most accurately describes the N release from both urea and NCPC-based N fertilizers in the studied soils. Among the formulations, NCPC(A) exhibited the lowest N release (42.94-53.76%), followed by NCPC(M) (51.05-61.70%), NCPC(W) (54.86-67.75%), and urea (74.33-84.27%) after 21 days of incubation. The rate of N release was lower in the Assam soil compared to the Delhi soil, with higher soil moisture and temperature levels accelerating the release. Starch addition improved the biodegradability of the NCPCs, with NCPC(W) showing the highest cumulative CO2-C evolution (18.18-22.62 mg g-1), followed by NCPC(M) (15.54-20.97 mg g-1) and NCPC(A) (10.89-19.53 mg g-1). In conclusion, NCPC-based slow-release fertilizers demonstrated a more gradual N release compared to conventional urea and the inclusion of starch enhanced their degradability in the soil, which confirms their potential for sustainable agricultural applications. However, soil properties and environmental factors influenced the N release and degradation rates of NCPCs.

Selecting an optimal sorghum cultivar can improve nitrogen availability and wheat yield in crop rotation.

Sorghum (Sorghum bicolor L. Moench) is a cereal crop known for its biological nitrification inhibition (BNI) capacity, a plant-mediated activity limiting nitrification pathway. The use of BNI-producing plants represents an environmentally friendly and cost-effective approach to reduce nitrogen (N) losses, such as nitrate (NO3 -) leaching and nitrous oxide (N2O) gas emissions. The present study aimed to test the effectiveness of different S. bicolor cultivars in rotation to retain ammonium (NH4 +) in soils and promote N availability for the subsequent wheat crop. A two-year field rotation was established with four sorghum cultivars followed by winter wheat (Triticum aestivum L.). Urea alone or combined with the urease inhibitor N-(n-butyl) thiophosphoric triamide was applied to promote a NH4 +-based fertilization regimes. AddingN-(n-butyl) thiophosphoric triamide maintained higher soil NH4 + content and reduced ammonia-oxidizing bacteria population during sorghum cultivation. However, the benefits of the inhibitor on sorghum growth were cultivar-dependent. Notably, the further reduction in ammonia-oxidizing bacteria abundance for sorghum Voyenn and the increased soil NH4 + content for Vilomene suggested a BNI potential for these cultivars. Importantly, the Vilomene precedent enhanced wheat yield for both fertilization regimes. Overall, the present study confirms that sorghum is a suitable catch crop and emphasizes the importance of selecting the proper sorghum cultivar to maximize the yield of the target wheat crop, at the same time as minimizing N losses. Furthermore, developing combined strategies with selected sorghum cultivars and the application of urease inhibitors enables to enhance sorghum productivity as forage, achieving added value to the rotation. © 2024 The Author(s). Journal of the Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Temporal variations of N and P losses via surface runoff from Chinese farmland after fertilisation

The loss of nitrogen (N) and phosphorus (P) via surface runoff induced by fertilisation leads to water pollution and aggravates water scarcity. Studies estimating N and P losses from farmland have focused on the efficacy of agricultural management actions at reducing the amount of N and P lost. However, a gap remains in understanding the dynamics of N and P losses from farmland, especially differences among types of farmland, crop and fertiliser. Thus, the temporal variations of N and P losses via surface runoff from farmland induced by fertilisation were estimated using 5530 groups of paired observations collected in China. The results showed that N and P losses via surface runoff from paddy fields associated with fertilisation were greater than losses from upland fields. However, after > 90 days post-fertilisation, the effects of fertilisation on N and P loss from paddy fields were non-significant, while the effects of fertilisation on N and P losses from upland fields remained significant. Organic fertilisation decreased N losses from upland and paddy fields, but at more than 60 days post-fertilisation, N and P losses from upland fields were greater with organic than chemical or combined fertilisation. Increasing the fertilisation rate led to higher N and P losses from upland and paddy fields and extended the occurrence time of N and P loss from paddy fields. Overall, this study demonstrates the dynamic processes associated with fertilisation underlying N and P losses from farmland via surface runoff.

Warming exacerbates global inequality in forest carbon and nitrogen cycles

Forests are invaluable natural resources that provide essential services to humanity. However, the effects of global warming on forest carbon and nitrogen cycling remain uncertain. Here we project a decrease in total nitrogen input and accumulation by 7 ± 2 and 28 ± 9 million tonnes (Tg), respectively, and an increase in reactive nitrogen losses to the environment by 9 ± 3 Tg for 2100 due to warming in a fossil-fueled society. This would compromise the global carbon sink capacity by 0.45 ± 0.14 billion tonnes annually. Furthermore, warming-induced inequality in forest carbon and nitrogen cycles could widen the economic gap between the Global South and Global North. High-income countries are estimated to gain US$179 billion in benefits from forest assets under warming, while other regions could face net damages of US$31 billion. Implementing climate-smart forest management, such as comprehensive restoration and optimizing tree species composition, is imperative in the face of future climate change.

Long-term recovery of compacted reclaimed farmland soil in coal mining subsidence area

During the reclamation process of coal mining subsidence areas, mechanical compaction hinders the rapid recovery of reclaimed mine soil (RMS) functions to their pre-mining levels. To optimize reclaimed farmland management, which can promote the recovery of compacted soils, this study aims to explore the key factors and underlying mechanisms affecting RMS recovery from a systemic perspective using complex network theory (CNT). Soil samples from reclaimed farmland at different recovery stages (0, 2, 6, 12, 16, and 22 years) and adjacent non-subsided cultivated soils (NCS) were collected at a depth of 0 ∼ 20 cm in the eastern plains mining region of China. Twenty-four soil indicators were measured, and their evolution over RMS recovery was analyzed. CNT was employed to systematically analyze the complex network relationships among these indicators, identifying key factors and underlying mechanisms affecting RMS recovery. The results indicated that compaction led to soil macroaggregate (MA) destruction, mineralization losses of organic carbon and nitrogen, reduced microbial activity, degraded soil fertility, and increased complexity and disorder in the relationships among soil indicators. Re-cultivation had a positive effect on the recovery of RMS. After 22 years of cultivation, significant improvements in soil structure were observed, with MA increasing by 30.95 % (P < 0.05). Based on this, organic carbon gradually accumulated, with soil organic carbon (SOC) increasing by 250.94 % (P < 0.05). Microbial abundance similarly improved, with total microbial biomass (TB) increasing by 123.07 % (P < 0.05). Soil fertility was also enhanced, with alkali-hydrolyzed nitrogen (AN), available phosphorus (AP), and available potassium (AK) increasing by 125.96 %, 304.84 %, and 61.90 %, respectively. However, RMS indicators and system structure remained distinct from those of the NCS. The first approximately 12 years after re-cultivation represented a critical period during which soil structure improvements drove RMS functional recovery, with a focus on MA recovery. Increasing particulate organic carbon (POC) accumulation is an effective strategy to promote aggregation in compacted RMS. Microbially mediated carbon–nitrogen cycling emerged as a crucial driver of the gradual recovery of the RMS system after re-cultivation.

Using an ensemble Kalman filter method for a soil nitrogen transport model in the real rice field

The overuse of nitrogen fertilizer in rice field of China leads to nitrogen loss and serious water pollution, so it is vital to accurately predict soil nitrogen transport in rice field. But the prediction errors of soil nitrogen transport are great due to complex chemical and reactive conditions and uncertain parameters in real rice fields. In this study, a prediction model of soil nitrogen transport in a rice field was established via modifying the HYDRUS-1D source code, and a data assimilation method called the ensemble Kalman filtering (EnKF) was coupled, based on the observed NH4+-N and NO3–-N concentrations at different depths in a real rice field. Study results for two different protocols of assimilating observed NH4+-N and NO3–-N concentrations simultaneously and separately were compared. It indicated the predictions accuracy of NH4+-N and NO3–-N concentrations was improved significantly via the EnKF method, and the former protocol is better than the latter. Moreover, for the latter protocol, observations of NO3–-N concentrations were more efficient than NH4+-N to improve the predictions accuracy of NH4+-N and NO3–-N concentrations at different depths. Inversed parameters of urea hydrolysis, NH4+-N volatilization, soil adsorption of NH4+-N, nitrification and denitrification increased over time. On the whole, the inversed model parameters were more stable at deep soil than shallow soil, which were different at different depths. With soil depths increase, parameters of the NH4+-N adsorption and NO3–-N denitrification increased, while parameters of urea hydrolysis, NH4+-N volatilization and nitrification decreased. This study improved the model predictions accuracy and inversed the model parameters, revealing the mechanism of nitrogen loss in real rice fields, which can provide scientific basis to reduce serious environmental problems caused by the overuse of nitrogen fertilizer.

Mechanisms of Irrigation Water Levels on Nitrogen Transformation and Microbial Activity in Paddy Fields

Nitrogen is a vital nutrient for rice growth; however, its inefficient use often results in nutrient loss, environmental degradation, and the emission of greenhouse gases. In this study, a rice paddy simulation was conducted under different water levels (1–4 cm), incorporating a comprehensive analysis of nitrogen dynamics, environmental factors, and microbial communities to evaluate the impact of water levels on nitrogen concentrations and microbial composition. The results indicated that the water level had a greater impact on nitrogen concentrations in surface water than in soil water. Compared to low water level conditions (1 cm), the average concentrations of ammonium nitrogen, nitrate nitrogen, and nitrite nitrogen in surface water under 2–4 cm water levels decreased by approximately 53.8%, 36.7%, and 78.9%, respectively. Water levels also influenced the microbial composition and nitrogen cycling in paddy soil, with lower water levels promoting aerobic processes such as nitrification, while higher water levels facilitated anaerobic processes such as denitrification and dissimilatory nitrate reduction to ammonium. Correspondingly, microbial composition shifted, with aerobic bacteria predominating in shallow water conditions and anaerobic bacteria flourishing under deeper water. These findings suggest that optimized water management, particularly through shallow irrigation, may mitigate nitrogen loss and improve nitrogen use efficiency. Nevertheless, additional field studies are necessary to validate these results and explore their interaction with other agricultural practices.