Soil Nitrogen Content Research Articles

Moss Cover Modulates Soil Fungal Functional Communities and Nutrient Cycling in Alpine Forests

Moss–cyanobacteria associations serve as significant nitrogen fixers and represent the primary nitrogen sink in boreal forests. Fungi, which are essential for soil biogeochemical cycling, have community structures intrinsically linked to forest ecosystem health and productivity. Using high-throughput sequencing, we investigated differences between moss-covered and non-moss soils in two alpine forests (both plantation and natural forests) by examining soil nitrogen contents, fungal community structure, composition, and functional guilds. Results demonstrated that moss cover enhanced soil nutrient contents, including total carbon, total nitrogen, and inorganic nitrogen. It also altered fungal community characteristics, resulting in higher Chao1 and Shannon diversity indices, as well as a more complex fungal network. Notable changes in functional guilds included an increase in saprotrophic fungi abundance and a decrease in ectomycorrhizal fungi. Our findings support the concept that moss cover creates distinct soil environments: moss-covered soils attract decomposers and nutrient-mobilizing fungi (particularly saprotrophs and ectomycorrhiza), while non-moss soils favor ectomycorrhizal fungi that relieve nutrient limitation through extensional mycelial networks. These findings highlight the critical role of moss cover in sustaining forest soil health and resilience, positioning it as a cornerstone of carbon and nutrient cycling within forest ecosystems.

Long-term nitrogen fertilization alters the partitioning of amino acids between citrus leaves and fruits

IntroductionThe growth of evergreen fruit trees is influenced by the interaction of soil nitrogen (N) and leaf amino acid contents. However, information on free amino acid contents in leaves of fruiting and non-fruiting branches during long-term N fertilizer application remains scarce.MethodsHere, a four-year field experiment (2018-2021) in a citrus orchard revealed consistently lower total N and amino acid contents in leaves of fruiting compared to non-fruiting branches.Results and discussionAppropriate N fertilizer application increased free amino acid and total N contents in leaves of both types of branches and fruits, but excessive amounts led to decreases. Correlation analysis showed that, in the early stage of fruit development, leaves on both types of branches can meet the N requirements of the fruit (R²=0.77 for fruiting, R²=0.82 for non-fruiting). As fruits entered the swelling stage, a significant positive correlation emerged between fruiting branch leaves and fruit total N content (R²=0.68), while the R² for leaves on non-fruiting branches dropped to 0.47, indicating a shift in N supply towards leaves on fruiting branches. Proline and arginine are the most abundant amino acids in these leaves. At fruit maturity, these amino acids account for more than half of the total amino acids in the fruit (29.0% for proline and 22.2% for arginine), highlighting their crucial role in fruit development. Further research is needed to investigate amino acid transport and distribution mechanisms between citrus leaves and fruits.

Response of Plant Leaf Traits to Environmental Factors in Climax Communities at Varying Latitudes in Karst Regions

Exploring the changes in plant functional traits and their relationship with the environment in karst climax communities across different latitudes can enhance our understanding of how these communities respond to environmental gradients. In this study, we focus on climax karst climax plant communities in Guizhou Province, China. We selected three sample sites located at varying latitudes and analyzed the variations in functional traits of the plant communities at these latitudes. Additionally, we examined the relationship between functional traits and environmental factors, integrating species characteristics and community structure into our analysis. The results indicated that (1) there were significant differences in both the community leaf aspect ratio and the community-specific leaf area. (2) Soil organic carbon content exhibited significant variations across different latitudes, while soil nitrogen content was notably higher in mid-latitude and low-latitude regions compared to high-latitude areas. The distribution of soil factors was more concentrated in high and mid-latitude regions, whereas low-latitude areas displayed more pronounced variability. (3) The primary environmental factors influencing the climax community in the karst study area included soil water content (SPMC), soil bulk density (BD), soil organic carbon content (SOC), soil nitrogen content (SNC), and soil phosphorus content (SPC). Our findings suggest that karst plant communities exhibit specific combinations of functional traits at distinct latitudes. With increasing latitude, the community demonstrated a gradual shift in ecological strategy from conservative to more opportunistic. Most environmental factors imposed limiting effects on plant functional traits, with plants primarily constrained by BD during growth. Among the responses of plant functional traits to environmental factors, community-weighted leaf area and community-weighted chlorophyll content were the most sensitive to soil conditions.

Experiences with grassland aerator with blades in Karcag

In 2023-24, we examined the effects of a lawn aerator with blades on plant structure, nitrogen, and total organic carbon content in a near-natural grass association in Karcag, characterized by saline soil. Following the aeration in October, by the following May, the nitrogen and total organic carbon content of the grass soil decreased. There was a decline in species diversity and the cover value of leguminous grass species. In contrast, the cover proportion of moderately oligotrophic, community-forming Festuca pseudovina increased. Additionally, the cover value of the dominant grass species, Alopecurus pratensis, also rose due to the two-time intervention with the blade roller. Summarizing our results, the application of lawn aeration in sensitive plant structures of near-natural grass associations is justified with great care.

Challenges in alpine meadow recovery: The minor effect of grass restoration on microbial resource limitation.

Microorganisms play a vital role in restoring soil multifunctionality and rejuvenating degraded meadows. The availability of microbial resources, such as carbon, nitrogen, and phosphorus, often hinders this process. However, there is limited information on whether grass restoration can alleviate microbial resource limitations in damaged slopes of high-altitude regions. This study focused on alpine bare land impacted by engineering activities, with the goal of using grass seeds to improve soil resource availability and multifunctionality. High-throughput sequencing and enzyme stoichiometry (vector analyses) were employed to analyze microbial community composition and assess resource limitations. Our findings suggested that soil carbon, nitrogen, and phosphorus contents were low, ranging from 7.67 to 12.6gkg-1for carbon, 0.61 to 0.98gkg-1,for nitrogen, and 0.65 to 0.78gkg-1for phosphorus. Nevertheless, the standardized scores for high yield and resource acquisition strategies remained at 0.26 and 1.36 in the four groups, which were lower than those of the stress tolerance strategy. Microorganisms primarily employed the stress tolerance strategy, focusing on repairing injured cells rather than promoting cell growth, which suggests that microbial growth and metabolism were only marginally enhanced. Because of this strategy's limited impact on enhancing microbial community diversity and fostering a co-occurrence network, the resultant levels remained comparable to those observed in degraded meadows. In this case, microbial resource limitations persisted, with phosphorus remaining a constraint. Consequently, grass restoration alone offered limited relief for microbial resource limitations in alpine meadows, underscoring the challenges of solely relying on grass seeds to recover damaged alpine ecosystems.

Assessment In Depth on the Anti‐seasonal Water Fluctuations and Vegetation Dynamic Trends in a Plateau Lake, Southern China

ABSTRACTHuman activities, such as dam construction for flow regulation, modify the natural hydrological regimes of lakes and rivers. The altered flow regimes substantially influence plant growth in the water level fluctuation zone, impacting both vegetation patterns and success. The relationships among above‐ground vegetation, soil seed bank and soil microorganisms remain unexamined. This study was performed in Lashi Lake, a plateau lake in southern China characterized by anti‐seasonal water level fluctuations, and Jizi Reservoir, a reference site exhibiting natural seasonal water level variations. The primary aim was to assess the distribution pattern of plant, soil seed bank and their corresponding soil microorganism over the three flood gradients, and the relationships among them were analysed simultaneously. The findings indicated that both plant community variety and seed bank diminished as the area of soil flooding increased. The soil seed bank was a strong indication of community diversity, particularly throughout late spring and late summer. Additionally, significant correlations between the alpha diversity of soil microorganisms and the concentrations of soil carbon, nitrogen and moisture were found across the flooding gradients. The organization and diversity of soil microbial communities were significantly correlated with the alpha diversity of the plant community and the soil seed bank. The findings demonstrate that both seed banks and soil bacteria play a dynamic role in the restoration of vegetation in areas experiencing anti‐seasonal water fluctuations.

Examining the Impact of Microbial Compost from Anaerobic Digestion on Soil Fertility and Maize Crop Nutrient Uptake

This research study was to evaluate the effects of combining microbial compost and mineral fertilizer on soil properties, maize growth, and nutrient uptake. Therefore, after selecting normal soil, 10 kg of soil was placed in each pot. Nine treatments with three replications were applied by using a Completely Randomized Design (CRD) for the study layout. The results revealed that the maximum plant height (101.73 cm), shoot fresh weight (69.36 g), shoot dry weight (128.6 g), root fresh weight (1.68 g), and root dry weight (0.89 g), as well as the highest content of nitrogen (1.66%), the highest phosphorus concentration (1.04%), and the maximum potassium concentration (2.13%) were noted in SF+MM + ½ NPK, while contents of iron (80.2 mg/kg), zinc (98.46 mg/kg), copper (78.66 mg/kg), and manganese (67.7 mg/kg) were also recorded in SF+MM + ½ NPK compared to other treatments. After harvesting maize crops, the lowest pH (7.27), highest EC (0.38 dS/M), and the highest contents of organic matter (1.03%) were recorded in SF+MM + ½ NPK. Maximum nitrogen content in soil (37 mg/kg), phosphorus content in soil (19.7 mg/kg), and potassium content in soil (105.8 mg/kg) were recorded in T8, while maximum contents of iron (4.88 mg/kg), zinc (1.80 mg/kg), copper (0.51 mg/kg), and manganese (1.95 mg/kg) were recorded in SF+MM + ½ NPK. The combination of SF+MM + ½ NPK showed to be the most effective treatment, whereas the usage of compost and chemical fertilizer alone remained the least effective.

The Nitrogen Fixation Characteristics of Terrestrial Nitrogen-Fixing Cyanobacteria and Their Role in Promoting Rice Growth

Cyanobacteria, ubiquitous phototrophic prokaryotes, can enhance soil fertility and crop productivity by promoting biological nitrogen fixation, phosphate dissolution, and mineral release. In this study, five nitrogen-fixing cyanobacteria were isolated and purified from paddy soil in Jilin Province. The effects of nitrogen-fixing cyanobacteria on soil fertility and rice seedling growth were examined through a pot experiment to clarify their growth and nitrogen-fixing characteristics. The results showed that the application of nitrogen-fixing cyanobacteria led to a significant increase in soil nitrogen content. GD2 and GD8 have the highest nitrogenase activity, at 75.33 U·mg−1 and 50.34 U·mg−1, respectively. It also enhanced the activities of urease, sucrase, phosphatase, and catalase in rice soil. In addition, it significantly promoted root development and plant height in rice plants. The total number of microorganisms in rice soil increased by 133–366%. Remarkably, the Desmonostoc muscorum GD2 strain was found to exhibit higher growth state indicators, including the growth curve, chlorophyll content, carbon and nitrogen content, and biomass accumulation, compared to other algae strains. The total nitrogen content of rice leaves treated with GD2 increased by 48.73%, and the soluble protein content increased by 52.89%. GD2 has great potential as an excellent nitrogen-fixing cyanobacteria inoculant for rice, suitable for agricultural production. In conclusion, the application of these nitrogen-fixing cyanobacteria significantly increased soil nitrogen levels and activated key enzyme activities involved in plant nitrogen metabolism. Moreover, it improved nitrogen utilization rates and promoted plant growth.

Optimization of Irrigation and Fertilization in Maize–Soybean System Based on Coupled Water–Carbon–Nitrogen Interactions

Effective water and nitrogen management plays a pivotal role in enhancing crop yields while simultaneously reducing greenhouse gas emissions. This study differs from previous research by investigating the effects of water–nitrogen co-regulation involving organic carbon on the yield increase and emission mitigation in a soybean–maize system. A dryland experiment was conducted, employing 20 distinct combinations of water and nitrogen treatments that were meticulously designed for the maize–soybean system. The DSSAT crop model was employed to quantitatively elucidate the intricate interactions between water and nitrogen. A multi-objective optimization model, integrating experimental data and mechanistic insights, was constructed and refined using the NSGA-III genetic algorithm to identify the optimal water and nitrogen application ratios. An analysis of maize and soybean data from Acheng in Heilongjiang, China, indicates that optimized irrigation and nitrogen application regimes—152.2 mm and 247.1 kg·ha−1 for maize and 91.7 mm and 106.2 kg·ha−1 for soybean—substantially enhanced the net economic returns within the dryland ecosystem. There is a significant positive correlation between the yield (Y), soil nitrogen content, and soil organic carbon (SOC). Nitrate nitrogen has a significant positive correlation with CO2 gas emissions. Organic carbon changes the soil’s carbon to nitrogen ratio by participating in the water and nitrogen cycles, thereby affecting nitrogen and phosphorus loss and carbon emissions. This study presents a sustainable method for regulating water and nitrogen in the maize–soybean system.

Impacts of Vetiver Grass and DT2008 Soybean Cover Crop Practices on Soil Quality in Citrus Orchards in Cao Phong, Hoa Binh

This study investigated the efficiency of biomass management, residue quantity, and quality from Vetiver grass and DT2008 soybean cover crops in improving soil quality, including carbon and nitrogen content and soil physiochemical properties. Mesocosm experiments in pots were conducted with six treatments, each was replicated three times: CT0 (control), CT1 (2% Vetiver grass mulch), CT2 (2% DT2008 mulch), CT3 (1% Vetiver grass and 1% DT2008 mulch), CT4 (1% Vetiver grass and 1% DT2008 buried), and CT5 (2% DT2008 buried). After 12 months, significant increases in total carbon, nitrogen, and humic and fulvic acids were observed, indicating enhanced soil physiochemical properties. CT5 and CT4 showed the highest carbon, nitrogen, and cation exchange capacity (CEC) improvements. Soil moisture, pH in water (pHH2O), pH in KCl (pHKCl), and hydrolytic acidity were higher in CT1, CT2, and CT3. Nitrogen accumulation efficiency was relatively lower than carbon (24.44% to 86.67%), while carbon accumulation efficiency was much higher (41.94% to 91.72%). The most effective methods were to bury soybean biomass or mulch Vetiver grass over a soybean plant mulching layer, with Vetiver grass mulch recommended for enhancing and conserving soil fertility.

Wheat productivity and nitrogen use efficiency in no-till systems: a comparative analysis of crop-pasture and continuous cropping rotations in Uruguay

IntroductionUruguayan agriculture’s transition to no-till farming and intensified practices, replacing crop-pasture (CP) systems with continuous cropping (CC) rotations, has disrupted biological nitrogen fixation (BNF). Despite this, diversified cropping sequences, including C4 species, have maintained the soil organic carbon (SOC) balance under no-till management, with limited overall impacts on productivity and sustainability. The effects of these changes on wheat productivity and nitrogen use efficiency (NUE) need to be further investigated.MethodsThis study, conducted within a long-term experiment (LTE) under rainfed conditions, compared wheat productivity in CP and CC rotations. Wheat following CP and CC were analyzed over three seasons. Variables measured included soil nitrogen (N) concentration, wheat grain yield (WGY), grain protein concentration (GPC), and NUE. Four N fertilizer levels were applied to each rotation system to assess their impact.ResultsCC rotation consistently outperformed CP in WGY, with 2425 and 1668 kg ha−1 averages, respectively. CP showed slightly higher GPC (10.92%) than CC (10.48%). Nitrate-N levels at tillering positively correlated with WGY and negatively with GPC, but the relationship differed by rotation. Soil NUE indices were higher in CC rotations.DiscussionThe study’s findings highlighted the potential of CC rotation, especially when including C4 species in the crop sequence, to achieve higher wheat productivity in the short term due to healthier soil conditions compared to wheat seeded after post-pasture in CP. Additionally, our study highlights that the effect of the previous crop on yield and NUE in wheat was more relevant than the expected residual effect of the pasture phase in CP, primarily due to the quality of residues and the temporary adverse effects of soil compaction caused by livestock trampling.

Optimizing Low-Efficiency Robinia pseudoacacia Forests on the Loess Plateau Based on an Evaluation of the Ecological Functions of Soil and Water Conservation

The vegetation for water and soil conservation on the Loess Plateau has resulted in the formation of large areas of low-quality and inefficient forests during its growth process, thereby hindering the high-quality development of such vegetation and compromising the sustainability of the ecological functions of soil and water conservation. This study focuses on Robinia pseudoacacia forests in the Caijiachuan watershed in the Loess region of western Shanxi. A comprehensive evaluation system for the ecological functions of soil and water conservation has been established to conduct a comprehensive assessment of the Robinia pseudoacacia forests. Additionally, the study identifies low-efficiency Robinia pseudoacacia forests and proposes reasonable regulation and control measures. The main research conclusions are as follows: (1) There are significant differences in the water and soil conservation functions among different Robinia pseudoacacia forests. The degree of inefficiency in these forests increases with forest density, and Robinia pseudoacacia forests with slopes between 35° and 40° are all low-efficiency forests. (2) The average density of high-efficiency Robinia pseudoacacia forests is 1655 trees per hectare, medium-efficiency forests average 1780 trees per hectare, and low-efficiency forests average 1927 trees per hectare. By substituting forest density, diameter at breast height (DBH), tree height, and crown width into the low-efficiency forest discrimination function, low-efficiency forests can be identified. The main influencing factors of low-efficiency forests are the Margalef richness index of shrubs, the total soil nitrogen content; and the nitrate nitrogen content. (3) Regulation measures for low-efficiency forests include controlling forest density to 1655 trees per hectare, increasing the richness of understory shrubs, and enhancing total soil nitrogen and nitrate nitrogen content by planting leguminous plants such as Lespedeza bicolor, Sophora davidii, and Vicia sepium. The research results can construct a comprehensive evaluation system for the ecological functions of Robinia pseudoacacia forests for water and soil conservation, identify low-efficiency forests, and provide precise regulation based on the causes of inefficiency, ensuring the sustainable function of Robinia pseudoacacia forests for water and soil conservation.

Effects of Downed Log Decomposition on Soil Properties and Enzyme Activities in Southwest China

Downed logs play crucial roles in carbon and nutrient cycling within forest ecosystems, influencing soil nutrients and revealing their functional roles in these environments. This study focuses on an evergreen broadleaf forest at Ailaoshan Station for Subtropical Forest Ecosystem Studies, Yunnan, and specifically examines three dominant tree species whose logs are heavily decayed: Lithocarpus xylocarpus (L. xylocarpus), Lithocarpus hancei (L. hancei), and Castanopsis wattii (C. wattii). Soil samples were collected from three depths (0–10 cm, 10–20 cm, and 20–30 cm) beneath the downed logs and from control plots without downed logs. The physicochemical properties and enzyme activities of these soils were analyzed to explore the effects of downed log decomposition on the soil properties. The results revealed several key findings: (1) Downed logs significantly increased the soil organic carbon (SOC) and total nitrogen (TN) content in the surface soil (0–10 cm), with the SOC and TN contents under L. xylocarpus logs being 368.20% and 65.32% higher than those in the CK plots, respectively, substantially increasing soil nutrient accumulation. (2) Downed log decomposition significantly increased the soil enzyme activities, with the highest activities observed in the surface soil (0–10 cm) under L. xylocarpus. In deeper soil layers (20–30 cm), L. xylocarpus and C. wattii still presented higher enzyme activities than those in the CK plots did (p < 0.05). (3) The SOC, TN, and C/N were significantly positively correlated (r > 0.95 and p < 0.01), whereas the correlations were weak or nonexistent in the CK plots. The release of organic acids from downed logs enhanced the microbial activity, significantly reducing the soil pH (p < 0.05). (4) Different tree species exhibited distinct effects during downlog decomposition, with L. xylocarpus showing the most significant improvements in the SOC, TN, and enzyme activities, followed by C. wattii, whereas L. hancei limited carbon accumulation due to faster nitrogen release, resulting in a relatively lower C/N. Overall, this study demonstrated that the interaction between downed log decomposition and soil enzyme activity plays a key role in improving soil fertility and promoting nutrient cycling. This research provides evidence for understanding the impact of downed logs on forest soil ecological functions and microbial functional activity and their role, thereby contributing valuable insights into carbon cycling in subtropical forest ecosystems.

Comparative Effects of Organic Nutrient Sources on Green Gram (Vigna radiata L.) Quality and Soil Properties

A field experiment was conducted during summer season of the year 2020-21 on organic certified plot A-7 at Agronomy Farm, B. A. College of Agriculture, Anand Agricultural University, Anand, Gujarat. Different sources of organic manures were tested using randomized block design with four replications. The treatment T7 (50% N through FYM followed by Seed treatment of Rhizobium) recorded significantly higher available nitrogen content (212 kg/ha) in soil and also same behaviour observed in available phosphorus content in soil. The treatment T9 (50% N through castor cake followed by Seed treatment of Rhizobium) recorded significantly higher available phosphorus content in soil. Significantly higher value of EC of soil (0.18) was found in treatment T1, which was significantly higher EC of soil (0.11) which was recorded with treatment T9. Higher organic carbon (0.65%) of soil after harvest of green gram was observed in treatment T8. Significantly higher nitrogen content in seed of green gram was obtained with application of treatments T10. Treatment T2 [Rhizobium (5.0 mL/kg seed treatment and 1.0 L/ha soil application)] recorded significantly higher Rhizobium population in soil at harvest of green gram. Subsequent, treatment T6 (100 % N through neem cake) recorded significantly higher phosphorus solubilising bacteria (PSB) population in soil as compared to control. The maximum net return 63287 INR/ha was obtained with application of treatment T10 (50% N through NC + Rhizobium seed treatment) followed by treatment T7 (50% N through FYM + Rhizobium seed treatment) with net realization of 54063 INR/ha. With respect to benefit cost ratio, the highest 3.62 BCR was achieved with Treatment T7, which closely followed by treatment T2 (Rhizobium seed treatment + 1.0 L/ha soil application) having BCR of 3.52.

Study on the carbon sequestration effect of biochar in vegetable fields

This study was conducted using a field experiment methodology aimed at assessing the effects of biochar application on tomato growth and soil properties in greenhouse greenhouses. Biochar, a carbon-rich material produced by pyrolysis of biomass under anoxic conditions, has attracted attention for its potential in soil amelioration, carbon sequestration, and soil fertility enhancement. In this experiment, three biochar application levels of 0, 20, and 40 t/ha were designed to investigate the effects of different application rates on soil chemical properties and tomato growth.The study results showed that biochar application significantly increased soil pH by 0.05 to 0.1 units, which was beneficial in regulating acidic soil. Meanwhile, biochar application significantly increased total soil carbon content by 7.5 to 28.8%, indicating its effectiveness in enhancing soil carbon sequestration capacity. Although the enhancement of total soil nitrogen content by biochar was small (3.1 to 7.8%), this increase had a positive effect on crop growth. Considering the cost-effectiveness, this study recommends a one-time application of 40 t/ha of biochar, which can maintain the effect for at least 2 years, reducing the need for frequent applications and the associated economic costs.This study provides recommendations for optimization of biochar application and provides a scientific basis for sustainable agricultural development. By improving soil properties and increasing crop yields, this study contributes to the promotion of green development of agriculture and ecological civilization, and the realization of carbon and nutrient cycling in agroecosystems.The significance of this research focuses on evaluating the effects of biochar on soil properties and tomato production, thereby providing a scientific basis for fine-tuning application levels. Such optimization promotes sustainable farming practices, reduces agricultural waste emissions, enhances carbon and nutrient dynamics within agroecosystems, and reinforces the scientific foundation essential for progressing green agricultural development and building an ecological civilization.

Influence of Annual Ryegrass (Lolium multiflorum) as Cover Crop on Soil Water Dynamics in Fragipan Soils of Southern Illinois, USA

Fragipans are dense subsurface soil layers that severely restrict root penetration and water movement. The presence of shallow fragipan horizons limits row crop production. We hypothesized that the roots of cover crop might improve soil physiochemical properties and biological activity, facilitating drainage and increasing effective soil depth for greater long-term soil water storage. To evaluate annual ryegrass as one component of a cover crop (CC) mix for promoting the characteristics and distribution of soil water, on-farm studies were conducted at Marion and Springerton in southern Illinois, USA. Soil samples were collected at 15 cm increments to 60 cm (Marion) and 90 cm (Springerton) depths during the fall of 2022. Both sites had low total soil carbon and nitrogen contents and acidic soil pH (≤6.4). A soil water retention curve was fitted using the van Genuchten equation. At Springerton, the CC treatment increased saturated (thetaS) and residual (thetaR) soil water contents above those of the no cover crop (NCC) at the 60–75 cm and 75–90 cm depths. Changes in volumetric soil water content were measured using a multi-depth soil water sensor for the Springerton site during late July to early August of the soybean growing phase of 2022; NCC had higher soil water than CC within the 0–15 cm depth, but CC had higher soil water than NCC at the 30–45 cm depth. These findings indicate that cover crop mix has the potential to improve soil water movement for soils with restrictive subsoil horizon, possibly through reducing the soil hydraulic gradient between the surface and restrictive subsurface soil layers.

The Reduction of Nitrogen Fertilizer Rate Shifted Soil Bacterial Community Structure in Rice Paddies

In order to achieve reasonable yield while keeping environmental risks low, nitrogen fertilizer reduction has been adopted for in rice cultivation. The response of the soil microbial community structure to this management is not fully understood. In this study, the treatments comprising conventional farming practices (330 kg ha−1), reduced N application (270 kg ha−1 and 300 kg ha−1, respectively), and a control without N application were set up in order to reveal the effects of N application rate on the soil microbial community composition in rice paddies. It was discovered that Proteobacteria, Acidobacteria, Actinobacteria, and Chloroflexi represented the most abundant bacterial phyla in all samples. The assembly of the soil bacterial community differed among the treatments, with NH4+-N, available phosphorus (AP), and organic matter (OM) as key drivers. The reduction of N application by 20% decreased soil NO3− up to 32% and increased the abundance of the total functional pathways, especially those associated with carbon fixation, N, S, and CH4 metabolism, whereas N reduction by 10% increase soil N accumulation and soil bacterial richness. In summary, a reduction of N fertilizer by up to 20% compared to the amount used in traditional practices could most effectively regulate the soil bacterial community composition and increase the predicted functional groups associated with N transformation, while maintaining lower soil nitrogen contents.

The soil microclimate and microbial characteristics jointly drive the response of vegetation productivity to changes in snow cover — A global meta-analysis

Recent climate warming has greatly shaped snow-cover patterns globally. Variances in snow cover are expected to affect soil microclimate and microorganisms, which may cause vegetation productivity to vary. However, exactly how snow cover influences the productivity of terrestrial vegetation remains unclear. In this study, we conducted a global meta-analysis of the response of vegetation productivity to variances in snow cover from near-complete depletion to increasing snow depth. Globally, complete snow-cover depletion was shown to reduce vegetation productivity by about 33.6 %, with cropland productivity decreasing the most. In contrast, increasing snow depth did not have an observable effect on vegetation productivity. The response of vegetation productivity to snow-depth variations was shown to be controlled by in-situ soil temperature and moisture and variations in soil-microbial-generated differences in soil carbon (C) and nitrogen (N) content. Based on modelled future snow-cover change (from present to the start of the 22nd century), cropland productivity is projected to decline, especially under a high CO2-emission scenario, such as IPCC's emission scenario SSP5–8.5. Our findings advance our understanding of future implications of snow-cover depletion on vegetation productivity.

Evaluation of Environmental Parameters and Economic Efficiency of Integrated Farming System on Acidic Soil and Saltwater Intrusion in The Coastal Area: A Case Study of Mekong Delta, Vietnam

The shift to growing sedge plants, combining raising snails and tilapia in coastal areas could improve the soil nutritional environment, income, and land use efficiency compared to rice monoculture. This study aims to evaluate soil and water environmental factors and to compare the financial efficiency of integrated farming with rice monoculture farming. These experiments were arranged on field land affected by drought and saltwater intrusion in two ecological regions of Kien Giang province. The research found the adaptation of crops (rice, sedge) and aquatic species (snails, tilapia) to the characteristics of acidic and saline soils in coastal areas. The results showed that an integrated farming system reduced soil salinity, but increased soil pH, nitrogen, phosphorus, potassium, and organic matter content more than rice monoculture farming. In addition, this system improved pH, reducing salinity, temperature, and TDS of water more than rice monoculture farming. Acidity and salinity factors affect the rice yield of Winter-Spring crops. The sedge grass (Cyperus malaccensis) grew well under the pH and salinity conditions, but the sedge yield in the dry season was higher than in the rainy season. The weight gain of tilapia (Oreochromis niloticus) was from 0.45 to 0.96 g/day, but fish yield was still low (226 - 541 kg/ha); due to low survival rate (30-36%). Snails (Pila gracilis) adapted well to experimental conditions and the survival rate reached 53-79%. The data analysis of financial efficiency showed that the profit of integrated farming was higher than rice monoculture farming (10,905 to 11,146 USD compared to 904-1,672 USD/ha/year). Therefore, diversified land use in coastal areas to grow sedge grass combined with snails and tilapia increased household income in these study sites.

Estimation of Soil Nitrogen Content Influenced by Different Nitrogen-Based Management Practices within Rice-Based Cropping Using Diffuse Reflectance Spectroscopy and Machine Learning

ABSTRACT Reflectance spectroscopy has been widely utilized by researchers to characterize and predict soil nitrogen (N). This study explores the potential of reflectance spectroscopy combined with machine learning to estimate soil N levels under different N-based management practices in rice-based cropping systems. A five-year field experiment (2015–2020) was conducted at Kalyani D Block Farm, Bidhan Chandra Krishi Viswavidyalaya, Nadia, West Bengal, India, testing rice-rice, rice-wheat, and rice-potato systems with N treatments: control (N₀), 100% Neem Coated Urea (NCU), 75% NCU with 25% organics, 100% Polymer Sulfur Coated Urea (PSCU), and 75% PSCU with 25% organics. Soil samples from 0 to 15 cm depth were collected post-harvest of rabi crops (wheat and potato) and summer rice for analysis, revealing the highest available N (AN) (189.6 kg ha− 1) in PSCU-treated summer rice plots, with maximum AN in wheat (290.6 kg ha− 1) and potato (431.4 kg ha− 1) found in 75% NCU + 25% organic plots. Rice yield reached a high of 5.58 t ha− 1 with PSCU treatment, while wheat and potato produced 3.87 and 16.07 t ha− 1 with NCU + vermicompost (VC), respectively. Spectral reflectance measurements were conducted in a controlled lab environment using the ASD Field Spec 4 spectroradiometer, showing significant variability in soil spectral behavior with soil organic carbon (SOC) and N levels. Pre-processing techniques, including first-order derivation (FOD), log (1/R) transformation, and continuum removal (CR), were applied to enhance spectral data quality. Machine learning models, Support Vector Machine Regression (SVMR) and Partial Least Squares Regression (PLSR) were used to estimate SOC, AN and total N (TN) from spectral data (350–2500 nm range). Results showed that SVMR consistently outperformed PLSR for all soil properties, with continuum-removed spectra achieving R2 values of 0.98, 0.97, and 0.92, and RMSEs of 0.02%, 37.1, and 948.8 kg ha− 1 for SOC, AN and TN, respectively. This study highlights the value of integrating spectral data with machine learning for rapid, accurate soil N estimation, enabling optimized fertilizer applications to enhance crop yields and reduce environmental impact.