Soil Total Nitrogen Content Research Articles

Spatiotemporal Dynamics of Fine Root Biomass in Chinese Fir (Cunninghamia lanceolata) Stumps and Their Impacts on Soil Chemical Properties

Stumps are residuals from artificial forest harvesting, persist in forest ecosystems, and have garnered attention for their ecological roles in soil and water conservation, carbon sequestration, and forest regeneration. However, the spatiotemporal dynamics of stump fine root biomass and their impact on soil nutrient cycling remain unclear. This study focuses on the fine roots of Chinese Fir (Cunninghamia lanceolata) stumps generated during the construction of national reserve forests at Xishan State Forest Farm, Linwu County, Hunan Province, from 2014 to 2022. Employing a space-for-time substitution approach, we investigated the spatiotemporal dynamics of fine root biomass (FRB) and its effects on soil chemical properties. The results indicated that the Chinese Fir stump FRB significantly differed with increasing residual time across various soil layers and distances, with an average annual loss rate of 8.40%–9.96%. The living fine root biomass (LFRB) was predominantly concentrated in the 0–20 cm soil layer and decreased with increasing soil depth. Initially, the LFRB was closer to the stumps; however, this proximity effect diminished over time. There were no significant differences in the fine root loss coefficients between layers, within the vertical soil profile with 95% root loss over a time span of 15.1–15.9 years. However, there were horizontal differences, with a 95% root loss over a time span of 13.7–17.0 years. The changes in soil organic matter (SOM) and total nitrogen (STN) content over the study period exhibited a trade-off relationship with the loss of LFRB, with SOM and STN peaking 1 year after the peak of dead fine root biomass (DFRB), suggesting a combined effect of living root exudates and dead root decomposition on SOM and STN enhancement. The trend of LFRB loss was generally inverse to the changes in the soil’s total phosphorus (STP) content, which gradually increased with extended stump retention, indicating that stumps provide a long-term source of phosphorus for the soil. The study also revealed that living fine roots of Chinese Fir stumps can persist in forest soils for a relatively long time and that their biomass dynamics positively affect soil nutrients and carbon storage. These findings provide theoretical support for forest management and suggest that retaining stumps in post-harvest forest management can maintain soil fertility and ecological functions.

Enhancement of Fertilizer Efficiency Through Chinese Milk Vetch and Rice Straw Incorporation.

The incorporation of rice straw (RS) and Chinese milk vetch (CMV) with reduced chemical fertilizers (CFs) is a viable solution to reduce the dependency on CF. However, limited research has been conducted to investigate the impact of CMV and RS with reduced CF on rice production. A field trial was conducted from 2018 to 2021 with six treatments: CK (no fertilizer), F100 (100% NPK fertilizer (CF)), MSF100 (100% CF+CMV and RS incorporation), MSF80 (80% CF+CMV+RS), MSF60 (60% CF+CMV+RS), and MSF40 (40% CF+CMV+RS). The results revealed that compared with the F100, the MSF80 treatment maintained a significantly higher mean grain yield over the four years, with an increase of 5.8~24.5%. MSF80 treatment also improved nitrogen (N), phosphorus (P), and potassium (K) use efficiencies, sustainable yield index, and partial factor productivity. Soil organic matter (SOM), total nitrogen (TN), ammonium N (NH4+-N), nitrate N (NO3--N), available phosphorus (AP), and available potassium (AK) contents were significantly enhanced under MSF80 across different growth stages in both 2020 and 2021 seasons over F100. Pearson correlation analysis revealed a strong positive correlation among SOM, TN, NH4+-N, AP, AK, and rice yield. Additionally, Partial Least Squares Path Modeling (PLS-PM) demonstrated significant relationships between organic amendments, soil nutrients, nutrient uptake, and yield. The above findings suggest that combining RS returning with CMV incorporation is a long-term sustainable strategy for maintaining soil health, and it could reduce fertilizer addition by 20% without prejudicing rice grain yield under a rice-green manure rotation system.

Effects of biogas slurry drip irrigation on growth performance of Brassica chinensis L. and soil nutrient dynamics

The optimal amount of biogas slurry was determined to improve both the yield of Brassica chinensis L. (BL) and soil quality. An experiment was set up with six sets of drip irrigation gradients (1:3 mix of biogas and water) of 12 (BS-1), 15 (BS-2), 18 (BS-3), 21 (BS-4), 24 (BS-5), and 27 (BS-6) L. Each treatment was repeated three times and irrigated eight times. The radius of drip irrigation was 1.2 m, and the dripping speed was 2 L/h. The highest plant height, fresh weight, dry weight, soluble sugar content, and protein content of 25.2 cm, 16.7 g, 1.10 g, 0.61 g/100 g, and 1.90 mg/g, respectively, were obtained under the BS-5 treatment. Soil total nitrogen, available phosphorus, and organic matter content under the BS-4 treatment increased 5.29%, 230.75%, and 1.00%, respectively, compared with those before drip irrigation treatment. The soil available potassium content was highest under the BS-3 treatment and had increased 20.4% compared with that before drip irrigation treatment. The most remarkable influence on the yield and quality of BL was observed when the drip irrigation amount was 24 L. Drip irrigation with 21 L of biogas slurry is conducive to improving soil physical and chemical properties.

Unveiling the impact of biodegradable polylactic acid microplastics on meadow soil health.

Soil microplastics (MPs) pollution has garnered considerable attention in recent years. The use of biodegradable plastics for mulching has led to significant quantities of plastic entering agro-ecosystems. However, the effects of biodegradable polylactic acid (PLA) plastics on meadow soils remain underexplored. This study investigates the impacts of PLA-MPs of varying particle sizes and concentrations on soil physicochemical properties, enzyme activities, and microbial communities through a 60-day incubation experiment. PLA-MPs increased the pH, soil organic matter, total nitrogen (TN) and available potassium (AK) content, as well as enhanced the activities of superoxide dismutase (S-SOD), peroxidase (S-POD), soil catalase (S-CAT), β-glucosidase (S-β-GC) and urease (S-UE) activities. Conversely, a decrease in alkaline phosphatase (S-ALP) activity was observed. The influence of PLA-MPs on soil physicochemical properties was more pronounced with larger particle sizes, whereas smaller particles had a greater effect on enzyme activities. Additionally, PLA-MPs led to an increase in the abundance of Acidobacteriota, Chloroflexi, and Gemmatimonadota, while the abundance of Proteobacteria, Actinobacteriota, and Patescibacteria declined. Mantel test analysis showed that changes in microbial community composition affected soil properties such as pH, AK, S-UE and S-β-GC. Phylogenetic Investigation of Communities by Reconstruction of Unobserved States (PICRUSt2) analysis demonstrated that PLA-MPs modify bacterial metabolic pathways. Our results suggest that particle size and concentration of PLA-MPs differentially affect soil nutrients and microbial community structure and function, with more significant effects observed at larger particle sizes and higher concentrations.

A meta-analysis of the effects of nitrogen fertilizer application on maize (Zea mays L.) yield in Northwest China.

Nitrogen fertilizer application is an important method for the production of high-quality maize. However, nitrogen fertilizer addition patterns vary according to regional climate, field management practices, and soil conditions. In this study, a meta-analysis was used to quantify the yield effects of nitrogen addition on maize, and meta-regression analysis and a random forest model were used to study the main factors affecting the yield effects of nitrogen addition on maize. The results showed that nitrogen addition significantly increased maize yield by 50.26%-55.72%, and a fluctuating increasing trend was observed with the advancement of the experimental year. The increase in maize yield upon nitrogen addition was the highest in Gansu Province, and showed a decreasing trend with the rise in average annual temperature, but did not change significantly with the average annual precipitation. Among the field management factors, the increase in maize yield was better with the variety Qiangsheng 51, topdressing at the jointing and tasseling stages (JS, TS), nitrogen application rate of 175-225 kg·ha-1, and controlled release of nitrogen fertilizer and urea (CRNFU) or the application of a combination of organic and inorganic nitrogen (OIF). Moreover, the positive effects of nitrogen fertilizer application on maize yield improved with soil pH, organic matter, available potassium, available phosphorus, and total nitrogen content; decreased with soil carbon and nitrogen ratio and available nitrogen (AN) content; and were enhanced in chestnut soil, clay, and at a bulk density of 1.2-1.4 g·cm-3. Random forest model and multifactorial optimization revealed that the effects of nitrogen addition on maize yield in Northwest China were primarily influenced by experimental year, variety, soil type, AN, and soil pH.

A comparative evaluation of rehabilitation approaches for ecological recovery in arid limestone mine sites.

Limestone mining in arid regions, particularly within fragile environments, leads to severe environmental pollution and ecological degradation. Developing a scientifically sound and effective ecological rehabilitation strategy is therefore critical. This study constructed a three-dimensional ecological rehabilitation model integrating soil amelioration and vegetation reconstruction. Seven resilient shrub species (Caragana korshinskii, Corethrodendron scoparium, Atriplex canescens, Calligonum mongolicum, Caryopteris mongholica, Nitraria tangutorum, and Tamarix laxa) and four soil matrix reconstruction treatments-sand:soil:organic fertilizer (8:1:1), sand:soil:compound fertilizer (8:1:1), sand:soil (8:2), and soil:organic fertilizer (9:1)-were evaluated for their effects on soil, plant, and microbial indicators. A comprehensive evaluation system was established to identify the optimal rehabilitation approach. The results indicate that organic fertilizer treatments reduced soil EC by 16.39% and increased microbial biomass carbon (MBC), MBC/nitrogen (MBC/MBN), and MBC/phosphorus (MBC/MBP) by over 41.50%, while improving the height and canopy of C. korshinskii by 71.05% and 180.00%, respectively. Plant species significantly influenced soil properties, with T. laxa achieving the highest soil organic matter and total nitrogen content. Soil matrix amendments and plant species both significantly affected microbial β-diversity. Ultimately, the combination of T. laxa and the sand:soil:organic fertilizer treatment was identified as the optimal rehabilitation strategy. These findings provide critical insights for rehabilitating degraded limestone mine areas in arid regions.

Characteristics of latosol soil after application of rice husk biochar in Bogor Regency, Indonesia

Latosol soil is one of the predominant soil types in the Bogor region, but it is characterized by low nutrient content. One approach to improving soil conditions is the use of biochar as a soil amendment. Biochar, being rich in carbon, has the potential to enhance soil quality. This study aimed to examine the characteristics of soil after the application of rice husk biochar. The application of rice husk biochar was found to influence the characteristics of latosol soil. Higher biochar doses resulted in increased soil electrical conductivity and total carbon content, with the highest values recorded at a treatment level of 125 tons/ha, reaching 335.7 μS/cm and 4.71%, respectively. In this study, the addition of biochar had no effects on soil pH and total nitrogen content. Additionally, silicon content in the soil was enhanced by the application of rice husk biochar. Overall, the application of rice husk biochar can improve the quality of latosol soil in Bogor Regency.

Effects of vegetation restoration on soil aggregate characteristics and soil erodibility at gully head in Loess hilly and gully region

Vegetation restoration can be effective in containing gully head advance. However, the effect of vegetation restoration type on soil aggregate stability and erosion resistance at the head of the gully is unclear. In this study, five types of vegetation restoration—Pinus tabulaeformis (PT), Prunus sibirica (PS), Caragana korshinskii (CKS), Hippophae rhamnoides (HR), and natural grassland (NG, the dominant species is Leymus chinensis)—in the gully head were studied. Soil aggregate composition and nutrient contents in the 0–20, 20–40, and 40–60 cm soil layers were also determined, and the soil stability parameters were used to evaluate the soil conditions. The soil erodibility (K) was then determined by measuring the granulometric composition and organic matter. The results showed that the particle size of soil aggregates under different vegetation restoration types was mainly < 0.25 mm, and the percentage of aggregate disruption (PAD) was 22.08–76.07%. This further indicated that in Loess hilly and gully regions, water-stable aggregates were more reflective of the stability of soil aggregates in a gully head under vegetation restoration. The > 0.25 mm aggregates (R> 0.25 mm), geometric mean diameter (GMD), and mean weight diameter (MWD) values of the three soil layers were the highest in PT and the lowest in NG, while the opposite was true for fractal dimension (D) and the percentage of aggregate disruption (PAD). The K ranged from 0.052 to 0.065 t·hm2·h·MJ− 1 mm− 1·hm− 2. GMD can be used to characterize the anti-erosion ability of soil, and increasing the soil organic carbon, total nitrogen, and clay content can effectively reduce soil erodibility. The comprehensive analysis indicated that the soil aggregates of arbors planted in the gully head had the highest stability and anti-erodibility, followed by shrubs and grasslands, and can be used to evaluate vegetation restoration measures in gully heads.

Effects of a Multifunctional Cover Crop (LivinGro®) on Soil Quality Indicators in Zaragoza, Spain

Soil degradation is a significant threat to agricultural systems and contemporary societies worldwide, especially in the context of climate change. Proper management of agricultural systems is a priority for maintaining food security and achieving sustainable development. It is therefore important to assess the efficacy of different interventions that are designed to improve the quality of agricultural soils. Measurements of physical, chemical, and biological indicators of soil quality can be used to examine the efficacy of strategies or methods that were designed to prevent soil degradation. We measured seven physicochemical indicators of soil quality at a representative experimental plot of nectarines in the province of Zaragoza (Spain) over three years (2020–2023) and compared the effect of a multifunctional cover crop (LivinGro® MCC, Basel, Switzerland) with conventional treatment (control) on soil quality. Soil samples were collected every two months from the treelines and inter-rows (paths for farming vehicles). In general, the MCC zones in the treelines and inter-rows had better soil health, especially in key indicators such as basal soil respiration, organic matter, nitrogen, and porosity. Climatic variability, especially seasonal differences in rainfall, also affected multiple soil indicators. During many sample periods, the MCC zones of the treelines and inter-rows had significantly increased soil organic matter, basal respiration, total nitrogen, nitrate, total porosity, and available water content, but the MCC and control zones had no significant differences in bulk density. The differences between the MCC zones and control zones, especially in basal soil respiration, were greater during the wet seasons. Our results indicate that the LivinGro® MCC prevented degradation of agricultural soils in a region with a continental Mediterranean climate.

Analysis of Soil Microbial Community Structure and Function in Morchella esculenta Habitats in Jilin Province

Morel mushrooms (Morchella spp.), a globally distributed edible and medicinal fungus, possess significant economic and nutritional values. This study investigated rhizosphere soil samples collected from wild Morchella esculenta in three regions of Jilin Province. Metagenome sequencing technology was employed to analyze the structure and function of the rhizosphere microbial communities. The results indicated significant differences in microbial community composition among the samples, with the bacterial community being dominant, followed by the archaeal community. Pseudomonadota and Nitrospirae emerged as the dominant phyla, while Bradyrhizobium and Nitrospira were the co-dominant genera. A correlation analysis of environmental factors revealed that the genera Luteibacter, Streptomyces, Micromonospora, Nocardia, Actinomadura, and Paenibacillus were positively correlated with soil total nitrogen, total phosphorus, and organic matter content. In contrast, Candidatus Nitrosocosmicus showed a significant positive correlation with rapidly available nutrients. The functional annotation analysis of soil microorganisms, based on the KEGG database, revealed that within level A (highest tier), metabolic activities were the most prominent. In contrast, at level B (secondary tier), global and overview maps, carbohydrate metabolism, and amino acid metabolism were dominant. Among the top 10 pathway-level annotations, metabolic pathways, the biosynthesis of secondary metabolites, and microbial metabolism in diverse environments were significant. Environmental factors and KEGG gene network maps indicated that the available potassium, available phosphorus, and pH were closely related to level A genes, which exhibited a higher abundance of metabolism genes. This study was dedicated to deepening the understanding of the structure and function of the rhizosphere microbial community of Morchella esculenta, and providing new perspectives and insights for habitat investigations, the development of biomimetic cultivation techniques, and the domestication of wild strains to Morchella esculenta in Jilin Province.

Pair-Soil-Spectra: An Approach for NIRS-Based Soil Total Nitrogen Content Detection with Feature Metrics in Cases of Small Sample Sizes.

Soil total nitrogen (STN) plays an important role in plant growth, and rapid and nondestructive detection of STN content is essential for agricultural production. Near-infrared spectroscopy (NIRS) takes advantage of the fast detection speed, low cost, and nondestructiveness, and it can be used for STN content detection. Typically, NIRS-based approaches require a large number of samples for detection model training. However, it is difficult to collect sufficient samples due to various causes (e.g., time-varying state, high assay costs, etc.) in practical application. To tackle this problem, a feature metric approach is introduced to detect the STN content based on NIRS in this work, and a new approach (named Pair-Soil-Spectra) is proposed to mine fine-grained features by contrasting different soil sample pairs, which takes full advantage of soil particle heterogeneity and NIRS penetration. For the validation of this study, three different soil datasets with various collection sources are selected as research subjects, and the performance of Pair-Soil-Spectra is analyzed from different perspectives. According to the results, Pair-Soil-Spectra has significantly improved the performance of STN content detection models (e.g., partial least-squares (PLS), Cubist, extreme learning machine (ELM), and random forest (RF)) in small sample cases. Of these, the coefficient of determination of RF has improved by 0.13, 0.42, and 0.10, and the root-mean-square of prediction has decreased by 0.15, 0.52, and 0.01 g/kg with different datasets, which has gained the greatest improvement. Meanwhile, this approach can be easily expanded to cover other domains.

A Study of the Effects of Wetland Degradation on Soil-Microbial-Extracellular Enzyme Carbon, Nitrogen, and Phosphorus and Their Ecological Stoichiometry

Due to the unique geographic location of A’er Xiang, there is a natural landscape where sandy land and lake-marsh wetlands coexist. However, the wetland degradation caused by the disturbance of anthropogenic activities has led to the change in land use. In this study, the spatial-temporal substitution method was used to select five sample plots: the original wetland converted to forest land for reuse area of five years and ten years; the original wetland converted to cropland for reuse area of five years and ten years; and the native wetland. It aims to investigate the variations in carbon, nitrogen, and phosphorus and their stoichiometric characteristics of soil-microorganisms-extracellular enzymes before and after reuse, and to analyze potential interactions among these elements. The results indicated that following wetlands degradation, changes in land use for five years did not significantly affect the content of soil organic carbon (TOC), total nitrogen (TN), or total phosphorus (TP). However, after ten years, both TOC and TN, except for TP, decreased significantly. Microbial biomass carbon (MBC) and microbial biomass nitrogen (MBN) contents in cropland were consistently higher than those in WL, showing a trend of first increasing and then decreasing with longer conversion periods. In contrast, forest land values were lower than in WL and increased as the conversion period lengthened. The microbial biomass phosphorus (MBP) content was ranked across the five sample sites as follows: 10 CL &gt; 5 CL &gt; 5 FL &gt; 10 FL &gt; WL. β-1,4-glucosidase (BG) activity was significantly increased after conversion to forest land and significantly decreased after conversion to cropland. β-1,4-N-glucosidase (NAG) and L-leucine aminopeptidase (LAP) activities were ranked as follows among the five sites: 5 FL &gt; WL &gt; 5 CL &gt; 10 FL &gt; 10 CL. Phosphatase (PHOS) activity showed no significant changes post-conversion, though it was consistently lower compared to WL.

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 &lt; 0.05). (3) The SOC, TN, and C/N were significantly positively correlated (r &gt; 0.95 and p &lt; 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 &lt; 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.

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.

Co-application of sheep manure and commercial organic fertilizer enhances plant productivity and soil quality in alpine mining areas.

The addition of organic fertilizers and sheep slat manure have important effects on soil quality in alpine mining areas, but how they affect soil physicochemical properties and microorganisms is not yet known. The current study employed field-controlled experiments and high-throughput sequencing technology to investigate differences in soil physicochemical properties, microbial community structures, and diversity under four treatments: no fertilization (CK), 100% sheep manure (SM), a combination of 50% sheep manure and 50% commercial organic fertilizer (MF), and 100% commercial organic fertilizer (OF). Aboveground biomass increased by 191.93, 253.22, and 133.32% under SM, MF and OF treatments, respectively, when compared to CK treatment. The MF treatment resulted in significantly higher soil total nitrogen, total phosphorus, organic matter, and available nitrogen content compared to other treatments. Soil total nitrogen content, total phosphorus content, organic matter, available nitrogen content and available phosphorus content were 211, 120, 380, 557, and 271% higher, respectively, under the MF treatment than the CK treatment. Different nutrient additions significantly influenced soil microbial community composition. The SM and MF treatments notably increased soil bacterial and fungal community Operational Taxonomic Units (OTUs) indices and Chao 1 indices, while nutrient addition had no meaningful effect on the Simpson indices for microbial communities. There was a highly significant positive correlation between aboveground biomass and observed soil nutrient content. The combined application of sheep manure and commercial organic fertilizer is more conducive to improving soil quality and enhancing plant productivity in alpine mining areas.

Crop Rotation of Sainfoin on the Longzhong Loess Plateau Has a Positive Effect on Enhancing Soil Carbon Sequestration Potential

The impact of various crop rotation systems on the potential for soil carbon sequestration and stoichiometric characteristics is not yet fully understood, which poses challenges for effective land management and utilization. This study selected three typical crop rotation methods in the Longzhong Loess Plateau: maize–alfalfa rotation (MA), maize–sainfoin rotation (MS), and maize–wheat rotation (MW). Soil physical and chemical indices were measured, and the soil carbon density and soil stoichiometry were calculated and analyzed. The results show that the soil C/N of the surface soils was low across the rotation methods, indicating a rapid rate of organic matter decomposition and mineralization, which may hinder soil nutrient accumulation. The soil N/P was found to be lower than the national average of 8.0, indicating that nitrogen is a limited nutrient in the soil under the three crop rotation systems in this region. The soil total nitrogen content can be increased by rotation with leguminous forage. Sainfoin rotation can enhance the soil total carbon and organic carbon content, thereby improving the soil’s carbon sequestration potential. The research findings provide a theoretical foundation for the selection of appropriate rotation methods and the maintenance of the stability of agricultural ecosystems in semi-arid regions.

Carbon dioxide exchange and temperature sensitivity of soil respiration along an elevation gradient in an arctic tundra ecosystem

Generally, with increasing elevation, there is a corresponding decrease in annual mean air and soil temperatures, resulting in an overall decrease in ecosystem carbon dioxide (CO2) exchange. However, there is a lack of knowledge on the variations in CO2 exchange along elevation gradients in tundra ecosystems. Aiming to quantify CO2 exchange along elevation gradients in tundra ecosystems, we measured ecosystem CO2 exchange in the peak growing season along an elevation gradient (9–387 m above sea level, m.a.s.l) in an arctic heath tundra, West Greenland. We also performed an ex-situ incubation experiment based on soil samples collected along the elevation gradient, to assess the sensitivity of soil respiration to changes in temperature and soil moisture. There was no apparent temperature gradient along the elevation gradient, with the lowest air and soil temperatures at the second lowest elevation site (83 m). The lowest elevation site exhibited the highest net ecosystem exchange (NEE), ecosystem respiration (ER) and gross ecosystem production (GEP) rates, while the other three sites generally showed intercomparable CO2 exchange rates. Topography aspect-induced soil microclimate differences rather than the elevation were the primary drivers for the soil nutrient status and ecosystem CO2 exchange. The temperature sensitivity of soil respiration above 0 °C increased with elevation, while elevation did not regulate the temperature sensitivity below 0 °C or the moisture sensitivity. Soil total nitrogen, carbon, and ammonium contents were the controls of temperature sensitivity below 0 °C. Overall, our results emphasize the significance of considering elevation and microclimate when predicting the response of CO2 balance to climate change or upscaling to regional scales, particularly during the growing season. However, outside the growing season, other factors such as soil nutrient dynamics, play a more influential role in driving ecosystem CO2 fluxes. To accurately upscale or predict annual CO2 fluxes in arctic tundra regions, it is crucial to incorporate elevation-specific microclimate conditions into ecosystem models.

Organic matter accumulation encouraged K-strategy bacteria increase and metabolism variation in karst vegetation restoration

Vegetation restoration plays a critical role in terrestrial carbon sink increase, especially in subtropic Southwest China which has been the hotspot of vegetation restoration areas in recent decades. However, the variations in microbial community diversity resulting from this intervention remain unclear, and further research is needed to elucidate the complex interactions between microorganisms and soil nutrient elements. Soil samples were collected from three vegetation restoration stages in a karst rocky desertification (KRD) valley of Southwest China, which were named dry cropland (CL), 3–8 years grassland (WL), and afforestation land that recovered more than 20 years (AL), to investigate the soil nutrient and bacterial diversity variation during vegetation restoration course. The soil organic carbon (SOC) and total nitrogen (TN) contents are significantly higher in the afforestation land soil compared to the cropland and grassland soils, while the available nutrient contents decrease during the vegetation restoration course. The soil dominant bacteria genus shifts from R-strategy bacteria in cropland to K-strategy bacteria in afforestation land, and the relative abundances of R-strategy genera remain similar in the grassland and cropland soil. The dual-relative bacteria network evaluates from simple correlation net to very complex ones during the vegetation restoration, of which the core influenced factor alters from available nutrients to organic matter. The results of this study suggest that it will take a relatively longer period for the soil nutrient conditions and bacterial community to recover fully, although vegetation restoration could reduce the impacts of agricultural activities. This study refers to the ecological preservation and restoration strategies under the global climate change background, elucidating the nutrient metabolism variation induced by the accordance variation of organic matter accumulation and soil bacterial life strategy during the ecosystem restoration course.