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Organic manure amendments into the rainfed agricultural soil could change the carbon saturation deficit. This study was conducted in the central Himalayan region of India to assess the impact of varying quantities of farmyard manure (FYM) and vermicompost (VC) on changes of soil carbon saturation deficit in the rainfed agricultural system. The experimental plots with three replications and three different amendment rates, such as 15, 30, and 60 Mg ha−1 of FYM and VC were used on the traditional paddy-wheat-finger millet-fallow cropping system. The soil amended with FYM and VC showed significant (p <.05) variations in the soil carbon content, nitrogen content, total microbial activity, β-glucosidase activity, and acid phosphatase activity with an increasing rate of both the manures in each cropping season. The mean soil carbon saturation deficit values varied from 25 to 36% and 19 to 28% in the first year cropping and second year cropping seasons, respectively. Our results demonstrate that the VC amendment was better than FYM for the accumulation of more carbon content in the rainfed agricultural soils of Himalaya, whereas the organic manure amendment rates must be considered for climate change impact mitigation action policy in the future. [ABSTRACT FROM AUTHOR]

Few studies have investigated how one-time targeted tillage of long-term no-till fields impacts topsoil properties and weed dynamics. An on-farm trial was implemented in 2020 to test the effects of occasional tillage (OT) in Morocco with a long-term no-tillage (NT) system and rainfed field crops: durum wheat (Triticum durum), faba bean (Vicia faba minor), and chickpea (Cicer arietinum). Four treatments were established, namely, continuous NT with crop residues maintained ("NT + residue"); continuous NT with crop residues not maintained ("NT-residue"); shallow inversion tillage ("shallow OT"); and deep non-inversion tillage ("deep OT"). Weassessed the effect of these treatments on soil physical and chemical properties in 0-10 and 10-20 cm soil depths after crop harvest of the 2020-2021 (year 1) and 2021-2022 (year 2) growing seasons corresponding to 1 and 2 years after OT, respectively. In addition, we evaluated the effect of the treatments on weed populations and the effect of the legume crop rotated with wheat on soil nitrogen (N) and weed density. In year 1, deep OT reduced the water content at field capacity and available water capacity at 0-10 cm compared to continuous NT; the cation-exchange capacity (CEC) under deep OT was lower than in NT-residue and NT + residue at 0-10 cm and 10-20 cm, respectively. Furthermore, deep OT increased ammonium-N (NH4-N) at 0-10 and 10-20 cm compared to NT + residue but reduced exchangeable potassium (K) at 10-20 cm depth compared to NT-residue. In year 2, shallow OT had lower total porosity at 10-20 cm than NT + residue, while shallow and deep OT recorded higher waterstable aggregates at 0-10 cm than NT + residue; at 10-20 cm, deep OT recorded lower CEC than NT + residue. However, deep OT had higher nitrate-N (NO3-N) and available sulfur (S) than NT-residue at 10-20 cm. Occasional tillage did not significantly affect 10 out of 19 of the soil properties evaluated, including soil organic matter (SOM), in all the years and did not help reduce the stratification of soil nutrients in NT. In year 1, 50 days after OT, deep OT reduced the weed density by 46% compared to NT + residue, while in year 2, 406 days after OT, shallow OT reduced weed density by 53% compared to NT-residue. Regarding the effect of the legume rotated with wheat, faba bean appeared to be the better preceding or following wheat crop as it resulted in higher residual soil mineral N and lower weed infestation than chickpea. [ABSTRACT FROM AUTHOR]

Introduction: Intercropping practices play a crucial role in enhancing and maintaining the biodiversity and resiliency of agroecosystems, as well as promoting stable and high crop yields. Yet the relationships between soil nitrogen, microbes, and yield in maize cultivated under maize/soybean intercropping systems remain unclear. Methods: To fill that knowledge gap, here we collected maize rhizosphere soil at the staminate stage after 6 consecutive years of maize/soybean intercropping, to investigate how intercropping and nitrogen application rates affected nitrogen utilization by crops and soil microbial community composition and function. We also examined correlations of those responses with yields, to clarify the main ways that yield is enhanced via intercropping and by nitrogenous fertilizer gradient changes generated by different nitrogen application rates. Results: The amount of applied fertilizer was 240 kg N ha-1 was best for obtaining a high maize yield and also led to the greatest nitrogen-use efficiency and bacterial diversity. Under the same N application rate, intercropping increased the maize yield by 31.17% and soil nitrogen (total, ammonium and nitrate nitrogen) by 14.53%, on average, in comparison to monocropping. The enrichment of Gemmatimonas and Bradyrhizobium significantly increased the soil nitrogen content, and a greater relative abundance of Sphingomonas and Gemmatimonas increased the maize yield, whereas enrichment of Candidatus_Udaeobacter and Bradyrhizobium decreased it. The benefits of intercropping mainly arise from augmenting the abundance of beneficial microorganisms and enhancing the efficiency of N use by crop plants. Discussion: This study's findings are of key importance to bolster the stability of agro-ecosystems, to guide the scientific rational use of nitrogen fertilizers, and to provide a sound theoretical basis for achieving the optimal management of intensive crop-planting patterns and green sustainable development. [ABSTRACT FROM AUTHOR]

The secretion of root exudates plays a crucial regulatory role in the process of soil carbon cycling. It is also significantly affected by global change factors (GCFs), yet the general patterns of these changes have not been fully explored, which greatly limits the accurate establishment of carbon cycling models under the background of global change.To address this, we conducted a meta‐analysis that included 1926 data pairs to examine the effects of global variability on root exudates. Furthermore, we performed multi‐model inference using Akaike's information criterion (AIC) to assess the relative importance of multiple factors such as annual average temperature (AAT), type of ecosystem, intensity of treatment, duration and more.The findings revealed that GCFs generally improved the production of root exudates. While the addition of nitrogen and its interaction with increased temperature significantly reduced the rate of root carbon secretion, all other factors significantly promoted it. Interestingly, as the intensity of warming increased, the rate of root carbon secretion caused by warming displayed a downward trend, with a threshold of 3.6°C. Furthermore, the influence of GCFs on root carbon secretion was found to be regulated by soil nitrogen, confirming the importance of nutrients from the rhizosphere in this process.These results underscore the importance of GCFs in root exudates and emphasize the crucial role of soil total nitrogen in the regulation of root carbon secretion. They also provide valuable scientific parameters for the development of more accurate models for the global‐change carbon cycle. Read the free Plain Language Summary for this article on the Journal blog. [ABSTRACT FROM AUTHOR]

At the optimum temperature, which is the ideal range in which seeds germinate most efficiently, seed germination may be lower than expected under favorable conditions, and this is indicative of seed dormancy. Also, germination may be enhanced by additional and interacting factors, such as nitrate and light. However, little is known about the interplay between temperature, nitrate, and seed germination. Using seeds from 22 accessions of four Plantago species that occupy distinct pedoclimates, we applied a factorial experimental design to assess the relationship between exogenously applied nitrate (KNO3) and temperature on germination in a Petri dish experiment. The data explore the relationship between seed germination, temperatures, and seed- and maternal-source soil N content as either nitrite (NO2−), nitrate (NO3−), or ammonium (NH4+). The interpretation also considered the total N and C contents of seeds, and the soil of the maternal plant (of the test seed) sources. Significant interspecific effects of nitrate and temperature on seed germination were observed. The capacity of nitrate to enhance final germination may be diminished substantially at supra-optimum temperatures, e.g., P. lagopus germination at 15 °C was 7% lower than that seen for water-only treatment. In contrast, at sub-optimum and alternating temperatures, nitrate enhanced final germination differentially across the species tested. This suggests a shift to enhanced germination at lower temperatures in the presence of sufficient soil nitrate, facilitating seedling establishment earlier in the growing season. The seeds of some Plantago species showed increased germination as a function of nitrate and temperature, particularly those of P. lagopus. The findings indicate that species (and genotype) responses correlated with the prevailing temperature and rainfall patterns of the locality; such local adaptation would ensure that seed germination and establishment occur during a period when environmental conditions are optimal. [ABSTRACT FROM AUTHOR]

At the optimum temperature, which is the ideal range in which seeds germinate most efficiently, seed germination may be lower than expected under favorable conditions, and this is indicative of seed dormancy. Also, germination may be enhanced by additional and interacting factors, such as nitrate and light. However, little is known about the interplay between temperature, nitrate, and seed germination. Using seeds from 22 accessions of four Plantago species that occupy distinct pedoclimates, we applied a factorial experimental design to assess the relationship between exogenously applied nitrate (KNO3) and temperature on germination in a Petri dish experiment. The data explore the relationship between seed germination, temperatures, and seed- and maternal-source soil N content as either nitrite (NO2−), nitrate (NO3−), or ammonium (NH4+). The interpretation also considered the total N and C contents of seeds, and the soil of the maternal plant (of the test seed) sources. Significant interspecific effects of nitrate and temperature on seed germination were observed. The capacity of nitrate to enhance final germination may be diminished substantially at supra-optimum temperatures, e.g., P. lagopus germination at 15 °C was 7% lower than that seen for water-only treatment. In contrast, at sub-optimum and alternating temperatures, nitrate enhanced final germination differentially across the species tested. This suggests a shift to enhanced germination at lower temperatures in the presence of sufficient soil nitrate, facilitating seedling establishment earlier in the growing season. The seeds of some Plantago species showed increased germination as a function of nitrate and temperature, particularly those of P. lagopus. The findings indicate that species (and genotype) responses correlated with the prevailing temperature and rainfall patterns of the locality; such local adaptation would ensure that seed germination and establishment occur during a period when environmental conditions are optimal.

Interactions between plant roots and rhizosphere bacteria modulate nitrogen (N)-cycling processes and create habitats rich in low molecular weight compounds (exudates) and complex organic molecules (decaying root litter) compared to those of bulk soil. Microbial N-cycling is regulated by edaphic conditions and genes from many interconnected metabolic pathways, but most studies of soil N-cycling gene expression have focused on single pathways. Currently, we lack a comprehensive understanding of the interplay between soil N-cycling gene regulation, spatial habitat, and time. We present results from a replicated time series of soil metatranscriptomes; we followed gene expression of multiple N transformations in four soil habitats (rhizosphere, detritusphere, rhizo-detritusphere, and bulk soil) during active root growth for the annual grass, Avena fatua. The presence of root litter and living roots significantly altered the trajectories of N-cycling gene expression. Upregulation of assimilatory nitrate reduction in the rhizosphere suggests that rhizosphere bacteria were actively competing with roots for nitrate. Simultaneously, ammonium assimilatory pathways were upregulated in both rhizosphere and detritusphere soil, which could have limited N availability to plants. The detritusphere supported dissimilatory processes DNRA and denitrification. Expression of nitrification genes was dominated by three phylotypes of Thaumarchaeota and was upregulated in bulk soil. Unidirectional ammonium assimilation and its regulatory genes (GS/GOGAT) were upregulated near relatively young roots and highly decayed root litter, suggesting N may have been limiting in these habitats (GS/GOGAT is typically activated under N limitation). Our comprehensive analysis indicates that differences in carbon and inorganic N availability control contemporaneous transcription of N-cycling pathways in soil habitats. IMPORTANCE Plant roots modulate microbial nitrogen (N) cycling by regulating the supply of root-derived carbon and nitrogen uptake. These differences in resource availability cause distinct micro-habitats to develop: soil near living roots, decaying roots, near both, or outside the direct influence of roots. While many environmental factors and genes control the microbial processes involved in the nitrogen cycle, most research has focused on single genes and pathways, neglecting the interactive effects these pathways have on each other. The processes controlled by these pathways determine consumption and production of N by soil microorganisms. We followed the expression of N-cycling genes in four soil microhabitats over a period of active root growth for an annual grass. We found that the presence of root litter and living roots significantly altered gene expression involved in multiple nitrogen pathways, as well as tradeoffs between pathways, which ultimately regulate N availability to plants.

Aim: Mycorrhizal fungi play key roles in the functioning of terrestrial ecosystems. The main types of mycorrhizal associations are arbuscular mycorrhizae, ectomycorrhizae, ericoid mycorrhizae and orchid mycorrhizae. Previous studies have shown that the abundance of plants with different types of mycorrhizal associations change gradually along latitudinal and altitudinal gradients driven by the effects of climate and soil nutrients. We aimed to understand how altitude and climatic and soil variables shape the distribution patterns of tropical plant mycorrhizal types and nitrogen‐fixing plants along altitudinal gradients in the Andes. Location: Colombian Andean mountain range. Time Period: Present day. Major Taxa Studied: Plants (vascular and non‐vascular). Methods: We used a herbarium plant records database and assigned mycorrhizal type to each plant species based on the available literature. Bioclimatic and soil variables were also compiled at a resolution of 10 km. We calculated the proportion of each mycorrhizal association type per grid cell and created a diversity index to explore their spatial distribution and association with abiotic factors based on LMs. Results: The diversity of mycorrhizal associations increased with altitude and peaked around 3000 m, in an ecotone belt known as the subpáramo recognised by the high abundance of Ericaceae species. Soil carbon stock and soil total nitrogen were also positively correlated with the diversity of mycorrhizal types. Moreover, the abundance of arbuscular mycorrhizal plants was highest at low elevations and increased with the proportion of nitrogen‐fixing plants per cell. Main Conclusions: Our results indicate that mycorrhizal associations gradually change along altitudinal gradients in the tropical Andes. Climatic factors and the interactions between climatic and edaphic factors have the greatest explanatory power to predict the distribution of types of mycorrhizal associations along the altitudinal gradient. Based on these results we expect that climate change could potentially alter the distribution of mycorrhizal types in tropical mountains with unknown consequences for ecosystem functions. [ABSTRACT FROM AUTHOR]

Nitrification inhibitors, such as nitrapyrin (NI), are increasingly co‐applied with nitrogen (N) fertilizers as part of sustainable agricultural practice. Several studies in temperate regions have documented the effectiveness of NI in retaining soil ammonium (NH4+), minimizing N loss and increasing crop yields. However, less is known about the effects of NI in Mediterranean regions, where agricultural production is challenging and requires intensive irrigation and fertilization. We investigated the short‐term impact of the nitrification inhibitor nitrapyrin (2‐chloro‐6‐(trichloromethyl)pyridine) in a two‐factor mesocosm experiment, using a typical Mediterranean soil, where NI was co‐applied with a selection of urea‐based fertilizers: urea (U), U with urease inhibitors (U + UI), methylene urea (MU) and zeolite‐coated urea (ZU). NI co‐applied with urea fertilizers resulted in higher availability of soil NH4+ and a concurrent increase in NH3 volatilization. Net cumulative soil NH4+ availability was 1.5–3.3 fold greater when NI was applied. Concurrently, net cumulative nitrate (NO3−) and nitrite (NO2−) availability was reduced by 10%–60%; this was found for all the tested fertilizer types except MU fertilizer, where the net cumulative soil NO3− and NO2− doubled. Nitrous oxide (N2O) emissions from urea fertilization were reduced by 40% with UI, 50% with NI and 66% with NI + UI. Interestingly, after 28 d, the composition of soil microbial communities was distinctly different, due to NI application. Specifically, NI application dramatically reduced the abundance of ammonia‐oxidizing and denitrifying bacterial functional groups. NI was effective in reducing N2O emissions in this calcareous soil; however, NH3 emissions were remarkably enhanced. These findings have important implications for the large‐scale adoption of inhibitor technologies in Mediterranean agroecosystems and for the reduction of greenhouse gas emissions. [ABSTRACT FROM AUTHOR]

Soil tillage and maize residues return are important practices for tackling and promoting soil quality and improving crop yield in the North China Plain (NCP), where winter wheat production is threatened by soil deterioration. Although maize residues incorporation with rotary tillage (RS) or deep plowing tillage (DS) is widespread in this region, only few studies have focused on rotation tillage. Four practices, namely RT (continuous rotary tillage without maize residues return), RS, DS, and RS/DS (rotary tillage every year and deep plowing interval of 2 years), were evaluated under field conditions lasting a period of 5 years. After a 5-year field experiment, the mean soil bulk density of the 0–30 cm soil layer decreased significantly with RS, DS, and RS/DS, i.e., by 4.19%, 6.33%, and 6.71% compared with RT, respectively. The treatments greatly improved the total soil porosity, soil aggregate size distribution, soil aggregate stability, and the root length density in the 0–30 cm soil layers. Residues return with DS and RS/DS treatments significantly increased the soil organic carbon (SOC) and total nitrogen (TN) storage in the 0–30 cm soil layer, mainly owed to the increases in the SOC and TN pool associated with the macro-aggregate. A positive trend in the grain yield was noted under both DS and RS/DS conditions, whereas a decreasing tendency was presented in continuous rotary treatments. In summary, RS/DS treatment significantly increased the amount of SOC and TN, improved the particle size distribution of soil aggregates, and thus improved the soil's physicochemical properties, which is beneficial for wheat to achieve high yields. Our results suggested that RS/DS was a highly efficient practice to improve soil quality and increase crop production in the NCP. [ABSTRACT FROM AUTHOR]

Much attention has been given to the distribution of soil organic carbon and nitrogen in alpine grasslands, but the important role of the deep soil layers has been understudied. In this study, the soil organic carbon and nitrogen contents in the shallow (0–30 cm), middle (30–100 cm) and deep (100–300 cm) layers were examined, and the effects of climatic, soil and vegetation factors were investigated along a climatic gradient on the Tibetan Plateau. We found that although soil organic carbon and nitrogen on the Tibetan Plateau declined logarithmically with depth, the total soil organic carbon and nitrogen in the middle and deep layers accounted for more than two‐thirds of the total carbon and nitrogen in the 3‐m depth soil profile. Carbon to nitrogen ratio increased with soil depth in 1 m soil, but it remained consistent in 1–3 m soil. The surface carbon and nitrogen contents were positively correlated with precipitation. The comprehensive research has revealed that soil carbon and nitrogen contents are mainly influenced by the local humid climate, vegetation productivity, and soil properties, which strongly depend on soil depth. Therefore, more attention should be given to the changes in carbon and nitrogen in deep soils in alpine regions. Plain Language Summary: The Tibetan Plateau's permafrost region is crucial for the global carbon and nitrogen cycle as climate change intensifies. Environmental factors such as climate, vegetation, and soil features influence soil carbon and nitrogen distributions. However, the vertical distribution of carbon and nitrogen in multiple soil layers remains understudied, especially in alpine grasslands. We sampled soil carbon and nitrogen contents in surface, middle, and deep soil layers along a climatic gradient on the Tibetan Plateau and analyzed their associations with climate, soil, and vegetation variables. Our findings show that soil carbon and nitrogen concentrations decrease markedly from the surface to deep layers, and the total contents in the middle and deep layers account for more than 2/3 of the total. Carbon: nitrogen ratio increases with soil depth in 1 m soil but remains stable in 1–3 m soil. In the surface soil layer, the carbon and nitrogen concentrations increase sharply with precipitation. Further analysis reveals that the local humid climate, vegetation production, and soil properties regulate the soil carbon and nitrogen status, but directly or indirectly depending on the soil layer. Therefore, more attention should be given to carbon and nitrogen stocks in deep soils in the alpine region. Key Points: Concentrations of soil carbon/nitrogen decrease logarithmically with soil depthCarbon/nitrogen stored in soil below 30 cm accounts for more than two‐thirds of that stored in the total profileCarbon to nitrogen ratio increases with soil depth in 1 m soil but remains consistent in 1–3 m soil [ABSTRACT FROM AUTHOR]

Cardamine diphylla is an understory herb of rich forests that exhibits a wintergreen life history strategy in western North Carolina. Unlike many forest floor plants, C. diphylla is able to persist under the evergreen shrub Rhododendron maximum, which is known to inhibit the growth of woody and herbaceous plants. We compared morphological and chemical characteristics of C. diphylla leaves in areas of a mesic cove forest with and without R. maximum during the winter. We also compared soil properties and the taxonomic richness of co-occurring herbaceous and woody plants. Results showed that C. diphylla growing under R. maximum produced significantly less foliar biomass but had significantly higher levels of foliar nitrogen and sulfur. Plants under R. maximum also had a higher proportion of green (rather than purple) abaxial leaf surfaces. Soils under R. maximum contained significantly less total nitrogen and humic matter, but cation exchange capacity and pH did not differ between the two areas. Compared to the surrounding forest, plots in R. maximum thickets supported 35% fewer woody taxa and 41% fewer herbaceous taxa, demonstrating the challenges of this microhabitat to understory plants. The ability of C. diphylla to persist under R. maximum may be advantageous if R. maximum continues its opportunistic expansion in southern Appalachian forests. [ABSTRACT FROM AUTHOR]

The utilisation of leguminous groundnut (Arachis hypogaea) has been recognised for its advantageous effects, including nitrogen (N) fixation, which consequently enhances the soil N availability. The objective of this study was to analyse the impact of a mixed intercropping system involving pepper (Piper nigrum) and groundnut on soil total N. Additionally, the study aimed to assess the influence of N on various parameters, including the Normalised Difference Vegetation Index (NDVI), chlorophyll content, and gas exchange rate of black pepper. The study employed a randomized complete block design in a field experiment, with two treatments that were reproduced 15 times. The treatments consisted of the control group (M0), which involved a pepper plot without groundnut intercropping, and the mixed intercropping system (M1), which involved a pepper plot with groundnut intercropping. The soil total N content exhibited a statistically significant increase (p < 0.05) in the context of a mixed intercropping system. The intercropping treatment resulted in considerably higher values (p < 0.05) for pepper NDVI, foliar chlorophyll concentration, photosynthetic rates (A), stomatal conductance (gs), and transpiration (E) compared to the control treatment. Moreover, a positive correlation has been seen between the chlorophyll content of pepper leaves and the total N content in the soil. Similarly, a positive association has been established between the A of pepper plants and the total N content in the soil. As a result, the observed elevation in A under high N circumstances was ascribed to an augmentation in chlorophyll concentration. Consequently, the integration of groundnut within pepper cultivation systems over an extended period has the potential to enhance crop productivity through the amelioration of soil conditions. [ABSTRACT FROM AUTHOR]

Climate warming and human disturbance are supposed to have significantly impacted the alpine grasslands. However, it is still unclear how human activity affects the community composition and niche characteristics in response to warming. We conducted a two-factorial experiment in an alpine meadow, and set up four treatments: warming, mowing, warming with mowing, and control. Based on the investigation of community composition and niche characteristics, we evaluated the impacts of soil carbon, nitrogen, and phosphorus on species niche overlap. The results showed that mowing significantly increased species richness of Grass, Sedge, Forbs and the importance value of Sedge compared to warming (P < 0.05). The niche breadth of species (>50 %) was reduced by warming, but increased under mowing. The niche overlap mainly occurred between Grass and Forbs in warming, while it was evenly distributed among species after mowing, which alleviated the negative effects of warming on interspecific competitiveness. Warming increased the number of species pairs with a niche overlap value >0.9 by 24.15 %, while warming with mowing decreased it by 2.7 %. The number of species pairs with niche overlap was significantly correlated with soil total nitrogen and soil available nitrogen (P < 0.05). In particular, the species pairs with highly competitive showed a greater dependency on soil nitrogen. Our work highlights that moderate utilization and soil nitrogen are two crucial factors influencing the response of community structure in alpine meadows to future climate change. The study provides an important reference for predicting and addressing the impact of global climate change on adaptive management and grassland protection.

The surge in urbanization has correspondingly given rise to exacerbated carbon footprint and burgeoning heavy metal (HM) contamination, constituting a critical impediment to the realization of environmentally sustainable urban development pathways. Therefore, it is highly essential to investigate the impacts of urbanization process on soil carbon, heavy metals (HMs), as well as their interrelationships. Employing remote sensing and land use data within a 45 km radius in Chongqing, this study selected 31 sites to assess the variation in urban green spaces (UGSs) carbon sequestration capabilities and associated HM pollution risks across differing urbanization levels. Results showed that urbanization dynamics and land use history play a more decisive role than current anthropogenic management in shaping the distribution of soil carbon and HMs within urban environments. The average soil organic carbon (SOC) distribution of UGSs is 8.47 mg ha−1 (1.50–24.20 mg ha−1), concurrent with moderate HM pollution showing Ni: 32.03–33.50 mg kg−1, Pb: 27.93–29.65 mg kg−1, Cu: 26.97–41.20 mg kg−1, while Cd exhibits the most severe pollution range of 0.23–0.30 mg kg−1. The rate of urbanization significantly influences SOC stocks, exhibiting an increase when the urbanization rate is below 70.79 % and a decrease upon surpassing this threshold. The concentration of HMs is predominantly determined by the historical usage of the land, with a marked escalation correlating with the duration of land utilization history. These relationships were quantitatively modeled through the application of fitted linear functions. The structural equation model demonstrated that UGSs operating without anthropogenic disturbance tend towards degradation, indicating that temporary homeostasis might be sustained via the addition of N and P nutrients and pH modulation. In conclusion, we formulate an Urban Green Spaces Development Hypothesis that aims to shed light on the multifaceted challenges encountered by cities amidst varying degrees of urbanization and, concurrently, to probe potential ameliorative strategies.

Few studies have investigated how one-time targeted tillage of long-term no-till fields impacts topsoil properties and weed dynamics. An on-farm trial was implemented in 2020 to test the effects of occasional tillage (OT) in Morocco with a long-term no-tillage (NT) system and rainfed field crops: durum wheat (Triticum durum), faba bean (Vicia faba minor), and chickpea (Cicer arietinum). Four treatments were established, namely, continuous NT with crop residues maintained (“NT + residue”); continuous NT with crop residues not maintained (“NT-residue”); shallow inversion tillage (“shallow OT”); and deep non-inversion tillage (“deep OT”). We assessed the effect of these treatments on soil physical and chemical properties in 0–10 and 10–20 cm soil depths after crop harvest of the 2020–2021 (year 1) and 2021–2022 (year 2) growing seasons corresponding to 1 and 2 years after OT, respectively. In addition, we evaluated the effect of the treatments on weed populations and the effect of the legume crop rotated with wheat on soil nitrogen (N) and weed density. In year 1, deep OT reduced the water content at field capacity and available water capacity at 0–10 cm compared to continuous NT; the cation-exchange capacity (CEC) under deep OT was lower than in NT-residue and NT + residue at 0–10 cm and 10–20 cm, respectively. Furthermore, deep OT increased ammonium-N (NH4-N) at 0–10 and 10–20 cm compared to NT + residue but reduced exchangeable potassium (K) at 10–20 cm depth compared to NT-residue. In year 2, shallow OT had lower total porosity at 10–20 cm than NT + residue, while shallow and deep OT recorded higher water-stable aggregates at 0–10 cm than NT + residue; at 10–20 cm, deep OT recorded lower CEC than NT + residue. However, deep OT had higher nitrate-N (NO3-N) and available sulfur (S) than NT-residue at 10–20 cm. Occasional tillage did not significantly affect 10 out of 19 of the soil properties evaluated, including soil organic matter (SOM), in all the years and did not help reduce the stratification of soil nutrients in NT. In year 1, 50 days after OT, deep OT reduced the weed density by 46% compared to NT + residue, while in year 2, 406 days after OT, shallow OT reduced weed density by 53% compared to NT-residue. Regarding the effect of the legume rotated with wheat, faba bean appeared to be the better preceding or following wheat crop as it resulted in higher residual soil mineral N and lower weed infestation than chickpea.

Wine quality is affected by environmental factors in the location where the vines are cultivated, in particular the soil and the climate. Major soil-related factors influencing vine development, yield, and berry composition (and thus wine quality) include soil water availability, soil temperature, and soil nutrients, particularly nitrogen. These can be impacted by soil depth and soil compaction. Mapping these factors with classical field-based methods is constraining and expensive. Near surface geophysics (NSG) can be useful in increasing the resolution of data acquisition and, possibly, its cost. Among these techniques, many are already commercially available, but some of them, including Magnetic Resonance Sounding, Induced Polarization and Spectral Analysis of Surface Waves, require a high degree of expertise for acquisition and processing. These should be further developed in order to enlarge the application possibilities. This article reviews soil-related parameters relevant to terroir expression in vineyards and how these can be measured with NSG techniques.

To study the characteristics of nitrogen (N) loss on slopes, different vegetation (bare soil, alfalfa), slopes (5°, 10°, 15°), and rainfall intensities (40, 60, 80 mm/h) were set as variable factors in simulated rainfall experiments. Surface runoff accounts for 60.38–96.16% of total runoff and most N loss (57.69–88.67% of NO3−-N). Alfalfa can reduce average concentrations of N loss in runoff and reduce N loss in surface runoff by more than 48.29%, as well as subsurface runoff by 3.8%. Average N loss in subsurface runoff exceeds that of surface runoff. Rainfall intensity most affects N loss from surface runoff in bare soil conditions, and slope most affects N loss in subsurface runoff. Rainfall intensity in alfalfa treatments most influences runoff volume and N loss. The comprehensive effects of rainfall intensity, slope, and vegetation cover on the total loss of various forms of nitrogen in surface runoff can be described using a linear correlation equation, with a correlation coefficient between 0.84 and 0.91. [ABSTRACT FROM AUTHOR]

Invasive plants are often attacked by both introduced specialist and native generalist natural enemies in new ranges. Soil fertility can potentially alter the interactions of these natural enemies with native versus invasive plants in ways that have largely unexplored implications for biological invasions and biological control.A common garden experiment was conducted to compare the performance of an introduced specialist flea beetle, Agasicles hygrophila, and/or a native generalist nematode, Meloidogyne incognita, on invasive alligator weed, Alternanthera philoxeroides, and its native congener sessile joyweed, Alternanthera sessilis, under different levels of soil nitrogen (N) and phosphorus (P).At a relatively low or moderate N and P levels, the flea beetle and the nematodes were not significantly affected by each other. Under these conditions, alligator weed responded plastically by producing more branches and biomass, as well as longer stolons, in response to attack by the flea beetle and/or the nematode, compared to sessile joyweed responses to similar levels of damage. However, under a relatively high N and P levels, nematode infestations significantly reduced flea beetle damage on alligator weed, resulting in significantly greater above‐ and below‐ground biomass and longer stolons than plants without herbivory. In contrast, beetle herbivory significantly increased the level of nematode infestations on sessile joyweed, resulting in significantly fewer fine and coarse roots, and lower above‐ and below‐ground biomass compared to plants without herbivory.Synthesis and applications. Our findings illustrate the importance of soil fertility in mediating interactions between specialist biocontrol agents and native generalists on native versus invasive plants. High phenotypic plasticity seems to be an important attribute that contributes to the success of invasive plants like alligator weed in relatively nutrient‐poor environments. However, nutrient‐rich environments could potentially confer greater growth benefits on invasive plants than on native ones by changing herbivore–herbivore interactions on plants differently. There is a great need to fully investigate the direct and indirect interactions between biocontrol agents and generalists across food webs following classical biocontrol releases. Nutrient measurements of both soil and water bodies should also be incorporated into all stages of biocontrol programmes. [ABSTRACT FROM AUTHOR]

Intercropping is a widely recognised technique that contributes to agricultural sustainability. While intercropping leguminous green manure offers advantages for soil health and tea plants growth, the impact on the accumulation of theanine and soil nitrogen cycle are largely unknown. The levels of theanine, epigallocatechin gallate and soluble sugar in tea leaves increased by 52.87% and 40.98%, 22.80% and 6.17%, 22.22% and 29.04% in intercropping with soybean–Chinese milk vetch rotation and soybean alone, respectively. Additionally, intercropping significantly increased soil amino acidnitrogen content, enhanced extracellular enzyme activities, particularly β‐glucosidase and N‐acetyl‐glucosaminidase, as well as soil multifunctionality. Metagenomics analysis revealed that intercropping positively influenced the relative abundances of several potentially beneficial microorganisms, including Burkholderia, Mycolicibacterium and Paraburkholderia. Intercropping resulted in lower expression levels of nitrification genes, reducing soil mineral nitrogen loss and N2O emissions. The expression of nrfA/H significantly increased in intercropping with soybean–Chinese milk vetch rotation. Structural equation model analysis demonstrated that the accumulation of theanine in tea leaves was directly influenced by the number of intercropping leguminous green manure species, soil ammonium nitrogen and amino acid nitrogen. In summary, the intercropping strategy, particularly intercropping with soybean–Chinese milk vetch rotation, could be a novel way for theanine accumulation. Summary statement: The theanine content of tea leaves increased by 52.87% and 40.98% when intercropped with soybean–Chinese milk vetch rotation and soybean alone, respectively. The accumulation of theanine in tea leaves was directly influenced by the intercropping green manure species and their quantity, as well as the levels of soil ammonium nitrogen and amino acid nitrogen. [ABSTRACT FROM AUTHOR]

Essential soil functions such as plant productivity, C storage, nutrient cycling and the storage and purification of water all depend on soil biological processes. Given this insight, it is remarkable that in modeling of these soil functions, the various biological actors usually do not play an explicit role. In this review and perspective paper we analyze the state of the art in modeling these soil functions and how biological processes could more adequately be accounted for. We do this for six different biologically driven processes clusters that are key for understanding soil functions, namely i) turnover of soil organic matter, ii) N cycling, iii) P dynamics, iv) biodegradation of contaminants v) plant disease control and vi) soil structure formation. A major conclusion is that the development of models to predict changes in soil functions at the scale of soil profiles (i.e. pedons) should be better rooted in the underlying biological processes that are known to a large extent. This is prerequisite to arrive at the predictive models that we urgently need under current conditions of Global Change. [ABSTRACT FROM AUTHOR]

Nitrogen (N) and phosphorus (P) are the two most important macronutrients supporting forest growth. Unprecedented urbanization has created growing areas of urban forests that provide key ecosystem services for city dwellers. However, the large‐scale patterns of soil N and P content remain poorly understood in urban forests. Based on a systematic soil survey in urban forests from nine large cities across eastern China, we examined the spatial patterns and key drivers of topsoil (0–20 cm) total N content, total P content, and N:P ratio. Topsoil total N content was found to change significantly with latitude in the form of an inverted parabolic curve, while total P content showed an opposite latitudinal pattern. Variance partition analysis indicated that regional‐scale patterns of topsoil total N and P contents were dominated by climatic drivers and partially regulated by time and pedogenic drivers. Conditional regression analyses showed a significant increase in topsoil total N content with lower mean annual temperature (MAT) and higher mean annual precipitation (MAP), while topsoil total P content decreased significantly with higher MAP. Topsoil total N content also increased significantly with the age of urban park and varied with pre‐urban soil type, while no such effects were found for topsoil total P content. Moreover, topsoil N:P ratio showed a latitudinal pattern similar to that of topsoil total N content and also increased significantly with lower MAT and higher MAP. Our findings demonstrate distinct latitudinal trends of topsoil N and P contents and highlight a dominant role of climatic drivers in shaping the large‐scale patterns of topsoil nutrients in urban forests. [ABSTRACT FROM AUTHOR]

The investigation into trade-offs among plant functional traits sheds light on how plants strategically balance growth and survival when facing environmental stress. This study sought to evaluate whether trade-offs observed at both community and individual species levels could indicate adaptive fitness across an intensity of flooding intensity. The study was conducted at 25 sampling sites spanning approximately 600 km along the riparian zone in the Three Gorges Reservoir area, China. The findings revealed that, along the flooding gradient, the overall riparian community did not exhibit significant trade-offs between leaf and root traits. Examining three broadly distributed dominant species (Cynodon dactylon, Xanthium strumarium, and Abutilon theophrasti), perennial plants showed pronounced trade-offs under low flooding intensity, while annuals exhibited trade-offs under moderate and low flooding intensity. The trade-offs were evident in traits related to nitrogen-carbon resources, such as specific leaf area, root tissue density, and photosynthetic rate. However, under strong flooding intensity, the relationship between leaf and root traits of the species studied was decoupled. Furthermore, the study identified a significant correlation between soil nitrogen and the trade-off traits under moderate and low flooding intensity. Integrating results from the CSR (Competitors, Stress-tolerators, Ruderals) strategy model, species niche breath analysis, and nitrogen-regulated trade-off, the study revealed that, in the face of high flooding intensity, perennial species (C. dactylon) adopts an S-strategy, demonstrating tolerance through a conservative resource allocation that decouples leaf-root coordination. Annual species (X. strumarium and A. theophrasti), on the other hand, exhibit niche specialization along the flooding gradient, employing distinct strategies (R- and C-strategy). As flooding stress diminishes and soil nitrogen level decreases, plant strategies tend to shift towards an R-strategy with a competition for reduced N resources. In conclusion, the study highlighted the pivotal roles of soil nitrogen and flooding intensity acting as the dual determinants of species growth and tolerance. These dynamics of growth-tolerance balance were evident in the diverse trade-offs between leaf and root traits of individual plant species with different life histories, underscoring the array of adaptive strategies employed by riparian plants across the flooding intensity gradient. [ABSTRACT FROM AUTHOR]

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Copyright of Acta Agriculturae Zhejiangensis is the property of Acta Agriculturae Zhejiangensis Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Land use plays a crucial role in the stock of soil organic carbon (SOC) and soil nitrogen (SN). The aim of this study was to assess and characterize the effects of various soil management practices on the physicochemical properties of soil in a Mediterranean region in southeastern Spain. Texture, soil moisture, bulk density, pH, electrical conductivity, equivalent CaCO3 (%), soil organic matter and carbon, and Kjeldahl nitrogen were determined for the surface topsoil (0–5 cm, 180 samples) under three types of land cover: cropland, grassland, and urban soil. The main soil textures were silt, silt loam, and sandy loam with low percentages of soil moisture in all soil samples and lower bulk density values in cropland and grassland areas. The pH was alkaline and the electrical conductivity as well as the equivalent calcium carbonate content were moderate to high. Organic matter estimated using the LOI and WB methods varied in the order cropland > grassland > urban soil. The results obtained for SOC and SN indicate that cropland presented the highest stocks, followed by grassland and urban soil. The values determined for the C/N ratio were close to 10 in cropland and grassland, indicating that organic matter readily undergoes decomposition at these sites. Our results emphasize the importance of evaluating the effects and identifying the impacts of different soil management techniques, and further research is needed to better understand the potential to improve soil organic carbon and nitrogen storage in semiarid regions. [ABSTRACT FROM AUTHOR]

Switchgrass (Panicum virgatum L.) production for biofuel has the potential to produce reasonable yields on lands not suited for conventional agriculture. We assessed nine switchgrass cultivars representing lowland and upland ecotypes grown for 11 years at a site in the upper Midwest USA for belowground differences in soil carbon and nitrogen stocks, soil organic matter fractions, and standing root biomass to 1 m depth. We also compared potential nitrogen mineralization and carbon substrate use through community‐level physiological profiling in surface soils (0–10 cm depth). Average yields and standing root biomass differed among cultivars and between ecotypes, but we found no significant cultivar‐related impacts on soil carbon and nitrogen stocks, on the distribution of particulate and mineral‐associated soil organic matter fractions, nor on potential nitrogen mineralization or microbial community‐level physiological profiles. That these traits did not differ among cultivars suggests that soil carbon and nitrogen gains under switchgrass are likely to be robust with respect to cultivar differences, and to this point not much affected by breeding efforts. [ABSTRACT FROM AUTHOR]

Freeze–thaw cycles (FTCs) occur during the nongrowing season, and residual nitrogen (N) increases the risk of N loss with melting water. To study the effect of FTCs on soil N, rice fields in improved irrigated saline soil in northeast China were selected as the research subjects. Water content (10%, 20%, and 30%), different N fertilizer levels (180 and 220 kg/ha), and multiple FTCs of soil samples were used to clarify the effects of N fertilizer application and water content on N efficiency. The results indicate that, after the third FTC, the soil ammonium nitrogen (NH4+-N) level increased significantly. NH4+-N increased with an increase in the initial soil moisture content and decreased with fertilizer levels. Nitrate nitrogen (NO3−-N) decreases with increasing initial soil moisture. The inorganic N increased significantly compared with that in the unfrozen stage, indicating that FTCs promote soil N mineralization. However, high fertilization rates inhibit mineralization. Analysis of variance showed that NO3−-N is sensitive to the N application rate, water content, and salinity (p < 0.05). FTCs and artificial fertilization are the factors that affect N mineralization (p < 0.05). The research results are significant for preventing nitrate leaching and soil acidification during spring plowing and providing a scientific basis for fertilization systems and water environment pollution in improved saline soils. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Ecology & Rural Environment is the property of Journal of Ecology & Rural Environment Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Land use plays a crucial role in the stock of soil organic carbon (SOC) and soil nitrogen (SN). The aim of this study was to assess and characterize the effects of various soil management practices on the physicochemical properties of soil in a Mediterranean region in southeastern Spain. Texture, soil moisture, bulk density, pH, electrical conductivity, equivalent CaCO3 (%), soil organic matter and carbon, and Kjeldahl nitrogen were determined for the surface topsoil (0–5 cm, 180 samples) under three types of land cover: cropland, grassland, and urban soil. The main soil textures were silt, silt loam, and sandy loam with low percentages of soil moisture in all soil samples and lower bulk density values in cropland and grassland areas. The pH was alkaline and the electrical conductivity as well as the equivalent calcium carbonate content were moderate to high. Organic matter estimated using the LOI and WB methods varied in the order cropland > grassland > urban soil. The results obtained for SOC and SN indicate that cropland presented the highest stocks, followed by grassland and urban soil. The values determined for the C/N ratio were close to 10 in cropland and grassland, indicating that organic matter readily undergoes decomposition at these sites. Our results emphasize the importance of evaluating the effects and identifying the impacts of different soil management techniques, and further research is needed to better understand the potential to improve soil organic carbon and nitrogen storage in semiarid regions.

Nitrogen is the crucially sustainable element for most ecosystem including grassland. Fenced alpine meadow grassland (FG), lightly, moderately and heavily degraded (LD, MD and HD) alpine meadow in spring, summer and winter were studied to clear the effects of alpine meadow degradation on soil total nitrogen (TN), available nitrogen (AN), ammonium nitrogen (NH4+-N), nitrate nitrogen (NO3–-N), inorganic nitrogen (IN) content and the ratio of inorganic nitrogen to available nitrogen (IN/AN), and to find practical management strategies on the background of alpine meadow degradation and ecological environment restoration in the Eastern Qilian Mountains area, northwest China. The results showed that soil total nitrogen contents of the alpine meadow types were at a low level, ranged from 1.60 g·kg−1 to 5.15 g·kg−1, but soil available nitrogen contents was at a high level, ranged from 373.2 mg·kg−1 to 650.8 mg·kg−1in the study area. Alpine meadow degradation can seasonally change soil nitrogen status. Degraded alpine meadow had more inorganic nitrogen than fenced meadow in surface soil. Degradation only changed soil NO3−-N profile distribution in winter and had no significant effect on profile distribution of TN, AN, NH4+-N and IN. There were significant interactions of alpine meadow types, seasons and soil depth on soil available nitrogen, NH4+-N, NO3–-N and inorganic nitrogen content. Although soil available nitrogen increased under degradation, nitrogen input is needed in the restoration of heavily degraded alpine meadow during the summer growing season to improve vegetation coverage because of the low soil inorganic nitrogen and IN/AN ratio in summer growing season in 10–20 cm and 20–30 cm depth. [ABSTRACT FROM AUTHOR]

Based on the continuous watermelon greenhouses in Daxing District, Beijing, this paper investigated the dynamic transformation characteristics and surplus risk of soil nitrogen in greenhouses of different cropping years and proposed a reasonable nitrogen fertilizer reduction potential for greenhouses of different continuous cropping years. Based on the results, (1) The total nitrogen inputs gradually decreased with the increase of cropping years. The soil nitrogen was accumulated mainly in the 0∼30 cm tillage layer. The nitrogen supply capacity of the soil gradually increased over 20 years (a) of continuous cropping and declined after >20a. (2) The environmental risk levels of soil nitrogen surpluses with different cropping years in the study area had all reached heavy levels and above. The nitrogen fertilizer reduction potential was large, in which the lowest recommended nitrogen application rate was for the greenhouses with 1∼5a of continuous cropping, and the highest was for the greenhouses with 11∼20a of continuous cropping. For watermelon greenhouses with different continuous cropping years, the range of the highest reasonable nitrogen fertilizer reduction potential to ensure the economic benefits of farmers was 74.18% to 87.28%, and the lowest environmentally safe nitrogen fertilizer reduction potential to safeguard environmentally safe conditions was 69.22 to 78.11%. [ABSTRACT FROM AUTHOR]

There is considerable interest devoted to old-growth forests and their capacity to store carbon (C) in biomass and soil. Inventories of C stocks in old-growth forests are carried out worldwide, although there is a lack of information on their actual potential for C sequestration. To further understand this, soil organic carbon (SOC) was measured in one of Italy’s best-preserved old-growth forests, the Sasso Fratino Integral Nature Reserve. This reserve is on the World Heritage List along with other ancient beech forests of Europe, and it is virtually untouched due to the steepness of the terrain, even before legal constraints were imposed. Although the sandstone-derived soils are often shallow, they are rich in organic matter. However, no quantification had been carried out. By systematically sampling the topsoil across the forest, we accurately determined the average amount of SOC (62.0 ± 16.9 Mg ha–1) and nitrogen (4.0 ± 1.2 Mg ha–1) in the top 20 cm. Using the CENTURY model, future dynamics of SOC stocks were predicted to 2050 according to two climate scenarios, A1F1 and B2, the first of high concern and the second more optimistic. The model projected an increase of 0.2 and 0.3 Mg ha–1 a–1 by 2030 under the A1F1 and B2 scenarios, respectively, suggesting that the topsoil in old-growth forests does not reach equilibrium but continues accumulating SOC. However, from 2030 to 2050, a decline in SOC accumulation is predicted, indicating SOC net loss at high altitudes under the worst-case scenario. This study confirms that soils in old-growth forests play a significant role in carbon sequestration. It also suggests that climate change may affect the potential of these forests to store SOC not only in the long term but also in the coming years. [ABSTRACT FROM AUTHOR]

Question: Patchiness of herbaceous species is a common feature of degraded alpine grasslands on the Qinghai–Tibet Plateau; however, the impact of this phenomenon on vegetation, soil seed bank (SSB), and soil carbon (C) and nitrogen (N) is largely unknown. We asked how different herbaceous patches affect above‐ground vegetation, the SSB and soil organic C (SOC) and total N (TN) contents in alpine meadows. Location: An alpine meadow on the Qinghai–Tibetan Plateau, China. Methods: We used field and greenhouse experiments to evaluate above‐ground vegetation parameters, the SSB composition, and SOC and TN contents of four commonly distributed herbaceous patches (Leymus secalinus, Kobresia humilis, Leontopodium nanum and Pedicularis kansuensis) and non‐patch vegetation (control). Results: There were significant differences in the species composition of above‐ground vegetation, with the plant species richness, Shannon–Wiener index, Simpson index, and Pielou evenness index reduced in the four patches compared to the control. In addition, patches had increased above‐ground biomass (AGB) and a lower below‐ground biomass to above‐ground biomass ratio (BGB:AGB); while the species diversity indices did not change considerably among the patches. The species composition of the SSB in the four patches differed from that in the control and the seed density increased markedly, but the species richness and diversity of the SSB remained unaltered. Moreover, the contents of SOC, total C, TN, microbial biomass C, and microbial biomass N in the four patches were markedly lower than in the control. Conclusions: These findings suggest that patchiness of herbaceous species can alter the flora composition of alpine meadows and reduce plant species diversity, as well as the SOC and TN contents, which will adversely impact grassland biodiversity conservation and soil C sequestration, and then may intensify the degradation of alpine meadows on the Qinghai–Tibet Plateau. [ABSTRACT FROM AUTHOR]

[Objective] The effects of waterlogging during flowering on dry matter accumulation and transport, yield and soil mineral nitrogen content of wheat plants under different nitrogen application rates were discussed, in order to provide a theoretical basis for the water-resistant and high-yield cultivation of wheat in the Jianghan Plain. [Method] The wheat varieties Xiangmai 55 and Yangmai 23 suitable for planting in the middle and lower reaches of the Yangtze River were used as materials. Three nitrogen application levels including NO (no nitrogen application), N1 (pure nitrogen 135 kg/hm²), N2 (pure nitrogen 180 kg/hm²) were set and watered for 7 days at the flowering stage by potting method. The changes of SPAD value in flag leaves, dry matter accumulation and transport in the ground, grain yield and soil mineral nitrogen content of wheat were analyzed. [Result] Waterlogging during flowering period significantly decreased SPAD value in flag leaves and dry matter accumulation in aboveground parts of wheat. SPAD value in flag leaves and dry matter accumulation in aboveground parts decreased by 8.61% to 39.78%, and dry matter accumulation in aboveground parts decreased by 4. 49% 12. 24%, and the decreasing range decreased with the increase of nitrogen application rate. Under waterlogging, with the increase of nitrogen application rate, pre-flowering dry matter transfer and contribution rate of wheat, post-flowering dry matter accumulation increased by 35.39%-58.37%, 6.04% -21.88% and 8.94% -29.32%, respectively. During waterlogging period (0-7 days after anthesis), soil nitrate nitrogen content decreased significantly by 41.81% 63.50%; The content of ammonium nitrogen increased significantly by 21.89%-62.15%. After removing water, the nitrate nitrogen content increased and the ammonium nitrogen content decreased from 7 to 21 days. From 21 to 28 days, nitrate nitrogen content decreased and ammonium nitrogen content increased. Under waterlogging treatment, when increasing nitrogen application, nitrate nitrogen and ammonium nitrogen content increased. Waterlogging in flowering period led to wheat yield reduction, and the 1000-grain weight reduction was the main factor. The wheat yield of N1 and N2 was increased by 229.75%-235.32% and 290.28%-358.12% respectively under waterlogging conditions compared with no N application. [Conclusion] Waterlogging significantly decreased SPAD value, dry matter accumulation, yield and nitrate nitrogen content of wheat flag leaves, but increased ammonium nitrogen content of soil. Under the condition of 0-180 kg/hm², increasing nitrogen application could alleviate the damage of waterlogging and reduce the decrease of wheat yield. [ABSTRACT FROM AUTHOR]

Converting degraded croplands into perennials has been proposed as an effective method of soil N sequestration, however, the dynamics of deep soil N (>100 cm) following cropland conversion are not well understood. In this study, we synthesized 3049 observations to detect the changes in deep soil N content following cropland conversion on the arid and semiarid Loess Plateau. Our results showed that converting croplands into perennials significantly increased the soil N content by an average of 57.4%, 23.1%, and 29.5% in the surface (0–20 cm), subsurface (20–100 cm), and deep (100–200 cm) layers, respectively. The extent of the increase was influenced significantly by the land‐use conversion types and tree species. Specifically, the conversion of croplands into deep‐rooted forests or shrubs, particularly Robinia pseudoacacia and Caragana microphylla, exhibited higher advantages in deep soil N sequestration. Moreover, deep soil N sequestration increased significantly with time since cropland conversion (p < 0.001), and the rates in deep soils were approximately 26.1% and 66.7% of that in 0–20 and 20–100 cm soils, respectively. In the long term, converting croplands into forests and shrubs showed higher potential for deep soil N sequestration. Linear regression analysis showed that the changes of deep soil N sequestration were influenced significantly by initial soil N content (p < 0.001) and humidity index (p < 0.001), with the slopes in >100 cm layers being 2 to 3 times than that in the top meter, indicating higher sensitivity in deep soils. Overall, this study provides evidence that converting degraded croplands into perennials may contribute to deep soil N accumulation in N‐limited regions, which could potentially alleviate N limitation and sustain long‐term ecosystem carbon sequestration. [ABSTRACT FROM AUTHOR]

Anaerobic digestate is proposed as an alternative to inorganic fertilisers, but a better understanding of how anaerobic digestates impact the soil and how plant growth is influenced is needed for wider acceptance. In this study, a series of pot experiments were conducted growing spring barley (Hordeum vulgare L.) in a range of soils with the application of digestate or synthetic fertiliser. Two application rates corresponding to total nitrogen at 120 and 480 kg ha−1 were used together with unfertilised soil as a control. Growth characteristics were measured as plant height, number of tillers, straw biomass, grain biomass and total biomass. Most growth characteristics (tillering, and straw and grain yield) increased with increasing application rates of nitrogen. An increase of 7–20% in plant height was observed with anaerobic digestate compared to synthetic fertilisers. However, results differed depending on the source of digestate and soil type. The nitrogen balance index (the ratio of the chlorophyll to polyphenolic compounds, which is linked to the nitrogen status of the crop) showed an increase of 40–50% for digestate applied at a nitrogen rate of 480 kg ha−1 compared to the control. By measuring nitrogen as ammonium, nitrate and nitrite in the different soils over 35 days, differential nitrogen release was also demonstrated, with soil water concentrations of ammonium decreasing rapidly after an early peak in all the treatments, and nitrate peaking after days 3–4. Results suggest that digestate may be used to replace synthetic fertilisers when applied in a range of soils. [ABSTRACT FROM AUTHOR]

Tree-ring δ15N may depict site-specific, long-term patterns in nitrogen (N) dynamics under N2-fixing species, but field trials with N2-fixing tree species are lacking and the relationship of temporal patterns in tree-ring δ15N to soil N dynamics is controversial. We examined whether the tree-ring δ15N of N2-fixing red alder (Alnus rubra Bong.) would mirror N accretion rates and δ15N of soils and whether the influence of alder-fixed N could be observed in the wood of a neighboring conifer. We sampled a 27-year-old replacement series trial on south-eastern Vancouver Island, with red alder and coastal Douglas-fir (Pseudotsuga menziesii [Mirb.] Franco) planted in five proportions (0/100, 11/89, 25/75, 50/50 and 100/0) at a uniform stem density. An escalation in forest floor N content was evident with an increasing proportion of red alder, equivalent to a difference of ~750 kg N ha−1 between 100% Douglas-fir versus 100% alder. The forest floor horizon also had high δ15N values in treatments with more red alder. Red alder had a consistent quadratic fit in tree-ring δ15N over time, with a net increase of |$\sim$| 1.5‰, on average, from initial values, followed by a plateau or slight decline. Douglas-fir tree-ring δ15N, in contrast, was largely unchanged over time (in three of four plots) but was significantly higher in the 50/50 mix. The minor differences in current leaf litter N content and δ15N between alder and Douglas-fir, coupled with declining growth in red alder, suggests the plateau or declining trend in alder tree-ring δ15N could coincide with lower N2-fixation rates, potentially by loss in alder vigor at canopy closure, or down-regulation via nitrate availability. [ABSTRACT FROM AUTHOR]

Species coculture can increase agro-biodiversity and therefore constitutes an ecological intensification measure for agriculture. Rice–aquatic animal coculture, one type of species coculture, has been practiced and researched widely. Here, we review recent studies and present results of a quantitative analysis of literature on rice–aquatic animal coculture systems. We address three questions: (i) can rice yield and soil fertility be maintained or increased with less chemical input through rice–aquatic animal coculture? (ii) how do aquatic animals benefit the paddy ecosystem? (iii) how can coculture be implemented for ecological intensification? Meta-analysis based on published papers showed that rice–aquatic animal cocultures increased rice yield, soil organic carbon and total nitrogen and decreased insect pests and weeds compared with rice monocultures. Studies also showed that rice–aquatic animal cocultures reduced pesticide and fertilizer application compared with rice monocultures. Rice plants provide a beneficial environment for aquatic animals, leading to high animal activities in the field. Aquatic animals, in turn, help remove rice pests and act as ecological engineers that affect soil conditions, which favor the growth of rice plants. Aquatic animals promote nutrient cycling and the complementary use of nutrients between rice and aquatic animals, which enhances nutrient-use efficiency in the coculture. To generate beneficial outcomes, how to develop compatible partnerships between rice and aquatic animals, and compatible culturing strategies for coculture systems are the key points. Investigating which traits of aquatic animals and rice varieties could best match to create productive and sustainable coculture systems could be one of the future focuses. [ABSTRACT FROM AUTHOR]

Replacement of polyethylene (PE) film mulch (PM) to biodegradable film mulch (BM) can significantly reduce plastic pollution and carbon footprint in agricultural production. However, the effects of BM on nitrogen dynamics in soil-plant system remain elusive. A field experiment with two cropping seasons was conducted to investigate the effects of biodegradable film on soil nitrogen mineralization, nitrate accumulation and leaching, and plant nitrogen uptake. Although the distribution of soil water and nitrate under treatment BM was similar to that under treatment PM at early growth stage of potato plants, the decomposition of biodegradable film during later growth stage of potato plants caused a reduction in soil water content and nitrogen mineralization, leading to a decrease in soil nitrate accumulation under treatment BM. In addition, the degradation of biodegradable film enhanced the translocation of nitrate from upper to deeper soil layers. However, there was no difference in tuber yield or plant nitrogen uptake between treatments BM and PM, suggesting the decomposition of biodegradable film at later growth stage has limited effect on potato nitrogen uptake and tuber yield. Therefore, the PLA/PBAT-based biodegradable mulch film is a promising substitution to PE film for winter potato production.

Nitrous oxide (N2O) is one of the most significant contributors to greenhouse forcing and is the biggest contributor to ozone depletion in the 21st century, and roughly 70% of anthropogenic nitrous oxide emissions are from agriculture and soil management. Agricultural nitrous oxide emissions are shown to spike during hotspot events, and according to the data used in this study, over 78% of nitrous oxide flux occurred during just 15% of the recorded data points. Due to the complex biogeochemical processes governing nitrous oxide formation, machine learning and process-based models often fail to predict agricultural nitrous oxide flux. A novel informed neural network was developed that combined the trainability of neural networks with the rigorous differential equation-based framework of process-based models. Differential equations that explained the variability of various nitrogen-containing compounds in soil were derived, and integrated into the network loss. The informed model explained ∼85% of variation in the data and had an F1 score of 0.75, a marked improvement over the classical model explaining ∼30% of variation and having a score of 0.53. The informed network was also able to perform exceptionally well with only small subsets of the training data, having an F1 score of 0.41 with only 25% of training data. The model not only shows great promise in the remarkably accurate prediction of these hotspots but also serves as a potential new paradigm for physics-informed machine learning techniques in environmental and agricultural sciences.

Soil tillage and maize residues return are important practices for tackling and promoting soil quality and improving crop yield in the North China Plain (NCP), where winter wheat production is threatened by soil deterioration. Although maize residues incorporation with rotary tillage (RS) or deep plowing tillage (DS) is widespread in this region, only few studies have focused on rotation tillage. Four practices, namely RT (continuous rotary tillage without maize residues return), RS, DS, and RS/DS (rotary tillage every year and deep plowing interval of 2 years), were evaluated under field conditions lasting a period of 5 years. After a 5-year field experiment, the mean soil bulk density of the 0–30 cm soil layer decreased significantly with RS, DS, and RS/DS, i.e., by 4.19%, 6.33%, and 6.71% compared with RT, respectively. The treatments greatly improved the total soil porosity, soil aggregate size distribution, soil aggregate stability, and the root length density in the 0–30 cm soil layers. Residues return with DS and RS/DS treatments significantly increased the soil organic carbon (SOC) and total nitrogen (TN) storage in the 0–30 cm soil layer, mainly owed to the increases in the SOC and TN pool associated with the macro-aggregate. A positive trend in the grain yield was noted under both DS and RS/DS conditions, whereas a decreasing tendency was presented in continuous rotary treatments. In summary, RS/DS treatment significantly increased the amount of SOC and TN, improved the particle size distribution of soil aggregates, and thus improved the soil’s physicochemical properties, which is beneficial for wheat to achieve high yields. Our results suggested that RS/DS was a highly efficient practice to improve soil quality and increase crop production in the NCP.

Soil salinization is a critical environmental issue restricting agricultural production. Deep return of straw to the soil as an interlayer (at 40 cm depth) has been a popular practice to alleviate salt stress. However, the legacy effects of straw added as an interlayer at different rates on soil organic carbon (SOC) and total nitrogen (TN) in saline soils still remain inconclusive. Therefore, a four-year (2015–2018) field experiment was conducted with four levels (i.e., 0, 6, 12 and 18 Mg ha–1) of straw returned as an interlayer. Compared with no straw interlayer (CK), straw addition increased SOC concentration by 14–32 and 11–57% in the 20–40 and 40–60 cm soil layers, respectively. The increases in soil TN concentration (8–22 and 6–34% in the 20–40 and 40–60 cm soil layers, respectively) were lower than that for SOC concentration, which led to increased soil C:N ratio in the 20–60 cm soil depth. Increases in SOC and TN concentrations in the 20–60 cm soil layer with straw addition led to a decrease in stratification ratios (0–20 cm:20–60 cm), which promoted uniform distributions of SOC and TN in the soil profile. Increases in SOC and TN concentrations were associated with soil salinity and moisture regulation and improved sunflower yield. Generally, compared with other treatments, the application of 12 Mg ha–1 straw had higher SOC, TN and C:N ratio, and lower soil stratification ratio in the 2015–2017 period. The results highlighted that legacy effects of straw application as an interlayer were maintained for at least four years, and demonstrated that deep soil straw application had a great potential for improving subsoil fertility in salt-affected soils.

Grassland provides many ecosystem services; therefore, sustainable management practices of grassland are crucial for maintaining and enhancing its ecosystem health and resilience. Rotational grazing at a high stocking density (a.k.a., ultrahigh stocking density) is purported to sequester greater amounts of carbon (C) in grassland soils than rotational grazing at low stocking densities. This study was conducted in the Nebraska Sandhills meadows for eight years to evaluate how rotational grazing with different stocking densities can affect soil C and total nitrogen (TN) in bulk soils, soil organic matter fractions, and sequestration rate. The grazing management included a high stocking density with one grazing cycle (MOB), a 4-pasture rotation system with one grazing cycle at a low stocking density (4PR1), and no grazing (CNT). Results showed that soil C and N contents were higher in the total particulate organic matter fraction than in the soil mineral-associated organic fraction at the 0–10 cm depth and visa verse at the 10–20 cm depth. Grazing management did not affect C and N contents in the bulk soils (SOC averaged 28.19 g C kg−1 and TN averaged 2.67 g N kg−1 at the 0–10 cm depth). Both MOB and 4PR1 grazing treatments recorded similar C and N contents in all SOM fractions. However, the MOB grazing treatment increased C and N contents in the macro-aggregate occluded particulate and dissolved organic matter fractions compared to the CNT. The 4PR1 grazing treatment increased soil C and N contents in the dissolved organic matter and mineral-associated organic matter fractions and increased SOC sequestration rate compared to the CNT. Rotational grazing at a low stocking density for one cycle appears to enhance long-term SOC accumulation in these Sandhills meadows soil.

The aim of this study was to better understand how soil carbon (C) and nitrogen (N) contents and the C:N ratio are related to soil texture, pH, and exchangeable aluminum and calcium in forest soils.For this purpose, we studied 1992 temperate and boreal forest soils located all over Sweden. We measured organic C and N as well exchangeable aluminum, calcium, and pH in the organic layer and three depth increments in the mineral soil (down to 65 cm), and analyzed the relationship between element contents, soil texture, and soil pH as well as their interactions.Soil C concentration and the C:N ratio were negatively related to soil pH. The C concentration was on average 2.6 times higher in very acidic soils (pH ≤ 4.0) than in soils with pH > 5.0, in the uppermost 10 cm of the mineral soil. In contrast, N varied much less with pH, particularly in the organic layer, but was related to soil texture. The N concentration was 2.3 times higher in clayey and fine silty soils than in sandy soils, while the C concentration was only 1.85 times higher in clayey and fine silty soils than in sandy soils (in the uppermost 10 cm). Differences in C and N concentrations between clayey and fine silty soils compared to sandy soils were largest in the class of soils with pH > 5.0 and smallest in the class of soils with pH ≤ 4.0. Furthermore, C and N concentrations were both positively correlated with the concentration of exchangeable aluminum in the mineral soil, and these correlations were stronger in coarse-textured than in fine-textured soils. In addition, the C concentration was positively correlated with the concentration of exchangeable calcium in the organic layer.In conclusion, our results show that C concentration varied much more strongly with pH than N concentration, likely due to effects of pH on microbial respiration. The N concentration was more strongly related to soil texture than the C concentration, which is very likely due to the high charge density of organic N, which gives organic N a high affinity to adsorb to mineral surfaces. Furthermore, exchangeable aluminum seems to play an important role in the sorptive stabilization of organic matter in the mineral soil.

Purpose: The application of soil conditioner has become one of the most important strategies to reduce nitrogen (N) losses from agricultural fields. However, it is still unclear about the effect of conditioners on soil profile N accumulation and crop N utilization under different irrigation levels. Materials and methods: In this study, the effects of combination of N fertilizer (255 kg/ha) and different doses of soil conditioner (mixture of anionic polyacrylamide, polyvinyl alcohol, and manganese sulfate) (0 (N), 0.008 (P1N), 0.016 (P2N), and 0.024 (P3N) g/kg) on soil - oat crop N transport and oat crop N utilization were explored under different irrigation levels (conventional irrigation volume (4.1 × 106 L/ha), W100; 80% of the conventional irrigation volume (3.28 × 106 L/ha), W80). Results and discussion: The combination of conditioner and N fertilizer increased soil capillary moisture capacity (CWC), field capacity (FC), total porosity (TP), and capillary porosity (CP) in the 0–40 cm (W80) and 20–60 cm (W100) soil layers, and reduced non-capillary porosity (N-CP) of the 0–40 cm soil layer (W100). Besides, it also positively affected the total N storage (STN) and nitrate N storage (SNN) in the 0–80 cm soil layer, especially under the W100 condition (the STN and SNN in the combination treatments of conditioner and N fertilizer (P1N, P2N, and P3N) increased by 5.5%–9.2% and 14.6%–16.3%, respectively compared with those in the single N treatment). Correlation analysis of N fractions and soil physical properties showed that STN was significantly positively correlated with CP; SNN was significantly negatively correlated with CP under the W80 condition, but there was no significant correlation between them under the W100 condition. Finally, the combination of different doses of conditioner and N fertilizer increased grain N accumulation and oat yield, especially under the W80 condition. Conclusions: The addition of conditioner had a higher N loss risk under the W100 condition than under the W80 condition, although it was beneficial to reducing N loss (31.8%–32.2%) and increasing inorganic N accumulation (14.5%–16.0%) during the reproductive period. We suggest that the combination of 12 kg/ha conditioner, 255 kg/ha N, and 80% of the conventional irrigation volume could be widely used to increase oat crop yield and reduce production cost and environmental pollution risk in the study area. [ABSTRACT FROM AUTHOR]