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Root-associated fungal endophytes may facilitate nitrogen (N) absorption in plants, leading to benefits in photosynthesis and growth. Here, we investigated whether endophytic insect pathogenic fungi (EIPF) are capable of transferring soil N to the crop species Chenopodium quinoa. We evaluated nutrient uptake, carbon allocation, and morpho-physiological performance in C. quinoa in symbiosis with two different EIPF (Beauveria and Metarhizium) under contrasting soil N supply. A controlled experiment was conducted using two plant groups: (1) plants subjected to low N level (5 mM urea) and (2) plants subjected to high N level (15 mM urea). Plants from each group were then inoculated with different EIPF strains, either Beauveria (EIPF1+), Metarhizium (EIPF2+) or without fungus (EIPF-). Differences in N and C content, amino acids, proteins, soluble sugars, starch, glutamine synthetase, glutamate dehydrogenase, and physiological (photosynthesis, stomatal conductance, transpiration), and morphological performance between plant groups under each treatment were examined. We found that both Beauveria and Metarhizium translocated N from the soil to the roots of C. quinoa, with positive effects on photosynthesis and plant growth. These effects, however, were differentially affected by fungal strain as well as by N level. Additionally, an improvement in root C and sugar content was observed in presence of EIPF, suggesting translocation of carbohydrates from leaves to roots. Whereas both strains were equally effective in N transfer to roots, Beauveria seemed to exert less demand in C. quinoa for photosynthesis-derived carbohydrates compared to Metarhizium. Our study revealed positive effects of EIPF on N transfer and morpho-physiological performance in crops, highlighting the potential of these fungi as an alternative to chemical fertilizers in agriculture systems. [ABSTRACT FROM AUTHOR]

Background and aims: The introduction of ley in cropping systems can provide multiple services, including high quality forage production and C and N inputs into arable soils. Little is known about the dynamics of these services in degrading grassland and the extent to which trade-offs regarding the use of fixed N for either forage production or as a source of N in the rotation can be found. Methods: A six-year field experiment compared the performance of an alfalfa-tall fescue (A-FE) mixture versus the single species alone (A, FE) in terms of forage production, forage quality and root biomass available as residues for the following crop. N mineralisation potential was then simulated for different grassland destruction scenarios using the STICS model. Result: The forage production, proportion of legumes, and forage quality all declined in the A-FE mixture after year 3 to reach less than 7 T.ha−1 and 20% legume in year 6. The yield advantage of A-FE compared to monospecific grasslands increased over time and was strongly associated with greater species complementarity, resulting from higher N transfer to grasses and increased asynchrony in the seasonal growth of A and FE. Root residue quantities and the potential for N supply to the rotation were not reduced when a degraded legume proportion was reached. Conclusion: The advantage of A-FE mixture over monospecific stands was greater integrated over a long period of time. No major risk of losing the N legacy effect by delaying mixture destruction was detected up to the first year after a sharp legume decline. [ABSTRACT FROM AUTHOR]

Root-associated fungal endophytes may facilitate nitrogen (N) absorption in plants, leading to benefits in photosynthesis and growth. Here, we investigated whether endophytic insect pathogenic fungi (EIPF) are capable of transferring soil N to the crop species Chenopodium quinoa. We evaluated nutrient uptake, carbon allocation, and morpho-physiological performance in C. quinoa in symbiosis with two different EIPF (Beauveria and Metarhizium) under contrasting soil N supply. A controlled experiment was conducted using two plant groups: (1) plants subjected to low N level (5 mM urea) and (2) plants subjected to high N level (15 mM urea). Plants from each group were then inoculated with different EIPF strains, either Beauveria (EIPF1+), Metarhizium (EIPF2+) or without fungus (EIPF-). Differences in N and C content, amino acids, proteins, soluble sugars, starch, glutamine synthetase, glutamate dehydrogenase, and physiological (photosynthesis, stomatal conductance, transpiration), and morphological performance between plant groups under each treatment were examined. We found that both Beauveria and Metarhizium translocated N from the soil to the roots of C. quinoa, with positive effects on photosynthesis and plant growth. These effects, however, were differentially affected by fungal strain as well as by N level. Additionally, an improvement in root C and sugar content was observed in presence of EIPF, suggesting translocation of carbohydrates from leaves to roots. Whereas both strains were equally effective in N transfer to roots, Beauveria seemed to exert less demand in C. quinoa for photosynthesis-derived carbohydrates compared to Metarhizium. Our study revealed positive effects of EIPF on N transfer and morpho-physiological performance in crops, highlighting the potential of these fungi as an alternative to chemical fertilizers in agriculture systems.

The interest in growing pulse crops and oilseeds together as intercrop combinations is increasing. However, little is known about nutrient dynamics in pulse–oilseed intercropping systems in western Canada, particularly the contributions from biological nitrogen fixation (BNF). Kabuli chickpea and brown flax were grown without added fertilizer as monocrops and as intercrops in mixed and alternate seed row configurations at sites located in the Brown (Central Butte, SK) and Black (Redvers, SK) soil zones in 2019 and 2020. Comparison was made of grain and straw yields, nitrogen (N) and phosphorus (P) uptake of grain and straw, and proportion and amount of biologically fixed N contributed from the chickpea and transferred to the flax. The intercrop grain yield land equivalent ratio (LER) and N and P uptake LER values were at or above 1 for the four site-years, indicating benefit from intercropping in increasing total yield and crop N and P uptake from the land area. The proportion of N derived from BNF was not enhanced in this intercrop combination, but considerable biologically fixed N (8%–22%) was transferred from the chickpea to the flax during the growing season. This was associated with reduced depletion of soil N compared to monocrop flax in part due to the contribution of biologically fixed N in the chickpea–flax intercrop system. [ABSTRACT FROM AUTHOR]

Though the effects of soil microorganisms, plants, and their interaction on methane (CH4) oxidation have been well documented, the roles of animals in this process are less known. We examined how a local common carp, Cyprinus carpio, affects CH4 oxidation in surface soil (that is, soil–water interface) in a 1200-year-old agriculture heritage rice–fish system. A 5-year experiment (field experiment 1) showed that rice yield and soil nitrogen (N) were higher under rice–fish co-culture than rice monoculture. Fish presence did not change CH4 emission but increased CH4 production archaea (methanogens), and aerobic CH4 oxidation bacteria (methanotrophs) and CH4 oxidation. Food component analysis by δ13C and δ15N showed that fish foraged paddy-dwelling organisms (for example, duckweeds, algae, phytoplankton, zooplankton, and zoobenthos). A survey on zooplankton Daphnia showed that fish decreased Daphnia abundance. Mesocosm experiment 1 further indicated that the absence of Daphnia increased methanotrophs and CH4 oxidation. Fish swimming and feeding activity in the paddy circulated the N they excreted and egested. 15N tracing in field experiment 2 demonstrated that N from fish feed was enriched in rice, paddy-dwelling organisms, and fish, while N released by the fish accumulated in soil surface layer (0–1 cm). Mesocosm experiment 2 further indicated that fish-released N increased methanotrophs and CH4 oxidation. 15N labeled-deoxyribonucleic acid (DNA) stable-isotope probing disclosed that fish feces-N was used by methanotrophs. Our work reveals that the fish enhances surface soil CH4 oxidation in the rice–fish system by increasing methanotrophs through feeding interactions that cause trophic cascades and drive N transfer. [ABSTRACT FROM AUTHOR]

Plastic film mulch systems are used widely in arid areas, and the associated tillage measures affect soil properties, root and crop growth, and nutrient uptake. However, much debate surrounds the most suitable tillage method for plastic film mulch systems. We conducted a two-year field experiment to explore the impact of three tillage treatments - rotary tillage before ridge–furrow plastic film mulch (MR), no-tillage before ridge–furrow plastic film mulch (MZ), and plow tillage before ridge–furrow plastic film mulch (MP) - on soil total nitrogen, available nitrogen, root stratification structure, nitrogen transfer and utilization, and maize yield. The results showed that MP had better soil quality than either MR or MZ over 2019 and 2020, with higher nitrate-nitrogen and total nitrogen in the 0–40 cm soil layer. MP improved the soil physicochemical properties more than the other treatments, producing significantly higher root numbers and root biomass for the aerial and underground nodal roots than MR and MZ. At harvest, MP had the highest root biomass density, root length density, and root surface area density in the different soil layers (0–20, 20–40, and 0–40 cm). Significant correlations occurred between root biomass and aboveground nitrogen accumulation during maize growth. During grain filling, MP had the greatest nitrogen transfer amount, significantly increasing root and aboveground nitrogen transfer by 19.63–45.82% and 11.15–24.56%, respectively, relative to the other treatments. MP significantly produced 1.36–26.73% higher grain yields and a higher grain crude protein content at harvest than MR and MZ. MP also had higher values for the nitrogen harvest index, nitrogen uptake efficiency, and partial factor productivity of nitrogen fertilizer than MR and MZ. In conclusion, plow tillage combined with a ridge–furrow plastic film mulch system facilitated maize root development and improved nitrogen utilization, thereby increasing maize yield more than the other treatments.

The effects of vegetation restoration on soil moisture dynamics and nutrient content have been widely studied; however, the knowledge on variation in rainfall redistribution and soil nitrogen component characteristics remain limited, particularly with respect to their relationship in restored ecosystems. Therefore, the characteristics of plant community structure, rainfall redistribution, and soil nitrogen components from farmland and Robinia pseudoacacia (RP) plantations of four restoration ages (12, 20, 30, and 45 a) were investigated and measured in the Wuliwan watershed in the Loess Plateau, China. The results showed that changes in plant community structure affected the rainfall redistribution processes. The throughfall and moisture entering the soil (MES) had the largest proportions (79.50 % and 60.25 %) in the initial and second distributions of atmospheric rainfall, respectively. With the increase in restoration age, the content of soil total nitrogen (STN), soil nitrate nitrogen (SNN), soil soluble total nitrogen (SSTN), soil soluble organic nitrogen (SSON), and soil soluble inorganic nitrogen (SSIN) all increased with restoration age in the upper soil (0–40 cm), fluctuated in the middle soil (40–100 cm), and increased and then decreased in the deeper soil (100–200 cm). In addition, the vegetation restoration process can indirectly affect soil nitrogen content and distribution patterns by affecting the rainfall redistribution process. In the upper soil, litter interception (LI) had a significant effect on STN by affecting SSIN and SSON. In the middle soil, both LI and MES had significant effects on STN through SSIN and SSON, respectively. In the deeper soil, LI had no significant effect on any nitrogen component, whereas MES had a significant effect on STN by affecting SSIN. Overall, this study indicates that RP plantation restoration has the potential to transform rainfall redistribution and soil nitrogen distribution, providing an important reference for the reciprocal feedback relationship between water and nitrogen.

Sulfoximines and sulfonimidamides are of interest as design options for medicinal chemists. This article describes the development of methods for the synthesis of sulfoximines by metal-free NH-transfer to sulfoxides, and NH/O transfer to sulfides, using convenient sources of ammonia and hypervalent iodine reagents. Similarly, sulfonimidamides are prepared from sulfenamides. Methods for the preparation of enantioenriched sulfonimidoyl fluorides are also described, as are their stereospecific reactions with amines and Grignard reagents. This work was presented at the 29th International Symposium on the Organic Chemistry of Sulfur (Guelph, July 2022). [ABSTRACT FROM AUTHOR]

Nitrogen (N) inputs from legume residues over the long-term contribute to improve soil N cycling and the productivity of succeeding plants in species-diverse ecosystems. Litter mixtures enhance soil fertility, thus enhancing biomass production, which in turn creates positive diversity–productivity feedback in the long-term. Positive effects of litter diversity on the composition and diversity of soil organisms increase over time. Residue-borne pathogens and pests gradually accumulate through litter input from monocultures, whereas diverse plant-litter mixtures reduce the incidence and spread of residue-borne pathogens and pests in the long-term. Plant litter can strengthen biodiversity–ecosystem functioning relationships in both natural and managed ecosystems. Appropriate management of residues from plant mixtures across multiple growing seasons can promote the sustainability of food production systems. Plant biodiversity–productivity relationships become stronger over time in grasslands, forests, and agroecosystems. Plant shoot and root litter is important in mediating these positive relationships, yet the functional role of plant litter remains overlooked in long-term experiments. We propose that plant litter strengthens biodiversity–ecosystem functioning relationships over time in four ways by providing decomposing detritus that releases nitrogen (N) over time for uptake by existing and succeeding plants, enhancing overall soil fertility, changing soil community composition, and reducing the impact of residue-borne pathogens and pests. We bring new insights into how diversity–productivity relationships may change over time and suggest that the diversification of crop residue retention through increased residue diversity from plant mixtures will improve the sustainability of food production systems. [ABSTRACT FROM AUTHOR]

To determine the potential impacts of exogenous nitrogen (N) enrichment on distribution and transfer of N in Suaeda salsa marsh in the Yellow River Estuary, the variations of N in plant-soil system during the growing season were investigated by field N addition experiment. The experiment included four treatments: NN (no N input treatment, 0 gN m−2 yr−1), LN (low N input treatment, 3.0 gN m−2 yr−1), MN (medium N input treatment, 6 gN m−2 yr−1) and HN (high N input treatment, 12 gN m−2 yr−1). Results showed that N additions generally increased the contents of total nitrogen (TN), ammonia nitrogen (NH4+-N) and nitrate nitrogen (NO3−-N) in different soil layers and the increasing trend was particularly evident in topsoil. Compared with the NN treatment, the average contents of TN in topsoil in the LN, MN and HN treatments during the growing season increased by 10.85%, 30.14% and 43.98%, the mean contents of NH4+-N increased by 8.56%, 6.96% and 14.34%, and the average contents of NO3−-N increased by 35.73%, 45.99% and 46.66%, respectively. Although exogenous N import did not alter the temporal variation patterns of TN contents in organs, the N transfer and accumulation differed among tissues in different treatments. With increasing N import, both the N stocks in soil and plant showed increasing trend and the values in N addition treatments increased by 9.43%–38.22% and 13.40%–62.20%, respectively. It was worth noting that, compared with other treatments, the S. salsa in the MN treatments was very likely to have special response to N enrichment since not only the period of peak growth was prolonged by about 20 days but also the maximum of TN content in leaves was advanced by approximately one month. This paper found that, as N loading reached MN level in future, the growth rhythm of S. salsa and the accumulation and transference of N in its tissues would be altered significantly, which might generate great impact on the stability and health of S. salsa marsh ecosystem. [ABSTRACT FROM AUTHOR]

Arbuscular mycorrhizal fungi (AMF) form mutualistic symbiotic relationships with many land plants and play a key role in nitrogen (N) acquisition. NO3−-N and NH4+-N are the main sources of soil mineral N, but how extraradical mycelial transfer affects the different N forms and levels available to tomato plants is not clear. In the present study, we set up hyphal compartments (HCs) to study the efficiency of N transfer from the extramycelium to tomato plants treated with different N forms and levels of fertilization. Labeled 15NO3−-N or 15NH4+-N was placed in hyphal compartments under high and low N application levels. 15N accumulation in shoots and the expression of LeNRT2.3, LeAMT1.1, and LeAMT1.2 in the roots of tomato were measured. According to our results, both 15NO3−-N and 15NH4+-N were transported via extraradical mycelia to the shoots of plants. 15N accumulation in shoots was similar, regardless of the N form, while a higher 15N concentration was found in shoots with low N application. Compared with the control, inoculation with AMF significantly increased the expression of LeAMT1.1 under high N and LeNRT2.3 under low N. The expression of LeAMT1.1 under high N was significantly increased when NO3—N was added, while the expression of LeNRT2.3 was significantly increased when NH4+-N was added under low N. Taken together, our results suggest that the N transfer by extraradical mycelia is crucial for the acquisition of both NO3−-N and NH4+-N by the tomato plant; however, partial N accumulation in plant tissue is more important with N deficiency compared with a higher N supply. The expression of N transporters was influenced by both the form and level of N supply. [ABSTRACT FROM AUTHOR]

Purpose : Nitrogen (N) transfer from white clover (Trifolium repens cv.) to ryegrass (Lolium perenne cv.) has the potential to meet ryegrass N requirements. This study aimed to quantify N transfer in a mixed pasture and investigate the influence of the microbial community and land management on N transfer. Methods: Split root 15N-labelling of clover quantified N transfer to ryegrass via exudation, microbial assimilation, decomposition, defoliation and soil biota. Incorporation into the microbial protein pool was determined using compound-specific 15N-stable isotope probing approaches. Results: N transfer to ryegrass and soil microbial protein in the model system was relatively small, with one-third arising from root exudation. N transfer to ryegrass increased with no microbial competition but soil microbes also increased N transfer via shoot decomposition. Addition of mycorrhizal fungi did not alter N transfer, due to the source-sink nature of this pathway, whilst weevil grazing on roots decreased microbial N transfer. N transfer was bidirectional, and comparable on a short-term scale. Conclusions: N transfer was low in a model young pasture established from soil from a permanent grassland with long-term N fertilisation. Root exudation and decomposition were major N transfer pathways. N transfer was influenced by soil biota (weevils, mycorrhizae) and land management (e.g. grazing). Previous land management and the role of the microbial community in N transfer must be considered when determining the potential for N transfer to ryegrass. [ABSTRACT FROM AUTHOR]

To ascertain the possibility of cultivating maize using biological nitrogen fixation (BNF) by leguminous green manure crops in maize/leguminous green manure intercropping systems, BNF and nitrogen (N) transfer were studied in Xining and Wuwei, two typical northwestern Chinese cities. The experimental treatments included monocultured maize, monocultured green manures (hairy vetch and common vetch), and their intercropping systems. The proportions of N derived from the atmosphere (%Ndfa) in intercropping systems were not significantly different from that in monocultured green manure systems at either experimental site, except for that in hairy vetch (HV) in Xining. The amount of N derived from the atmosphere (Ndfa) of common vetch (CV) significantly decreased from 1.16 and 1.10 g/pot in monoculture to 0.77 and 0.55 g/pot when intercropped with maize, in Xining and Wuwei, respectively, and the Ndfa of HV when intercropped significantly decreased from 1.02 to 0.48 g/pot in Xining. In the intercropping systems in Xining and Wuwei, the amounts of N transferred (Ntransfer) from CV to maize were 21.54 and 26.81 mg/pot, accounting for 32.9 and 5.9% respectively of the N accumulation in maize, and the values of Ntransfer from HV to maize were 39.61 and 46.22 mg/pot, accounting for 37.0 and 23.3%, respectively, of the N accumulation in maize. Path analysis showed that soil nutrient and green manure biomass were mainly related to Ndfa, and that δ15N had a primary relationship with Ntransfer. We found that 5.9–37.0% of N accumulation in maize was transferred from green manures, and that the N transfer ability to maize of HV was higher than that of CV. In conclusion, intercropping with leguminous green manures provided a feasible way for maize to effectively utilize biologically fixed N.

Intercropping systems can flexibly use resources such as sunlight, heat, water, and nutrients in time and space, improve crop yield and land utilization rates, effectively reduce continuous cropping obstacles and the occurrence of diseases and insect pests, and control the growth of weeds. Thus, intercropping is a safe and efficient ecological planting mode. The legume–cereal intercropping system is the most common planting combination. Legume crops fix nitrogen from the atmosphere through their symbiotic nitrogen fixation abilities, and the fixed nitrogen can be transferred to and utilized by cereal crops in various ways. The symbiotic nitrogen fixation efficiency of legume crops was improved by reducing the inhibition of soil nitrogen on nitrogenase activity through competitive absorption of soil nitrogen. However, the effects of nitrogen transformation and distribution in intercropping systems and microbial community structure characteristics on nitrogen transfer need to be further explored. In this review, (ⅰ) we present the transformation and distribution of nitrogen in the legume–cereal intercropping system; (ⅱ) we describe the soil microbial community characteristics in intercropping systems; and (ⅲ) we discuss the advantages of using modern biological molecular techniques to study soil microorganisms. We conclude that intercropping can increase the diversity of soil microorganisms, and the interaction between different plants has an important impact on the diversity and composition of the bacterial and fungal communities. The extensive application of modern biological molecular techniques in soil microbial research and the great contribution of intercropping systems to sustainable agriculture are particularly emphasized in this review. [ABSTRACT FROM AUTHOR]

The production of food crops in sustainable agriculture demands the use of renewable resources, which include the potential role of arbuscular mycorrhiza fungi (AMF) and Biological Nitrogen Fixation (BNF) for supplying nitrogen (N) for crops. Associative action of AMF in legumes has a great impact on root, shoot development and phosphorous uptake which results in the enhancement of nodulation and nitrogen fixation. Biological nitrogen fixing crops can contribute N to the neighbouring crops by N transfer. N compounds (NH4+, NO3-, amino acids, ureides, peptides and proteins) released from nodulated roots, decomposed legume debris, or root exudates to soil solution are absorbed by AM hyphae as the first direct pathway of N transfer. Absorbed N by AMF is translocated as NH4+, amino acids, and peptides from fungal cell to neighbouring plant cells. This transfer could involve NH4+ and NO3- transporters, amino acid permeases and peptide transporters. Plants could be interconnected by mycorrhizal mycelia to form common AM networks that provide the another direct pathways for N transfer from one plant to another. Although the relatively small role of common AM networks in N transfer, the overall AMF contributions to N transfer are considered to be of great importance for legume and non-legume intercropping systems in sustainable agriculture.

Abstract Background The mixing of Eucalyptus with N2-fixing trees species (NFTs) is a frequently successful and sustainable cropping practice. In this study, we evaluated nitrogen (N) transfer and conducted a proteomic analysis of the seedlings of Eucalyptus urophylla × E. grandis (Eucalyptus) and an NFT, Dalbergia (D.) odorifera, from intercropping and monocropping systems to elucidate the physiological effects and molecular mechanisms of N transfer in mixed Eucalyptus and D. odorifera systems. Results N transfer occurred from D. odorifera to Eucalyptus at a rate of 14.61% in the intercropping system, which increased N uptake and growth in Eucalyptus but inhibited growth in D. odorifera. There were 285 and 288 differentially expressed proteins by greater than 1.5-fold in Eucalyptus and D. odorifera roots with intercropping vs monoculture, respectively. Introduction of D. odorifera increased the stress resistance ability of Eucalyptus, while D. odorifera stress resistance was increased by increasing levels of jasmonic acid (JA). Additionally, the differentially expressed proteins of N metabolism, such as glutamine synthetase nodule isozyme (GS), were upregulated to enhance N competition in Eucalyptus. Importantly, more proteins were involved in synthetic pathways than in metabolic pathways in Eucalyptus because of the benefit of N transfer, and the two groups of N compound transporters were found in Eucalyptus; however, more functional proteins were involved in metabolic degradation in D. odorifera; specifically, the molecular mechanism of the transfer of N from D. odorifera to Eucalyptus was explained by proteomics. Conclusions Our study suggests that N transfer occurred from D. odorifera to Eucalyptus and was affected by the variations in the differentially expressed proteins. We anticipate that these results can be verified in field experiments for the sustainable development of Eucalyptus plantations.

• Effect of point bar on nitrogen transport & reaction in riparian zones was studied. • Point bars alter groundwater velocity field, resulting in higher flow velocities and shorter subsurface residence times. • Nitrogen removal and transfer depths of key species increase with point-bar area/curvature. Point bars formed by riverbank deposition are an important part of the hyporheic zone, where surface water and groundwater are actively exchanged; they play a key role in the nitrogen biogeochemical processes of river ecosystems. In this study, we aimed to investigate the effects of point bars on nitrogen transport and reactions in riparian zones. A two-dimensional (2D) coupled flow-reactive transport model was developed, and three key chemical reactions, namely, aerobic respiration, nitrification, and denitrification, were considered to study the effects of the curvature and size of a point bar on the nitrogen distribution and chemical reaction rate in the hyporheic zone. The results indicated that the point bar altered the groundwater velocity field, resulting in higher flow velocity and shorter subsurface residence time, which significantly increased the depth of the four key species [dissolved oxygen (DO), nitrate (NO 3 −), dissolved organic carbon (DOC), and ammonium (NH 4 +)] that are generally transported to riparian zones. This phenomenon played a significant role in increasing the nitrification and denitrification rates. In the scenario wherein a point bar was formed, the amount of nitrogen removed was 4.29 times higher than that in the scenario wherein no point bar was formed. Furthermore, the transfer depths of DO, NO 3 −, DOC, and NH 4 + and the amount of nitrogen removed increased with the curvature/area of the bar. This study indicates that the presence of a point bar can accelerate the nitrogen cycle and increase the nitrogen removal capacity in riparian zones. [ABSTRACT FROM AUTHOR]

A lab-scale study of the symbiotic ecosystem between Tubificidae and microbes (SETM) was carried out. The sludge reduction ability and ammonia removal performance of the system were investigated, and the nitrogen transfer pathway in the system was studied. In SETM, the substrates, microbes, and Tubificidae interacted with each other and reached equilibrium. During the experimental period (50 days), the amount of SETM sludge reduced by 30% compared to the control group (without Tubificidae). A considerable amount of nutrients was released in the presence of Tubificidae. Conceptual models of nitrogen flow were proposed, and the nitrogen transfer in the systems was described. In SETM, 21% more nitrogen was removed via assimilation compared with the control group, and the net nitrogen removal (including endogenous nitrogen) was higher than in the control group. The effective ammonia removal in SETM was 13% higher than in the control group. This result was supported by fluorescent in situ hybridization data showing that ammonia-oxidizing bacteria were 5% more prevalent in SETM than in the control group. [ABSTRACT FROM AUTHOR]

Legumes as green manure allow adding N from the air to the soil through their biological fixation. The objective was to evaluate the effect of legume crops as green manure at the beginning of the rotation on soil quality and their N input to the following onion crop (Allium cepa L. var. cepa). Five crops were sown: faba-bean (Vicia faba L.), field pea (Pisum sativum L.), oat-vetch mixture (Avena sativa L. + Vicia atropurpurea Desf.), white lupin (Lupinus albus L.), and oat as control treatment, with four replicates. Prior to sowing soil was prepared with 20 Mg ha-1 compost and 715 kg ha-1 rock phosphate. Then, at 50% grain filling stage these crops were incorporated as green manure to the soil, followed by the onion crop. Biological N fixation (BNF) by 15N natural abundance technique parameters of green manure, yield, leaf N content of the legumes and onion, and soil bio-physicochemical properties were measured and analyzed by ANOVA and Tukey's test for mean separation (P = 0.05). Faba-bean treatment had the highest BNF (388 and 369 kg N ha-1 fixed in 2017 and 2018, respectively). For onion yield, just faba-bean and oat-vetch in 2018 reached the Chilean mean yield with 54.39 and 49.08 Mg ha-1, respectively. Control treatment yield was not significantly different. Leaf N content in onion remained within a normal range in all treatments. Adding green manure together with compost to the soil improved soil N and K contents. [ABSTRACT FROM AUTHOR]

Shrub encroachment induced by global change and human disturbance strongly affects ecosystem structure and function. In this study, we explore the degree to which invading leguminous shrubs affected neighboring grasses, including via the transfer of fixed nitrogen (N). We measured N concentrations and natural abundance (15)N of shoot tissues from three dominant grasses from different plant functional groups across seven distances along a local transect (up to 500 cm) to the leguminous shrub, Caragana microphylla. C. microphylla did transfer fixed N to neighboring grasses, but the amount and distance of N transferred were strongly species-specific. Shoot N concentrations decreased significantly with distance from C. microphylla, for a rhizomatous grass, Leymus chinensis, and a bunchgrass, Achnatherum sibiricum. However, N concentrations of another bunchgrass, Stipa grandis, were higher only directly underneath the shrub canopy. Shoot δ(15)N values of L. chinensis were enriched up to 500 cm from the shrub, but for S. grandis were enriched only below the shrub canopy. In contrast, δ(15)N of A. sibiricum did not change along the 500-cm transect. Our results indicated the rhizomatous grass transferred fixed N over long distances while bunchgrasses did not. The presence of C. microphylla increased the shoot biomass of L. chinensis but decreased that of S. grandis and A. sibiricum. These findings highlight the potential role of nutrient-acquisition strategies of neighboring grasses in moderating the interspecific variation of fixed N transfer from the leguminous shrub. Overall, leguminous shrubs have either positive or negative effects on the neighboring grasses and dramatically affect plant community composition and structure.

Recent years have seen a marked increase in the occurrence of sulfoximines in the chemical sciences, often presented as valuable motifs for medicinal chemistry. This has been prompted by both pioneering works taking sulfoximine containing compounds into clinical trials and the concurrent development of powerful synthetic methods. This review covers recent developments in the synthesis of sulfoximines concentrating on developments since 2015. This includes extensive developments in both S−N and S−C bond formations. Flow chemistry processes for sulfoximine synthesis are also covered. Finally, subsequent transformations of sulfoximines, particularly in N‐functionalization are reviewed, including N−S, N−P, N−C bond forming processes and cyclization reactions. [ABSTRACT FROM AUTHOR]

Arbuscular mycorrhizal fungi (AMF) form mutualistic symbiotic relationships with many land plants and play a key role in nitrogen (N) acquisition. NO3−-N and NH4+-N are the main sources of soil mineral N, but how extraradical mycelial transfer affects the different N forms and levels available to tomato plants is not clear. In the present study, we set up hyphal compartments (HCs) to study the efficiency of N transfer from the extramycelium to tomato plants treated with different N forms and levels of fertilization. Labeled 15NO3−-N or 15NH4+-N was placed in hyphal compartments under high and low N application levels. 15N accumulation in shoots and the expression of LeNRT2.3, LeAMT1.1, and LeAMT1.2 in the roots of tomato were measured. According to our results, both 15NO3−-N and 15NH4+-N were transported via extraradical mycelia to the shoots of plants. 15N accumulation in shoots was similar, regardless of the N form, while a higher 15N concentration was found in shoots with low N application. Compared with the control, inoculation with AMF significantly increased the expression of LeAMT1.1 under high N and LeNRT2.3 under low N. The expression of LeAMT1.1 under high N was significantly increased when NO3—N was added, while the expression of LeNRT2.3 was significantly increased when NH4+-N was added under low N. Taken together, our results suggest that the N transfer by extraradical mycelia is crucial for the acquisition of both NO3−-N and NH4+-N by the tomato plant; however, partial N accumulation in plant tissue is more important with N deficiency compared with a higher N supply. The expression of N transporters was influenced by both the form and level of N supply.

The fixation and transfer of biological nitrogen from peanuts to maize in maize-peanut intercropping systems play a pivotal role in maintaining the soil nutrient balance. However, the mechanisms through which root interactions regulate biological nitrogen fixation and transfer remain unclear. This study employed a 15 N isotope labelling method to quantify nitrogen fixation and transfer from peanuts to maize, concurrently elucidating key microorganisms and genera in the nitrogen cycle through metagenomic sequencing. The results revealed that biological nitrogen fixation in peanut was 50 mg and transfer to maize was 230 mg when the roots interacted. Moreover, root interactions significantly increased nitrogen content and the activities of protease, dehydrogenase (DHO) and nitrate reductase in the rhizosphere soil. Metagenomic analyses and structural equation modelling indicated that nrfC and nirA genes played important roles in regulating nitrogen fixation and transfer. Bradyrhizobium was affected by soil nitrogen content and DHO, indirectly influencing the efficiency of nitrogen fixation and transfer. Overall, our study identified key bacterial genera and genes associated with nitrogen fixation and transfer, thus advancing our understanding of interspecific interactions and highlighting the pivotal role of soil microorganisms and functional genes in maintaining soil ecosystem stability from a molecular ecological perspective., (© 2024 John Wiley & Sons Ltd.)

Nitrogen-containing motifs are widely present in natural products, bioactive molecules, and drugs. Accordingly, effective synthetic methods with high efficiency and diversity are highly desirable. Here, we present the invention of a facile, visible light-mediated decarboxylative C(sp3)-N bond-forming reaction by employing abundant carboxylic acids as the feedstock and a commercial diazirine as a nitrogen donor. This process is amenable to access both imines and diaziridines, as the corresponding masked amines and hydrazines, through a selectable single or double nitrogen transfer from the diazirine, respectively. This divergent approach works well in both directions with various alkyl carboxylic acids, including primary, secondary, and tertiary acids, as well as natural products and drugs, thus affording a rapid, metal-free approach to build nitrogen-containing molecule libraries with considerable structural diversity, which could thus benefit the related study in context of chemical biology and drug discovery. [ABSTRACT FROM AUTHOR]

Intercropping systems can flexibly use resources such as sunlight, heat, water, and nutrients in time and space, improve crop yield and land utilization rates, effectively reduce continuous cropping obstacles and the occurrence of diseases and insect pests, and control the growth of weeds. Thus, intercropping is a safe and efficient ecological planting mode. The legume–cereal intercropping system is the most common planting combination. Legume crops fix nitrogen from the atmosphere through their symbiotic nitrogen fixation abilities, and the fixed nitrogen can be transferred to and utilized by cereal crops in various ways. The symbiotic nitrogen fixation efficiency of legume crops was improved by reducing the inhibition of soil nitrogen on nitrogenase activity through competitive absorption of soil nitrogen. However, the effects of nitrogen transformation and distribution in intercropping systems and microbial community structure characteristics on nitrogen transfer need to be further explored. In this review, (ⅰ) we present the transformation and distribution of nitrogen in the legume–cereal intercropping system; (ⅱ) we describe the soil microbial community characteristics in intercropping systems; and (ⅲ) we discuss the advantages of using modern biological molecular techniques to study soil microorganisms. We conclude that intercropping can increase the diversity of soil microorganisms, and the interaction between different plants has an important impact on the diversity and composition of the bacterial and fungal communities. The extensive application of modern biological molecular techniques in soil microbial research and the great contribution of intercropping systems to sustainable agriculture are particularly emphasized in this review.

Split-root assays have been used widely in studies focused on understanding the complex regulatory mechanisms in legume–rhizobia symbioses, root nitrogen rhizodeposition, and belowground nitrogen transfer, and the effects of different biotic/abiotic factors on this symbiotic interaction. This assay allows a plant to have a root system that is physically divided into two distinct sections that are both still attached to a common shoot. Thus, each root section can be treated separately to monitor local and systemic plant responses. Different techniques are used to establish split-root assemblies, including double-pot systems, divided growth pouches, elbow root assembly, twin-tube systems, a single pot or chamber with a partition in the center, and divided agar plates. This review is focused on discussing the various types of split-root assays currently used in legume-based studies, and their associated advantages and limitations. Furthermore, this review also focuses on how split-root assays have been used for studies on nitrogen rhizodeposition, belowground nitrogen transfer, systemic regulation of nodulation, and biotic and abiotic factors affecting legume–rhizobia symbioses. [ABSTRACT FROM AUTHOR]

Background: The mixing of Eucalyptus with N2-fixing trees species (NFTs) is a frequently successful and sustainable cropping practice. In this study, we evaluated nitrogen (N) transfer and conducted a proteomic analysis of the seedlings of Eucalyptus urophylla × E. grandis (Eucalyptus) and an NFT, Dalbergia (D.) odorifera, from intercropping and monocropping systems to elucidate the physiological effects and molecular mechanisms of N transfer in mixed Eucalyptus and D. odorifera systems. Results: N transfer occurred from D. odorifera to Eucalyptus at a rate of 14.61% in the intercropping system, which increased N uptake and growth in Eucalyptus but inhibited growth in D. odorifera. There were 285 and 288 differentially expressed proteins by greater than 1.5-fold in Eucalyptus and D. odorifera roots with intercropping vs monoculture, respectively. Introduction of D. odorifera increased the stress resistance ability of Eucalyptus, while D. odorifera stress resistance was increased by increasing levels of jasmonic acid (JA). Additionally, the differentially expressed proteins of N metabolism, such as glutamine synthetase nodule isozyme (GS), were upregulated to enhance N competition in Eucalyptus. Importantly, more proteins were involved in synthetic pathways than in metabolic pathways in Eucalyptus because of the benefit of N transfer, and the two groups of N compound transporters were found in Eucalyptus; however, more functional proteins were involved in metabolic degradation in D. odorifera; specifically, the molecular mechanism of the transfer of N from D. odorifera to Eucalyptus was explained by proteomics. Conclusions: Our study suggests that N transfer occurred from D. odorifera to Eucalyptus and was affected by the variations in the differentially expressed proteins. We anticipate that these results can be verified in field experiments for the sustainable development of Eucalyptus plantations. [ABSTRACT FROM AUTHOR]

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Copyright of Experimental Technology & Management is the property of Experimental Technology & Management 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.)

Biological nitrogen fixation (BNF) is an important nitrogen source for both N2-fixers and their neighboring plants in natural and managed ecosystems. Biological N fixation can vary considerably depending on soil conditions, yet there is a lack of knowledge on the impact of varying soils on the contribution of N from N2-fixers in mixed swards. In this study, the amount and proportion of BNF from red clover were assessed using three grassland soils. Three soil samples, Hallsworth (HH), Crediton (CN), and Halstow (HW) series, were collected from three grassland sites in Devon, UK. A pot experiment with 15N natural abundance was conducted to estimate BNF from red clover, and the proportion of N transferred from red clover to the non-N2 fixing grass in a grass-clover system. The results showed that BNF in red clover sourced from atmosphere in the HH soil was 2.92 mg N plant-1, which was significantly lower than that of the CN (6.18 mg N plant-1) and HW (8.01 mg N plant-1) soils. Nitrogen in grass sourced from BNF via belowground was 0.46 mg N plant-1 in the HH soil, which was significantly greater than that in CN and HW soils. However, proportionally there were no significant differences in the percentage N content of both red clover and grass sourced from BNF via belowground among soils, at 65%, 67%, 65% and 35%, 27%, 31% in HH, CN, and HW, respectively. Our observations indicate that the amount of BNF by red clover varies among grassland soils, as does the amount of N sourced from BNF that is transferred to neighboring plants, which is linked to biomass production. Proportionally there was no difference among soils in N sourced from BNF in both the red clover plants and transferred to neighboring plants. [ABSTRACT FROM AUTHOR]

Nitrogen (N) transfer to runoff contributed to nutrient loss and water pollution. Experiments were conducted to study the ammonia nitrogen (NH4-N), nitrate nitrogen (NO3-N) and total nitrogen (TN) transfer from loam soil to runoff in response to various rainfall intensities (RIs) (0.4±0.02, 1.0±0.04, and 1.8±0.11 mm min-1) and slope gradients (SGs) (5°, 10°, 15° and 20°). A typical mathematical model based on effective mixing depth (hm) and a refined model which replaced the time-average hm in this typical model with a time-increasing hm were both applied to predict N transfer to runoff. These models were verified with experimental data to evaluate the applications in simulations of surface N dynamics. NH4-N and TN concentrations in overland flow presented large deviations but NO3-N concentration highly declined from the initiation of runoff and then stabilized with slight deviations. The effective mixing depth deduced from fitted results coincided positively with RI but negatively with SG. The linear regressions between model prediction and experimental results revealed better agreements for NO3-N (r² = 0.696; Slope = 1.1617) than NH4-N (r² = 0.2538; slope = 0.7916) and TN (r² = 0.224; slope = 0.6658). The refined model showed improved performance compared with the original model for the NO3-N (r² = 0.8267; slope = 0.9996; intercept = -0.2675 versus r² = 0.696; slope = 1.1617; intercept = -0.0438). [ABSTRACT FROM AUTHOR]

Arbuscular mycorrhizal fungi (AMF) provide many benefits in agroecosystems including improved soil tilth, carbon sequestration, and water and nutrient transfer to plants. AMF are known to affect plant nitrogen (N) dynamics and transfer N to plants, but there have been few studies addressing whether the amount of N transferred to plants by AMF is agronomically relevant. We used δ15N natural abundance methods and δ15N mass balance equations to estimate the amount of plant N derived from AMF transfer in perennial grasses managed for bioenergy production under different N addition treatments (0, 56, and 196 kg N/ha). Differentiation of δ15N among plant, soil N, and AMF pools was higher than anticipated leading to calculations of 34–55% of plant N transferred by AMF in the treatments receiving no N addition to 6–22% of plant N transferred to plants in high‐N addition treatments. AMF extra‐radical hyphae biomass was significantly reduced in the high‐N (196 kg N/ha) addition treatments, which was negatively correlated to enriched plant δ15N. Our results suggest that N addition decreases AMF N transfer to plants. When N was limiting to plant growth, AMF supplied agronomically significant amounts of plant N, and a higher proportion of overall plant N. Because differentiation between N pools was greater than expected, stable isotope measurements can be used to estimate N transfer to AMF plant hosts. [ABSTRACT FROM AUTHOR]

Copyright of Acta Prataculturae Sinica is the property of Acta Prataculturae Sinica 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.)

Aims: Mycorrhizae and root exudates have been considered the two important pathways for nitrogen (N) transfer from legume to non-legume plants. The present study aimed to investigate contribution of the relative importance of arbuscular mycorrhizal fungi and root exudates in short-term N transfer. Methods: A field experiment was conducted to explore N transfer from alfalfa to maize under two different N application levels using 15N leaf labeling. Results: N transfer amount ranged from 7 to 10 mg N plant−1 from alfalfa to maize and significantly decreased (by 11%–22%) with N fertilizer application. Intercropping of 4 rows of maize and 6 rows of alfalfa with 30 cm intra-row spacing (IMA43) was the optimal intercropping mode, which increased N transfer, total N uptake and yield by 18%, 15% and 11%, respectively. The relative importance of arbuscular mycorrhizal fungi and root exudates on N transfer was dependent on soil N availability. Under no N addition, hyphal length density (HLD) of rhizosphere soil explained the largest significant amount (50%) of the variability in N transfer and crop yield. However, root exudates explained 77% of the variability in N transfer and crop yields with N fertilizer application. Conclusions: Our findings highlighted that N transfer is reliant more on arbuscular mycorrhizal fungi than root exudates in N-deficient soil, whereas root exudates play a more important role in N-fertilized soil. [ABSTRACT FROM AUTHOR]

[Display omitted] • Vegetation structure changes the process of rainfall redistribution. • Upper soil nitrogen increased, lower soil increased first then decreased. • Rainfall redistribution affects nitrogen components and distribution pattern. • Litter interception affects upper soil nitrogen. • Moisture entering the soil affects lower soil nitrogen. The effects of vegetation restoration on soil moisture dynamics and nutrient content have been widely studied; however, the knowledge on variation in rainfall redistribution and soil nitrogen component characteristics remain limited, particularly with respect to their relationship in restored ecosystems. Therefore, the characteristics of plant community structure, rainfall redistribution, and soil nitrogen components from farmland and Robinia pseudoacacia (RP) plantations of four restoration ages (12, 20, 30, and 45 a) were investigated and measured in the Wuliwan watershed in the Loess Plateau, China. The results showed that changes in plant community structure affected the rainfall redistribution processes. The throughfall and moisture entering the soil (MES) had the largest proportions (79.50 % and 60.25 %) in the initial and second distributions of atmospheric rainfall, respectively. With the increase in restoration age, the content of soil total nitrogen (STN), soil nitrate nitrogen (SNN), soil soluble total nitrogen (SSTN), soil soluble organic nitrogen (SSON), and soil soluble inorganic nitrogen (SSIN) all increased with restoration age in the upper soil (0–40 cm), fluctuated in the middle soil (40–100 cm), and increased and then decreased in the deeper soil (100–200 cm). In addition, the vegetation restoration process can indirectly affect soil nitrogen content and distribution patterns by affecting the rainfall redistribution process. In the upper soil, litter interception (LI) had a significant effect on STN by affecting SSIN and SSON. In the middle soil, both LI and MES had significant effects on STN through SSIN and SSON, respectively. In the deeper soil, LI had no significant effect on any nitrogen component, whereas MES had a significant effect on STN by affecting SSIN. Overall, this study indicates that RP plantation restoration has the potential to transform rainfall redistribution and soil nitrogen distribution, providing an important reference for the reciprocal feedback relationship between water and nitrogen. [ABSTRACT FROM AUTHOR]

N2-fixing species play a crucial role in mixed-plantations as they improve stand productivity. To quantify the N transfer from N2-fixing species to Eucalyptus (Eucalyptus urophylla × E. grandis) in N2-fixing species/Eucalyptus plantations, we established a pot experiment and confirmed the occurrence of this process under natural conditions. The 15N was traced in labeled species as well as in neighboring tree species after labeling, and the growth was evaluated in short-term natural trials. Our results showed that a bidirectional N transfer occurred. The amount of net N transfer was 21.8–127.0 mg N plant−1, which was equal to 1.5–21.2% of the total nitrogen (TN) that accumulated in Eucalyptus plants under pot conditions, was transferred from Dalbergia odorifera to Eucalyptus. The amount of N transferred significantly decreased with the increasing N application rate but increased with time after labeling. Compared with the results for the Eucalyptus monocrop, the soil N concentration (including NO3−-N and NH4+-N) greatly improved when D. odorifera was introduced together with Eucalyptus under both field and pot conditions. Furthermore, the results under field conditions were consistent with the results of the pot experiment. The dry matter (DM) yield (14.5–16.4%) and the N content (5.1–9.6%) in Eucalyptus increased when mixed together with D. odorifera, but the N content in and DM yield of D. odorifera slightly decreased. It is concluded that the N transfer between Eucalyptus and D. odorifera is a much more important dynamic process than previously recognized, and Eucalyptus and legume intercropping is a successful management practice because N transfer provides a significant amount of N required for Eucalyptus productivity.

The formation of a common mycorrhizal network (CMN) between roots of different plant species enables nutrient transfers from one plant to another and their coexistence. However, almost all studies on nutrient transfers between CMN-connected plants have separately, but not simultaneously, been demonstrated under the same experimentation. Both conspecific and heterospecific seedlings of Cinnamomum camphora, Bidens pilosa, and Broussonetia papyrifera native to a karst habitat in southwest China were concurrently grown in a growth microcosm that had seven hollowed compartments (six around one in the center) being covered by 35.0-μm and/or 0.45-μm nylon mesh. The Ci. camphora in the central compartment was supplied with or without Glomus etunicatum and 15N to track N transfers between CMN-connected conspecific and heterospecific seedlings. The results showed as follows: significant greater nitrogen accumulations, biomass productions, 15N content, % Ntransfer, and the Ntransfer amount between receiver plant species ranked as Br. papyrifera≈Bi. pilosa > Ci. camphora under both M+ and M−, and as under M+ than under M− for Ci. camphora but not for both Bi. Pilosa and Br. papyrifera; the CMN transferred more nitrogen (15N content, % Ntransfer, and Ntransfer amount) from the donor Ci. camphora to the heterospecific Br. papyrifera and Bi. pilosa, with a lower percentage of nitrogen derived from transfer (%NDFT). These findings suggest that the CMN may potentially regulate the nitrogen transfer from a donor plant to individual heterospecific receiver plants, where the ratio of nitrogen derived from transfer depends on the biomass strength of the individual plants. [ABSTRACT FROM AUTHOR]

The composition of MSW is complex, but nitrogen in MSW mainly exists in kitchen waste, fabric and rubber. The emission of nitrogen oxides from municipal solid waste incineration and the environmental problems caused by incineration can’t be ignored. Further study on the formation and mechanism of NOx in MSW incineration process, especially the precipitation and transformation of fuel-N in the pyrolysis process of MSW, is of positive significance for further reducing the emission of NOx in incineration process and guides the development of low-NOx combustion technology and NOx emission control technology. It is generally believed that the main precursors of NOx are NH3, HCN and HNCO. Studying the generation rules of NH3, HCN and HNCO is an important segment in studying the law of NOx formation. There are two main ways to study the law of NH3, HCN and HNCO produced by biomass pyrolysis: Studying biomass itself and related model compounds. Many researchers had studied the formation of NOx precursors in the pyrolysis of protein/amino acid model compounds. Up to now, there has been no report on the precipitation of NOx precursors in the pyrolysis of typical components of MSW. The typical components of three types of MSW with high nitrogen content were selected; the pyrolysis property and NOx precursors’ release property of different kinds of typical constituents were studied. The results indicate that the pyrolysis of cloth and rubber show mono peak, but that of the kitchen waste shows two peaks and the pyrolysis temperature appears to be lower for kitchen waste. The main pyrolysis temperature ranges of fabric, rubber and orange peel were 400-500, 350-500 and 150-400 ℃, respectively. The higher the heating rate, the higher the peak value of DTG curve is. The peak of DTG curve moves to the high temperature zone, the wider the peak width of DTG curve, and the temperature range corresponding to the weight loss increases. NH3 is the main NOx precursor for cloth and rubber, and the kitchen waste principally produces HCN and NH3. In conclusion, for different constituents, the selectivities for HCN, NH3 and HNCO are different. With the increase of heating rate, the peak of NOx precursors’ release rate increases and the peak moves towards high temperature zone. The decrease of heating rate increases the degradation of the tar-N at high temperature which produces HCN, NH3 and HNCO. The combination of these impacts leads to different results of the NOx precursors’ release when heating rate changes. [ABSTRACT FROM AUTHOR]

A 6-year laboratory study was conducted to explore the performance of the vermifilter (VF) on reducing sewage sludge. Sewage sludge was found to be reduced significantly in the VF and exhibited a better performance of sludge reduction as compared with the conventional biofilter (BF), which could be traced through the nitrogen-rich organic matter. The nitrogen stable isotope technology was applied to study the matter flow of sewage sludge in the VF process and the influence of earthworms Eisenia fetida on sewage sludge reduction. Results showed that (1) the protein material could be consumed more than the polysaccharide and lipid materials, respectively, in the VF; (2) the presence of earthworms could enhance the consumption capacity of the VF on the protein-rich material of the sewage sludge; (3) earthworms played a leading role on the nitrogen lifting of the sewage sludge, leading to the performance difference of the effluent sludge or biofilm sludge between the VF and BF; (4) in the VF, nitrogen-isotope accumulation in either biofilms or earthworms happened more significantly in the lower layer than in the upper one, while nitrogen transfer of sewage sludge happened more significantly in the upper layer than in the lower one; (5) earthworms improved the feeding environment of organisms (microorganisms in biofilms, moth fly larvae, Limacidaes, and Lymnaeidaes); (6) biofilms, Limacidaes, and moth fly larvae performed better than leeches, Lymnaeidaes, and moth fly adults at nitrogen transfer of sewage sludge. [ABSTRACT FROM AUTHOR]

Drought is a limiting factor for crop production, especially in arid and semi-arid climates. In this study, Sorghum bicolor plants were inoculated, or not, with Rhizophagus irregularis, an arbuscular mycorrhizal (AM) strain typical for temperate climates, or Rhizophagus arabicus, a strain endemic to hyper-arid ecosystems. Plants were grown under well-watered or drought conditions in compartmented microcosms. Transpiration rates, plant growth, and nutrient uptake (using 15N as a tracer) were determined to assess the impact of drought stress on sorghum plants in AM symbiosis. Although AM colonization did not affect the bulk biomass of host plants, R. arabicus improved their transpiration efficiency and drought tolerance more than R. irregularis. Moreover, R. arabicus was able to extract more 15N from the soil under both water regimes, and AM-driven enhancement of the nitrogen and phosphorus content of sorghum, especially when water was limiting, was greater for R. arabicus-inoculated plants than for R. irregularis-inoculated plants. Our work demonstrates close links between AM hyphal phosphorus and nitrogen transport and uptake by AM plants for both AM fungal species. It also underscores that, under the drought stress conditions we applied, R. arabicus transfers significantly more nitrogen to sorghum than R. irregularis. [ABSTRACT FROM AUTHOR]

The degradation of tropical pastures sown with introduced grasses (e.g., Urochloa spp.) has dramatic environmental and economic consequences in Latin America. Nitrogen (N) limitation to plant growth contributes to pasture degradation. The introduction of legumes in association with grasses has been proposed as a strategy to improve N supply via symbiotic N2 fixation, but the fixed N input and N benefits for associated grasses have hardly been determined in farmers’ pastures. We have carried out on-farm research in ten paired plots of grass-alone (GA) vs. grass-legume (GL) pastures. Measurements included soil properties, pasture productivity, and sources of plant N uptake using 15N isotope natural abundance methods. The integration of legumes increased pasture biomass production by about 74%, while N uptake was improved by two-fold. The legumes derived about 80% of their N via symbiotic N2 fixation. The isotopic signature of N of grasses in GA vs. GL pastures suggested that sources of grass N are affected by sward composition. Low values of δ15N found in some grasses in GA pastures indicate that they depend, to some extent, on N from non-symbiotic N2 fixation, while δ15N signatures of grasses in GL pastures pointed to N transfer to grass from the associated legume. The role of different soil–plant processes such as biological nitrification inhibition (BNI), non-symbiotic N2 fixation by GA pastures and legume–N transfer to grasses in GL pastures need to be further studied to provide a more comprehensive understanding of N sources supporting the growth of grasses in tropical pastures.

Background and aims: Cover crops can potentially increase nitrogen (N) retention in agroecosystems. However, only a small fraction of the N released from cover crop residues may be transferred to the grain crop, and N losses to the surrounding environment can occur following termination. We applied 15N tracer in fall in two years to plots of a cover crop field experiment to assess the cover crop effect on N retention and to quantify N transfer from cover crops to the subsequent corn crop.By swapping 15N-labelled and non-labeled cover crop shoots reciprocally between paired plots, 15N from cover crop shoots and the belowground pool (soil and cover crop roots) were tracked separately. Both cover crop monocultures (oats or red clover) and mixtures (3-way or 10-way mixtures) were compared, and for winter-hardy species, we examined both fall and spring termination.At termination, cover crops increased 15N retention by 2–3 times relative to the no cover crop control (20–60% of the added 15N), with the majority retained belowground. At corn harvest, 25–50% of 15N was recovered in soil, and less than 10% in corn. 15N recovery for cover crop treatments was up to 25% higher than that of the no cover crop control, and spring termination of clover resulted in the greatest belowground 15N retention. There were no significant differences in corn 15N recovery between cover crop monocultures and mixtures.Our results demonstrate the effectiveness of cover crops in increasing N retention in the belowground N pool.Methods: Cover crops can potentially increase nitrogen (N) retention in agroecosystems. However, only a small fraction of the N released from cover crop residues may be transferred to the grain crop, and N losses to the surrounding environment can occur following termination. We applied 15N tracer in fall in two years to plots of a cover crop field experiment to assess the cover crop effect on N retention and to quantify N transfer from cover crops to the subsequent corn crop.By swapping 15N-labelled and non-labeled cover crop shoots reciprocally between paired plots, 15N from cover crop shoots and the belowground pool (soil and cover crop roots) were tracked separately. Both cover crop monocultures (oats or red clover) and mixtures (3-way or 10-way mixtures) were compared, and for winter-hardy species, we examined both fall and spring termination.At termination, cover crops increased 15N retention by 2–3 times relative to the no cover crop control (20–60% of the added 15N), with the majority retained belowground. At corn harvest, 25–50% of 15N was recovered in soil, and less than 10% in corn. 15N recovery for cover crop treatments was up to 25% higher than that of the no cover crop control, and spring termination of clover resulted in the greatest belowground 15N retention. There were no significant differences in corn 15N recovery between cover crop monocultures and mixtures.Our results demonstrate the effectiveness of cover crops in increasing N retention in the belowground N pool.Results: Cover crops can potentially increase nitrogen (N) retention in agroecosystems. However, only a small fraction of the N released from cover crop residues may be transferred to the grain crop, and N losses to the surrounding environment can occur following termination. We applied 15N tracer in fall in two years to plots of a cover crop field experiment to assess the cover crop effect on N retention and to quantify N transfer from cover crops to the subsequent corn crop.By swapping 15N-labelled and non-labeled cover crop shoots reciprocally between paired plots, 15N from cover crop shoots and the belowground pool (soil and cover crop roots) were tracked separately. Both cover crop monocultures (oats or red clover) and mixtures (3-way or 10-way mixtures) were compared, and for winter-hardy species, we examined both fall and spring termination.At termination, cover crops increased 15N retention by 2–3 times relative to the no cover crop control (20–60% of the added 15N), with the majority retained belowground. At corn harvest, 25–50% of 15N was recovered in soil, and less than 10% in corn. 15N recovery for cover crop treatments was up to 25% higher than that of the no cover crop control, and spring termination of clover resulted in the greatest belowground 15N retention. There were no significant differences in corn 15N recovery between cover crop monocultures and mixtures.Our results demonstrate the effectiveness of cover crops in increasing N retention in the belowground N pool.Conclusion: Cover crops can potentially increase nitrogen (N) retention in agroecosystems. However, only a small fraction of the N released from cover crop residues may be transferred to the grain crop, and N losses to the surrounding environment can occur following termination. We applied 15N tracer in fall in two years to plots of a cover crop field experiment to assess the cover crop effect on N retention and to quantify N transfer from cover crops to the subsequent corn crop.By swapping 15N-labelled and non-labeled cover crop shoots reciprocally between paired plots, 15N from cover crop shoots and the belowground pool (soil and cover crop roots) were tracked separately. Both cover crop monocultures (oats or red clover) and mixtures (3-way or 10-way mixtures) were compared, and for winter-hardy species, we examined both fall and spring termination.At termination, cover crops increased 15N retention by 2–3 times relative to the no cover crop control (20–60% of the added 15N), with the majority retained belowground. At corn harvest, 25–50% of 15N was recovered in soil, and less than 10% in corn. 15N recovery for cover crop treatments was up to 25% higher than that of the no cover crop control, and spring termination of clover resulted in the greatest belowground 15N retention. There were no significant differences in corn 15N recovery between cover crop monocultures and mixtures.Our results demonstrate the effectiveness of cover crops in increasing N retention in the belowground N pool. [ABSTRACT FROM AUTHOR]

The influence of soil fumigation on microorganisms involved in transforming nitrogen remains little understood, despite the use of fumigants for many decades to control soil-borne pathogens and plant-parasitic nematodes. We used real-time PCR (quantitative polymerase chain reaction) and 16S rRNA gene amplicon sequencing techniques to monitor changes in the diversity and community structure of microorganisms associated with nitrogen transfer after the soil was fumigated with dazomet (DZ). We also examined nitrous oxide (N2O) emissions from these microorganisms present in fumigated fluvo-aquic soil and lateritic red soil. Fumigation with DZ significantly reduced the abundance of 16S rRNA and nitrogen cycling functional genes (nifH, AOA amoA, AOB amoA, nxrB, narG, napA, nirK, nirS, cnorB, qnorB, and nosZ). At the same time, N2O production rates increased between 9.9 and 30 times after fumigation. N2O emissions were significantly correlated with NH4+, dissolved amino acids and microbial biomass nitrogen, but uncorrelated with functional gene abundance. Diversity indices showed that DZ temporarily stimulated bacterial diversity as well as caused a significant change in bacterial community composition. For example, DZ significantly decreased populations of N2-fixing bacteria Mesorhizobium and Paenibacillus, nitrifiers Nitrosomonas, and the denitrifiers Bacillus, Pseudomonas, and Paracoccus. The soil microbial community had the ability to recover to similar population levels recorded in unfumigated soils when the inhibitory effects of DZ fumigation were no longer evident. The microbial recovery rate, however, depended on the physicochemical properties of the soil. These results provided useful information for environmental safety assessments of DZ in China, for improving our understanding of the N-cycling pathways in fumigated soils, and for determining the potential responses of different N-cycling groups after fumigation.

The influence of soil fumigation on microorganisms involved in transforming nitrogen remains little understood, despite the use of fumigants for many decades to control soil-borne pathogens and plant-parasitic nematodes. We used real-time PCR (quantitative polymerase chain reaction) and 16S rRNA gene amplicon sequencing techniques to monitor changes in the diversity and community structure of microorganisms associated with nitrogen transfer after the soil was fumigated with dazomet (DZ). We also examined nitrous oxide (N2O) emissions from these microorganisms present in fumigated fluvo-aquic soil and lateritic red soil. Fumigation with DZ significantly reduced the abundance of 16S rRNA and nitrogen cycling functional genes (nifH , AOA amoA , AOB amoA, nxrB, narG, napA, nirK, nirS, cnorB, qnorB , and nosZ). At the same time, N2O production rates increased between 9.9 and 30 times after fumigation. N2O emissions were significantly correlated with NH 4 + , dissolved amino acids and microbial biomass nitrogen, but uncorrelated with functional gene abundance. Diversity indices showed that DZ temporarily stimulated bacterial diversity as well as caused a significant change in bacterial community composition. For example, DZ significantly decreased populations of N2-fixing bacteria Mesorhizobium and Paenibacillus , nitrifiers Nitrosomonas , and the denitrifiers Bacillus, Pseudomonas , and Paracoccus. The soil microbial community had the ability to recover to similar population levels recorded in unfumigated soils when the inhibitory effects of DZ fumigation were no longer evident. The microbial recovery rate, however, depended on the physicochemical properties of the soil. These results provided useful information for environmental safety assessments of DZ in China, for improving our understanding of the N-cycling pathways in fumigated soils, and for determining the potential responses of different N-cycling groups after fumigation. [ABSTRACT FROM AUTHOR]