Nitrogen Storage Research Articles

Impacts of Soil Aggregation on Nitrogen Storage and Supply in Biomass Incorporated Sandy-Loam Acidic Soil

Impacts of Soil Aggregation on Nitrogen Storage and Supply in Biomass Incorporated Sandy-Loam Acidic Soil

Surface soil sampling underestimates soil carbon and nitrogen storage of long-term cover cropping

Cover cropping is a promising management practice for soil health and climate change mitigation by improving soil organic carbon (SOC) and total nitrogen (TN) stocks. However, limited studies focused on deeper soil layers (>30 cm depth) where soil C is more stable than that in surface soil (≤30 cm depth). Here, deep soil sampling was conducted in a 15-year cover cropping experiment, in a horticulture-grain system on sandy loam soil. The SOC and TN stocks were expressed on an equivalent soil mass basis using a cubic spline model. Overall, long-term cover cropping had significantly greater SOC and TN stocks by 22 % (95 %CI: 5–43 %) and 26 % (95 %CI: 6–49 %), respectively in the 0–120 cm depth, compared to no cover cropping. Additionally, the mean SOC and TN sequestration rate (0–30 cm depth) was 0.53 Mg C ha−1 yr−1 and 0.06 Mg N ha−1 yr−1, respectively. However, if only 0–15 cm depth was evaluated, long-term cover cropping did not significantly affect SOC and TN stocks. These results indicated that shallow sampling (<15 cm depth) may not provide comprehensive information on the effect of long-term cover cropping on soil C and N storage. To better understand the mechanism of bulk soil C and N storage, we investigated their distribution between particulate and mineral-associated organic matter pools (POM and MAOM). We found POM pool was the main store of bulk SOC and TN stocks in surface soils while it was the MAOM pool in deeper soil layers, without soil texture change with soil depth. These findings indicated that soil C and N sources for bulk SOC and TN accrual differed in surface and deeper soils. Our study demonstrated that long-term cover cropping can facilitate SOC accumulation in the soil below 15 cm deep, which calls into question carbon capture protocols that focus on shallow soil depths.

Investigation of heat leakage calculations and experiments for a wide-mouth liquid nitrogen tank

ABSTRACT With the continuous development of biomedicine, the long-term low-temperature storage of biological samples has become essential. In order to meet the demand for long-term storage of liquid nitrogen to keep samples safe, a study on the evaporated gas recycling storage of liquid nitrogen tanks will be carried out. This research utilizes new approach to accurately calculate the heat leakage of the liquid nitrogen tank. The experimental results show that the theoretical heat leakage is 6.16 W, and the actual heat leakage is 7.07 W. By incorporating the insulating plug, the actual heat leakage was reduced by 61.2%, decreasing to 2.74 W, and the calculated heat leakage is 2.47 W. The error margin in both cases was approximately 10%. Furthermore, in contrast to existing investigations, this experiment with the 8W@77K pulse tube cryocooler for recovering nitrogen is conducted under environmental pressure rather than overpressure, and it also takes into account the sensible heat issues caused by ambient pressure. The ratio of 1.81 W of sensible heat to 2.74 W of latent heat is 2:3, indicating that under ambient pressure conditions, the impact of sensible heat cannot be ignored. The key improvement methods are given to improve the success rate of the experiment. The research results provide a useful reference for the re-cycling and storage of liquid nitrogen.

CRISPR/Cas9 editing of two adenine phosphoribosyl transferase coding genes reveals the functional specialization of adenine salvage proteins in common bean.

Adenine metabolism is important for common bean (Phaseolus vulgaris L) productivity since this legume uses ureides derived from the oxidation of purine nucleotides, as their primary nitrogen storage molecules. Purine nucleotides are produced from de novo synthesis or through salvage pathways. Adenine phosphoribosyl transferase (APRT) is the enzyme dedicated to adenine nucleobase salvage for nucleotide synthesis, but it also acts on the inactivation of cytokinin bases. In common bean, the APRT enzyme is encoded by four genes. Gene expression analysis, biochemical properties and subcellular location suggest functional differences among the common bean APRT isoforms. CRISPR/Cas9 targeted downregulation of two of the four PvAPRTs followed by metabolomics and physiological analyses of targeted hairy roots reveals that, although the two proteins have redundant functions, PvAPRT1 mostly participates in the salvage of adenine, whereas PvAPRT5 is the predominant form in the regulation of cytokinin homeostasis and stress responses with a high impact in root and nodule growth.

Arabidopsis thaliana argininosuccinate lyase structure uncovers the role of serine as the catalytic base

Arginine is an important amino acid in plants, as it not only plays a structural role and serves as nitrogen storage but is also a precursor for various molecules, including polyamines and proline. Arginine is produced by argininosuccinate lyase (ASL) which catalyzes the cleavage of argininosuccinate to arginine and fumarate. ASL belongs to the fumarate lyase family and while many members of this family were well-characterized, little is known about plant ASLs. Here we present the first crystal structures of ASL from the model plant, Arabidopsis thaliana (AtASL). One of the structures represents the unliganded form of the AtASL homotetramer. The other structure, obtained from a crystal soaked in argininosuccinate, accommodates the substrate or the reaction products in one of four active sites of the AtASL tetramer. Each active site is located at the interface of three neighboring protomers. The AtASL structure with ligands allowed us to analyze the enzyme-substrate and the enzyme-product interactions in detail. Furthermore, based on our analyses, we describe residues of AtASL crucial for catalysis. The structure of AtASL gives the rationale for the open-to-close transition of the GSS mobile loop and indicates the importance of serine 333 from this loop for the enzymatic action of the enzyme. Finally, we supplemented the structural data with the identification of sequence motifs characteristic for ASLs.

Integrated physiological response by four species of Rhodophyta to submarine groundwater discharge reveals complex patterns among closely-related species

Algal physiological ecology on submarine groundwater discharge (SGD) influenced reefs is likely shaped by intermittent, tidally-driven estuarine conditions that occur with SGD fluxes of fresh-to-brackish groundwater from the subterranean estuary to reef ecosystems. SGD is a common inconspicuous feature worldwide on reefs of basaltic high islands and continental margins. Yet, SGD-driven dynamics of algal physiology are not well understood. To understand how invasive species have physiologically outcompeted native species on many SGD-influenced reefs, physiology in tissue water potential (TWP) regulation, photosynthesis, nitrogen storage, and cellular anatomy were measured across a gradient of SGD-influence, for four Rhodophyte species. Compared with non-SGD conditions, SGD was associated with higher TWP, larger medulla cells with thinner walls, and thinner cortical cell walls for two invasives, Gracilaria salicornia and Acanthophora spicifera, higher photosynthetic rates in G. salicornia, greater nitrogen concentration for A. spicifera and G. salicornia, and increased δ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\delta$$\\end{document}15N ratios for A. spicifera, G. salicornia, and native Laurencia dendroidea. Distinct physiological strategies were measured for the two invasive species across the gradient of SGD-influence, and for L. dendroidea and Gracilaria perplexa offshore. This study illuminates species-specific physiological response, and how introduced opportunistic species may outcompete native species under conditions of SGD.

Characteristics and Drivers of Soil Carbon, Nitrogen, and Phosphorus Ecological Stoichiometry at the Heavy Degradation Stage of the Alpine Meadow

An in-depth understanding of the soil nutrient status and balance relationship can help the effective recovery and management of alpine degraded meadows. In order to study the balance relationship among soil carbon, nitrogen, and phosphorus nutrients during the heavy degradation stage of meadows, field sampling and investigation, indoor analysis, and mathematical statistics were used to explore the characteristics and driving factors of changes in soil carbon, nitrogen, and phosphorus content, storage, and ecological stoichiometry during the heavy degradation stage of alpine meadows in the Sanjiangyuan region. The results showed that in the heavy degradation stage, miscellaneous grass plants occupied absolute dominance, soil C∶N∶P was approximately 32.83∶3.87∶0.67, and there was certain nitrogen limitation. The coefficients of variation of soil carbon, nitrogen, and phosphorus content were in the following order： organic carbon （1.09） &gt; total nitrogen （0.63） &gt; total phosphorus （0.29）. The organic carbon content and the carbon and nitrogen ratio showed a significant linear decreasing trend with the increase in the grassland degradation index （GDI）, while the total phosphorus content and organic carbon storage showed a significant non-linear change, in which the total phosphorus content showed a significant gentle U-shaped distribution, and the organic carbon storage decreased more gently at the beginning of the heavy degradation stage and then decreased sharply when the GDI was 57.9. The results of Mantel correlation analysis showed that the soil carbon to nitrogen ratio, carbon to phosphorus ratio, and nitrogen to phosphorus ratio showed significant correlation with organic carbon content and storage and total nitrogen storage. The results of structural equation modeling indicated that soil water content had direct effects as well as indirect through vegetation factors, soil carbon, nitrogen, and phosphorus ecological stoichiometry ratios, and soil water content and vegetation factors （height, cover, and biomass） were key environmental factors affecting soil ecological stoichiometry. The research results can provide scientific basis and practical guidance for the restoration of heavily degraded grassland in alpine meadows.

Optimized irrigation practices with fertilizer utilization strategies to improve photo-fluorescence efficiency, vascular bundles and maize production in semi-arid regions

The mechanism of irrigation models combined with fertilizer utilization strategies under the biodegradable film mulching could greatly promote crop photosynthesis, vascular bundles structure; resource utilization and maize production are unclear in semi-arid areas. Unfortunately, this mechanism provides a scientific basis for improving irrigation and fertilizer utilization. A field study was carried out during 2021–2022 years. Seven treatments were established: two nitrogen levels: low-N (150 kg N ha−1) and high-N (300 kg N ha−1) combined with three different irrigation models: drip irrigation (DI), ridge irrigation (RI) and border irrigation (BI) under the biodegradable film mulching with (CK) treatment have no irrigation, fertilizer and mulching. Our results revealed that DIH treatment considerably increased soil water storage, enhanced photosynthesis rate (Pn) of maize by mainly to facilitate stomatal opening compared to the rest of all treatments. In addition, it also enhances the differentiation of the vascular bundle system and maintains its post silk function under better environmental conditions, greatly improving nitrogen storage in soil and plants, and enhancing maize productivity. DIH and RIH treatments significantly increased net photosynthesis rate (Pn), stomatal conductance (Gs), transpiration rate (Tr), maximum quantum yield of PSII photochemistry (Fv/Fm), and effective quantum yield of PSII photochemistry (ΦPSII), photochemical quenching (qP), non-photochemical quenching (NPQ), and yield were observed, but evapotranspiration (ET) decreased at different growth stages. The results showed that DIH treatment was an effective tillage strategy, which increased biomass yield by 32.6 %, grain yield by 46.0 %, water use efficiency (WUE) by 46.2 %, and nitrogen use efficiency (NUE) by 86.4 % compared to other treatments. Given these results, thus we recommend the drip irrigation combined with a high-N level under a biodegradable film mulching increase photo-fluorescence efficiency, maize production and resource utilization efficiency in semi-arid regions.

Assessing the of carbon and nitrogen storage potential in Khaya spp. stands in Southeastern Brazil

The objective of this study was to assess the dynamics of carbon and nitrogen in soil, forest floor, and aboveground biomass in 9.5 years-old planted stands of three Khaya spp. (K. grandifoliola, K. ivorensis, and K. senegalensis). The study was conducted at the Reserva Natural Vale (RNV), Brazil. The stands were planted at 5 × 5 m spacing, distributed over rectangular plots of 1250 m2. Soil bulk density at the evaluated depths, as well nitrogen contents, were similar among the species. However, K. ivorensis exhibited higher carbon concentration in the soil. In general, there were no differences in carbon and nitrogen content in soil between the three species; however, the values obtained are comparable to those of the reference area–Native Forest. The carbon stocks in the aboveground biomass for K. grandifoliola, K. ivorensis, and K. senegalensis averaged 37.97, 33.66 and 33.86 Mg ha−1, respectively (p ≤ 0.05). These values collectively represent about 28% of the total carbon stocks across the observed compartments. Notably, the nitrogen content within the aboveground biomass did not differ among these species. Therefore, African mahogany possesses a robust potential to store both carbon and nitrogen.

Montane evergreen forest deforestation for banana plantations decreased soil organic carbon and total nitrogen stores to alarming levels

Forest conversion to agricultural land has been shown to deplete soil organic carbon (SOC) and soil total nitrogen (STN) stocks. However, research on how soil properties respond to forest conversion to shifting cultivation has produced conflicting results. The conflicting findings suggest that the agricultural system may influence the response of SOC and STN to forest conversion to agriculture, depending on the presence of vegetative cover throughout the year. Due to the unique characteristics of montane evergreen forests (MEF) and banana plantations (BP), SOC and STN response to MEF conversion to BP may differ from existing models. Nevertheless, research on how soil properties are affected by MEF conversion to BP is scarce globally. In order to fill this research gap, the goal of this study was to evaluate how much deforestation for BP affects SOC, STN, and soil quality by analysing these soil parameters in MEF and BP fields down to 1-m depth, using standard profile-based procedures. Contrary to the specified hypothesis that SOC and STN losses would be restricted to the upper 20-cm soil layer, SOC losses were extended to the 40-cm depth layer and STN losses to the 60-cm depth layer. The soils lost 18.56 Mg ha – 1 (37%) of SOC from the upper 20 cm and 33.15 Mg ha – 1 (37%) from the upper 40 cm, following MEF conversion to BP. In terms of STN, the upper 20, 40, and 60 cm lost 2.98 (43%), 6.62 (47%), and 8.30 Mg ha – 1 (44%), respectively. Following MEF conversion to BP, the SOC stratification ratio decreased by 49%, implying a decline in soil quality. Massive exportation of nutrients, reduced C inputs due to complete removal of the arboreal component and crop residues, the erodibility of the soils on the study area’s steep hillslopes, and the potential for banana plantations to increase throughfall kinetic energy, and splash erosion through canopy dripping are thought to be the leading causes of SOC and STN losses. More research is needed to identify the extent to which each cause influences SOC and STN losses.

Cover cropping enhanced soil aggregation and associated carbon and nitrogen storage in semi-arid silage cropping systems

Wind and water erosion in arid and semi-arid regions significantly degraded soil, reduced soil organic carbon (SOC) storage, and exacerbated the impact of climate change on agricultural productivity. Cover cropping is one of the approaches to improve soil health and reduce climate change impacts, yet its impacts on soil aggregation and associated SOC and nitrogen (N) storage in water-limited environments are poorly understood. This study aimed to evaluate soil aggregate dynamics and aggregate-associated SOC and soil total N in irrigated silage sorghum [Sorghum bicolor L. (Moench)] − corn (Zea mays L.) rotations with various cover crop mixtures: grasses + brassicas + legumes (GBL), grasses + brassicas (GB), grasses + legumes (GL), and no cover crops (NCC). Results showed in the second year of the study that, at 0–0.1 m depth, mean weight diameter and geometric mean diameter of dry aggregates were 22–23 % and 6 % greater, respectively, with cover crops than NCC. At the same depth, cover crop treatments had 15–17 %, 15–16 %, and 13 % greater SOC in 0.25–2, 0.053–0.25, and < 0.053 mm aggregate classes, respectively, compared to NCC. Similarly, at 0–0.1 m depth, N in < 0.053 mm fraction was 8–10 % greater with cover crops than without. In the fourth year of the study, water-stable aggregates (WSA) percent did not differ among treatments, but WSA-associated SOC was 31–37 % and 12–16 % greater with cover crops at 0–0.1 and 0.1–0.2 m depths, respectively, than without. The WSA-associated N at 0–0.1 m was 21–33 % greater with cover crops than without. Despite the inconsistencies in soil aggregate stability results, cover crop-integrated silage systems showed greater SOC and N within aggregate classes and water stable aggregates. This insight is crucial for advancing sustainability in silage production systems, particularly in the context of increasing climate change and variability in erosion-prone soils of arid and semi-arid regions.

Vermicompost and flue gas desulfurization gypsum addition to saline-alkali soil decreases nitrogen losses and enhances nitrogen storage capacity by lowering sodium concentration and alkalinity

Saline-alkali soils have poor N storage capacity, high N loss and inadequate nutrient supply potential, which are the main limiting factors for crop yields. Vermicompost can increase organic nutrient content, improve soil structure, and enhance microbial activity and function, and the Ca2+ in flue gas desulfurization (FGD) gypsum can replace Na+ and neutralize alkalinity in saline-alkali soils though chemical improvement. This study aimed to determine if vermicompost and FGD gypsum addition could improve the N storage capacity through decreasing NH3 volatilization and 15N/NO3− leaching from saline-alkali soils. The results indicate that the combined application of vermicompost and FGD gypsum led to the displacement and leaching Na+ in the upper soil layer (0–10 cm), as well as the neutralization of HCO3− by the reaction with Ca2+. This treatment also improved soil organic matter content and macroaggregate structure. Also, these amendments significantly increased the abundance of nifH and amoA genes, while concurrently decreasing the abundance of nirK gene. The structural improvements and the lowering of Na + concentration in and alkalinity decreased cumulative NH3 volatilization, and leaching of 15N and NO3− to the deep soil layer (20–30 cm). FGD gypsum increased the 15N stocks and inorganic N stocks of saline-alkali soil, whereas vermicompost not only increased the 15N and inorganic N stocks, but also increased the total N stocks, the combination of vermicompost and FGD gypsum can not only increase the available N storage capacity, but also enhance the potential for N supply. Therefore, vermicompost and FGD gypsum decrease N loss and increase N storage capacity through structural improvement, and lowering of Na+ concentration and alkalinity, which is crucial for improving the productivity of saline-alkali soil.

Biomass Carbon and Nitrogen Content of Hardwoods in Novi Pazar (Serbia)

To investigate and compare hardwood species based on their carbon (C) and nitrogen (N) storage capacity, a study of the C and N content of the bark and wood of nine common hardwood broadleaves in Novi Pazar, southwestern Serbia, was conducted. Compared with sycamore maple, Norway maple, common ash, common hornbeam, black locust, European beech, Turkey oak, and sessile oak, field maple has the highest C/N ratio in wood (37.05 ± 3.23), representing the best hardwood species for biomass production.

Utilization of Reactive Nitrogen Compounds for Nitrogen Circular Economy.

Nitrogen oxides (NOx) should be purified according to environmental regulations, being restricted increasingly year by year. A wide variety of denitration technologies, such as selective catalytic reduction (SCR) of NOx to nitrogen (N2) and NOx storage reduction (NSR) to N2 by injecting reducing agents like ammonia (NH3), has so far been developed practically. Sophisticated catalytic approaches are perhaps mandatory for the sustainability in energy including complete purification of NOx. As one of the solutions to overcome problems for environment and resource simultaneously, this concept article focuses on the utilization of reactive nitrogen (Nr) compounds, mainly NOx, for encouraging an opening to consider nitrogen circular economy. For the recycling of NOx via NH3, a challenging but rational catalytic technology can be proposed by an alternate switching the inlet gas between NOx containing oxidative gas and H2 containing reductive one without an operation to change the reaction temperature. Considering the reactivity of NOx higher than that of N2, this kind of NOx to NH3 (NTA) process is promising for synthesizing NH3, being valuable not only as fertilizer but also as fuel in near future.

Response of Soil Carbon and Nitrogen Storage to Nitrogen Addition in Alpine Meadow of Qinghai-Tibet Plateau

Response of Soil Carbon and Nitrogen Storage to Nitrogen Addition in Alpine Meadow of Qinghai-Tibet Plateau

Nitrogen availability and its related enzyme activities affect microbial residue nitrogen accumulation during Chinese fir plantation development

Microbial growth, metabolism, and reproductive activities have a significant role in the generation, transformation, and storage of soil nitrogen (N). However, the time-integrated effect of microorganisms on long-term N sequestration in plantation forests remains poorly understood. We investigated the microbial residue N (MRN) and its contribution to soil total N (TN) among the young (8-year), middle (16-year), near-mature (24-year), mature (34-year), and over-mature (106-year) stands of Chinese fir plantation (CFP) in subtropical China. The soil TN content showed a general pattern of increasing with stand age, ranging from 2.61 to 3.42 g kg−1, and was higher in the over-mature and mature stands than in the other three stands (p < 0.001). In addition, soil carbon (C), N, phosphorus (P), and hydrolase stoichiometric ratios indicated that P limitation was widespread during all stages of CFP development. The average ratio of soil fungal residue N (FRN) to bacterial residue N (BRN) was 3.64:1. The MRN content and its contribution to soil TN exhibited a falling and then rising pattern from young to over-mature stands, ranging from 1.24 to 1.70 g kg−1 and 38.8 % to 57.5 %, respectively. Soil N fraction contents and hydrolase activities were higher in the 0–5 cm soil layer than in the 5–30 cm soil layer (p < 0.05). Regression analysis showed that soil MRN content increased with soil N fraction contents, C-N-P stoichiometric ratios, and hydrolase activities (p < 0.001). Redundancy analysis and partial least squares path modeling revealed that soil available N (AN) and N hydrolase were the main factors affecting MRN accumulation. These parameters may partially indicate the dynamics of MRN accumulation. Our study discovered that the long-term development of CFP promotes soil N sequestration, with microbial residues playing a significant role in contributing to N pools.

SMMP: A Deep-Coverage Marine Metaproteome Method for Microbial Community Analysis throughout the Water Column Using 1 L of Seawater.

Marine microbes drive pivotal transformations in planetary-scale elemental cycles and have crucial impacts on global biogeochemical processes. Metaproteomics is a powerful tool for assessing the metabolic diversity and function of marine microbes. However, hundreds of liters of seawater are required for normal metaproteomic analysis due to the sparsity of microbial populations in seawater, which poses a substantial challenge to the widespread application of marine metaproteomics, particularly for deep seawater. Herein, a sensitive marine metaproteomics workflow, named sensitive marine metaproteome analysis (SMMP), was developed by integrating polycarbonate filter-assisted microbial enrichment, solid-phase alkylation-based anti-interference sample preparation, and narrow-bore nanoLC column for trace peptide separation and characterization. The method provided more than 8500 proteins from 1 L of bathypelagic seawater samples, which covered diverse microorganisms and crucial functions, e.g., the detection of key enzymes associated with the Wood-Ljungdahl pathway. Then, we applied SMMP to investigate vertical variations in the metabolic expression patterns of marine microorganisms from the euphotic zone to the bathypelagic zone. Methane oxidation and carbon monoxide (CO) oxidation were active processes, especially in the bathypelagic zone, which provided a remarkable energy supply for the growth and proliferation of heterotrophic microorganisms. In addition, marker protein profiles detected related to ammonia transport, ammonia oxidation, and carbon fixation highlighted that Thaumarchaeota played a critical role in primary production based on the coupled carbon-nitrogen process, contributing to the storage of carbon and nitrogen in the bathypelagic regions. SMMP has low microbial input requirements and yields in-depth metaproteome analysis, making it a prospective approach for comprehensive marine metaproteomic investigations.

Coupling Imports of Dissolved Inorganic Nitrogen and Particulate Organic Matter by Aquaculture Sewage to Zhangjiang Estuary, Southeastern China

Estuary ecosystems serve as crucial connectors between terrestrial and marine environments, thus playing vital roles in maintaining the ecological balance of coastal marine ecosystems. In recent years, the eutrophication in estuaries caused by aquaculture sewage has been revealed, highlighting the necessity to understand its influence on the nutrient conditions and carbon storage of estuaries. In this study, δ15N and δ18O were used to indicate the contribution of aquaculture-derived sewage to dissolved inorganic nitrogen in Zhangjiang Estuary, and δ13C and C:N ratio were used to reveal its effects on the particulate organic matter. The major results are as follows: (1) Aquaculture water contributed 62~86% and 60~100% of the total nitrate and ammonium in Zhangjiang Estuary, respectively, and the drainage periods of the cultured species has a great influence on the content and composition of dissolved inorganic nitrogen. (2) Aquaculture water was also the major source of particulate organic matter (24~33% of the total content) here, most of which may be derived from crab ponds. (3) The imports of nutrients by aquaculture water may potentially regulate particulate organic matter in Zhangjiang Estuary by promoting the growth of phytoplankton and zooplankton. Our study revealed the coupling effects of aquaculture activities on the nitrogen and carbon storage in an estuarine ecosystem. It also indicates that isotopes may be efficient in the monitoring of a coastal environment, which may further aid the management of inshore cultivation.

Managing Residue Return Increases Soil Organic Carbon, Total Nitrogen in the Soil Aggregate, and the Grain Yield of Winter Wheat

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.

Deciphering the impact of nitrogen morphologies distribution on nitrogen and biomass accumulation in tobacco plants.

Nitrogen (N) distribution in plants is intricately linked to key physiological functions, including respiration, photosynthesis, structural development, and nitrogen storage. However, the specific effects of different N morphologies on N accumulation and plant growth are poorly understood. Our research specifically focused on determining how different N morphologies affect N absorption and biomass accumulation. This study elucidated the impact of different application rates (CK: 0 g N/plant; T1: 4 g N/plant; T2: 8 g N/plant) of N fertilizer on N and biomass accumulation in tobacco cultivars Hongda and K326 at different growth stages. Our findings emphasize the critical role of N distribution in various plant parts, including leaves, stems, and roots, in determining the complex mechanisms of N and biomass accumulation in tobacco. We found that in relation to total N, a greater ratio of water-soluble N (N w) in leaves facilitated N accumulation in leaves. In contrast, an increased ratio of SDS (detergent)-insoluble N (N in-SDS) in leaves and non-protein N (N np) in roots hindered this increase. Additionally, our results indicate that a greater proportion of N np in leaves has a negative impact on biomass accumulation in leaves. Furthermore, elevated levels of N in-SDS, N w, and N np in roots, and N np in leaves adversely affected biomass accumulation in tobacco leaves. The Hongda cultivar exhibited greater biomass and N accumulation abilities as compared to K326. Our findings highlight the significant role of distribution of N morphologies on plant growth, as well as N and biomass accumulation in tobacco plants. Understanding N distribution allows farmers to optimize N application, minimizing environmental losses and maximizing yield for specific cultivars. These insights advance sustainable agriculture by promoting efficient resource use and reducing environmental impact.