Residual Nitrogen Research Articles

Innovative strategies for ammonia nitrogen removal in rare earth tailings: An advanced element recycling process using leaching, chemical precipitation and adsorption

Residual ammonium salt in closed rare earth mining sites leads to elevated levels of ammonia nitrogen in the surrounding environment. To mitigate ammonia nitrogen pollution at its source, a cost-effective and environmentally friendly recycling process was proposed. This process involves leaching residual ammonia nitrogen using a magnesium sulfate solution, followed by chemical precipitation for ammonia nitrogen removal. Additionally, nitrogen can be recovered as ammonia gas through the thermal decomposition of precipitates, allowing for further ammonia nitrogen adsorption from the leachate. The residual ammonium salts leaching rate reached 96.38 % with a 0.1 mol/L magnesium sulfate solution at a flow rate of 0.6 mL/min. The chemical precipitation method achieved a maximum nitrogen removal rate of 86.87 %, with an activation energy of 2.6 kJ/mol, indicating a relatively rapid process. At 190 °C, the ammonia nitrogen release rate of precipitates was 82.5 % after 2 h of thermal decomposition. The adsorption process was consistent with pseudo-second-order kinetics models using thermal decomposition products. Overall, the comprehensive removal rate of residual ammonium salts from the closed rare earth mining site was approximately 83.3 % in recycling process, optimizing the utilization of phosphorus, magnesium, and nitrogen and achieving efficient and environmentally friendly nitrogen removal.

Effects of Recommended Fertilizer Application Strategies Based on Yield Goal and Nutrient Requirements on Drip-Irrigated Spring Wheat Yield and Nutrient Uptake

Excessive application of fertilizers in drip-irrigated wheat production can suppress yields, lower nutrient utilization efficiency, and lead to economic and environmental issues such as nitrogen residues in the soil. Based on a recommended fertilizer application (RF) strategy that takes into account target yield and nutrient requirements, this study explores the responses of wheat plant traits, changes in topsoil and subsoil nutrients, fertilizer utilization, and economic benefits under this strategy. From 2022 to 2023, a field experiment was conducted in a typical oasis spring wheat production area at the northern foot of the Tianshan Mountains in Xinjiang. The treatments included no fertilizer control (CK), the farmer’s conventional practice (FP), recommended fertilizer (RF), RF with nitrogen omission (RF-N), phosphorus omission (RF-P), and potassium omission (RF-K). The results showed that compared with FP, the RF reduced 91 kg N ha−1 (30.3%) and 33 kg P2O5 ha−1 (24.8%) in 2022, and 69 kg N ha−1 (23.0%) and 2 kg P2O5 ha−1 (1.5%) in 2023. The effect in 2023 was better; RF also decreased the NO3−1-N residue in the 0–100 cm soil layer by 40.1 kg N ha−1 compared with FP, with no significant difference in wheat grain yield (RF: 5382.9 kg ha−1) or economic benefit (RF: USD 1613.1 ha−1). Furthermore, there were no significant differences between RF and FP in pre-anthesis NP transport or post-anthesis NP accumulation; however, RF significantly increased pre-anthesis potassium transport volume (15.8%) and transport rate (12.5%). RF led to a 16.3% increase in nitrogen utilization efficiency (NUE), while there was no significant difference in phosphorus utilization efficiency (PUE) compared with FP. The fertilizer yield effect for RF was evaluated as N > P > K. Correlation analysis indicated that grain yield was significantly positively correlated with pre-anthesis NPK transport and post-anthesis NP accumulation. It was also positively correlated with organic matter, alkali-hydrolyzed nitrogen, and Olsen-P content in both the topsoil (0–20 cm) and subsoil (20–40 cm), but not with available potassium in the soil. Therefore, conducting soil tests and determining fertilizer recommendations based on the proposed RF method at harvest can reduce fertilizer usage and achieve a balance between the conflicting objectives of environmental protection, increased crop yields, nutrient utilization efficiency, and improved economic benefits in oasis agricultural areas facing excessive fertilizer application.

Effect of Liquid Microbial Consortium on Physio Chemical Properties of Rice Field (Oryza Sativa) in a Vertisol

A study was conducted during kharif 2020 on "Effect of liquid microbial consortium (Azotobacter, Azospirillum, PSB (Pseudomonas mallei, Pseudomonas cepaceae, Penicillium sp.) and KSB) on physio chemical properties and microbial population of rice field (Oryza sativa) in a Vertisol" at the Indira Gandhi Krishi Vishwavidyalaya's Research cum instructional farm in Raipur (C.G.). Experiment included seven treatments viz. control (no fertilizer, no liquid NPK microbial consortia), two independent applications of 75 % RDF (90:45:30) and 100% RDF ((120: 60: 40) N, P2O5, and K2O kg ha-1 and four various combinations of seed and soil application of liquid NPK microbial consortia. Seed coating with NPK consortia @5ml kg-1, with 75% and 100% RDF and Seed coating with NPK consortia @5ml kg-1 + Soil application of NPK consortia @3 L ha-1 at 21 DAS with 75%RDF and 100%RDF. In the experiment, liquid biofertilizer products, such as liquid microbial NPK consortia were used. The population of Azotobacter, Azospirillum, phosphorous solubilizing bacteria (PSB), potassium solubilizing bacteria (KSB) and total bacterial population were significantly influenced by application of consortia as seed treatment @ 5ml kg-1 only and by a combination of seed treatment @ 5ml kg-1 seed + soil application @ 3 L ha-1 at 21 DAT with 75 or 100 % recommended dose of fertilizers and showed statistically significant higher microbial population in comparisons with the treatments of untreated alone applications of 75 or 100 % RDF. The results showed that the soil reaction, (pH) salt concentration (Electrical conductivity) and organic carbon status were not significantly influenced by the different treatments of fertilizer levels and microbial consortia applied. Slight decrease in the soil reaction (pH) and slight increase in the OC status after the harvesting of rice were observed from their initial soil values (before application of treatments). It might be due to the addition of organic matter as plant residues (straw and roots) of rice crop gown in the field. As compared to untreated- control (T1) a slight decrease in pH and increase in organic carbon content due to application of fertilizer and microbial consortia were also recorded. The residual available nitrogen in the soil after the harvesting of rice was not significantly influenced by the fertilizer levels and NPK consortia applied. The initial status of the experimental soil was low for available nitrogen (224 kg ha-1), medium for available phosphorus (24.5 kg ha-1) and high for available potassium (384 kg ha-1). Due to the addition of nitrogen through the fertilizer (90-120 kg ha-1) and less uptake of native nitrogen from the soil, a marginal increase in the residual available N in the soil from the initial level was observed in all treatments except the control (no fertilizer, no consortia). The residual status of available potassium was also not significantly influenced by the applied fertilizer doses and NPK consortia. A marginal decrease in the residual available K status after the harvesting of rice was observed in all treatments. A decrease was found in the control plot. A decrease in the K status (from the initial level) was observed less where a full dose of NPK fertilizers (100%) was applied with the NPK consortia. Ramlakshmi et al. [1], also observed slight reduction in soil pH and increase in organic carbon content in biofertilizer inoculated treatments as compared to the un-inoculated control soil [2].

Effects of biochar on the transformation and utilization of nitrogen fertilizer in the black soil region of Northeast China

Nitrogen (N) fertilizer is often used in production practice to effectively maintain crop productivity; however, low nitrogen use efficiency (Nue) has always been a problem. Specifically, the transformation and utilization of nitrogen fertilizer by biochar and the driving mechanisms remain unclear. We used four biochar application rates (0, 3750, 7500, and 11,250 kg·ha−1) and analyzed the effects of biochar on nitrogen fertilizer utilization, residue, and loss over three years using 15N isotope tracer technology. The results showed that (1) biochar improved the nitrogen use efficiency of maize plants, reduced total nitrogen loss, and increased the maize yield. Compared to the control treatment in the same year, the application of 7500 kg·ha−1 biochar increased the nitrogen use efficiency by 24.27 %, 27.77 %, and 35.82 %, and the yield increased by 21.1 %, 26.7 %, and 24.5 %, respectively. (2) Biochar increased the proportion of mineral nitrogen supplied by fertilizer in the mineral nitrogen pool. The application of 7500 kg·ha−1 biochar increased mineral nitrogen by 3.05 %, 3.22 %, and 3.8 %, respectively, compared to the control treatments in the same year. Biochar promoted the transformation of nitrogen in the 0–40 cm soil layer to three different soil nitrogen pools, especially the organic nitrogen pool. (3) Biochar significantly improved the soil bacterial community and increased the abundances of N transformation functional genes. The redundancy analysis (RDA) showed that the gdhA mineralization gene was the driving factor of nitrogen fertilizer transformation, contributing 43.6 % of the variance. In summary, the application of 7500 kg·ha−1 of biochar for two consecutive years was conducive to maintaining farmland soil fertility, while its use would not be recommended for more than three consecutive years.

Nutrient Dynamics in Integrated Crop–Livestock Systems: Effects of Stocking Rates and Nitrogen System Fertilization on Litter Decomposition and Release

Current fertilizer recommendations often neglect nutrient cycling across crop rotations. This study aimed to assess the decay rate and nutrient (N, P, K) release patterns of sorghum, black oat, and corn residues (omitido) in an integrated crop–livestock system. The experiment used factorial treatments based on two sward heights (high and low) and two nitrogen fertilization levels (N-pasture at 200 kg N ha−1 and N-corn at 0 kg N ha−1). Litter bags were collected at various intervals from each crop to measure nutrient release patterns and decomposition rates. The results showed that pasture height and nitrogen fertilization significantly influenced decomposition and nutrient release, affecting the subsequent grain crop phase. Potassium was released rapidly and in high amounts. Nitrogen fertilization during the pasture phase prevented nitrogen and phosphorus immobilization in black oat residue and reduced immobilization in corn residue. These findings highlight the importance of accounting for nutrient cycling and decomposition rates in fertilization strategies to enhance the sustainability of integrated crop–livestock systems.

Computational investigation of novel synthetic analogs of C-1′β substituted remdesivir against RNA-dependent RNA-polymerase of SARS-CoV-2

Remdesivir, a C-nucleotide prodrug binds to the viral RNA-dependent-RNA polymerase (RdRp) and inhibits the viral replication by terminating RNA transcription prematurely. It is reported in literature that interaction between the C-1’β–CN moiety of Remdesivir (RDV) and the Ser861 residue in RdRp enzyme, causes a delayed chain termination during the RNA replication process and is one of the important aspect of its mechanism of action. In the pursuance of increasing the biological activity of RDV and enhancing the SAR studies, against RNA viruses, we have designed its fourteen C1’β substituted analogs, 10 –23 bearing 4/5-membered heterocyclic rings. The docking and 100 ns molecular dynamics (MD) simulations of 10-23 to the RdRp protein (PDB ID: 7L1F) revealed important interactions between 2’,3’-diol, oxo group of phosphoramidate, nitrogen residues of heterocyclic rings of synthetic molecules with Arg555, Arg553, Ser759, Cys622, Asn691, Asp623 amino acid residues of protein. The docking score of 2-ethylbutyl ((S)-(((2R,3S,4R,5R)-5-(4-aminopyrrolo[2,1-f][1,2,4]triazin-7-yl)-3,4-dihydroxy-5-(1H-1,2,3-triazol-4-yl)tetrahydrofuran-2-yl)methoxy)(phenoxy)phosphoryl)-L-alaninate, 11 was found to be the higher than RDV among 14 new compounds i.e. -5.20 kcal/mol. Out of 3 compounds, 10, 12 and 13 submitted for MD simulations and Molecular Mechanics Poisson-Boltzmann Surface Area (MMPBSA) analysis, trifluoro-oxadiazole derivative, 13 showed higher binding energy as compared to Remdesivir. The predicted ADMET properties of 14 compounds showed their potential for being drug candidates. The present study suggests that substitution at the C1’β position by 4/5-membered rings plays an important role in the interactions between nucleoside/tide and target protein.

Optimization of Lipid Production of Rhodosporidium toruloides from Various Substrates

Background and Aim: In recent years, bioenergy has received a lot of attention from a technical point of view due to its ability to use reversible resources and its applicability worldwide. Biodiesel is a non-toxic, safe, renewable, and degradable fuel that is obtained from natural sources, such as vegetable oils, food waste oils, animal fats, algae, and microorganisms. This study aimed to optimize the lipid production of Rhodosporidium toruloides as a biofuel from different substrates. Materials and Methods: In this experimental laboratory study, after lipid extraction from Rhodosporidium toruloides CECT1137, cell biomass, nitrogen, and sugar consumption were measured according to the Bly and Dyer method. Then, using gas chromatography, the produced lipid compounds were identified, and lipid production was optimized by the one-factor method (type of nitrogen source and KH2PO4) and the Taguchi method (carbon and nitrogen source, temperature, pH, centrifuge, and time). Finally, the feasibility of mutation was investigated using UV to optimize lipid production. Results: The amount of lipid produced by Rhodosporidium toruloides was 4.95 g/l, which, after optimization by the Taguchi method, reached 8.54 g/l. Cell biomass, residual nitrogen, and consumed sugar were measured as 14.05, 0.19, and 28.85 g/l, respectively. Optimal production conditions were estimated by Taguchi, including 80 g/l carbon source, 1 g/l nitrogen source, 25 ° C, pH = 5.5, centrifuge at 180 rpm, and 96 hours. Most lipids produced were oleic acid and palmitic acid. Lipid production increased after UV exposure. Conclusion: The results showed that Rhodosporidium toruloides can accumulate a significant amount of lipid in its cells and can be a good alternative to plants and other sources of fuel production.

The response of a sorghum sudangrass cover crop to residual nitrogen and its relationship with spectral sensors

AbstractA sorghum sudangrass (SSG) cover crop grown after a cash crop could take up residual nitrogen (N) before it is lost. As in‐field monitoring of SSG properties is laborious, predicting biomass and N concentrations with spectral sensors could be useful. At two sites in Live Oak, Florida, we evaluated the response of SSG to residual N from previous N fertilization and the performance of handheld and satellite sensors in estimating SSG properties. We quantified aboveground biomass, plant N, leaf greenness (NDVI), net potential N mineralization (PNM), and soil permanganate oxidizable carbon (POXC). Residual N did not affect SSG properties, PNM was highest at the highest N input rate in one site, and soil POXC was correlated with SSG properties (biomass and plant N). NDVI measured from a handheld sensor better predicted SSG properties than satellite imagery in these small plots, suggesting a greater potential to be a useful management tool.

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.

Refinement of cast microstructure of A517 steel by addition of TiB2

AbstractThe effect of TiB2 addition on microstructure refinement of the as-cast and reheated A517 steel has been investigated. 0.1 wt.% TiB2 addition resulted in a reduction in equiaxed γ grain size from 990 ± 183 to 116 ± 35 μm and an increase in the volume fraction of equiaxed γ grain region from 5% to 67% in the as-cast A517 steel ingots. Microstructure analysis identified TiN particles rather than TiB2. This is attributed to the low thermodynamic stability of TiB2, leading to its decomposition into free Ti and B elements at an elevated temperature. Then, chemical reaction between the free Ti and residual nitrogen in the liquid resulted in the formation of TiN. Hence, it is considered that TiN acted as heterogeneous nucleation sites for the δ-ferrite. This initiated the refinement and columnar to equiaxed transition of δ-dendrites. As a result, the subsequently formed γ grains were correspondingly refined. Such microstructure refinement led to improvement of the yield strength and ultimate tensile strength of the as-cast A517 steel. However, the reheating of the as-cast A517 steel resulted in a marginal microstructure refinement in the samples with low TiB2 addition. This is attributed to the limited pinning effect of the coarse TiN particles formed during casting process. Consequently, the tensile properties of the reheated A517 steel remained unaffected by the TiB2 addition.

Tillage, crop residue management and nitrogen application impacts on soil properties under maize–wheat (Zea mays–Triticum aestivum) cropping system

Tillage intensity, crop residue retention and nitrogen application can significantly impact the soil properties and crop productivity. We studied the effect of tillage (deep tillage [DT] vs. shallow tillage [ST]) in main plots and residue management viz. conventional tillage without residue (CT-R), conventional tillage with residue (CT+R), minimum tillage without residue (MT-R) and minimum tillage with residue (MT+R) in sub plots and fertilizer-N at 75, 100 and 125% N (viz. N75, N100 and N125) in sub-sub plots. Field treatments were established in maize-wheat (Zea mays-Triticum aestivum) cropping system during 2016-2019 at two different locations in north-western India and were arranged in split-split plot design. The soil penetration resistance was significantly lower under deep tillage (3.4 to 3.7%) as compared to shallow tillage. CT+R recorded lowest penetration resistance as compared to other tillage and residue combinations but other soil properties like OC, available NPK, soil aggregation, infiltration rate did not differ significantly. The addition of crop residue both under minimum and conventional tillage significantly increased the soil microorganism count and dehydrogenase enzyme activity at both locations. CT-R recorded lowest microorganism count and dehydrogenase enzyme activity. The available soil nitrogen, microorganism count and dehydrogenase enzyme activity significantly increased with increasing nitrogen doses at both locations and were highest under 125% N level as compared to 75% and 100% levels. In both crops, the grain yield was not significantly affected by tillage and crop residue combinations while the different levels of nitrogen fertilizer significantly affected the grain yield. From soil health and sustainability point of view, CT+R treatment with 100% recommended dose of nitrogen in maize-wheat crop rotation seemed beneficial.

Carbon budget of paddy ecosystems in China simulated by denitrification‐decomposition model

AbstractQuantifying the carbon budget in rice paddy ecosystems is fundamental to understanding the role of paddy fields as carbon sinks or sources and to mitigating global climate change. This study used a process‐based model of the denitrification‐decomposition (DNDC) model to estimate greenhouse gas (GHG) emissions and carbon sinks in the paddy ecosystem across China. The simulation results showed that the GHG emissions were 0.147 Pg C‐equivalent year−1 and that the carbon sequestration in rice plants and soils reached 0.253 Pg C year−1 in 2016, indicating high carbon sequestration potential of the Chinese paddy ecosystem. Land management had a great influence on carbon budgets, among which straw residue incorporation rate and nitrogen fertilizer applications had a stronger influence on carbon budgets, particularly for double cropping rice. These results indicate that appropriate tillage practices can reduce GHG emissions and increase carbon sequestration of rice ecosystems while ensuring rice yields.

Spaceborne imaging spectroscopy enables carbon trait estimation in cover crop and cash crop residues

PurposeCover crops and reduced tillage are two key climate smart agricultural practices that can provide agroecosystem services including improved soil health, increased soil carbon sequestration, and reduced fertilizer needs. Crop residue carbon traits (i.e., lignin, holocellulose, non-structural carbohydrates) and nitrogen concentrations largely mediate decomposition rates and amount of plant-available nitrogen accessible to cash crops and determine soil carbon residence time. Non-destructive approaches to quantify these important traits are possible using spectroscopy.MethodsThe objective of this study was to evaluate the efficacy of spectroscopy instruments to quantify crop residue biochemical traits in cover crop agriculture systems using partial least squares regression models and a combination of (1) the band equivalent reflectance (BER) of the PRecursore IperSpettrale della Missione Applicativa (PRISMA) imaging spectroscopy sensor derived from laboratory collected Analytical Spectral Devices (ASD) spectra (n = 296) of 11 cover crop species and three cash crop species, and (2) spaceborne PRISMA imagery that coincided with destructive crop residue collections in the spring of 2022 (n = 65). Spectral range was constrained to 1200 to 2400 nm to reduce the likelihood of confounding relationships in wavelengths sensitive to plant pigments or those related to canopy structure for both analytical approaches.ResultsModels using laboratory BER of PRISMA all demonstrated high accuracies and low errors for estimation of nitrogen and carbon traits (adj. R2 = 0.86 − 0.98; RMSE = 0.24 − 4.25%) and results indicate that a single model may be used for a given trait across all species. Models using spaceborne imaging spectroscopy demonstrated that crop residue carbon traits can be successfully estimated using PRISMA imagery (adj. R2 = 0.65 − 0.75; RMSE = 2.71 − 4.16%). We found moderate relationships between nitrogen concentration and PRISMA imagery (adj. R2 = 0.52; RMSE = 0.25%), which is partly related to the range of nitrogen in these senesced crop residues (0.38–1.85%). PRISMA imagery models were also influenced by atmospheric absorption, variability in surface moisture content, and some presence of green vegetation.ConclusionAs spaceborne imaging spectroscopy data become more widely available from upcoming missions, crop residue trait estimates could be regularly generated and integrated into decision support tools to calculate decomposition rates and associated nitrogen credits to inform precision field management, as well as to enable measurement, monitoring, reporting, and verification of net carbon benefits from climate smart agricultural practice adoption in an emerging carbon marketplace.

Decomposition of Foliar Litter from Dominant Plants of Desert Riparian Forests in Extremely Arid Regions

Litter decomposition is important for understanding the effects of habitat on nutrient cycling. In this study, we investigated the decomposition characteristics, decomposition variability, and regulatory factors restricting the decomposition rates of leaf litter in three different habitats: a flood disturbance habitat, an arid habitat, and a high-salinity habitat. The litter decomposition rates of the habitats decreased in the following order: flood disturbance habit &gt; arid habitat &gt; high-salinity habitat. The organic carbon, total nitrogen, and lignin residues of the litter during the decomposition period were highest in the high-salinity habitat. The litter quality was the main regulator of the release of phosphorus and cellulose residues, which exhibited different release processes and patterns in these three habitats. The litter decomposition coefficient was negatively correlated with litter carbon residue in the flood disturbance habitats, the lignocellulose index in the arid habitats, and soil urease in the high-salinity habitats. It was positively correlated with the lignocellulose index in flood disturbance habitats and litter carbon residue in high-salinity habitats. The litter quality in the flood disturbance area played a significant role in litter decomposition, while environmental quality and litter quality were the dominant factors under arid and high-salt conditions. Litter quality in the flood disturbance area played a significant role in litter decomposition, while both environmental quality and litter quality were the dominant factors under arid and salt conditions.

Rock Phosphate and Biochar Effects on Greenhouse Gas Emissions and Soil Fertility in Southern Alberta Potato Field

The application of biochar soil amendment and rock phosphate fertilizer to the soil could lead to achieving net zero emissions and food security; however, the effectiveness of using biochar and rock phosphate in southern Alberta brown chernozemic soil is not yet assessed. In the first trial of this study, varying levels of urea (N), with varying levels of biochar (B) were applied. The same level of rock phosphate (RP) and triple super phosphate (TSP) were applied to compare efficiency of the two fertilizers. The second trial involved applying the same nutrients, but with higher levels than the first trial. The results indicated that the fertilizer application rates did not affect the growth and yield of potatoes because of the application rates of the fertilizer and fertility status of the soil, whereas in the second trial, TSP and RP treatments had the same growth and yield. Furthermore, the high application rate of nitrogen fertilizer and RP with or without biochar in the potato plot emitted high nitrous oxide gas emissions while the low application rate of nitrogen fertilizer and RP kept the carbon dioxide in the soil. Nevertheless, in the second experiment, the application of biochar and rock phosphate reduced nitrous oxide and carbon dioxide emissions. We observed high residual nitrogen and manganese nutrients after harvest in the plot treated to rock phosphate and biochar. Therefore, rock phosphate and biochar have the potential to increase food production and mitigate climate change.

Optimizing the Mulching Pattern and Nitrogen Application Rate to Improve Maize Photosynthetic Capacity, Yield, and Nitrogen Fertilizer Utilization Efficiency.

Residual film pollution and excessive nitrogen fertilizer have become limiting factors for agricultural development. To investigate the feasibility of replacing conventional plastic film with biodegradable plastic film in cold and arid environments under nitrogen application conditions, field experiments were conducted from 2021 to 2022 with plastic film covering (including degradable plastic film (D) and ordinary plastic film (P)) combined with nitrogen fertilizer 0 (N0), 160 (N1), 320 (N2), and 480 (N3) kg·ha-1. The results showed no significant difference (p > 0.05) in dry matter accumulation, photosynthetic gas exchange parameters, soil enzyme activity, or yield of spring maize under degradable plastic film cover compared to ordinary plastic film cover. Nitrogen fertilizer is the main factor limiting the growth of spring maize. The above-ground and root biomass showed a trend of increasing and then decreasing with the increase in nitrogen application level. Increasing nitrogen fertilizer can also improve the photosynthetic gas exchange parameters of leaves, maintain soil enzyme activity, and reduce soil pH. Under the nitrogen application level of N2, the yield of degradable plastic film and ordinary plastic film coverage increased by 3.74~42.50% and 2.05~40.02%, respectively. At the same time, it can also improve water use efficiency and irrigation water use efficiency, but it will reduce nitrogen fertilizer partial productivity and nitrogen fertilizer agronomic use efficiency. Using multiple indicators to evaluate the effect of plastic film mulching combined with nitrogen fertilizer on the comprehensive growth of spring maize, it was found that the DN2 treatment had the best complete growth of maize, which was the best model for achieving stable yield and income increase and green development of spring maize in cold and cool irrigation areas.

Enhancing cotton (Gossypium hirsutum L.) productivity and quality with magnetized ionized water and Bacillus subtilis intervention under film-mulched drip irrigation in saline soil in Xinjiang

ContextSoil salinity stress and limited nutrient availability significantly impede crop production. Addressing these challenges, the activation of irrigation water and soil enhancement strategies have proven increasingly effective in improving crop production in saline soils. In particular, magnetized ionized water technology has been shown to augment the leaching of soil salinity, while Bacillus subtilis has been applied to increase nutrient availability. However, information on the synergistic effects of magnetized ionized water and B. subtilis are presently limited. ObjectiveThis study aimed to investigate the potential of utilizing B. subtilis in combination with magnetized ionized water to enhance cotton (Gossypium hirsutum L.) production and understand its underlying driving mechanism. MethodsA two-year field experiment explored the impact of varying amounts of B. subtilis, with two types of irrigation water [non-magnetized-ionized water (NMIW) and magnetized ionized water (MIW)] on soil conditions (pH, salt accumulation, and nutrient content), and cotton growth (dry matter, nutrient accumulation, seed cotton yield, and quality) in southern Xinjiang's saline soil. The experiment included five B. subtilis levels (0, 15, 30, 45, and 60 kg ha−1) with NMIW (designated as B0, B1, B2, B3, and B4) and MIW (designated as MB0, MB1, MB2, MB3, and MB4). ResultsMIW and B. subtilis significantly (p < 0.05) reduced soil pH and salt accumulation, while B. subtilis significantly (p < 0.01) increased soil residual nitrate nitrogen and residual available phosphorus content in the 0–40 cm soil layers compared to B0. Furthermore, a significant increase (p < 0.05) in cotton dry matter, nitrogen, and phosphorus accumulation was observed with both measures compared to B0. Seed cotton yield (Y), water productivity (WP), and fiber quality index (FQI) also showed significant improvements (p < 0.05). Compared with the NMIW treatments, the MIW treatments resulted in an average increase in Y of 5.7%, WP of 3.7%, and FQI of 20.2%. Similarly, B. subtilis treatments, compared to no B. subtilis treatments, led to an average increase in Y by 10.6%, WP by 6.9%, and FQI by 29.1%. Quadratic function relationships with Y, WP, and FQI were established using B. subtilis amount as an independent variable. The appropriate range of B. subtilis amount under MIW treatment, corresponding to 99.5% of the maximum values of Y, WP, and FQI, was determined to be 51.1–56.4 kg ha−1. ConclusionMIW and B. subtilis have been found to increase nutrient accumulation in cotton by reducing 0–40 cm soil salinity and alkalinity and increasing 0–40 cm soil nutrient content, thereby enhancing cotton production. To optimize the cotton cultivation under film-mulched drip irrigation in saline soil of southern Xinjiang, China, it is recommended to apply 51.1–56.4 kg ha−1B. subtilis under MIW.

Upcycling nitrogen and curbing greenhouse gas emissions from wastewater through H2-driven assimilatory mixotrophic metabolism

Biological nitrogen assimilation is an emerging technique for the removal and upcycling of nitrogen from wastewater in the form of microbial protein (MP). For this purpose, a mixed hydrogen-oxidizing bacteria (HOB) culture capable of growing mixotrophically was evaluated for the treatment of synthetic and real wastewater under different carbon-to-nitrogen (C/N) ratios. The same mixed HOB culture was grown under heterotrophic conditions to compare treatment and process performances in terms of ammonium nitrogen (N-NH4+) removal and assimilation, chemical oxygen demand (COD) removal, CO2 release, biomass concentration, yield and protein content. Under mixotrophic conditions, the highest biomass concentration was 342.5 mg VSS∙L−1, doubling that obtained under heterotrophic conditions (161.2 mg VSS∙L−1). Discharge limits for both COD and total N were met under mixotrophic conditions, with nitrogen removal and assimilation into protein-rich biomass achieving up to 99 %. On the contrary, under heterotrophic conditions, the high content of residual nitrogen as nitrite (up to 26 mg∙L−1 of N-NO2−) did not allow to meet discharge limits for total N. The mixed HOB culture gave promising results in terms of biomass yield (0.32 g VSS·g CODH2+acetate−1) and protein content (up to 56 % of VSS) when grown mixotrophically. Under heterotrophic conditions, instead, the biomass yield (0.25 g VSS·g CODacetate−1) and protein content (35 %) were substantially lower. This study suggests that the H2-driven assimilatory mixotrophic metabolism can be successfully applied for wastewater treatment to produce effluents that meet discharge limits while mitigating greenhouse gas emissions (CO2 and N2O) and upcycling nitrogen into MP.

Optimized Nitrogen Application Rate Significantly Increases Total Economic Value and Quality of Flue-Cured Tobacco due to the Improvement of Superior Tobacco Yield

Summary With the improvement of irrigation and transportation infrastructures, single tobacco cultivation has been converted into tobacco–vegetable double cultivation in Yunnan Province. High residual nitrogen (N) levels in soil before tobacco transplanting induced by the excessive N input during the vegetable cultivation season resulted in a reduction of economic income and the quality of flue-cured tobacco. Therefore, the objective of this paper is to describe the optimization of N management and to provide a better understanding of the mechanism of optimal N application rate on the economic benefit and quality of tobacco. A field experiment with six N application rates (0, 45, 60, 75, 90, and 105 kg N ha−1) was carried out with a randomized block design in 2021 and 2022 in Yunnan Province. The economic value and yield, intrinsic chemical and processing quality, leaf growth rate and agronomic characters were determined. Compared with the currently recommended 105 kg N ha−1 rate, 75 kg N ha−1 significantly increased the total economic value and superior tobacco yields, improved the integrated grade of chemical compounds and resulted in leaf midrib proportions in an appropriate range. The total economic value positively correlated with the superior tobacco leaf yields (R2 = 0.91, p &lt; 0.001), while not with medium and inferior leaf yield. The daily leaf growth rate in prosperous growth stage significantly correlated with the yield of superior tobacco and reached its maximum at a N rate of 75 kg N ha−1. The sum of N application rate and soil residual N before transplanting correlated with the total economic value (R2 = 0.66, p &lt; 0.05) and superior leaf yield (R2 = 0.64, p &lt; 0.05), respectively. Based on the amount of soil residual N before transplanting, the optimal N application rate was 66 kg N ha−1 which was 39 kg N ha−1 lower than the currently recommended N rate (105 kg N ha−1). Our results highlighted that the technical consultants and farmers should adjust the N application rate appropriately according to the residual N amount before transplanting and optimize the water and fertilizer management especially in the prosperous growth stage. An optimized N rate is not only of economic benefit and the improvement of quality of tobacco cultivation, but also environment friendly.

Plant nutrient removal and soil residual chemical properties as impacted by maize planting date and density.

This study aimed to measure maize (Zea mays) plant nutrient content and nutrient removal in grain, and to evaluate the residual soil nitrogen, phosphorus, and potassium as impacted by planting date and density. Field experiments were conducted to evaluate six plant densities and seven planting dates using a split-split plot design with three replications. Besides the crop growth and yield parameters, six plants were collected at the maturity and soil was sampled from each plot for nutrient analysis. Plant N, P, and K concentrations varied with planting date and density and within the ranges of 0.6-1.024%, 0.054-0.127%, and 0.75-1.71%, respectively. Grain N, P, and K concentrations decreased with plant density and varied from 1.059 to 1.558%, 0.20 to 0.319%, and 0.29 to 0.43%, respectively. Soil residual nutrient varied with depth, planting density and date. Residual N concentration in the topsoil varied from 0.6 to 37.2 mg kg-1 in 2019 and from 1.5 to 11.2 mg kg-1 in 2020 and was high under the last two planting dates. Soil residual N concentration was higher in the second layer than in the topsoil. The N concentration in the third layer varied from 0.1 to 33.2 mg kg-1 and was impacted by plant density. Topsoil P did not vary among planting dates and densities. The second and third soil layers P concentration was not affected. There was 83% increase in topsoil K in 2020 compared to 2019, and a decrease of 65 and 23% in soil K was observed in the second and third soil layers, respectively. For maize production system sustainability, future research should use a holistic approach investigating the impact of planting date, plant density on crop growth, yield, nutrient uptake and remobilization, and soil properties under different fertilizer rates to develop the fertilizer recommendation for maize while reducing the environmental impact of the production system.