39,540 research outputs found
Effect of Nitrogen Fertilization and Liming on Rye-Ryegrass Yield and Soil pH Dynamics
No full textUsing ammonium based nitrogen fertilizers in crop production has been shown to acidify soils. Lime used to correct soil pH is an important cost to producers. Recommendations of the optimal level of nitrogen to apply typically ignore the cost of lime created by nitrogen fertilization. This study was aimed to estimate soil pH change in response to nitrogen and lime application, and determine the effect of considering the cost of lime on recommendations about the optimal level of nitrogen. Yield response and pH functions were estimated and used to determine optimal levels of inputs. The effect of the cost of lime on recommendations about the optimal level of nitrogen was found to be marginal. Nitrogen acidification was found to be more severe with nitrogen application amounts above recommended rates than with nitrogen that is used by the plant.Lime, Nitrogen, Soil pH, Rye-ryegrass, Crop Production/Industries, Production Economics,
Modelling long-term impacts of fertilization and liming on soil acidification at Rothamsted experimental station
No full textLiming is widely used to reduce the impacts of soil acidification and optimize soil pH for agricultural production. Whether models can simulate the effect of liming on soil pH, and base saturation (BS), and thereby guide lime application, is still largely unknown. Long-term experimental data from a grassland (Park Grass, 1965–2012)and arable land (Sawyers Field, 1962–1972) at Rothamsted Research, UK, were thus used to assess the ability of the VSD+ model to simulate the effects of long-term fertilization and liming on soil acidification. The VSD+model was capable of simulating observed soil pHand BS changes over time in the long-termliming experiments, except for a treatment in which sulphur (S) was added. NormalizedMean Absolute Errors (NMAE) and Normalized Root Mean Square Errors (NRMSE) of simulated and observed pH values, averaged over the observation periods varied between 0.02 and 0.08 (NMAE) and 0.01–0.05 (NRMSE). The acidity budget results for Park Grass suggest that nitrogen (N) transformations contributed most to acidity production, causing predominantly aluminium (Al) exchange in the topsoil (0–23 cm) followed by base cation (BC) release, but in the treatment with S addition, BC uptake had a nearly similar effect on acidity production.However, in Sawyers Field, the acidity budget suggested that BC uptakewas the dominant cause of soil acidification,while the impacts of N transformations were limited. Liming was found to sufficiently replenish BC and decrease Al exchange in the topsoil layer. Overall, the VSD+ model can adequately reconstruct the impacts of fertilizer and liming applications on acid neutralizing processes and related soil pH and BC changes at the soil exchange complex
Liming enhances soil priming effect in Chinese fir plantation induced by glycine rather than glucose and oxalic acid
No full textLiming is a widely adopted strategy to mitigate soil acidification and enhance forest productivity. However, the extent to which liming modulates forest soil priming effects, particularly those induced by distinct root exudate types, remains poorly understood. To address this, we conducted a 90-day incubation experiment using soils from a three-year field liming experiment in a Cunninghamia lanceolata plantation (treatments: control, soil pH = 4.4; low liming doses, soil pH = 4.7; high liming doses, soil pH = 5.4). We investigated priming effects by adding three major 13C-labeled root exudate components - 13C-glucose, 13C-glycine, and 13C-oxalic acid − each at 2 % of soil organic carbon. Results showed that all exudates consistently induced positive priming effects, with glycine eliciting the strongest response (51.6–89.8 μg C g−1 soil), followed by glucose (37.0–41.5 μg C g−1 soil) and oxalic acid (32.9–47.3 μg C g−1 soil). High liming amplified significantly glycine-induced priming effect by 70 % compared to the control, while priming effects induced by glucose and oxalic acid had no change among different doses of liming. This differential response indicates a synergistic effect between liming and glycine additions on the priming effect. Correlation analysis showed that both soil pH and the soil organic carbon mineralization rate (CMR) were positively correlated only with glycine-induced priming, and that glycine addition was the only treatment that increased NAG activity under high liming. These results suggest that liming enhanced soil pH, thereby stimulating microbial activity, and that the combined C and N supplied by glycine further promoted microbial and exoenzyme activity, ultimately intensifying glycine-induced priming in limed soils. Our findings suggested that liming effects on forest soil priming are jointly governed by root exudate type and soil physicochemical properties, advancing our understanding of liming-mediated soil C cycling
Minimizing N2O fluxes from full-scale municipal solid waste landfill with properly selected cover soil
No full textThe Bright Side of Price Volatility in Global Commodity Procurement
No full textThis paper studies two competing firms’ choices between the contingent-price contract (CPC) and fixed-price contract (FPC) in global commodity procurement. The FPC price is determined when signing the contract, whereas the CPC price is pegged to an underlying index and remains open until the delivery date. Under both contracts, each firm determines its order quantity based on the updated belief about the market demand. The unrealized CPC price correlates with the market demand, allowing a firm to update its belief about the CPC price using demand information, thereby generating a price-learning effect. We find that, contrary to conventional wisdom, a larger price volatility could benefit the firms, and, under differentiated contracts, a firm might benefit from the improvement of forecast accuracy at its rival. We further show that the price-learning effect plays a critical role in the firms’ contract choices. First, significant price volatility forces the firms to pursue the responsiveness of the CPC. Second, the firms may adopt differentiated contracts to enhance their responses to market changes and dampen competition, and a higher competition intensity more likely leads to contract differentiation. Third, the firms in a small market seek responsiveness and contract differentiation rather than cost efficiency. This study reveals the bright side of price volatility and takes a step toward understanding the effect of two-dimensional information updating
Research Data for Healthy adults with <i>Streptococcus pneumoniae</i> meningitis and <i>Streptococcus pneumoniae</i> subdural abscess: two case reports and a literature review
No full textResearch Data for Healthy adults with Streptococcus pneumoniae meningitis and Streptococcus pneumoniae subdural abscess: two case reports and a literature review by Fanxin Kong, Liling Li, Daxue Zhang, Baorong Lian, Xudong Liu, Shuqun Ren, Yu Zhang, Liming Cao in Journal of International Medical Research</p
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Asymmetric Gold(I) Catalysis Enabled by Chiral Bifunctional Ligands
No full textGold has experienced tremendous usage as a coinage metal throughout history due to its chemical inertness. As such, gold was not considered a viable metal for catalysis until the late 20th century when the unique soft π-Lewis acidic characteristics of cationic gold were discovered. The π-acidity of gold(I) enables the selective functionalization of unsaturated C-C bonds under mild conditions and has been an invaluable addition to the toolbox of synthetic organic chemistry. The Zhang Group has developed various bifunctional ligands to leverage the unique reactivity of gold(I) and demonstrated their applicability in asymmetric catalysis. This thesis will introduce gold(I) catalysis, ligand design, and cooperative gold(I) catalysis. The development of a highly enantioselective method of asymmetric protonation applicable to a wide scope of substrates featuring a variety of structural frameworks is discussed. This method was also applied in the stereoselective synthesis of cyclopentenones in a one-pot, two-step synthetic method consisting of tandem [3,3]-rearrangement and Nazarov cyclization followed by enantioselective protonation. This thesis will additionally discuss the development of a highly enantioselective and chemoselective method gold(I)-catalyzed ring expansion of allenyl cyclopropanols and allenyl ether cyclobutanols to the corresponding cyclobutanones and cyclopentanones, respectively. The application of cooperative gold(I) catalysis in asymmetric butenolide isomerization will be explored, including the development of this transformation and the techniques utilized to rationalize the findings, such as NMR spectroscopy, single crystal XRD, and DFT calculations
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Chiral Bifunctional Phosphine Ligand-Enabled Cooperative Asymmetric Coinage Metal Catalysis
No full textMost ligands used in asymmetric gold(I) catalysis are directly adopted from palladium catalysis. These ligands were initially designed to facilitate the chemistry of square-planar Pd(II) complexes and hence are hardly optimal for Au(I) catalysis, in which the catalysts display linear geometry. For the past several years, the Zhang Lab has designed various bifunctional biphenyl-2-ylphosphine ligands featuring a remote basic group to harness the linear Au(I) structure and enable ligand-metal cooperation. During the research of this dissertation, a new type of bifunctional phosphine ligands possessing a chiral center and a fluxional biphenyl axis were developed to enable asymmetric isomerization of propargylic alcohols and sulfonamides into chiral 2,5-dihydrofurans and chiral 3-pyrrolines, respectively. The synthetic potential of this methodology was demonstrated in a total synthesis of diplobifuranylone B. Notably, this type of chiral ligands is also suitable for Ag(I) and Cu(I) catalysis. β, γ-Butenolides was isomerized into chiral α, β-butenolides with high enantiomeric excesses via enantioselective γ-protonation under Cu(I) catalysis
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Rationally Designed Bifunctional Ligands for Cooperative Gold Catalysis
No full textOver the past twenty years, asymmetric gold(I)-catalysis has remained challenging due to the inherent linear structure of gold(I) complexes. The Zhang group has made significant advances in addressing this challenge via the development of ligand-enabled cooperative homogeneous gold catalysis for the past decade. However, cumbersome ligand synthesis limits the scope of available ligands and hinders further exploration of asymmetric catalysis. In my graduate research, a new and divergent synthesis of chiral bifunctional binaphthyl-2-ylphosphines was developed. This method enables the rapid construction of a chiral bifunctional gold catalyst library, including 23 new catalysts. With this catalyst library, asymmetric dearomatization of naphthols and phenols was achieved to access chiral spiro carbocycles with excellent enantioselectivities. Furthermore, we developed enantioselective desymmetrization and parallel kinetic resolution of ethynylcyclobutanols, leading to the synthesis of chiral α-methylenecyclopentanones. Extending beyond asymmetric gold catalysis, we also introduced a gold-catalyzed stererospecific trans-hydrogenation of internal alkynes, facilitated by a key hydrosilane-Lewis base interaction
sj-docx-3-lis-10.1177_09610006231224445 – Supplemental material for Information literacy of higher vocational college students in digital age
No full textSupplemental material, sj-docx-3-lis-10.1177_09610006231224445 for Information literacy of higher vocational college students in digital age by Liming Liu, Siping Wang, Juntao Chen, Hua Li, Jianting Gui and Ruifang Zhang in Journal of Librarianship and Information Science</p
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