Recovery of mineral fertiliser N and slurry N in continuous silage maize using the <Superscript>15</Superscript>N and difference methods

The stable isotope technique and the difference method are common approaches for estimating fertiliser N uptake efficiency. Both methods, however, have limitations and their suitability may depend on N management and environmental conditions. A field experiment was conducted on a humus sandy soil in northern Germany to estimate fertiliser N uptake efficiency of silage maize in the year of application (Zea mays L.) by the stable isotope and the difference method as influenced by the type of N fertiliser (mineral vs. cattle slurry), the application mode (separate or combined application), and N rate. Seven N treatments were included (0, 50, 100 and 150 kg mineral N ha⁻¹; 20, 40 m3 cattle slurry ha⁻¹; 50 kg mineral N ha⁻¹ plus 40 m3 slurry ha⁻¹), where either mineral N or slurry N was labelled, and mineral N was split into two dressings. In addition, 4.1 kg ha⁻¹ labelled mineral N was incorporated into otherwise unlabelled treatments (0, 20, 40 m3 ha⁻¹, and 50 kg mineral N ha⁻¹ plus 40 m3 ha⁻¹) to estimate N uptake from the upper soil layer. Uptake of ¹⁵N was followed in leaves, stalk, ear, and the whole crop. Fertiliser N uptake efficiency (FNUE_15N) of mineral fertiliser N obtained by the isotope technique ranged between 51 and 61%. Recovered fertiliser N was mainly found in the ear, while less labelled N remained in leaves and the stalk. The nitrogen rate tended to increase the amount of recovered N, but the effect was not consistent among plant parts and the whole crop. Plant N uptake from non-fertiliser N was found to increase N input up to 100 kg N ha⁻¹. Nitrogen recoveries of the two mineral N dressings were similar for the different plant parts as well as for the whole crop. Fertiliser N uptake efficiency (FNUE_diff) of mineral N estimated by the difference method resulted in substantially higher values compared to FNUE_15N, varying between 56 and 98%. More N was taken up from the upper soil layer with increasing N supply, which is regarded as a major error source of the difference method. Slurry N was taken up less efficient in the year of application than mineral fertiliser N as indicated by recovery rates of 21–22% (FNUE_15N) and 39–62% (FNUE_diff), respectively. When mineral N and slurry were applied together, the difference method estimated significantly lower N uptake efficiencies for both mineral and slurry N compared to a single application, while values obtained by the isotope method were not affected.     

Subsoil <Superscript>15</Superscript>N-N<Subscript>2</Subscript>O Concentrations in a Sandy Soil Profile After Application of <Superscript>15</Superscript>N-fertilizer

Studies on emissions of nitrous oxide (N₂O) from agricultural soils mostly focus on fluxes between the soil and the atmosphere or are limited to the atmosphere in the topsoil. However, in soils with shallow water tables, significant N₂O formation may occur closer to the groundwater. The aims of this study were (i) to determine the importance of subsoil N₂O formation in a sandy soil; and (ii) to obtain a quantitative insight in the contribution of subsoil N₂O to the overall losses of N₂O to the environment. We applied ¹⁵N labeled fertilizer at a rate of 5.22 kg ¹⁵N ha⁻¹; 50% as Ca(NO₃)₂ and 50% as NH₄Cl, on a mesic typic Haplaquod seeded with potatoes (Solanum tuberosum L.), and traced soil N₂O concentrations and fluxes over a one-year period. Throughout the year, total N₂O and the amount of ¹⁵N recovered in soil N₂O were highest in the subsoil, with a maximum concentration at 48 cm depth in mid-February of 19900 μl m⁻³ and 24 μg ¹⁵N m⁻³, respectively. The maximum concentration coincided with the highest water-filled pore space of 71%. The cumulative flux of N₂O was 446 g N₂O-N ha⁻¹, the recovery of ¹⁵N in this flux was 0.06%. During the summer, maximum fluxes followed high soil N₂O concentrations. During winter, no such relation was found. We concluded that the formation of N₂O was the highest in the subsoil, largely controlled by water-filled pore space rather than NO₃⁻ concentration or temperature. Although high subsoil N₂O concentrations did not lead to high surface fluxes of N₂O in the winter, artificial draining may lead to high indirect N₂O emissions through supersaturated drainage water.     

The role of <Superscript>15</Superscript>N-depleted fertilizers as tracers in N cycling studies in agroecosystems

A search of the literature (principally Google Scholar, using the keywords given below) revealed that 120 research papers have been published where ¹⁵N-depleted (¹⁴N-enriched) fertilizers, including ammonium sulfate, ammonium nitrate, urea and ammonia forms were used as tracers. The studies included annual cereals, vegetables, a grain legume and a fibre crop, and perennial crops including grasses, shrubs (berries), trees (fruits and nuts) and N₂-fixing forage, grain and woody legumes and an actinorhizal species. Other minor examples include perennial ornamentals and trees harvested for wood. Applications included estimation of fertilizer recovery in crops, in post-harvest soil and estimation of N losses in the soil–plant system by mass balance. The residual value of ¹⁵N-depleted fertilizers and the recovery of ¹⁵N-depleted legume residues have also been reported. ¹⁵N depleted fertilizers have played an important role in differentiating the relative uptake of fertilizer N to N mobilized in storage tissues with respect to the N nutrition of deciduous horticultural trees, shrubs and vines in spring. The symbiotic dependence of N₂-fixing species and transfer to companion non-legumes has been indirectly determined using ¹⁵N-depleted fertilizers. Thus ¹⁵N-depleted fertilizers have shared the same applications as their ¹⁵N-enriched counterparts. Because of their relative cheapness compared with ¹⁵N-enriched fertilizers, larger and more representative unconfined plots can be employed in field studies.     

Nitrogen input, <Superscript>15</Superscript>N balance and mineral N dynamics in a rice–wheat rotation in southwest China

A field experiment and farm survey were conducted to test nitrogen (N) inputs, ¹⁵N-labelled fertilizer balance and mineral N dynamics of a rice–wheat rotation in southwest China. Total N input in one rice–wheat cycle averaged about 448 kg N ha⁻¹, of which inorganic fertilizer accounted for 63% of the total. The effects of good N management strategies on N cycling were clear: an optimized N treatment with a 27% reduction in total N fertilizer input over the rotation decreased apparent N loss by 52% and increased production (sum of grain yield of rice and wheat) compared with farmers’ traditional practice. In the ¹⁵N-labelled fertilizer experiment, an optimized N treatment led to significantly lower ¹⁵N losses than farmers’ traditional practice; N loss mainly occurred in the rice growing season, which accounted for 82% and 67% of the total loss from the rotation in farmers’ fields and the optimized N treatment, respectively. After the wheat harvest, accumulated soil mineral N ranged from 42 to 115 kg ha⁻¹ in farmers’ fields, of which the extractable soil NO₃ ⁻–N accounted for 63%. However, flooding soil for rice production significantly reduced accumulated mineral N after the wheat harvest: in the ¹⁵N experiment, farmers’ practice led to considerable accumulation of mineral N after the wheat harvest (125 kg ha⁻¹), of which 69% was subsequently lost after 13 days of flooding. Results from this study indicate the importance of N management in the wheat-growing season, which affects N dynamics and N losses significantly in the following rice season. Integrated N management should be adopted for rice–wheat rotations in order to achieve a better N recovery efficiency and lower N loss.     

Characterization of fecal nitrogen forms produced by a sheep fed with <Superscript>15</Superscript>N labeled ryegrass

Little is known about nitrogen (N) forms in ruminant feces, although this information is important to understand N dynamics in agro-ecosystems. We fed ¹⁵N labeled ryegrass hay to a sheep and collected ¹⁵N labeled feces. Nitrogen forms in the feces were characterized by chemical extractions, solid-state cross polarization ¹⁵N nuclear magnetic resonance spectroscopy (SS CP/MAS ¹⁵N NMR) and Curie-point pyrolysis–gas chromatography/mass spectrometry (Cp Py-GC/MS). A 4 months incubation experiment was conducted to assess N release from the feces. Half of the fecal N could be ascribed to bacterial and endogenous debris and a third to undigested dietary N. About a tenth of the fecal N was mineralized during the incubation experiment. The ¹⁵N abundance of nitrate released during the incubation remained constant and close to the ¹⁵N abundance of the total feces N. The NMR analysis of the feces showed that most of the N was present in proteins, while some was present as heterocyclic N, amino acids and ammonium. The Cp Py-GC/MS analysis confirmed the presence of proteins, amino acids and heterocyclic N in the feces. Comparing these results to those obtained from the ¹⁵N labeled hay suggests that some N compounds present in the plant were not digested by the animal, and that the animal excreted de novo synthesized N compounds. The low content in ammonium and amino acids, the low rate of N release from these feces during the incubation and the relatively high fecal protein content, particularly the hard to mineralize undigested and microbially bound forms, can explain the low transfer of N from these feces to crops observed in a previous work.     

Biological nitrogen fixation by soybean and fate of applied <Superscript>15</Superscript>N-fertilizer in succeeding wheat under conventional tillage and conservation agriculture practices

Four field experiments were conducted to investigate biological N₂ fixation (BNF) by irrigated soybean under conservation agriculture (CA) as compared with conventional tillage when crop residue (CR) is retained on the soil surface, and the fate of ¹⁵N-labelled fertilizer in succeeding wheat in the semi-arid subtropical soil. Comparable amounts of BNF by soybean were obtained using ¹⁵N isotope dilution and ¹⁵N natural abundance methods, suggesting that the latter, a less costly method could be employed to estimate BNF. Soybean could fix 61–125 kg N ha^?1 (52–85% of total N uptake), depending upon tillage and CR management. Significant increases in BNF by soybean were recorded when CR was retained on the soil surface of CA plots presumably due to better activity of rhizobia because of the relatively cooler rhizosphere environment. Recovery of applied fertilizer N in the soil–plant system at harvest of the wheat crop showed that 36–47% of it was utilized by the crop, 37–49% was left in the soil profile and 5–27% was lost (unrecovered fertilizer N). The recovery of fertilizer N in the soil profile revealed that the majority of it was present in the first 15 cm (54–61%), although downward movement of fertilizer N was also evident up to 120 cm soil depth. These results illustrate enormous benefits of CA practices with CR retained on soil surface on BNF in soybean, and similar patterns in N uptake and translocation from vegetative parts to grain and utilization of applied fertilizer N by wheat in both tillage systems.     

Field-assisted diffusion of K<Superscript>+</Superscript>, Rb<Superscript>+</Superscript>, Cs<Superscript>+</Superscript>, Ag<Superscript>+</Superscript>, and Tl<Superscript>+</Superscript> ions in sodium silicate glass

The composition of the diffusion zone formed during the interaction between 20Na₂O · 80SiO₂ glass and molten silver, rubidium, cesium, and thallium nitrates with and without imposition of a constant electric field was determined using X-ray microanalysis. The interdiffusion coefficients and values of electrical mobility were calculated, and the parameters of temperature dependence were determined. The electrical mobility was almost independent of the size and chemical nature of a cation and was determined by the mobility of the cation included into the initial glass.     

Nitrogen Leaching from <Superscript>15</Superscript>N Labelled Cow Urine and Dung Applied to Grassland on a Sandy Soil

Nitrogen (N) leaching under grazed pastures can be very high directly under urine spots. The amount of N which is returned by one excretion of urine or dung can locally exceed 1000 kg ha⁻¹ a⁻¹ which is far more than the uptake by surrounding plants during one grazing period. We therefore quantified the contribution of N deriving from urine and dung to the total N leaching under urine and dung patches. Dung N and urine N was separately sampled from a cow feed with ¹⁵N labelled grassilage, and were amended on lysimeters in October 2000 and October 2001. Lysimeters (350 mm diameter and 800 mm length) were filled with sand, and an intact grass sod from a pasture, 4 lysimeter each were amended with the ¹⁵N labelled dung and urine; 4 lysimeters without an application of dung or urine served as control. During 11 months after dung and urine amendment the amount of leachate was monitored and leachate was analysed for nitrate, ammonium and total N. ¹⁵N in these fractions was measured. Dung and urine applications of 1052 and 1030 kg N ha⁻¹ in autumn increased N leaching. Leaching loss of nitrate and dissolved organic N deriving from dung was only 37 kg N ha⁻¹ in both years, whereas under urine patches 447 kg nitrate-N ha⁻¹, 108 kg N ha⁻¹ ammonia-N and 53 kg ha⁻¹ dissolved organic N leached on average of both experimental years. N not deriving from dung and urine exceeded the leached N under the control by about 36 and 136 kg ha⁻¹ on average of both years, suggesting the contribution of different priming processes.     

<Superscript>1</Superscript>H and <Superscript>13</Superscript>C NMR characterization and stereochemical assignments of bile acids in aqueous media

The unconjugated bile acids cholic acid, deoxycholic acid, and chenodeoxycholic acid; their glycine and taurine conjugated glycocholic acid, glycodeoxycholic acid, glycochenodeoxycholic acid, taurocholic acid, taurodeoxycholic acid, and taurochenodeoxycholic acid; and a taurine conjugated ursodeoxycholic acid, tauroursodeoxycholic acid, were characterized through ¹H and ¹³C NMR in aqueous media under the physiological pH region (7.4±0.1). Assignments of ¹H and ¹³C signals of all the bile acids were made using a combination of several one- and two-dimensional, homonuclear (¹H−¹H) and heteronuclear (¹H−¹³C) correlations as well as spectral editing NMR methods. Stereochemical assignment of the five-membered ring of the bile acids is reported here for the first time. The complete characterization of various bile acids in aqueous media presented here may have implications in the study of the pathophysiology of biliary diseases through human biliary fluids using NMR spectroscopy.     

Linseed oil and mixture with maleic anhydride: <Superscript>1</Superscript>H and <Superscript>13</Superscript>C NMR

It was shown that ¹H NMR allowed a rapid determination of the ratio of the linolenic residues over all the others (linoleic + oleic + saturated) and ¹³C NMR allowed a rapid determination of the ratio of linolenic over (linoleic + oleic) residues as well as the linoleic/oleic ratio in a few minutes on less than 20 mg of crude LO. After thermal treatment (220°C for 2 h, followed by cooling to room temperature), a 1∶1 mixture of linseed oil (LO) and maleic anhydride (MA), which was a suspension, became limpid and remained limpid. Moreover, the viscosity of the mixture was higher than that of pure LO treated in the same way. It was shown by ¹³C NMR and quantitative recovery of the constituents (LO and MA) through solvent separation that no reaction occurred between LO and MA during this thermal treatment. This result is in accord with DSC analysis of such a 1∶1 LO/MA mixture that exhibited an exothermic effect too small (about 34 kcal/mol) to correspond to formation of a C−C bond.     

<Superscript>1</Superscript>H- and <Superscript>13</Superscript>C-NMR Characterization of the Molecular Components of the Lipid Fraction of Pecorino Sardo Cheese

In this work the molecular fatty components of Pecorino Sardo Protected Designation of Origin (PS PDO) cheese were characterized through an exhaustive investigation of the ¹H- and ¹³C-NMR spectra of the extracted lipids. Several fatty acids (FA), such as long chain saturated, oleic, linoleic, linolenic, butyric, capric, caprylic, caproic, trans vaccenic, conjugated linoleic acid (cis9, trans11–18:2), and caproleic (9–10:1) were unambiguously detected. The positional isomery of some acyl groups in the glycerol backbone of triacylglycerols (TAG) was assessed. Furthermore, the NMR signals belonging to sn-1,2/2,3, sn-1,3 diacylglycerols (DAG), and free fatty acids (FFA) were analysed as a measure of lipolytic processes on cheese. Lastly, ¹H-NMR resonances of saturated aldehydes and hydroperoxides were detected, their very low intensity indicating that the lipid oxidation process can be considered to be of minor relevance in Pecorino Sardo cheese.     

Kinetics of <Superscript>14</Superscript>C distribution after tracer dose of <Superscript>14</Superscript>C-lutein in an adult woman

Lutein is an oxygenated carotenoid (xanthophyll) found in dark green leafy vegetables. High intakes of lutein may lower the risk of age-related macular degeneration. Current understanding of human lutein metabolism as it might occur in vivo is incomplete. Therefore, we conducted a feasibility study where we dosed a normal adult woman with ¹⁴C-lutein (125 nmol, 36 nCi ¹⁴C), dissolved in olive oil (0.5 g/kg body weight) and mixed in a banana shake. Blood, urine, and feces collected before the dose was administered served to establish baseline values. There-after, blood was collected for 63 d following the dose, while feces and urine were collected for 2 wk post-dose. The ¹⁴C contents in plasma, urine, and feces were measured by accelerator MS. The ¹⁴C first appeared in plasma 1 h after dosing and reached its highest level,≈2.08% of dose/L plasma, at 14 h post-dose. The plasma pattern of ¹⁴C did not include a chylomicrons/VLDL (intestinal) peak like that when the same subject received ¹⁴C-β-carotene (a previous test), suggesting that lutein was handled differently from β-carotene by plasma lipoproteins. Lutein had an elimination half-life (t _1/2) of≈10 d. Forty-five percent of the dose of ¹⁴C was eliminated in feces and 10% in urine in the first 2 d after dosing. Quantifying human lutein metabolism is a fertile area for future research.     

Hydrothermal synthesis of zeolite L in a Na<Superscript>+</Superscript>/K<Superscript>+</Superscript> mixed alkali system

Zeolite L was prepared from the substrate system of Na₂O-K₂O-Al₂O₃-SiO₂-H₂O at temperatures of 373–443 K by hydrothermal crystallization. The influence of various synthesis parameters such as the concentration ratios of the components, starting raw materials, synthesis temperature, gel aging, and stirring on the crystallization was investigated. Investigations revealed that the crystallinity of zeolite L crystals depends on molar ratios of the components such as SiO₂/Al₂O₃, (K₂O+Na₂O)/SiO₂, Na₂O/(K₂O+Na₂O), and H₂O/(K₂O+Na₂O). Pure and highly crystalline zeolite L could be obtained from a gel with the molar composition 5.4K₂O–5.7Na₂O-Al₂O₃-30SiO₂-500H₂O after 24 h at 443 K. It was found that the silica source affected the crystal size of zeolite L, and as the synthesis temperature increased, the average crystal size became larger. The crystal size could be decreased significantly by stirring the gel or subjecting the substrate mixture to an aging treatment at room temperature prior to the hydrothermal treatment. Thermal stability of the zeolite L crystals obtained was also briefly investigated.     

Visible up-conversion luminescence of CaWO<Subscript>4</Subscript>: Er<Superscript>3+</Superscript>,Yb<Superscript>3+</Superscript> and emission enhancement by tri-doping of Li<Superscript>+</Superscript> ions

Er³⁺,Yb³⁺ co-doped CaWO₄ polycrystalline powders were prepared by a solid-state reaction and their up-conversion (UC) luminescence properties were investigated in detail. Under 980 nm laser excitation, CaWO₄: Er³⁺,Yb³⁺ powder exhibited green UC emission peaks at 530 and 550 nm, which were due to the transitions of Er³⁺ (²H_11/2)→Er³⁺ (⁴I_15/2) and Er³⁺ (⁴S_3/2)→Er³⁺ (⁴I_15/2), respectively. Effects of Li+ tri-doping into CaWO₄: Er³⁺,Yb³⁺ were investigated. The introduction of Li⁺ ions reduced the optimum calcinations temperature about 100 °C by a liquid-phase sintering process and the UC emission intensity was remarkably enhanced by Li⁺ ions, which could be attributed to the lowering of the symmetry of the crystal field around Er³⁺ ions.     

Structural and Activity Investigation into Al<Superscript>3+</Superscript>, La<Superscript>3+</Superscript> and Ce<Superscript>3+</Superscript> Addition to the Phosphomolybdate Heteropolyanion for Isobutane Selective Oxidation

Abstract  

Twelve phosphomolybdate compounds were synthesized via cationic exchange and were of the form: M _x H_3–3x [PMo₁₂O₄₀] (M = Al, La or Ce; 0 ≤ x ≤ 1). These compounds were analyzed by XRD and adsorption isotherm. Aluminum addition causes a primitive cubic phase, while lanthanum and cerium yield body-centered structures. La and Ce addition reduces surface area of phosphomolybdate structure. Temperature-programmed experiments for the selective oxidation of isobutane yielded methacrolein, 3-methyl-2-oxetanone (lactone), acetic acid (not with aluminous compounds), propene (only with aluminous compounds), carbon dioxide and water. The preference for propene rather than acetic acid formation with Al³⁺ may be due to the smaller cation size, or primitive cubic structure. These products form via two distinct reaction processes, labeled categories 1 and 2. Category 1 formation is associated with isobutane forming products on the surface, but reaction rate determined by bulk migration of charged particles. Category 2 formation is concerned with isobutane penetrating deep within the bulk of the substrate and forming products which subsequently desorb in a series of bell-shaped humps. Methacrolein forms via both category 1 and 2, whilst all other products form via category 2 exclusively. Kinetic analysis showed apparent activation barriers for category 1 methacrolein formation range from 67 ± 2 kJ mol⁻¹ to >350 kJ mol⁻¹, and occur in groups with small, medium and large activation barriers. The addition of +3 metal cations to the phosphomolybdate anion increase thermal stability, significantly decreasing deactivation; IR spectroscopy shows that the Keggin structure remains intact during temperature-programmed experiments with the Al, La and Ce salts.     

Quantification of symbiotic nitrogen fixation by <Emphasis Type="Italic">Elaeagnus angustifolia</Emphasis> L. on salt-affected irrigated croplands using two <Superscript>15</Superscript>N isotopic methods

Afforestation with fast growing N-fixing trees is an option for ecological restoration of highly-salinized irrigated croplands, but information about the N-fixing capability of trees on saline soils is sparse. The ¹⁵N-enrichment technique (¹⁵NET) and the A value (AV) method were used to quantify in lysimeters the proportion of atmospheric N₂ (%Ndfa) fixed by Elaeagnus angustifolia L., with a reference to non-N-fixing Gleditsia triacanthos L. and Ulmus pumila L. Twenty kg N ha⁻¹ of 5 atom %¹⁵N excess ammonium nitrate (35% N) was applied to 1-year-old trees in 2007 and 2-year-olds in 2008. Since this rate was insufficient for the older reference trees, 60 kg N ha⁻¹ was applied in 2008. With ¹⁵NET, the %Ndfa of E. angustifolia in 2007 was 79% when referenced against U. pumila and 68% against G. triacanthos. With the AV method, the %Ndfa of 2-year-old E. angustifolia was 80 and 68% when referenced against U. pumila and G. triacanthos, respectively. Over 2 years, E. angustifolia fixed 17 kg N ha⁻¹ when related to U. pumila and 14 kg N ha⁻¹ with G. triacanthos (assumed density: 5,000 trees ha⁻¹). N-fixing E. angustifolia has the potential to be self-sufficient in N when planted in the strongly saline soils.     

Effect of Ni<Superscript>2+</Superscript>, V<Superscript>4+</Superscript> and Mo<Superscript>6+</Superscript> concentration on iron oxidation by <Emphasis Type="Italic">Acidithiobacillus ferrooxidans</Emphasis>

The ferrous oxidation ability of Acidithiobacillus ferrooxidans was studied in the presence of Ni²⁺, V⁴⁺ and Mo⁶⁺ in 9 K media in order to implement the culture in the bioleaching of spent catalyst. The rate of iron oxidation decreased with increasing concentration of metal ions, but the rate of inhibition was metal-ion dependent. The tolerance limit was critical at a concentration of 25 g/L Ni²⁺, 5 g/L V⁴⁺ and 0.03 g/L Mo⁶⁺. The growth rate of microorganisms was negligible at concentrations of 6 g/L V⁴⁺ and 0.04 g/L Mo⁶⁺. Levels and degree of toxicity of these ions have been quantified in terms of a toxicity index (TI). The toxicity order of metal ions was found to be Mo⁶⁺>V⁴⁺>Ni²⁺. The significance and relevance of multi-metal ion tolerance in Acidithiobacillus ferrooxidans has been highlighted with respect to bioleaching of spent refinery catalyst.     

Thermal Stability and Spectral Properties of Tm<Superscript>3+</Superscript>-Yb<Superscript>3+</Superscript> CO-Doped Tellurite Glasses

Glasses of the system 75TeO₂–20ZnO–5La₂O₃–0.8Tm₂O₃–xYb₂O₃ were prepared by high temperature melt cooling method. Results of differential scanning calorimetry indicate that, all glass samples have excellent thermal stability. Judd–Ofelt strength parameters, spontaneous emission probabilities, fluorescence branching rations, fluorescence radiative lifetime of Tm³⁺ ions in tellurite glass were calculated. The impact of Yb³⁺ concentration on the fluorescence properties of Tm³⁺ ions in the S band under the pumping wavelength of 465 nm was investigated in a suggestion that, ³H₄ radiative lifetimes will be prolonged and the performance of optical amplifier gain of Tm³⁺ in tellurite glass co-doped with 0.5 mol % Yb³⁺ ions will be improved.