Total and light fraction organic C in a thin Black Chernozemic grassland soil as affected by 27 annual applications of six rates of fertilizer N

Maintenance and sequestration of C is important to sustain and improve the quality and productivity of soils. The objective of this study was to determine the effects of 27 annual applications of six N rates (0, 56, 112, 168, 224 and 336 kg N ha^–1 yr^–1) on total organic C (TOC) and light fraction organic C (LFOC) in a thin Black Chernozemic loam soil. Nitrogen (ammonium nitrate) was surface-applied to bromegrass (Bromus inermis Leyss) managed as hay near Crossfield, Alberta, Canada. The concentration and mass of TOC and LFOC in the 0–5, 5–10, 10–15 and 15–30 cm soil layers increased with N rate and showed a quadratic response to N rate with significant R² values, with their maximum values at 336 kg N ha^–1 in the 0–5 cm layer and at 224 kg N ha^–1 in other layers. But the increase in TOC and LFOC per kg of N addition was maximized at 56 kg N ha^–1 and declined with further increase in N rate. These trends indicated that higher N rates would cause a faster build up of soil C, whereas lower N rates would achieve a greater increase in soil C per unit of N addition. Response of C mass to N application was much greater for LFOC (range of 697 to 156% increase) than for TOC (range of 67 to 17% increase). Percentage of LFOC in TOC mass increased with N rate. At the 168 to 336 kg N ha^–1 rates, almost all of the increase in TOC in the surface 10 cm soil occurred as LFOC. Thus, LFOC was more responsive to N application and was a good indicator of N effect on soil C. The trend of change in soil TOC and LFOC was similar to hay yield and C removal in hay, which suggests that increasing hay yield with N application concurrently also increases soil organic C. In conclusion, long-term annual applications of N fertilizer to bromegrass resulted in a substantial increase in TOC and LFOC in the soil, thereby indicating that N fertilization can be used to sequester more atmospheric C in prairie grassland soils.     

Uptake and apparent utilization of urea and ammonium nitrate in wheat seedlings

Intact wheat (Triticum aestivum cv. Quern) seedlings that were grown in presence or absence of NH₄NO₃ were exposed to solutions containing CO(NH₂)₂, NH₄NO₃, CO(NH₂)₂ + NH₄NO₃, CO(NH₂)₂ + KNO₃ and CO(NH₂)₂ + (NH₄)₂SO₄ for consecutive periods of 3, 3, 6, 12 and 24h and N uptake determined by solution depletion measurements. Differences in ethanol-soluble N and ethanol-insoluble N content of roots and shoots of control (zero time) seedlings and seedlings exposed to CO(NH₂)₂, NH₄NO₃ and CO(NH₂)₂ + NH₄NO₃ for 48 h were used to characterize N utilization during/following uptake.Regardless of initial N status, uptake of N from CO(NH₂)₂ was less than one-third of that from NH₄NO₃. Relative absorption of the CO(NH₂)₂ and NH₄NO₃ was not substantially altered by acidity control of the uptake solutions. There was a reciprocal antagonism between uptake of CO(NH₂)₂ and uptake of NH₄NO₃. Whereas CO(NH₂)₂ inhibited NH₄ absorption in each set of seedlings, it decreased NO₃ uptake only in seedlings that had been pretreated with N. Simultaneous presence of KNO₃ enhanced CO(NH₂)₂ uptake but presence of (NH₄)₂SO₄ decreased it to the same extent as NH₄NO₃. All absorption processes involving CO(NH₂)₂ and NH₄ were substantially restricted by pretreatment of the seedlings with NH₄NO₃. The results suggest that apparent utilization of ambient N was dependent on initial N status of the seedlings and on the nature of the N species to which they were exposed.     

Detectability of15N-depleted fertilizer N in soil and plant tissue during a corn-rye crop rotation

Use of¹⁵N-depleted fertilizer materials have been primarily limited to fertilizer recovery studies of short duration. The objective of this study was to determine if¹⁵N-depleted fertilizer N could be satisfactorily used as a tracer of residual fertilizer N in plant tissue and various soil N fractions through a corn (Zea mays L.) -winter rye (Secale cereale L.) crop rotation. Nitrogen as¹⁵N-depleted (NH₄)₂SO₄ was applied at five rates (0, 84, 168, 252, and 336 kg N ha^–1) to corn. Immediately following corn harvest a winter rye cover crop treatment was initiated. Residual fertilizer N was easily detected in the soil NO ₃ ^- -N fraction following corn harvest (140-d after application). Low levels of exchangeable NH ₄ ⁺ -N (<2.5 mg kg^–1) did not permit accurate isotope-ratio analysis. Fertilizer-derived N recovered in the soil total N fraction following corn harvest was detectable in the 0 to 30-cm depth at each N rate and in the 30 to 60 and 60 to 90-cm depths at the 336 kg ha^–1 N rate. Atom %¹⁵N concentrations in the nonexchangeable NH ₄ ⁺ -N fraction did not differ from the control at each N rate. Nitrogen recovery by the winter rye cover crop reduced residual soil NO ₃ ^- -N levels below the 10 kg ha^–1 level needed for accurate isotope-ratio analysis. Atom %¹⁵N concentrations in the soil total N fraction (approximately one yr after application) were indistinguishable from the control plots below the 168, 252, and 336 kg ha^–1 N rate at the 0 to 30, 30 to 60, and 60 to 90-cm depths, respectively. Recovery of residual fertilizer N by the winter rye cover crop was verified by measuring significant decreases in atom %¹⁵N concentrations in rye tissue with increasing N rates. The greatest limitation to the use of¹⁵N-depleted fertilizer N as a tracer of residual fertilizer N in a corn-rye crop rotation appears to be its detectibility from native soil N in the total N pool.Research partially supported by grants from the National Fertilizer and Environmental Research Center/TVA and the Virginia Division of Soil and Water Conservation.     

Anthropogenic emissions of NOX, NH3 and N2O in India

Emissions of NO_x, NH₃ and N₂O from anthropogenic activities in India have been estimated based on actual field measurements as well as available default methodologies. The NO_x emissions are mainly from the transport sector and contribute about 5% of the global NO_x emission from fossil fuel. NH₃ emissions from urea seems to be highly uncertain. However, emissions of NH₃ from fertilizers and livestock are estimated to be 1175 Gg and 1433 Gg, respectively. N₂O emissions seem to be derived predominantly from fertilizer applications, resulting in the release of 199–279 Gg N₂O. Other sources of N₂O, viz. agricultural residue burning, biomass burning for energy and nitric acid production are estimated to be 3, 35–187 and 2–7 Gg, respectively.     

Fate of Fertilizer15N applied as urea and ammonium sulphate in opium poppy (Papaver somniferum L.) grown under greenhouse conditions

Laboratory incubation and greenhouse experiments were conducted to investigate the comparative effectiveness of urea and ammonium sulphate in opium poppy (Papaver somniferum L.) using¹⁵N dilution techniques. Fertilizer treatments were control (no N), 600 mg N pot^–1 and 1200 mg N pot^–1 (12 kg oven dry soil) applied as aqueous solution of urea or ammonium sulphate. Fertilizer rates, under laboratory incubation study were similar to that under greenhouse conditions. A fertilizer¹⁵N balance sheet reveals that N recovery by plants was 28–39% with urea and 35–45% with ammonium sulphate. Total recovery of¹⁵N in soil-plant system was 77–82% in urea. The corresponding estimates for ammonium sulphate were 89–91%. Consequently the unaccounted fertilizer N was higher under urea (18–23%) as compared to that in ammonium sulphate (9–11%). The soil pH increased from 8.2 to 9.4 with urea whereas in ammonium sulphate treated soil pH decreased to 7.3 during 30 days after fertilizer application. The rate of NH₃ volatilization, measured under laboratory conditions, was higher with urea as compared to the same level of ammonium sulphate. The changes in pH of soil followed the identical trend both under laboratory and greenhouse conditions.     

Soil organic carbon,total nitrogen and grain yields under long-term fertilizations in the upland red soil of southern China

A long-term experiment with various fertilizations was carried out during 1990–2006 in a double cropping system rotated with wheat (Triticum Aestivium L.) and corn (Zea mays L.) in the red soil of southern China. The experiment consisted of eight treatments: non-fertilization (CK), nitrogen–phosphorus fertilization (NP), phosphorus–potassium fertilization (PK), nitrogen–phosphorus–potassium fertilization (NPK), pig manure (M), pig manure and NPK fertilization (NPKM), high rates of NPKM (hNPKM), and straw returned with inorganic fertilizers (NPKS). Applications of manure (i.e., M, NPKM and hNPKM) significantly increased soil organic carbon (SOC) and total nitrogen contents. Applications of inorganic fertilizers without manure showed small influences on SOC, but resulted in declines of soil total nitrogen over the long-term experiment. Grain yields were more than doubled under fertilizations for both wheat and corn, with the highest under the NPKM and hNPKM treatments and the lowest under non-fertilization. Long-term cropping practices without fertilization or with unbalanced fertilizations (e.g., NP and PK) caused low grain yields. The balanced fertilization of NPK increased grain yields. However, such practice was not able to maintain high grain yields during the last few years of experiment. Our analyses indicate that both wheat and corn grain yields are significantly correlated with SOC, total and available nitrogen and phosphorus. However, the relationships are stronger with total nitrogen (r = 0.5–0.6) than with available nitrogen (r = 0.26–0.3), indicating the importance of maintaining soil total nitrogen in agricultural practice.     

Nitrogen supply,tree growth and soil acidification

Nitrogen is absorbed by trees in quantities larger than any of the mineral nutrients. It can be taken up by trees as NH₄ and as NO₃, but the relative ease with which they are absorbed does not necessarily reflect the degree of preference shown by tree species for either of the N forms.In an experiment with larch trees grown on mineral soil in 60-liter containers and supplied with¹⁵N-enriched NH₄ or NO₃, it could be shown that NH₄ is absorbed more readily than NO₃. With information available on the NH₄ : NO₃ uptake ratio, a cation-anion uptake balance sheet could be constructed for larch trees, showing a large excess of cations absorbed over anions. The resulting acidifying effect on the soil must be viewed as one of the major causes of acidification of forest soils in the Netherlands. This process, however, is but one in a cyclic sequence of N transformations in forest ecosystems, each one having its specific influence on soilpH. A model of these N transformations is presented and discussed.     

Total and organic soil carbon in cropping systems of Nepal

The significance of soil organic matter (SOM) in sustaining agriculture has long been recognized. The rate of change depends on climate, cropping system, cropping practice, and soil moisture. A 3-yr on-farm study was conducted in two major agro-ecologies (hills with warm-temperate climate and plains with subtropical climate) of Nepal. The soils in warm-temperate climate are Lithic subgroups of Ustorthents with well-drained loamy texture, and in subtropical climate are Haplaquepts with imperfectly drained loamy texture. Farmers’ predominant cropping systems were selected from different cultivation length in addition to a reference sample collected from adjacent virgin forest. The objectives were to examine the effect of cultivation length and cropping system on total carbon, KMnO₄-oxidizable soil C, C storage, and C/N ratio in two climatic scenarios: warm-temperate and subtropical. A large difference in KMnO₄-oxidizable soil organic C was observed due to the effect of cultivation length and cropping system. However, TC remained similar during the 3-year study. The decrease in KMnO₄-oxidizable C due to cultivation was more in the surface layer (43–56%) than in the subsurface layer (20–30%). Total C in uncultivated, < 10-year cultivated, and > 50-year cultivated soil was 22, 13, and 10 g kg⁻¹ in warm-temperate climate and 10, 6, and 5 g kg⁻¹ in subtropical climate, respectively. During the 3-year study period in both climates, large changes in soil C were observed for KMnO₄-oxidizable C but not for TC, confirming our earlier work on the usefulness of the KMnO₄ oxidized fraction for detecting a relatively short-term increase or decrease in soil C pool. The TC storage in uncultivated, < 10-year cultivated, and > 50-year cultivated soil was 38, 25, and 19 Mg ha⁻¹ in warm-temperate climate and 22, 15, and 12 Mg ha⁻¹ in subtropical climate, respectively. The rice–wheat and maize–potato cropping systems were good in storing soil C of 30 and 20 Mg ha⁻¹ for 0–15-cm soil depth in warm-temperate climate. The rice–wheat cropping system was also good in storing soil C in subtropical climate (19 Mg ha⁻¹) compared with other cropping systems studied.     

A comparative study of different leaching processes for the extraction of Cu,Ni and Co from a complex matte

The extraction behaviors of Cu, Ni and Co from a complex matte under different leaching conditions have been discussed. The synthetic Cu-Ni-Co-Fe-S matte was prepared by melting the pure metals. The matte contained 24.95% Cu, 35.05% Ni, 4.05% Co, 11.45% Fe, 24.5% S, similar composition as is expected to be obtained by reduction smelting of the Pacific Ocean nodules followed by sulphidisation of the alloy. The different phases identified are CuFeS₂, CuS₂, (FeNi)₉S₈, (FeNi)S₂, Ni₉S₈, Ni₃S₂, (CoFeNi)₉S₈ and Co metal. The merits and demerits of each process of dissolution i.e., H₂SO₄/oxygen pressure leaching, atmospheric FeCl₃ leaching, NH₄OH/(NH₄)₂SO₄ pressure leaching are discussed in detail. Out of the three, the H₂SO₄/oxygen pressure leaching process is found to be the most suitable with more than 99% metal extraction efficiency within 1 h of leaching time. From the X-ray diffraction analysis, the different undissolved phases corresponding to different leaching processes have been identified. The metal extraction efficiency decreased in case of atmospheric FeCl₃ leaching and NH₄OH/(NH₄)₂SO₄ pressure leaching processes due to the formation of product layer such as elemental sulfur and goethite, respectively.     

Denitrification, leaching and immobilisation of applied 15N following legume and grass pastures in a semi-arid climate in Australia

Four consecutive ¹⁵N mass balance experiments lasting 18 months from February 1993 to August 1994 were carried out to assess the fate of applied ¹⁵N at 3 sites after 4 years of lucerne or snail medic and 20 years of Mitchell grass/naturalised medic pastures respectively in the Roma district of Queensland, Australia. ¹⁵N loss via denitrification was estimated from the difference between the recovery of applied Br(100kg Br/ha) and that of applied ¹⁵N(40kg N/ha) in the top 250mm at the end of each mass balance experiment. From February to August 1993, denitrification losses were 12–38% of applied ¹⁵N. N losses increased to 36–51% during August to November 1993, responding to the higher rainfall during this period. With even more rainfall during the period between November 1993 and March 1994, N losses were estimated to be 16–23%while displacement of ¹⁵N below 250 mm was 74–81%. When rainfall was much less between March 1994 and August 1994, N losses of only 15–19% of the applied ¹⁵N occurred at the 3 sites. It was found that although rainfall was the dominant factor controlling denitrification of the applied ¹⁵N, soil available carbon (C) (measured as water-soluble C) and the quantity of nitrate available were also important for soils already containing a considerable quantity of organic matter and N from residues of pasture legumes. This revised version was published online in June 2006 with corrections to the Cover Date.     

Environmental factors and cultural measures affecting the nitrate content in spinach

Environmental factors and cultural measures affecting the NO₃-content in spinach were studied indoors, in water-, sand- and soil-culture experiments. In the field, the influences of variations in N-fertilizing practices and in spinach varieties were also tested.High NO₃-contents in spinach were found with low light intensities, with low soil-moisture contents, and with high temperatures. NO₃-contents increased with increasing K-dressing (less so with KCl than with K₂SO₄), but decreased with increasing soil pH. In pot experiments, positive results were obtained with sulphur-coated urea, with farmyard manure and with pigmanure slurry.Application of Mo as a spray onto spinach leaves, and variations in P-dressings and in soil P-status were found not to affect the NO₃-content in spinach.In pot experiments, NO₃-contents decreased with progressing plant age (in autumn less so than in spring). Within spinach plants, NO₃-contents were highest in petioles and older leaves. Varietal differences in NO₃-contents were observed in a pot- and a field experiment.In pot- and field experiments, partial or complete replacement of NO₃-N by NH₄-N in general caused the NO₃-content in spinach to decrease. However, such a replacement was shown not always to result in lower NO₃-contents. Additional factors involved are e.g. the use and effectiveness of nitrification inhibitors, the soil type and the amount of available N.The amount of N added and, in the field, the amount of N available in the soil before sowing, strongly affected the NO₃-content in spinach. Under field conditions, nitrogen appeared to be taken up from the top 60 cm of the soil profile.The effects of variations in timing of nitrogen applications were absent in a pot experiment and not consistent in field experiments.List of abbreviations A = sum of inorganic anions (Cl + H₂PO₄ + SO₄ + NO₃) in meq per kg DM (H₂PO₄ stands for total P) - ADI = acceptable daily intake - C = sum of inorganic cations (Ca + Mg + Na + K) in meq per kg DM - C-A = excess of inorganic cations over inorganic anions in plants, meq per kg DM; NH₄-ions are not included - CEC = cation exchange capacity - DCD = dicyandiamide (C₂H₄N₄) - DM = dry matter - FW = fresh weight - FYM = farmyard manure - JECFA = Joint FAO/WHO Expert Committee on Food Additives - N-serve = nitrification inhibitor, containing 2-chloro-6-(trichloromethyl) pyridine (C₆H₃NCl₄), known as nitrapyrin, as active compound - org N = organic nitrogen (= total N — NO₃-N) - PMS = pig-manure slurry - SCU = sulphur-coated urea - WHC = water-holding capacity - WHO = World Health Organization     

Evaluation of compacted urea fertilizers prepared with acid and non-acid producing chemical additives in three soils varying in pH and cation exchange capacity; I. NH3 volatilization

Efficacy of different acid-producing chemical additives was evaluated in terms of pH, urea hydrolysis, NH₄-N dynamics and NH₃ volatilization in an Alfisol, a Vertisol and an Inceptisol. Compacting phosphogypsum (PG), diammonium phosphate (DAP), ZnSO₄ and KCl separately with urea slowed down urea hydrolysis and reduced NH₃ volatilization loss. Peak volatilization loss of NH₃ occurred between 2 to 4 days of fertilizer application in Vertisol and Alfisol, but between 4 to 6 days in Inceptisol. Cation exchange capacity (CEC) of soil influenced more in reducing NH₃ loss than native soil pH, as lower amount of NH₃ was lost from Vertisol (pH=8.0, CEC=43.92 cmol_c kg^-1) than from Alfisol (pH=5.8, CEC=13.82 cmol_c kg^-1). The loss from Inceptisol was in between the above two soils.     

Genome-Wide Identification and Expression Analysis of AMT and NRT Gene Family in Pecan (Carya illinoinensis) Seedlings Revealed a Preference for NH4+-N

Nitrogen (N) is a major limiting factor for plant growth and crop production. The use of N fertilizer in forestry production is increasing each year, but the loss is substantial. Mastering the regulatory mechanisms of N uptake and transport is a key way to improve plant nitrogen use efficiency (NUE). However, this has rarely been studied in pecans. In this study, 10 AMT and 69 NRT gene family members were identified and systematically analyzed from the whole pecan genome using a bioinformatics approach, and the expression patterns of AMT and NRT genes and the uptake characteristics of NH₄⁺ and NO₃⁻ in pecan were analyzed by aeroponic cultivation at varying NH₄⁺/NO₃⁻ ratios (0/0, 0/100,25/75, 50/50, 75/25,100/0 as CK, T1, T2, T3, T4, and T5). The results showed that gene duplication was the main reason for the amplification of the AMT and NRT gene families in pecan, both of which experienced purifying selection. Based on qRT-PCR results, CiAMTs were primarily expressed in roots, and CiNRTs were majorly expressed in leaves, which were consistent with the distribution of pecan NH₄⁺ and NO₃⁻ concentrations in the organs. The expression levels of CiAMTs and CiNRTs were mainly significantly upregulated under N deficiency and T4 treatment. Meanwhile, T4 treatment significantly increased the NH₄⁺, NO₃⁻, and NO₂⁻ concentrations as well as the Vmax and Km values of NH₄⁺ and NO₃⁻ in pecans, and Vmax/Km indicated that pecan seedlings preferred to absorb NH₄⁺. In summary, considering the single N source of T5, we suggested that the NH₄⁺/NO₃⁻ ratio of 75:25 was more beneficial to improve the NUE of pecan, thus increasing pecan yield, which provides a theoretical basis for promoting the scale development of pecan and provides a basis for further identification of the functions of AMT and NRT genes in the N uptake and transport process of pecan.     

Sequestration of electroactive materials in a high Tg, insulating polymer matrix for optoelectronic applications. Part 1. Light emitting diode devices

The use of a high T_g, insulating polymer to sequester low molecular weight electroactive materials at high addition levels for utility in LED devices has been demonstrated. The threshold for effective light emission appears to be in the range of 15 wt% electroactive compounds in agreement with the percolation theory of deGennes. The high T_g polymer allows for suppression or elimination of the undesired crystallization of the electroactive species and yields a significant increase in the T_g of the light emitting layer (also required). Additionally this approach offers the potential for easier (and lower cost) fabrication routes not generally employed for low molecular weight electroactive materials (e.g. spin coating, ink jet printing, roll-to-roll printing). The improved mechanical properties of the light emitting layer with high molecular weight polymer addition should allow for improved performance/durability in flexible displays. The simple blend approach should be an attractive alternative to other more common methods reported in the literature employing covalent bonding of electroactive species to polymeric backbones to achieve the same results. This approach also allows for multiple addition of dopants (e.g. laser dyes), hole transport materials and electron transport materials in a single light emitting layer. While these results demonstrate the concept, optimization was not conducted and significant improvements would be expected with proper adjustment of the many variables possible with this approach.     

Ferroelectric and structural instability of (Pb,Ca)TiO3 thin films prepared in an oxygen atmosphere and deposited on LSCO thin films which act as a buffer layer

Structural, microstructural and ferroelectric properties of Pb_0.90Ca_0.10TiO₃ (PCT10) thin films deposited using La_0.50Sr_0.50CoO₃ (LSCO) thin films which serve only as a buffer layer were compared with properties of the thin films grown using a platinum-coated silicon substrate. LSCO and PCT10 thin films were grown using the chemical solution deposition method and heat-treated in an oxygen atmosphere at 700 °C and 650 °C in a tube oven, respectively. X-ray diffraction (XRD) and Raman spectroscopy results showed that PCT10 thin films deposited directly on a platinum-coated silicon substrate exhibit a strong tetragonal character while thin films with the LSCO buffer layer displayed a smaller tetragonal character. Surface morphology observations by atomic force microscopy (AFM) revealed that PCT10 thin films with a LSCO buffer layer had a smoother surface and smaller grain size compared with thin films grown on a platinum-coated silicon substrate. Additionally, the capacitance versus voltage curves and hysteresis loop measurement indicated that the degree of polarization decreased for PCT10 thin films on a LSCO buffer layer compared with PCT10 thin films deposited directly on a platinum-coated silicon substrate. This phenomenon can be described as the smaller shift off-center of Ti atoms along the c-direction 〈001〉 inside the TiO₆ octahedron unit due to the reduction of lattice parameters. Remnant polarization (P_r) values are about 30 μC/cm² and 12 μC/cm² for PCT10/Pt and PCT10/LSCO thin films, respectively. Results showed that the LSCO buffer layer strongly influenced the structural, microstructural and ferroelectric properties of PCT10 thin films.     

Influence of the Type of Reducing Agent (H2, CO, C3H6 and C3H8) on the Reduction of Stored NOX in a Pt/BaO/Al2O3 Model Catalyst

In this investigation, a comparative study for a NO _X storage catalytic system was performed focusing on the parameters that affect the reduction by using different reductants (H₂, CO, C₃H₆ and C₃H₈) and different temperatures (350, 250 and 150 °C), for a Pt/BaO/Al₂O₃ catalyst. Transient experiments show that H₂ and CO are highly efficient reductants compared to C₃H₆ which is somewhat less efficient. H₂ shows a significant reduction effect at relatively low temperature (150 °C) but with a low storage capacity. We find that C₃H₈does not show any NO _X reduction ability for NO _X stored in Pt/BaO/Al₂O₃ at any of the temperatures. The formation of ammonia and nitrous oxide is also discussed.