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  • nitrogen  (32)
  • 42.80
  • Springer  (42)
  • Annual Reviews
  • Elsevier
  • 1990-1994  (37)
  • 1975-1979  (5)
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  • Springer  (42)
  • Annual Reviews
  • Elsevier
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  • 1
    ISSN: 1573-5036
    Keywords: ammonia volatilization ; denitrification ; grazing ; model ; nitrate leaching ; nitrogen ; simulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The model simulates the cycling of N in grassland systems grazed by beef cattle and predicts the annual amount of N in liveweight gain, and the amounts lost through ammonia volatilization, denitrification and leaching, on the basis of fertilizer application and soil and site characteristics. It aims to provide a better understanding of the way in which these various factors interact in their influence on N transformations. The model has been programmed to run on IBM-compatible personal computers and responds rapidly to changes in input parameters. The model has been constructed from the average annual amounts of N passing through various components of the N cycle in ten field systems grazed by beef cattle. The amounts were either measured directly or were calculated from empirical sub-models, assuming a balance between inputs to, and outputs from the soil inorganic N pool. The model is given wide applicability through the inclusion of a mineralization sub-model which is sensitive to soil texture, sward age, previous cropping history, and climatic zone. Another important sub-model determines the partitioning of soil inorganic N to either plant uptake or the processes of loss: the proportion partitioned to plant uptake decreases as the total amount of soil inorganic N increases. Outputs from the model indicate that fertilizer N has a strong influence on ammonia volatilization, denitrification and leaching at a given site but that, over a range of sites with a given rate of fertilizer N, total loss and the proportions lost by the three processes are greatly influenced by the amount of N mineralized by the soil. The model indicates how fertilizer N should be matched with mineralization to limit gaseous and leaching losses and to achieve optimum efficiency of N use in grazing systems.
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  • 2
    ISSN: 1432-0649
    Keywords: 33.00 ; 42.65 ; 42.80
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We report direct measurements of the excited singlet state absorption cross section and the associated nonlinear refractive cross section using picosecond pulses at 532 nm in solutions of phthalocyanine and naphthalocyanine dyes. By monitoring the transmittance and far field spatial beam distortion for different pulsewidths in the picosecond regime, we determine that both the nonlinear absorption and refraction are fluence (energy per unit area) rather than irradiance dependent. Thus, excited state absorption (ESA) is the dominant nonlinear absorption process, and the observed nonlinear refraction is also due to real population excitation.
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  • 3
    ISSN: 1573-5036
    Keywords: grassland ; leaching ; leaf litter ; macro-organic matter ; mineralization ; nitrogen ; ploughing ; roots ; stubble
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The amounts of organic matter in the stubble, litter, root and soil macro-organic matter fractions of two swards of perennial ryegrass that had received normal applications of either fertilizer or cattle urine were, on average for the four fractions, about 3000, 500, 11,500 and 8,800 kg ha−1. The swards had been established 8 or 15 years previously and each was sampled at intervals over a period of about one year. The amounts of N contained in the four fractions were, on average, 68, 12, 249 and 240 kg ha−1, a total of 569 kg N ha−1. With other swards, increasing rates of application of fertilizer N were found to have little effect on the amounts of organic matter in stubble and roots. Concentrations of N in the organic matter of the stubble and roots, however, increased significantly with increasing rate of fertilizer application, though, with stubble, moderate rates of application had little effect. Assessments based on these data, together with other published information, indicate that the amount of N mineralized from the combined stubble, litter, root and macro-organic matter fractions during the first year after ploughing may range from about 40 kg to at least 360 kg N ha−1 depending on the age of the sward and its recent management. The amount mineralized is likely to increase with age of sward, with increasing rate of fertilizer N and with utilisation by grazing rather than cutting.
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  • 4
    ISSN: 1573-5095
    Keywords: actinorhizae ; fertilization ; Frankia ; nitrogen ; nodulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract To determine if inoculation increases nodulation and yield of bare-root red alder (Alnus rubra Bong.), fumigated nursery plots were treated with inoculum and ammonium sulfate (28 kg N ha−1) in a factorial experiment. Inoculum was alder soil with 100 infective units of Frankia g−1. Seedlings were evaluated for nodulation at age 10 wk and when lifted, at age 9 mo. Inoculation produced earlier and more extensive nodulation and increased seedling root collar diameter, height, and dry weight. Fertilization decreased seedling height, but did not decrease nodulation. No interaction of fertilization with inoculation was found. Inoculated unfertilized plots had the highest yield of packable seedlings (257 m−2), and uninoculated fertilized seedlings had the lowest yield (126 m−2).
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  • 5
    ISSN: 1432-0649
    Keywords: 42.60 ; 42.65 ; 42.80
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract An optical parametric oscillator (OPO), as a novel kind of broadband Stokes source, is employed for coherent anti-Stokes Raman spectroscopy (CARS). Compared to the conventional dye laser configuration OPO-CARS offers practical advantages. The tunable OPO allows a fast and comfortable frequency tuning. The excitation bandwidth of about 35 cm−1 (FWHM) limits the spectral range of effective and stable single pulse CARS generation but can be used to enhance selected spectral structures.
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Applied physics 50 (1990), S. 355-359 
    ISSN: 1432-0649
    Keywords: 42.65 ; 42.80
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The interaction between two strong pump beams and two signal beams is investigated both theoretically and experimentally. It is shown that the frequencies of the beams need to satisfy the relation that the sum of the pump beam frequencies should be equal to the sum of the signal beam frequencies. The gain is shown to depend on the detuning of the pump beams relative to the incident signal beam and on the direction of the signal beam. Maximum gain is obtained when the signal beams bisect the pump beams.
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Applied physics 53 (1991), S. 119-120 
    ISSN: 1432-0649
    Keywords: 42.80
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A colliding-pulse-mode-locked dye ring laser was mounted on a rotary stage and the beat frequency of the two output pulse trains was measured as a function of the rotation rate. The measurements are in good agreement with the Sagnac theory.
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  • 8
    ISSN: 1432-0649
    Keywords: 42.10 ; 42.65 ; 42.80
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract In this paper we examine the nonlinear optical properties of molecular systems undergoing acis-trans photoisomerization process. Such a process gives rise to dynamic photochromism on a picosecond time scale significant for designing a molecular Spatial Light Modulator (SLM). A kinetic analysis of a generalcis-trans nonlinear organic absorber is performed. The analysis is used to derive an expression for the imaginary part of the complex nonlinear molecular index of refraction. The properties of a molecular SLM based on such an absorber are discussed by examining the azo-type molecular system. These calculation predict an optimum contrast ratio and fast on-off switching for the SLM performance, achieved at low read-write laser intensities.
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Nutrient cycling in agroecosystems 27 (1991), S. 129-140 
    ISSN: 1573-0867
    Keywords: Douglas-fir ; nitrogen ; mineral cycling ; growth and yield
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Forest managers in the Pacific Northwest (PNW) use fertilization as a means to increase timber yields in managed stands. Information on the biological basis for nutrient amendments and stand growth responses to fertilization is required to effectively use fertilization as a silvicultural tool, and research programs in mineral cycling and forest nutrition have been underway in the region for about four decades. Most PNW Douglas-fir forest sites are nitrogen deficient. Mineral cycling research has shown high C/N ratios and low nitrification rates for soils in the region. Research and development projects in the Pacific Northwest have produced an information base that is used to select sites and stands for fertilization and to forecast growth after treatment. Much of the basis for operational fertilization programs in western Oregon and Washington comes from cooperative research programs; current activities for these programs are directed toward improving site-specific response information. Forest fertilization in the Pacific Northwest has become a silvicultural practice of major significance over the past two decades. Forest industry and government organizations managing forest lands in western Oregon and Washington apply nitrogen fertilizer to Douglas-fir stands over a range of soil and stand types (operational fertilization of other species is minor). About 50,000 to 55,000 ha are fertilized each year, and future programs will likely be of similar magnitude. Most current plans for management regimes including fertilization call for multiple applications.
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Nutrient cycling in agroecosystems 34 (1993), S. 121-126 
    ISSN: 1573-0867
    Keywords: Controlled release fertilizers ; electroultrafiltration ; nitrogen ; ryegrass
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The efficiency of different nitrogenous fertilizers under forced leaching conditions was determined in pot experiments using ryegrass as an indicator plant in a sandy loam soil. Treatments were: ON (unfertilized), AN (ammonium nitrate), U (urea), DAP (diammonium phosphate), T (Triabon), FK (Floranid Komplett) and CDU (crotonylidendiurea). N source effects on N uptake, and N leached (as % of N applied) were evaluated. Results show that the fertilizers which behaved best with regard to N uptake were FK followed by Triabon and AN. The most soluble fertilizers, AN and urea, gave the highest N leaching losses. Significant correlations between EUF-NI (rapidly soluble fraction) and leaching, as well as between EUF-N (I + II) and N uptake by the plant (where EUF-N II relates to the slowly soluble fraction) were obtained.
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