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  • Nitrogen
  • Springer  (14)
  • American Chemical Society
  • Elsevier
  • 2000-2004
  • 1985-1989  (14)
  • 1989  (3)
  • 1986  (11)
Collection
Publisher
Years
  • 2000-2004
  • 1985-1989  (14)
Year
  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Biology and fertility of soils 8 (1989), S. 13-18 
    ISSN: 1432-0789
    Keywords: Bacteria ; Protozoa ; Predation ; Nitrogen ; Mineralization ; Plant uptake ; Soil
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Microbial N from 15N-labelled bacterial biomass was investigated in a microcosm experiment, in order to determine its availability to wheat plants. Sterilized soil was inoculated with either bacteria (Pseudomonas aeruginosa alone or with a suspension of a natural bacterial population from the soil) or bacteria and protozoa to examine the impact of protozoa. Plant biomass, plant N, soil inorganic N and bacterial and protozoan numbers were determined after 14 and 35 days of incubation. The protozoa reduced bacterial numbers in soil by a factor of 8, and higher contents of soil inorganic N were found in their presence. Plant uptake of N increased by 20010 in the presence of protozoa. Even though the total plant biomass production was not affected, the shoot: root ratios increased in the presence of protozoa, which is considered to indicate an improved plant nutrient supply. The presence of protozoa resulted in a 65010 increase in mineralization and uptake of bacterial 15N by plants. This effect was more pronounced than the protozoan effect on N derived from soil organic matter. It is concluded that grazing by protozoa strongly stimulates the mineralization and turnover of bacterial N. The mineralization of soil organic N was also shown to be promoted by protozoa.
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  • 2
    ISSN: 1432-1939
    Keywords: Compensatory growth ; Grazing ; Nitrogen ; Production ; Tropics ; Rainfall
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary We report the results of a pot experiment that examined the effects of three ecologically important factors controlling plant growth rates in savanna grasslands: defoliation, soil nitrogen and soil water availability. The experiment was conducted in the Amboseli region in east Africa, and was designed to simulate natural conditions as far as possible, using local soils and a grass species that is heavily grazed by abundant large herbivores. Productivity by different plant components was reduced, stimulated or unchanged by defoliation, depending on specific watering and fertilization treatments. Total above-ground production was stimulated by defoliation and was maximized at moderate clipping intensities, but this was statistically significant only when plants were watered infrequently (every 8 days), and most important, periods between clipping events were extended (at least 24 days). Under these conditions, plant growth rates were limited by water availability at the time of clipping, and soil water conserved in clipped, compared to unclipped plants. Within a given fertilization treatment, whole-plant production was never stimulated by defoliation because root growth was unaffected or inhibited by clipping. However, when fertilization was coupled to defoliation, as they are in the field, whole-plant production by fertilized and moderately clipped plants exceeded production by infertilized, unclipped plants. Under this interpretation, maximum whole-plant production coincided with optimum conditions for herbivores (maximum nitrogen concentration in grass leaves) when watering was frequent, and plants were moderately defoliated. However, these conditions were not the same as those that maximized relative above-ground stimulation of growth (infrequent watering and clipping). The results indicate that above-ground grass production can be stimulated by grazing, and when that is likely to occur. However, the results emphasize that plant production responses to defoliation can vary widely, contigent upon a complex interaction of ecological factors.
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Plant and soil 95 (1986), S. 191-200 
    ISSN: 1573-5036
    Keywords: Atmospheric input ; Douglas fir Fertilization ; Foliar analysis ; Forest nutrition ; N/P ratio ; Nitrogen ; Nutrient status ; Phosphorus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary A re-examination of earlier NPK fertilization experiments in Douglas fir stands on sandy soils shows the effects of high nitrogen input by air pollution during the last 10–15 years on plant nutrition at these sites. In 1960, experimental plots showed a positive growth reaction to nitrogen, phosphorus, and potassium fertilization. All suffered from severe phosphorus deficiency in 1984, low phosphorus in the needles was invariably accompanied by a high nitrogen content, with all N/P ratios between 20 and 30. The same conclusion emerges from an independent investigation of nutrient status of a selection of Douglas fir stands. Hence, if stand productivity and a balanced nutrient status of the trees is to be maintained, the increase in atmospheric input of nitrogen calls for supplementary fertilization. Given the current N/P ratios in the needles, a positive growth response to phosphorus fertilization is to be expected.
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Biology and fertility of soils 2 (1986), S. 109-112 
    ISSN: 1432-0789
    Keywords: Straw ; Phytotoxins ; Acetic Acid ; Wheat ; Barley ; Cultivar ; Nitrogen
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Acetic acid production over 10 days from fresh barley straw was greater than that from fresh wheat straw, but there were only minor consistent differences between different cultivars. The effect depended on the soil type on which the straw had been produced and acid production was greatest with the largest amounts of N fertilizer which had been used. The fertilizer also affected the C:N ratio of the straw
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Oecologia 71 (1986), S. 63-68 
    ISSN: 1432-1939
    Keywords: Rhus ; Lignotuber ; Nitrogen ; Water relations ; Fire
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Laurel Sumac (Rhus laurina) is a dominant member of the coastal chaparral community of southern California that survives periodic burning by wildfires by resprouting from a lignotuber (root crown). We investigated the physiological basis for resprouting by comparing shoot elongation, leaf nitrogen content, tissue water status, leaf conductance to water vapor diffusion, and photosynthetic rates of post-fire R. laurina to those of adjacent unburned shrubs. Resprouts had higher rates of shoot elongation, leaf conductance, and photosynthesis than mature, unburned shrubs. Leaf nitrogen contents were elevated in burned shrubs even though their leaves developed interveinal chlorosis. A comparison of soil water potential to predawn water potential indicated that roots of R. laurina remain active below 2 m during the first summer drought after wildfire. Our results support the hypothesis that lignotubers not only contain dormant buds that develop into aerial shoots after wildfire but they also supply nutrient resources that enhance shoot elongation. Because R. laurina is relatively sensitive to drought, yet very successful in its rapid recovery after fire, maintaining an active root system after shoot removal may be the primary function of the massive lignotuber formed by this species.
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  • 6
    ISSN: 1432-1939
    Keywords: Mimicry ; Nitrogen ; Herbivory ; Mistletoe ; Australia
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Leaves from many misletoe species in Australia strongly resemble those of their hosts. This cryptic mimicry has been hypothesized to be a means of reducing the likelihood of mistletoe herbivory by vertebrates. Leaf Kjeldahl nitrogen contents (a measure of reduced nitrogen and thus amines, amino acids and protein levels) of mistletoes and their hosts were measured on 48 mimetic and nonmimetic host-parasite pairs to evaluate hypotheses concerning the significance of crysis versus noncrypsis. The hypothesis that mistletoes mimicking host leaves should have higher leaf nitrogen levels than their hosts is supported; they may be gaining a selective advantage through crypsis (reduced herbivory). The second hypothesis that mistletoes which do not mimic their hosts should have lower leaf nitrogen levels than their hosts is also supported; they may be gaining a selective advantage through noncrypsis (reduced herbivory resulting from visual advertisement of their reduced nutritional status).
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  • 7
    ISSN: 1432-1939
    Keywords: Monoterpene ; Sesquiterpene ; Grand fir ; Nitrogen ; Allocation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Of ten terpenes that comprise most of the volatiles of grand fir foliage only four were affected by addition of nitrogen. Levels of beta-phellandrene, camphene and bornyl acetate and terpinolene were significantly reduced with nitrogen added to the equivalent amount of 44.8 g/m2. A quantity of 22.4 g/m2 did not affect terpene production. Several populations were examined and these did not respond consistently on a regional basis, yet a significant interaction effect was apparent between treatment and local population response. Overall, total yield of terpenes as a function of fertilization was not altered.
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  • 8
    ISSN: 1573-5036
    Keywords: Betula ; Clones ; Growth responses ; Nitrogen ; Salix ; Solution culture
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Growth of selected clones of birch and willow obtained from nitrogen deficient soils was compared with that of unselected controls in pot experiments using three levels of nitrogen. Unselected controls of both genera continued shoot growth, albeit very slowly, with a very low level of nitrogen (5 ppm), while selected clones of birch grew significantly more than the controls. Selected clones of willow, on the other hand, ceased shoot growth after 10 weeks with this low nitrogen treatment. Nevertheless, they remained healthy, their leaves containing similar concentrations of nitrogen to those of the plants which continued stem growth throughout the experiment. Furthermore, they had very high root: shoot ratios compared with those of control willows and both selected and unselected birch. The two genera may have developed different mechanisms for tolerating low nitrogen, birch producing a small, relatively efficient root system; willow a larger but less efficient one. Both appear equally effective in ensuring survival on low-nitrogen sites in the field since all the selected clones were obtained from such sites and have survived well in field trials on similar sites. Both birch and willow responded toincreased nitrogen availability with increasing shoot growth and a relative decline in root growth. However, whereas in willow the unselected plants responded significantly more than selected clones, a similar but less markeddifference was found in birch. It appears that in both genera, as in herbaceous plants originating from nitrogen deficient sites, selected clones are less able to respond to increasing nitrogen supply than control plants from more fertile habitats. Attempts to correlate the response of the selected clones to nitrogen in this experiment with that to added nitrogen fertilizer in field trials has been unsuccessful. Further work is required to determine the importance of the many interacting factors which influence the response of young trees to nitrogen under the unusual field conditions associated with restored mineral workings.
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Plant and soil 93 (1986), S. 373-382 
    ISSN: 1573-5036
    Keywords: Calcium ; Fertilizer ; Magnesium ; Nitrogen ; Nutrient content ; Phosphorus ; Pinus radiata ; Potassium ; Superphosphate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Nutrient contents of aPinus radiata stand, that is, aboveground tree, understorey, forest floor and soil to 200 mm depth, were estimated in a replicated fertilizer trial, treated 30 years previously. The fertilizer treatments were 0, 25, 50, 75 and 100 kg P/ha as broadcast superphosphate. Highly significant growth responses had been obtained to the applied P. Estimation of the P content of the stand showed that 129%, 89%, 72% and 67% of the applied P was found in the 25, 50, 75 and 100 kg P/ha treatments respectively. The larger losses of P at the higher application rates would explain the lack of increased response with the highest application rate, however, it also shows that significant quantities of P are still present after a period of 30 years, giving a basis for growth responses in the subsequent rotations. Elevated quantities of N, Ca, Mg and K were found in the treatments compared with the control and these could not be explained on the basis of atmospheric inputs. For the cations, uptake from deeper in the soil profile could explain most of the effect but not for the higher amounts of N which, in the case of the highest superphosphate treatment, amounted to an accumulation of 27 kg N/ha/yr. These nutrient changes together with increased soil organic matter contents are considered to have provided a long term increase to the site productivity.
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Plant and soil 91 (1986), S. 353-356 
    ISSN: 1573-5036
    Keywords: Hondeum vulgare L. ; Nitrogen ; NO2
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Exposure of the leaves of young barley plants to nitrogen dioxide (NO2) was shown to affect the rate of translocation of N, the form in which it is transported in the xylem stream and the partitioning of N between roots and shoots. Following its entry through the leaves, NO2 is assimilated by the plant into reduced nitrogenous compounds which accounted for the major increases in plant N content and growth. The various effects of atmospheric NO2 upon barley seedlings were strongly influenced by nitrate supply to the roots.
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