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  • 1
    Electronic Resource
    Electronic Resource
    Influence of dissimilarities in temporal and spatial N-uptake patterns on15N-based estimates of fixation and transfer of N in ryegrass-clover mixtures (1988)
    Springer
    Plant and soil 112 (1988), S. 167-175 
    Details
    ISSN: 1573-5036
    Keywords: clover ; Lolium multiflorum ; Lolium perenne ; 15N ; N-uptake ; nitrogen transfer ; nitrogen fixation ; Trifolium repens ; Trifolium pratense
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The temporal N-uptake patterns of white clover (Trifolium repens L.) mixed with perennial ryegrass (Lolium perenne L.) and of red clover (Trifolium pratense L.) mixed with Italian ryegrass (Lolium multiflorum Lam.) were determined in successive harvests of herbage within the growth cycles of a ley established near Zürich (Switzerland). Rooting patterns were examined by injecting15N-fertilizer at soil depths ranging from 10 to 40 cm. The results were analyzed to determine the effect of variations in time and depth of N-uptake on the15N-based measurement of N from symbiosis (Nsym) and N from transfer (Ntrans). Grasses in mixture appeared to have deeper rooting systems than grass monocultures, which led to an overestimation of N transfer from white clover to perennial ryegrass if15N was spread on the soil surface. White clover generally lagged behind grass in soil N- uptake. Soil N-uptake of red clover slowed down before that of the grass because % Nsym almost reached 100% during the second half of each growth cycle. However, the effect of these dissimilarities on the seasonal average of %Nsym did not exceed 2%. It is concluded that at the observed high levels of N2 fixation, failure to account for the N-uptake patterns of the test and reference crops only slightly affected the estimates of % Nsym and % Ntrans, and did not invalidate the observed differences between species.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02139992
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  • 2
    Electronic Resource
    Electronic Resource
    Symbiotically fixed nitrogen from field- grown white and red clover mixed with ryegrasses at low levels of15N-fertilization (1987)
    Springer
    Plant and soil 104 (1987), S. 219-226 
    Details
    ISSN: 1573-5036
    Keywords: clover ; legume/grass mixture ; Lolium multiflorum ; Lolium perenne ; 15N ; nitrogen fixation ; nitrogen transfer ; Trifolium pratense ; Trifolium repens
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract A field study was carried out near Zürich (Switzerland) to determine the yield of symbiotically fixed nitrogen (15N dilution) from white clover (Trifolium repens L.) grown with perennial ryegrass (Lolium perenne L) and from red clover (Trifolium pratense L.) grown with Italian ryegrass (Lolium multiflorum Lam.). A zero N fertilizer treatment was compared to a 30 kg N/ha per cut regime (90 to 150 kg ha−1 annually). The annual yield of clover N derived from symbiosis averaged 131 kg ha−1 (49 to 227 kg) without N fertilization and 83 kg ha−1 (21 to 173 kg) with 30 kg of fertilizer N ha−1 per cut in the seeding year. Values for the first production year were 308 kg ha−1 (268 to 373 kg) without N fertilization and 232 kg ha−1 (165 to 305 kg) with 30 kg fertilizer N ha−1 per cut. The variation between years was associated mainly with the proportion of clover in the mixtures. Apparent clover-to-grass transfer of fixed N contributed up to 52 kg N ha−1 per year (17 kg N ha−1 on average) to the N yield of the mixtures. Percentage N derived from symbiosis averaged 75% for white and 86% for red clover. These percentages were affected only slightly by supplemental nitrogen, but declined markedly during late summer for white clover. It is concluded that the annual yield of symbiotically fixed N from clover/grass mixtures can be very high, provided that the proportion of clover in the mixtures exceeds 50% of total dry mass yield.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02372535
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  • 3
    Electronic Resource
    Electronic Resource
    Nitrogen fixation by white clover when competing with grasses at moderately low temperatures (1991)
    Springer
    Plant and soil 133 (1991), S. 47-56 
    Details
    ISSN: 1573-5036
    Keywords: clover ; competition ; grass ; Lolium perenne ; 15N ; nitrogen fixation ; Phleum pratense ; temperature ; Trifolium repens
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract It was the aim of this study to determine the way in which low temperature modifies the effect of a competing grass on nitrogen fixation of a forage legume. White clover (Trifolium repens L.) was grown in monoculture or in different planting ratios with timothy (Phleum pratense L.) or perennial ryegress (Lolium perenne L.) in growth chambers at either 7.5/5°C (LoT) or 15/10°C (HiT) average day/night temperatures, and with 2.5 or 7.5 mM 15N-labelled nitrate in the nutrient solution. Competition with grass led to a marked increase in the proportion of clover nitrogen derived from symbiosis (% Nsym). This increase was slower at LoT where % Nsym was reduced considerably; it was closely related to the reduction in the amount of available nitrate as a result of its being utilized by the grass. Nitrogen concentration in white clover herbage and dry matter yield per clover plant were reduced, for the most part, when a competing grass was present. The amount of nitrogen fixed per plant of white clover decreased markedly with temperature. Low temperature consequently accentuated competition for nitrate. The capacity of white clover to compete successfully was limited by its slower growth and nitrogen accumulation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00011898
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  • 4
    Electronic Resource
    Electronic Resource
    Differences in nitrogen fixation among field-grown red clover strains at different levels of 15N fertilization (1994)
    Springer
    Euphytica 78 (1994), S. 67-174 
    Details
    ISSN: 1573-5060
    Keywords: red clover ; strains ; isotope dilution ; nitrogen fertilizer ; nitrogen fixation ; Trifolium pratense
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Genetic variation in fixed nitrogen (N) yield of red clover (Trifolium pratense L.) strains and cultivars was investigated using the 15N isotope dilution method under three regimes of N fertilization: 0.5, 30, and 60 N (kg N ha−1 per cut). The yield of fixed N per cut (the mean of eight cuts over 2 production years) varied among the strains (progenies of crosses between inbred parents) from 148 to 443 mg per plant at 0.5 N, from 76 to 324 mg at 30 N, and from 69 to 300 mg at 60 N. There were significant and consistent strain differences in the percentage of clover N derived from the atmosphere (% Ndfa). However, %Ndfa was positively correlated with dry mass yield. Consequently, ranking of the strains according to fixed N yield reflected that of dry mass yield. There were only minor strain × N fertilizer interactions, suggesting that selection for enhanced N fixation can be carried out at a single rate of fertilizer N. For a selected pair of strains, the difference in yield of fixed N was confirmed in an Italian ryegrass-red clover mixture, both without and with the addition of N fertilizer (50 kg N ha−1 per cut). Results with 7-week-old seedling plants in a growth chamber, although obtained in the presence of mineral N and with the isotope dilution method, did not adequately predict field performance. It is concluded that selection for dry matter or total N yield is likely to result in an enhanced yield of fixed N at any level of mineral N availability.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00027514
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