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  • ureides  (2)
  • Vigna umbellata  (1)
  • 1
    Electronic Resource
    Electronic Resource
    Measurement of N2 fixation in maize (Zea mays L.)—ricebean (Vigna umbellata [Thunb.] Ohwi and Ohashi) intercrops (1988)
    Springer
    Plant and soil 108 (1988), S. 125-135 
    Details
    ISSN: 1573-5036
    Keywords: intercropping ; N2 fixation ; natural15N abundance ; ureides ; Vigna umbellata ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The yield of N in maize (Zea mays L.) and ricebean (Vigna umbellata [Thumb.] Ohwi and Ohashi) were compared on a Tropoqualf soil in North Thailand in 1984 and 1985. Both species were grown in field plots in monoculture or as intercrops at a constant planting density equivalent to 8 maize or 16 ricebean plants per m2. The contribution of symbiotic N2 fixation to ricebean growth was estimated from measurements of the natural abundance of15N (δ15N) in shoot nitrogen and from analysis of ureides in xylem sap vacuumextracted from detached stems. The natural abundance of15N in the intercropped ricebean was found to be considerably less than that in monoculture in both growing seasons. Using maize and a weed (Ageratum conyzoides L.) as non-fixing15N reference plants the proportions (P 15N) of ricebean shoot N derived from N2 fixation ranged from 0.27 to 0.36 in monoculture ricebean up to 0.86 when grown in a 75% maize: 25% ricebean intercrop. When glasshouse-derived calibration curves were used to calculate plant proportional N2 fixation (Pur) from the relative ureide contents of field collected xylem exudates, the contribution of N2 fixation to ricebean N yields throughout the 1985 growing season were greater in intercrop than in monocrop even at the lowest maize:legume ratio (25∶75). Seasonal patterns of sap ureide abundance indicated that N2 fixation was greatest at the time of ricebean podset. The averagePur andP 15N in ricebean during the first 90 days of growth showed identical rankings of monocrop and intercrop treatments in terms of N2 fixation, although the two sets ofP values were different. Nonetheless, seasonal estimates of N2 fixation during the entire 147 days of legume growth determined from ureide analyses indicated that equivalent amounts of N could be fixed by ricebean in a 75∶25 intercrop and in monoculture despite the former being planted at one-quarter the density.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02370107
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Adaptation of methods for evaluating N2 fixation in food legumes and legume cover crops (1988)
    Springer
    Plant and soil 108 (1988), S. 143-150 
    Details
    ISSN: 1573-5036
    Keywords: legumes ; N2 fixation ; 15N analysis ; ureides ; xylem exudate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Methods for partitioning the nitrogen assimilated by nodulated legumes, between nitrogen derived from soil sources and from N2 fixation, are described as applied in peninsular Malaysia. The analysis of nitrogenous components translocated from the roots to the shoots of nodulated plants in the xylem sap is outlined, with some precautions to be observed for applications in the tropics. Some examples of the use of the technique in surverying apparent N2 fixation by tropical legumes, in studying interrow cropping in plantation systems and in assessing effects of experimental treatments on N2 fixation by food legumes, are described. Techniques for assesing N2 fixation by means of15N abundance have been used to show that applications of nitrogenous fertilizers commonly used in Malaysia for soybeans depress N2 fixation, that similar results are obtained with natural abundance and15N-enrichment methods and that, in at least two locations in Malaysia, differences between the natural abundance of15N in plant-available soil nitrogen and in atmospheric N2 are great enough to permit application to measurement of N2 fixation by leguminous crops.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02370109
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    Paper (German National Licenses)
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