Evaluation of reference plants by labelling with 35S in the estimation of N2 fixation by 15N isotope dilution

1992 ◽  
Vol 145 (2) ◽  
pp. 177-185 ◽  
Author(s):  
S. D. Hamilton ◽  
P. M. Chalk ◽  
C. J. Smith ◽  
P. Hopmans
Keyword(s):  
Isotope Dilution ◽  
N2 Fixation ◽  
15N Isotope Dilution ◽  
15N Isotope ◽  
Reference Plants

Field estimation of N2 fixation by Acacia spp. using 15N isotope dilution and labelling with 35S

1993 ◽  
Vol 56 (1-4) ◽  
pp. 297-313 ◽  
Author(s):  
S.D. Hamilton ◽  
P. Hopmans ◽  
P.M. Chalk ◽  
C.J. Smith
Keyword(s):  
Isotope Dilution ◽  
N2 Fixation ◽  
15N Isotope Dilution ◽  
15N Isotope ◽  
Field Estimation

Estimation of N2 fixation by 15N isotope dilution —The A-value approach

1996 ◽  
Vol 28 (9) ◽  
pp. 1123-1130 ◽  
Author(s):  
Phillip M. Chalk
Keyword(s):  
Isotope Dilution ◽  
N2 Fixation ◽  
15N Isotope Dilution ◽  
15N Isotope ◽  
A Value

Quantification of the contribution of N2 fixation to field-grown grain legumes—A strategy for the practical application of the 15N isotope dilution technique

1990 ◽  
Vol 22 (5) ◽  
pp. 649-655 ◽  
Author(s):  
Robert M. Boddey ◽  
Segundo Urquiaga ◽  
Maria Cristina P. Neves ◽  
Allert R. suhet ◽  
JoséRoberto Peres
Keyword(s):  
Isotope Dilution ◽  
N2 Fixation ◽  
Grain Legumes ◽  
15N Isotope Dilution ◽  
Practical Application ◽  
Dilution Technique ◽  
15N Isotope ◽  
Isotope Dilution Technique ◽  
15N Isotope Dilution Technique

Site variability effect on field measurement of symbiotic nitrogen fixation using the 15N isotope dilution method

1987 ◽  
Vol 19 (4) ◽  
pp. 405-409 ◽  
Author(s):  
K. Reichardt ◽  
G. Hardarson ◽  
F. Zapata ◽  
C. Kirda ◽  
S.K.A. Danso
Keyword(s):  
Nitrogen Fixation ◽  
Isotope Dilution ◽  
Field Measurement ◽  
Symbiotic Nitrogen Fixation ◽  
Isotope Dilution Method ◽  
Dilution Method ◽  
15N Isotope Dilution ◽  
15N Isotope ◽  
Site Variability

Effect of reference plant on estimation of nitrogen fixation by subterranean clover using 15N methods

1985 ◽  
Vol 36 (5) ◽  
pp. 663 ◽  
Author(s):  
SF Ledgard ◽  
JR Simpson ◽  
JR Freney ◽  
FJ Bergersen
Keyword(s):  
Isotope Dilution ◽  
Subterranean Clover ◽  
Trifolium Subterraneum ◽  
15N Isotope Dilution ◽  
Soil N ◽  
15N Isotope ◽  
Reference Plant ◽  
Reconstituted Soil ◽  
Isotope Technique ◽  
Indigenous Plant

Subterranean clover (Trifolium subterraneum L.) was grown in separate associations with annual ryegrass (Lolium rigidum Gaud.) and with phalaris (Phalaris aguatica L.) in reconstituted soil profiles (0-400 mm depth), and N2 fixation was measured by 15N isotope dilution and 15N natural abundance methods. In all experiments, two values were determined, viz. P, the percentage of clover nitrogen (N) iixed from atmospheric N2, and R, the ratio of N assimilated from added 15N-labelled N to N assimilated from indigenous soil N. Estimates of P that were negative were obtained for the clover/phalaris association, using 15N isotope dilution, during the first 16 days after 15N addition. This was due to the R value being higher for clover than for phalaris, which in turn was due to differences in their temporal pattern of growth interacting with a declining ISN enrichment of the plant-available soil N. The R values for clover and ryegrass, when grown together, were similar throughout the experiment, and estimates of P by 15N isotope dilution and natural 15N abundance were similar. The activity of plant roots in different soil layers was examined by injecting a solution of 15N-labelled nitrate at 50, 150 and 300 mm depths. Uptake of 15N was similar at all depths for phalaris and clover, whereas ryegrass assimilated a greater amount at 150 and 300 mrn. However, since the amounts of roots and indigenous plant-available soil N were small in the 100-400 mm zone relative to the 0-100 mm zone, the greater activity of ryegrass roots at depth had no significant effect on the estimates of P. In both plant associations, the estimates of P, by both of the 15N methods, increased with time, and were higher in the clover/ryegrass association than with clover/phalaris. Since this was associated with lower levels of inorganic soil N in the clover/ryegrass association, it must be recognized that the reference plant can induce real changes in P by influencing the soil N status, in the association, as well as causing erroneous estimates of P by the 15N isotope technique.

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