Nitrogen Fixation in a White Clover‐Fescue Pasture Using Three Methods of Nitrogen‐15 Application and Residual Nitrogen‐15 Uptake

Labandera, C.; Danso, S. K. A.; Pastorini, D.; Curbelo, S.; Martin, Victoria

doi:10.2134/agronj1988.00021962008000020022x

Cited by 25 publications

(11 citation statements)

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“…These comparisons would however have been valid and more meaningful if they had simply been restricted to an examination of the relative 15N enrichments or % Ndff within only the legumes harvested at 90 DAP (even though they had no reference crop). Furthermore, Hardarson et al (1984b) and Labandera et al (1988), indicated that direct 15N isotopic parameters, such as % ~SN a.e. or % Ndff in fixing crops are more sensitive and perhaps result in more accurate relative comparisons than other isotope-derived estimates (e.g., those involving reference crops).…”

Section: Non-obligatory Requirement For Reference Cropsmentioning

confidence: 99%

“…These results indicate that the effect of frequent, small 15N fertilizer additions on estimates of N 2 fixed, if any, were rather small, and may be of little consequence especially at high levels of fixation. and Labandera et al (1988) suggested that ~5N uptake from residual N in soil is often insignificant compared to the substantial N uptake from recent applications, for which reason they obtained satisfactory estimates from such sequential ~SN additions. Based on field studies, Steele and Littler (1987) have similarly suggested that estimates of N 2 fixed, following multiple application of 15N on plots appear to be mostly influenced by the most recent addition of 15N.…”

Section: Frequency Of 15n Applicationmentioning

confidence: 99%

“…For example, it is not clear how the suggested differences in rhizosphere N and thus ~SN enrichments of the fixing and reference crops would cause more serious errors when ~SN application is repeated on the same plots than when 15N is applied once, at planting. On the contrary, the consecutive application of N of higher 15N enrichment than that present in the soil could obliterate differences in soil R that are likely to develop with time under the rhizospheres of the fixing and reference crops, where the ~SN was applied only at planting (Danso et al, 1987;Labandera et al, 1988). In addition, a single N rate, in order not to inhibit N 2 fixation and yet be detected over several seasons, may have to be highly enriched (i.e.…”

Section: Frequency Of 15n Applicationmentioning

confidence: 99%

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Misconceptions and practical problems in the use of 15N soil enrichment techniques for estimating N2 fixation

1993

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The ~SN methods are potentially accurate for measuring N 2 fixation in plants. The only problem with those methods is, how to ensure that the ~SN/14N ratio in the plant accurately reflects the integrated tSN/14N ratio (R) in soil which is variable in time and with soil depth. However, the consequences of using an inappropriate reference plant vary with the level of N 2 fixation and the conditions under which the study was made. For example, the errors introduced into the values of N 2 fixation are higher at low levels of fixation, and decrease with increasing rates of fixation. At very high N 2 fixation rates, the errors are often insignificant. Also, the magnitude of error is proportional to the rate of decline of the 15N/14N ratio with time. Since N 2 fixation in most plants would be expected to below 60%, the question of how to select a good reference plant is still pertinent. In this paper, we have discussed some of the criteria to adopt in selecting reference plants, e.g. how to ensure that the reference plant is not fixing N2, is absorbing most of its N from the same zone as the fixing plant, and in the same pattern with time, etc. In addition, we have discussed ~SN labelling materials and methods that are likely to minimize any errors even when the fixing and reference plants don't match well in certain important criteria. The use of slow release ~SN fertilizer or 15N labelled plant materials results in slow changes in the ~SN/~4N ratio of soil, and is strongly recommended. Where L~N inorganic fertilizers are used, the application of the fertilizer in small splits at various intervals is recommended over a one-time application. The problem with the reference crop, which has sometimes discouraged potential users of the 15N methods, is surmountable, as discussed in this paper. * Figures in parenthesis represent relative ranking made using each method.

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Section: Non-obligatory Requirement For Reference Cropsmentioning

confidence: 99%

Section: Frequency Of 15n Applicationmentioning

confidence: 99%

Section: Frequency Of 15n Applicationmentioning

confidence: 99%

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Misconceptions and practical problems in the use of 15N soil enrichment techniques for estimating N2 fixation

1993

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“…In isotope dilution the mineral N in soil is enriched or depleted with 15N by adding fertilizer N. Because the nitrogen fixed by the legume is close to natural abundance values of 15N, transfer of this N to a companion grass makes the 15N content of the grass closer to the natural abundance value. Isotope dilution is more sensitive for detecting N transfer than total N difference because it is yield independent (Labandera et al, 1988). Also, N transfer can be measured in the presence of fertilizer N applications (Boiler and Nosberger, 1988).…”

Section: Introductionmentioning

confidence: 99%

Nitrogen transfer from arrowleaf clover to ryegrass in field plantings

Morris

Weaver

Smith³

et al. 1990

Plant Soil

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Arrowleaf clover (Trifolium vesiculosum Savi) and annual ryegrass Lolium multiflorum Lam.) commonly are overseeded in dormant bermudagrass (Cynodon dactylon L. Pers.) sod on coastal plain soils in the southeastern United States. Two field experiments were conducted in consecutive years at different sites to estimate the amount of N transferred from the clover to the annual grass. Nitrogen treatments included 50 k g N h a -1 as 15N depleted ammonium nitrate applied in either February or April, and a check (no N applied). Three clippings were made during the cool-season from March to June. In both experiments, less than 5 kg N ha-were transferred from the clover to the grass. Ryegrass yields of dry matter and total N were not increased by growing with clover. Clover growth was typical for the region; average dry matter yield in pure stand was 2,615 kg ha -1 over the two-year period. Clover in mixed stand fixed between 20 and 60 kg N/ha. Less than 13% of N contained in ryegrass was transferred from arrowleaf clover to ryegrass at any clipping while clover was actively growing. The quantity of N transferred over the entire season was not statistically significant.

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“…Some methodoligical problems have recently been reported by Broadbent et al (1982) and Chalk (1985), most common of which is the selection of a satisfactory reference crop. Some attempts have been made to determine experimental errors resulting from adopting various approaches of the N-15 methodology, and possible solutions Labandera et al, 1988;Witty and Ritz, 1984). These however represent only a small proportion of the 15N based measurements of N 2 fixation, and several aspects of the methodology have frequently been adopted without adequate verification.…”

Section: Introductionmentioning

confidence: 99%

Assessment of potential sources of error in nitrogen fixation measurements by the nitrogen-15 isotope dilution technique

Danso

Kumarasinghe

1990

Plant Soil

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Although the use of 15N fertilizers to measure nitrogen (N2) fixed in crops has increased substantially in recent years, some methodological uncertainties still remain unresolved. The results obtained from a greenhouse study of soybean [Glycine max. (L.) Merrill] inoculated by six different methods have been examined for potential errors arising from incorporating tSN labelled fertilizer into soil to estimate N 2 fixed in pods or shoots or the whole plant at three growth stages (50% flowering, pod-initiation and physiological maturity) using as reference crops, an uninoculated soybean cultivar and a non-nodulating soybean isoline.At the first harvest when N 2 fixed was very low, the estimates of N 2 fixed by the two reference crops did not match. At this stage the uninoculated soybean estimated about four times as much N 2 fixed in the symbiotic soybean as that measured using the non-nodulating soybean. For the second and third harvests, there were substantial increases in N 2 fixed, and both the non-nodulating and uninoculated soybean were equally suitable as reference crops for assessing N 2 fixed in the symbiotic soybean. These results indicate how critical and difficult the choice of the reference crop could be at early harvests, or when N 2 fixed is low. Even though there were significant differences in 15N enrichments in different organs (generally nodules < pods < roots < shoots), the estimates of N 2 fixed in soybean plants obtained by excluding roots and nodules did not differ much from those based on the whole plant. Of the above-ground organs, % N 2 fixed in pods (containing seeds) was closest to that of the whole plant (similar at P < 0.05 at physiological maturity). However, the total N z fixed in pods or shoots was substantially lower than that fixed by the whole plant (P<0.05), although that for the pods and enclosed seeds once again was closer to N 2 fixed in the whole plant than that in the shoots.

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Nitrogen Fixation in a White Clover‐Fescue Pasture Using Three Methods of Nitrogen‐15 Application and Residual Nitrogen‐15 Uptake

Cited by 25 publications

References 11 publications

Misconceptions and practical problems in the use of 15N soil enrichment techniques for estimating N2 fixation

Misconceptions and practical problems in the use of 15N soil enrichment techniques for estimating N2 fixation

Nitrogen transfer from arrowleaf clover to ryegrass in field plantings

Assessment of potential sources of error in nitrogen fixation measurements by the nitrogen-15 isotope dilution technique

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