An appraisal of recent field measurements of symbiotic N2 fixation by annual legumes

Unkovich, M.; Pate, John S.

doi:10.1016/s0378-4290(99)00088-x

Cited by 329 publications

(204 citation statements)

References 119 publications

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“…The less negative value of the 'B s ' values determined for plants grown in N-free medium may have been due to the lower total N accumulation of the plants under greenhouse conditions. Therefore Okito et al (2004) Okito et al (2004) suggest that the isotope fractionation associated with N 2 fixation in the intact Bradyrhizobium/soybean symbiosis is significant and may contradict the conclusion of Unkovich & Pate (2000) from their study on chickpea (Cicer arietinum),…”

Section: ----------------------------------------------------Mg Per Pmentioning

confidence: 99%

Bradyrhizobium strain and the 15N natural abundance quantification of biological N2 fixation in soybean

Guimarães¹,

Morais

Urquiaga

et al. 2008

Sci. agric. (Piracicaba, Braz.)

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In commercial plantations of soybean in both the Southern and the Cerrado regions, contributions from biological nitrogen fixation (BNF) are generally proportionately high. When using the 15 N natural abundance technique to quantify BNF inputs, it is essential to determine, with accuracy, the 15 N abundance of the N derived from BNF (the 'B' value). This study aimed to determine the effect of four recommended strains of Bradyrhizobium spp. (two B. japonicum and two B. elkanii) on the 'B' value of soybean grown in pots in an open field using an equation based on the determination of d 15 N natural abundance in a non-labelled soil, and estimate of the contribution of BNF derived from the use of 15 N-isotope dilution in soils enriched with 15 N. To evaluate N 2 fixation by soybean, three non-N 2 -fixing reference crops were grown under the same conditions. Regardless of Bradyrhizobium strain, no differences were observed in dry matter, nodule weight and total N between labelled and non-labelled soil. The N 2 fixation of the soybeans grown in the two soil conditions were similar. The mean 'B' values of the soybeans inoculated with the B. japonicum strains were -1.84 ‰ and -0.50 ‰, while those inoculated with B. elkanii were -3.67 ‰ and -1.0 ‰, for the shoot tissue and the whole plant, respectively. Finally, the 'B' value for the soybean crop varied considerably in function of the inoculated Bradyrhizobium strain, being most important when only the shoot tissue was utilised to estimate the proportion of N in the plant derived from N 2 fixation. 15 N, e estimativas da contribuição da FBN derivado do uso da técnica de diluição isotópica de 15 N em solo enriquecido com 15 N. Para avaliar a fixação de N 2 pela soja três plantas referenciam foram crescidas nas mesmas condições. Independente da estirpe de Bradyrhizobium, não foi observada diferença para matéria seca, massa de nódulos e N total entre solo marcado e não marcado. A fixação de N 2 em soja crescida nas duas condições de marcação do solo foi semelhante. Os valores médios de 'B' para plantas de soja inoculadas com estirpes de B. japonicum foram, em média, de -1,84 ‰ e -0,50 ‰ enquanto as inoculadas com B. elkanii apresentaram médias de -3,67 ‰ e -1,00 ‰, para parte aérea e planta inteira, respectivamente. Finalmente, o valor 'B' para a cultura da soja variou consideravelmente em função da estirpe de Bradyrhizobium inoculada, sendo mais importante quando se utiliza somente a parte aérea da planta para estimar a proporção do N da planta derivado da fixação de N 2 . Palavras-chave: Bradyrhizobium elkanii, Bradyrhizobium japonicum, Glycine max, valor de 'B' Biological N 2 fixation in soybean 517

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Section: ----------------------------------------------------Mg Per Pmentioning

confidence: 99%

Bradyrhizobium strain and the 15N natural abundance quantification of biological N2 fixation in soybean

Guimarães¹,

Morais

Urquiaga

et al. 2008

Sci. agric. (Piracicaba, Braz.)

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“…A plant's need for N increases progressively as the plant enters its exponential phase of growth and the demand for N outstrips the rate of supply from the soil (27). Crop legumes can fix 100-200 kg of N per hectare per year, but rates are often substantially lower, and over the past 25 years, soybeans and other legumes have shown a significant decline in N fixation (28,29).…”

mentioning

confidence: 99%

Pesticides reduce symbiotic efficiency of nitrogen-fixing rhizobia and host plants

Fox

Gulledge

Engelhaupt

et al. 2007

Proc. Natl. Acad. Sci. U.S.A.

266

141

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Unprecedented agricultural intensification and increased crop yield will be necessary to feed the burgeoning world population, whose global food demand is projected to double in the next 50 years. Although grain production has doubled in the past four decades, largely because of the widespread use of synthetic nitrogenous fertilizers, pesticides, and irrigation promoted by the ''Green Revolution,'' this rate of increased agricultural output is unsustainable because of declining crop yields and environmental impacts of modern agricultural practices. The last 20 years have seen diminishing returns in crop yield in response to increased application of fertilizers, which cannot be completely explained by current ecological models. A common strategy to reduce dependence on nitrogenous fertilizers is the production of leguminous crops, which fix atmospheric nitrogen via symbiosis with nitrogenfixing rhizobia bacteria, in rotation with nonleguminous crops. Here we show previously undescribed in vivo evidence that a subset of organochlorine pesticides, agrichemicals, and environmental contaminants induces a symbiotic phenotype of inhibited or delayed recruitment of rhizobia bacteria to host plant roots, fewer root nodules produced, lower rates of nitrogenase activity, and a reduction in overall plant yield at time of harvest. The environmental consequences of synthetic chemicals compromising symbiotic nitrogen fixation are increased dependence on synthetic nitrogenous fertilizer, reduced soil fertility, and unsustainable long-term crop yields.legume ͉ nitrogen fixation ͉ symbiosis ͉ Sinorhizobium meliloti

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“…Grasses, used as reference plants, are often more efficient than legumes in taking up soil N. Sainju et al (1998) concluded that rye had greater root density and scavenged more soil nitrate in early stages than crimson clover, when grown as winter cover crops. Cereals often have greater uptake of soil N than legumes during early growth, but legumes may accumulate more soil N over the growing season (Unkovich and Pate 2000).…”

Section: Breton Edmontonmentioning

confidence: 99%

“…The NA method is subject to variation from B values, and these values vary with species, plant age, growing conditions, and microsymbiont (Unkovich and Pate 2000). We used arbitrary B values of 0 for all seven clover species.…”

Section: Breton Edmontonmentioning

confidence: 99%

The green manure value of seven clover species grown as annual crops on low and high fertility temperate soils

Ross¹,

King²,

Izaurralde³

et al. 2009

Can. J. Plant Sci.

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, J. T. 2009. The green manure value of seven clover species grown as annual crops on low and high fertility temperate soils. Can. J. Plant Sci. 89: 465Á476. Annual and perennial clover species may differ in green manure value. Seven clover (Trifolium) species were grown as annual crops on low fertility (Breton) and high fertility (Edmonton) soils in Alberta. Four annual clovers [balansa (T. michelianum Savi), berseem (T. alexandrinum L.), crimson (T. incarnatum L.), and Persian (T. resupinatum L.)], three perennial clovers [alsike (T. hybridum L.), red (T. pratense L.), and white Dutch (T. repens L.)] and a non-legume reference crop [fall rye (Secale cereale L.)] were ploughed-down as green manure in autumn, and followed by barley (Hordeum vulgare L.). Annual clovers had greater biomass yields than perennial clovers, and berseem clover had the highest yield. At Breton, mean biomass N content was greater for perennial clovers (2.9 g N kg(1 ) than annual clovers (1.9 g N kg(1 ). Clover biomass at Breton yielded an average of 77 kg N ha (1 , with N derived from the atmosphere averaging 88% by N difference method and 75% by 15 N natural abundance method. At Edmonton, the green manures had few effects on soil nitrate and subsequent barley yields. At Breton, all clover green manures except balansa increased barley yields, and grain yields were greater following perennial clovers than annual clovers in one year. Annual clovers will provide forage biomass and add N in areas where rainfall is adequate, and they may be preferable under zero tillage. However there is no advantage of annual clovers, relative to perennial clovers, in terms of N supply. . Les espe`ces de tre`fle annuelles ont donne´plus de biomasse que les espe`ces vivaces, le tre`fle d'Alexandrie enregistrant le meilleur rendement. À Breton, la teneur en N moyenne de la biomasse e´tait plus e´leve´e pour les espe`ces vivaces (2,9 g de N par kg) que pour les espe`ces annuelles (1,9 g de N par kg). Toujours aB reton, la biomasse du tre`fle a donne´en moyenne 77 kg de N par hectare, l'azote issu de l'atmosphe`re en repre´sentant en moyenne 88 % quand on calcule sa proportion par soustraction et 75 % quand on la calcule en fonction de l'abondance de l'isotope 15 N dans la nature. À Edmonton, les engrais verts ont eu peu d'incidence sur les nitrates du sol et le rendement subse´quent de l'orge. À Breton, tous les engrais verts a`base de tre`fle sauf le tre`fle de Micheli ont accru le rendement de l'orge et le rendement ce´re´alier e´tait plus important apre`s la culture du tre`fle vivace qu'apre`s celle du tre`fle annuel. Les espe`ces annuelles de tre`fle produisent de la biomasse fourrage`re et ajoutent de l'azote au sol des endroits ou`il pleut suffisamment; il pourrait eˆtre pre´fe´rable de les cultiver quand on pratique le non-travail du sol. Ne´anmoins, cultiver des espe`ces annuelles plutoˆt que des espe`ces vivaces de tre`fle ne pre´sente aucun avantage en ce qui concerne l'apport de N.

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An appraisal of recent field measurements of symbiotic N2 fixation by annual legumes

Cited by 329 publications

References 119 publications

Bradyrhizobium strain and the 15N natural abundance quantification of biological N2 fixation in soybean

Bradyrhizobium strain and the 15N natural abundance quantification of biological N2 fixation in soybean

Pesticides reduce symbiotic efficiency of nitrogen-fixing rhizobia and host plants

The green manure value of seven clover species grown as annual crops on low and high fertility temperate soils

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