An evaluation of 15N methods for estimating nitrogen fixation in a subterranean clover-perennial ryegrass sward

1983 ◽  
Vol 34 (4) ◽  
pp. 391 ◽  
Author(s):  
FJ Bergersen ◽  
GL Turner
Keyword(s):  
Nitrogen Fixation ◽  
Perennial Ryegrass ◽  
N2 Fixation ◽  
Slow Growth ◽  
Subterranean Clover ◽  
Natural Abundance ◽  
Nitrogen Accumulation ◽  
Plant Parts ◽  
Natural Enrichment

Nitrogen (N2) fixation by nodulated subterranean clover, in swards with perennial ryegrass, was studied by using the natural abundance of 15N in sward components compared with a method using artificial enrichment of the soil with small amounts of K15NO3. Significant differences between the 15N concentrations in ryegrass and clover enabled yield-independent estimates of the proportion (P) of clover nitrogen fixed from atmospheric N2. Yield-dependent estimates of P were also made during intervals of growth in autumn and in spring. Values of P increased with time and during spring were close to l00%, when maximum fixation rates were approximately 4 kg N ha-1 day-1. Consistent differences in 15N concentration of shoots and roots had little effect on P. Early in the experiment, natural enrichment gave lower estimates of P than 15NO-3 -enriched treatments. Yield-independent and yield-dependent methods gave similar estimates of P. During winter, when no net growth or nitrogen accumulation was recorded, there appeared to be loss of 15N from the plants, possibly because of loss of highly labelled plant parts, balanced by slow growth of tissue containing a lower 15N concentration. During winter, calculation of P was therefore unreliable.

Sowing time and tillage practice affect chickpea yield and nitrogen fixation. 2. Nitrogen accumulation, nitrogen fixation and soil nitrogen balance

1996 ◽  
Vol 36 (6) ◽  
pp. 701 ◽  
Author(s):  
CP Horn ◽  
RC Dalal ◽  
CJ Birch ◽  
JA Doughton
Keyword(s):  
Nitrogen Fixation ◽  
N2 Fixation ◽  
N Balance ◽  
Grain Legume ◽  
Nitrogen Accumulation ◽  
Soil Nitrate ◽  
Soil N ◽  
Tillage Practice ◽  
Sowing Time ◽  
N Accumulation

Following long-term studies at Warra, on the western Darling Downs, chckpea (Cicer anetinum) was selected as a useful grain legume cash crop with potential for improvement of its nitrogen (N) fixing ability through management. This 2-year study examined the effect of sowing time and tillage practice on dry matter yield, grain yield (Horn et al. 1996), N accumulation, N2 fixation, and the subsequent soil N balance. Generally, greater N accumulation resulted from sowing in late autumn-early winter (89-117 kg N/ha) than sowing in late winter (76-90 kg N/ha). The amount of N2 fixed was low in both years (15-32 kg N/ha), and was not significantly affected by sowing time or tillage. The potential for N2 fixation was reduced in both years due to high initial soil nitrate levels and low total biomass of chickpea because of low rainfall. Nitrogen accumulation by grain was higher under zero tillage (ZT) than conventional tillage (CT) for all sowing times, and this affected the level of grain N export. The consequence of low N2 fixation and high N export in chickpea grain was a net loss of total soil N, (2-48 kg N/ha under CT and 22-59 kg N/ha under ZT). Management practices to ensure larger biomass production and lower soil nitrate-N levels may result in increased N2 fixation by chickpea and thus a positive soil N balance.

Nitrogen fixation in chickpea. II. Comparison of 15N enrichment and 15N natural abundance methods for estimating nitrogen fixation

1995 ◽  
Vol 46 (1) ◽  
pp. 225 ◽  
Author(s):  
JA Doughton ◽  
PG Saffigna ◽  
I Vallis ◽  
RJ Mayer
Keyword(s):  
Nitrogen Fixation ◽  
N2 Fixation ◽  
Full Range ◽  
15N Natural Abundance ◽  
Natural Abundance ◽  
Enrichment Method ◽  
Mineral N ◽  
Crop Establishment ◽  
15N Enrichment ◽  
15N Natural Abundance Method

The 15N enrichment and 15N natural abundance methods for estimating N2 fixation in chickpea were compared over a range of soil NO3-N levels at crop establishment varying from 10 to 326 kg N/ha (0-120 cm depth). Barley was used as a non-N2 fixing control crop. Both methods estimated reduced N2 fixation as soil NO3-N levels at crop establishment increased. Similar estimates of % N2 fixation were obtained at high values, but at low values the enrichment method gave lower estimates, some of which were negative. The 15N natural abundance method provided realistic estimates of % N2 fixation across all soil N03-N levels at crop establishment. An asymptotic curve described a close ( R2 = 0.95) relationship between these factors. Standard errors of estimates of means for the 15N natural abundance method remained acceptable and relatively stable over the full range of measurements; however, with the 15N enrichment method they became unacceptably large at low values of % N2 fixation. These large errors may have been partly due to legume and control plants assimilating mineral N of differing 15N enrichment. High mineral N levels associated with low values of % N2 fixation were also shown to reduce reliability of N2 fixation values estimated by the 15N enrichment method. These errors caused potentially greater inaccuracy at low values of % N2 fixation than at high values. To compare N2 fixation means statistically, transformations were necessary to stabilize variance and to impart lower weightings to plots with low values of % N2 fixation.

Herbage production and the accumulation of soil nitrogen under irrigated pastures on the Riverine Plain

1974 ◽  
Vol 14 (66) ◽  
pp. 49 ◽  
Author(s):  
CR Kleinig ◽  
JC Noble ◽  
AJ Rixon
Keyword(s):  
Perennial Ryegrass ◽  
Soil Nitrogen ◽  
White Clover ◽  
Accumulation Rate ◽  
Total Yield ◽  
Subterranean Clover ◽  
Nitrogen Accumulation ◽  
Total Soil ◽  
Total Soil Nitrogen ◽  
Applied Nitrogen

Herbage yield, herbage nitrogen, and soil nitrogen accumulation were followed over a five-year period (1958-63) under irrigated annual and perennial pastures established initially with different clovergrass proportions. Species sown in the annual pasture treatments were subterranean clover (Trifolium subterraneum cv. Tallarook) and annual ryegrass (Lolium rigidum cv. Wimmera). Those used in the perennial mixtures were white clover (T. repens cv. Irrigation) and perennial ryegrass (L. perenne cv. Victorian). In the treatments sown to annual or perennial ryegrass only, nitrogenous fertilizer as urea was applied annually at four rates. Total soil nitrogen (mat + 0-91 cm of soil) after five years did not differ significantly for annual pasture and bare ground. In contrast, total soil nitrogen under all perennial pasture treatments, particularly those with a white clover component, was significantly greater than for bare soil (5365 cf. 4181 kg ha-1). Where white clover was sown, nitrogen accumulated at the rate of 258 kg ha-1 per annum compared with 101 kg ha-1 per annum under subterranean clover, the latter barely matching the accumulation rate under perennial ryegrass sown alone without applied nitrogen (105 kg N ha-1 p.a.). Nitrogen accumulation (soil plus mat) was related to both legume and non-legume nitrogen. Perennial pasture, particularly if white clover was present, generally outyielded annual pasture. The total yield of white clover over five years was 29,970 kg ha-1 compared with 11,614 kg ha-1 for subterranean clover. Annual and perennial ryegrasses showed similar yield responses to applied nitrogen. Irrespective of the rate of urea application, nitrogen recovery was low (21-23 per cent).

Estimates of seasonal nitrogen fixation of annual subterranean clover-based pastures using the15N natural abundance technique

1995 ◽  
Vol 175 (1) ◽  
pp. 57-66 ◽  
Author(s):  
T. P. Bolger ◽  
J. S. Pate ◽  
M. J. Unkovich ◽  
N. C. Turner
Keyword(s):  
Nitrogen Fixation ◽  
Subterranean Clover ◽  
Natural Abundance

Variation in Natural Abundance of 15N among Plant Parts and in 15N/14N Fractionation during N2 Fixation in the Legume-Rhizobia Symbiotic System

1986 ◽  
Vol 27 (5) ◽  
pp. 791-799 ◽  
Author(s):  
Tadakatsu Yoneyama ◽  
Kounosuke Fujita ◽  
Tomio Yoshida ◽  
Tetsuo Matsumoto ◽  
Iwao Kambayashi ◽  
...  
Keyword(s):  
N2 Fixation ◽  
Natural Abundance ◽  
Symbiotic System ◽  
Plant Parts

Effects of Nitrate and Ammonium on Nitrogenase (C2H2 Reduction) Activity of Swards of Subterranean Clover, Trifolium subterraneum L

1986 ◽  
Vol 13 (2) ◽  
pp. 257 ◽  
Author(s):  
JH Silsbury ◽  
DW Catchpoole ◽  
W Wallace
Keyword(s):  
Nitrogen Fixation ◽  
Nitrate Reductase ◽  
Root System ◽  
N2 Fixation ◽  
Nitrogenase Activity ◽  
Alternative Hypothesis ◽  
Subterranean Clover ◽  
Mineral Nitrogen ◽  
Soluble Nitrogen ◽  
Split Root System

Small swards of subterranean clover plants were grown under controlled conditions without mineral nitrogen and allowed to establish an effective nitrogen fixation system. Nutrient solutions containing nitrate from 0 to 16 mM or of ammonium from 0 to 5 mM were then applied and changes in nitrogenase activity (NA) estimated by acetylene reduction assay (AR) and the rate of hydrogen evolution (HE) for periods of up to 35 days. In two experiments a split-root system was used to enable mineral nitrogen to be applied to only one-half of a nodulated root system whilst the NA of both halves was monitored. NA by subterranean clover was very sensitive to exogenous mineral nitrogen, concentrations as low as 0.5 mM NO3- suppressing activity significantly, and 3-5 mM stopping it almost completely within 7 days. The degree of inhibition induced by concentrations between 0.5 and 3 mM NO3- was less at a photon irradiance of 1000 compared with 300 �mol quanta s-1 m-2 . Under some conditions NA continued at a reduced but steady rate in the presence of nitrate. NH4+ also markedly depressed NA but a concentration greater than 5 mM was needed to effect the same response. After NO3- was applied to an active symbiosis, nitrate reductase activity increased as NA decreased. Our results do not support the hypothesis of a direct effect of NO3- on nitrogenase due to the accumulation of toxic NO2-. Although our results allow that assimilate might be diverted from the nodules after the application of NO3- thus reducing N2-fixation, an alternative hypothesis is proposed: that nitrogenase and nitrate reductase work in a complementary manner in supplying reduced nitrogen to whole plants, and NO3- depresses N2-fixation through a regulatory system involving the level of soluble nitrogen in the plant. We conclude that nitrogen fixation by subterranean clover in the field may be depressed below its potential due to the presence of soil mineral nitrogen.

Selection of reference plants for 15N natural abundance assessment of N2 fixation by crop and pasture legumes in south-west Australia

1994 ◽  
Vol 45 (1) ◽  
pp. 133 ◽  
Author(s):  
JS Pate ◽  
MJ Unkovich ◽  
EL Armstrong ◽  
P Sanford
Keyword(s):  
N2 Fixation ◽  
Subterranean Clover ◽  
15N Natural Abundance ◽  
Natural Abundance ◽  
Field Pea ◽  
Legume Species ◽  
Reference Species ◽  
Rooting Zone ◽  
South West ◽  
Reference Plants

The 15N natural abundance (S15N) of the shoot total N of a range of non-N2 fixing potential reference species was compared with that of nodulated field pea (Pisum sativum L.), narrow leafed lupin (Lupinus angustijolius L.) or subterranean clover (Trijolium subterraneum L.) across a range of field sites, to which N fertilizers had not been applied in the season of study. Shoot S15N values of reference species lay mostly within the range from +3 to +5%o and there was some evidence of lower S15N values in gramineaceous than dicotyledonous non-legume species. Continuous sampling within crops of each legume showed S15N values to differ consistently between and within potential reference species through the season. The S15N values of seedlings of four non legume species in a lupin crop were closer to that of soil N03-N (S15N = 4.2%o) than soil NH4-N (S15N = 7.9%0). Shoot S15N values of non-nodulated pea, lupin and subterranean clover, and a range of possible reference species all sand-cultured on a defined nitrate source (S15N = 7.5%), suggested little or no discrimination during utilization of nitrate. However, when four candidate reference species were sand cultured with nodulated actively fixing subterranean clover on the same nitrate source, the S15N of the ryegrass was lowered significantly below that of the NO3. Field plot comparisons of nine potential reference species with nodulated field pea showed certain species to resemble field pea more closely than others in terms of the S15N value of their shoots. Reference plants sampled within or well outside the rooting zone of an actively fixing legume (subterranean clover, field pea or lupin) showed significantly lower shoot S15N of mixed grass components when harvested in root contact with, as opposed to well distant from, subterranean clover. A similar effect was observed for barley within v. outside the rooting zone of pea, but no such effects were observed between capeweed and subterranean clover, pea and radish, or for any of five reference plants matched with lupin. The data are utilized to select appropriate reference plants for field assessments of N2 fixation under south-west Australian conditions.

Nitrogen and water flows under pasture - wheat and lupin - wheat rotations in deep sands in Western Australia. 1. Nitrogen fixation in legumes, net N mineralisation,and utilisation of soil-derived nitrogen

1998 ◽  
Vol 49 (3) ◽  
pp. 329 ◽  
Author(s):  
G. C. Anderson ◽  
I. R. P. Fillery ◽  
P. J. Dolling ◽  
S. Asseng
Keyword(s):  
Nitrogen Fixation ◽  
Western Australia ◽  
N2 Fixation ◽  
Supply And Demand ◽  
Subterranean Clover ◽  
High Rate ◽  
Organic N ◽  
N Mineralisation ◽  
Soil Cores ◽  
Inorganic N

Detailed studies on the eciency with which pastures and crops use soil-derived nitrogen (N) in southern Australia are limited. Inefficiencies in the N cycle are indicated by wide spread soilacidification and low N status in wheat grain. The aims of this study were to document rates of N2 fixation by subterranean clover-based pastures and narrow-leaf lupin, plant uptake of soil-derived N, mineralisation of organic N during legume and cereal phases, and export of N from pastures, lupin,and wheat in relation to climate and soil water. These measurements were undertaken in a rotation experiment conducted on a deep sand located in the northern wheat belt of Western Australia at a site with a long-term average rainfall of 460 mm. The rotations examined over 3 years were 2 years pasture-wheat and lupin-wheat. The 15N natural abundance technique was used to differentiate soil-derived N from atmospheric Nin legumes. Biomass production, grain yields, and N contents were standard plant measurements in all treatments. Net N mineralisation between growing seasons was as certained by measuring changes in soil inorganic N to 1·5 m. Growing season net N mineralisation was determined using an in situ method in which soil cores were isolated from plant roots. Anion exchange resin was used to trap NO-3 leached below the depth of the soil cores. Nitrogen fixation by subterranean clover in a mixed pasture ranged from 29 to 162 kg N/ha whereas N2 fixation by lupins was less variable, ranging from 90 to 151 kg N/ha. Pastures were large consumers of soil-derived N (range 58-154 kg N/ha), with capeweed being the most important sink (range 38-120 kg N/ha). In comparison, wheat and lupins were inefficient users of soil N, removing 29-51 kg N/ha within a season. Another 31-67 kg N/ha of inorganic N in soil was not utilised by wheat or lupin. Annual net N mineralisation ranged from 80 to 130 kg N, confirming the high rate of decomposition of organic matter in the sandy soil. Mineralisation over summer and autumn, when crop and pastures were not grown, supplied ~25% of the inorganic N produced in soil profiles in 1995 and 20-40% in1996. The study indicated that legumes used in rotations with cereals on deep sands were able to add adequate organic N to soil to insure rates of net N mineralisation sufficient to support cereal yieldsin excess of current shire averages. However, in practice, the asynchrony in supply and demand for N resulted in the inefficient use of soil-derived N by wheat.

Dry Matter and Nitrogen Accumulation and Partitioning in Field Grown Winged Bean

1991 ◽  
Vol 27 (3) ◽  
pp. 323-328 ◽  
Author(s):  
R. R. Weil ◽  
G. S. Belmont
Keyword(s):  
Seed Yield ◽  
Harvest Index ◽  
Dry Matter ◽  
Slow Growth ◽  
Leaf Tissue ◽  
Winged Bean ◽  
Nitrogen Accumulation ◽  
Plant Parts ◽  
Mature Seeds ◽  
Ground Material

SummaryGrowth and the partitioning of dry matter and nitrogen were studied in winged bean ‘SLS-40’ grown with single stake supports at two sites in Sri Lanka. Plant parts (leaves, petioles, stems, roots, nodules, flowers, green pods, mature seeds, and mature pod-walls) were collected periodically, if present, for up to 32 weeks after emergence. Slow growth up to the seventh week was followed by rapid growth (2.8 g plant−1 day−1) for the next 15–17 weeks. Little leaf senescence was observed and the nitrogen content of the leaf tissue remained close to 45 mg N g−1 throughout growth. The rate of nitrogen accumulation was 2.3–2.7 kg N ha−1 day−1 between weeks 13 and 32. The final accumulation of nitrogen in the above ground material was 280 to 312 kg N ha−1, only 34% of that being in the mature seed. The harvest index for dry matter was 17.5–20% and the dry seed yield almost 2 t ha−1.

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