A survey of proportional dependence of subterranean clover and other pasture legumes on N2 fixation in south-west Australia utilizing 15N natural abundance

1994 ◽  
Vol 45 (1) ◽  
pp. 165 ◽  
Author(s):  
P Sanford ◽  
JS Pate ◽  
MJ Unkovich
Keyword(s):  
Soil Ph ◽  
Coastal Region ◽  
Subterranean Clover ◽  
15N Natural Abundance ◽  
Natural Abundance ◽  
Mineral N ◽  
Pasture Production ◽  
Total N ◽  
Study Region ◽  
Plant Nitrogen

In an attempt to understand why pasture production in southern Australia has declined markedly in recent years a survey of the symbiotic performance of the legume component of annual pastures on 81 farms (243 sites) was undertaken in the southern coastal region of Western Australia. The 15N natural abundance technique was used to determine the percentage of plant nitrogen derived from the atmosphere (%Ndfa) using capeweed (Arctotheca calendula) as principal non-fixing reference species. %Ndfa values were then related to edaphic and management information, e.g. soil total nitrogen, soil pH, stocking rates and cropping history of the sites. The principal legume species encountered exhibited similar mean %Ndfa values but substantial variation in symbiotic performance was evident across the sites, viz, Trifolium subterraneum 72%Ndfa (n = 184, range of values encountered 0-100%), Medicago spp. 7l%Ndfa (n = 24, range 7-l00%), Lotus spp. 8l%Ndfa (n = 15, range 1-l00%), Ornithopus compressus 76%Ndfa (n = 15, range 25-100%) and Trifolium balansae 69%Ndfa (n = 7, range 0-100%). In the case of subterranean clover, the most widely occurring species, almost one third (29%) of sites surveyed recorded %Ndfa values within the range 0-65%, suggesting that symbiotic performance might well be quite widely limiting to herbage production in the study region. Of the 24 edaphic and management factors evaluated, only one, %A1 in shoot, DM showed a significant relationship with %Ndfa, with 40% of the pastures surveyed deemed at risk in terms of acidity related aluminium toxicity. Correlations of %Ndfa with soil pH and soil total N produced examples of high values %Ndfa for sub-clover being associated with very low soil pH or high soil N, suggesting possible adaptation of symbiotic partnerships to acidity or high mineral N.

Nitrogen fixation in grazed and ungrazed subterranean clover pasture in south-west Australia assessed by the 15N natural abundance technique

1995 ◽  
Vol 46 (7) ◽  
pp. 1427 ◽  
Author(s):  
P Sanford ◽  
JS Pate ◽  
MJ Unkovich ◽  
AN Thompson
Keyword(s):  
Subterranean Clover ◽  
Trifolium Subterraneum ◽  
15N Natural Abundance ◽  
Natural Abundance ◽  
Shoot Biomass ◽  
Pasture Grass ◽  
Mineral N ◽  
Plant Nitrogen ◽  
Winter Depression ◽  
Grazed Pasture

The progress of N2 fixation by subterranean clover (Trifolium subterraneum L.) was followed throughout a growing season in adjacent grazed and ungrazed portions of a pasture at Mount Barker, W.A. Proportions of plant nitrogen derived from the atmosphere (%Ndfa) were determined at a sequence of sampling times using the 15N natural abundance technique with capeweed (Arctotheca calendula L.) as non-fixing reference species. Cumulative yields of fixed N by above ground biomass of clover were determined from %Ndfa values, concurrent estimates of dry matter (DM) yields, and percentage nitrogen in clover shoot DM. Seasonal DM yields of clover, capeweed and mixed grasses were in the approximate ratio 60 : 20: 20. Total herbage yields were 11.8 and 7.8 t ha-1 for the grazed and ungrazed swards respectively. Poorer performance of the latter was attributed to shading by taller grasses late in the season. Starting from a low value of 58%, Ndfa of the ungrazed sward became uniformly high (73-88%) for the rest of the season. Clover of the more productive grazed sward behaved similarly except for a significant mid winter depression to 55%Ndfa, probably caused by excessive defoliation through overgrazing. Fixed N recovered from clover shoot biomass was 103 and 188 kg N ha-1 for ungrazed and grazed pasture respectively. Mineral N under the grazed sward first consisted mostly of nitrate, and then predominantly of ammonium. Soil-derived N was utilized roughly equally by clover, grasses and capeweed and a field study of %Ndfa of subterranean clover grown in varying proportion with either the main pasture grass (Lolium rigidum Gaudin) or capeweed indicated the grass to be the more effective competitor for soil N against the clover. The data suggested that reliable estimates of seasonal accumulation of fixed N by pastures would be obtained from assessments of cumulative biomass yield of clover N with a single determination of %Ndfa at peak productivity in mid to late spring.

Isotopic Discriminations During the Accumulation of Nitrogen by Soybeans

1988 ◽  
Vol 15 (3) ◽  
pp. 407 ◽  
Author(s):  
FJ Bergersen ◽  
MB Peoples ◽  
GL Turner
Keyword(s):  
N2 Fixation ◽  
Root Nodules ◽  
Xylem Sap ◽  
Vacuum Treatment ◽  
Natural Abundance ◽  
Mineral Nutrient ◽  
Similar Time ◽  
Total N ◽  
Plant Nitrogen ◽  
Nitrate Treatment

Soybeans were grown in a glasshouse in sand-vermiculite medium supplied daily with a mineral nutrient solution essentially free of combined N or containing 5 mM nitrate of known 15N abundance. The natural abundance of 15N in parts of plants and in nitrogen remaining in the medium was determined from 15 days after planting until fruiting. In nodulated plants completely dependent on N2 fixation for growth, the δ15N of plant nitrogen was uniformly negative at 56 days (overall mean: -0.90� 0.17) after adjustment for the effect of seed nitrogen. The δ15N of root nodules increased with time (max. 9.6‰), as that of shoots declined (min. - 1.3 ‰). The δ15N of every mainstem trifoliolate leaf and of the first (unifoliolate) leaf declined from initially positive values (0.5 to 2 ‰) to about - 2‰ with similar time courses, irrespective of the time of initiation. There were no significant losses of N from the plants during growth. There were differences between the δ15N of the total N of root-bleeding xylem sap and of sap extracted by vacuum treatment of stems. These were due to differences between the proportions of ureide-N and amino-N and between the δ15N values of these components. When nodulated plants were supplied daily with 5 mM nitrate (δ15N = 7.68‰) between 21 and 35 days, N2 fixation was reduced to 63% of N assimilated but growth and accumulation of nitrogen were affected little. Following removal of nitrate, there were changes in growth which led to enhanced nodulation and N2 fixation. The δ15N of the total N of trifoliolate leaves which were initiated or expanded before or during the period of nitrate treatment remained positive; those expanded or initiated after the treatment became negative in δ15N, as in the corresponding leaves of untreated nodulated plants. The δ15N of nodules was unaffected by the nitrate treatment. In plants (non-nod. Clark '63) supplied continuously with nitrate, the δ15N of the total N of entire plants rose quickly from values for seeds, but to values significantly higher than in the nitrate. These results are discussed in relation to the effects on the use of 15N natural abundance data for estimating utilisation of atmospheric N2 by nodulated plants.

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.

Nitrogen Balance of Field Pea Crops in South Western Australia, Studied Using the 15N Natural Abundance Technique

1994 ◽  
Vol 21 (4) ◽  
pp. 533 ◽  
Author(s):  
EL Armstrong ◽  
JS Pate ◽  
MJ Unkovich
Keyword(s):  
Western Australia ◽  
N Uptake ◽  
15N Natural Abundance ◽  
Natural Abundance ◽  
Field Pea ◽  
N Balance ◽  
Total N ◽  
Peak Biomass ◽  
Biomass N ◽  
Total Plant

The nitrogen economies of six contrasting field pea (Pisum sativum L.) genotypes were examined at three widely separated sites in south Western Australia, using the 15N natural abundance technique to asssess proportional dependence on fixed N, harvests at peak biomass to assess total N yields and harvests at crop maturity to examine partitioning of N between seed and non harvested crop residues. The budgets for one site (Wongan Hills) included N of nodulated roots which on average comprised 12% of total plant N at peak crop biomass and 25% of recoverable plant N after harvest of seed. At this site maximum potential (residual) benefits to a following crop (peak total plant biomass N - N uptake from soil and N taken off as harvested seed) varied between genotypes from 8 to 41 g N ha-1 (mean 26; n = 6). Data for the other two sites, based solely on N budgets of above-ground parts, provided evidence of substantial site- and genotype-specific differences in N balance in terms of shoot residues (i.e. + 7 to - 24 kg N ha-1 (mean - 5) at Avondale, + 40 to - 29 (mean + 3) at Mt Barker). The results collectively indicated a general relationship between peak biomass N of a crop and its potential or otherwise to effect a net input of residue N to the ecosystem. There were, however, considerable variations between genotypes and sites due to differences in proportional dependence on fixation (range across all sites and genotypes 60-91%) and crop harvest indices for N (corresponding range 53-90%). Correlation plots were constructed from the data for N2 fixed against crop dry matter yield and residual nitrogen benefit against nitrogen harvest index. Results are discussed in relation to values for N balance of field pea and other grain legumes obtained elsewhere by other investigators.

Differences in natural abundance of 15N in the extractable mineral nitrogen of cropped and fallowed surface soils

1987 ◽  
Vol 38 (1) ◽  
pp. 15 ◽  
Author(s):  
GL Turner ◽  
RR Gault ◽  
L Morthorpe ◽  
DL Chase ◽  
FJ Bergersen
Keyword(s):  
Total Nitrogen ◽  
Soil Nitrogen ◽  
Mineral Nitrogen ◽  
Natural Abundance ◽  
Mineral N ◽  
Plant Nitrogen ◽  
Red Earth ◽  
Time Courses ◽  
Soil Nitrogen Cycle ◽  
Made In

The natural abundances (S15N with reference to atmospheric N2) of the stable isotope of nitrogen (15N) in the total nitrogen and in KCl-extractable mineral nitrogen (typically 96% NO-3-N and 4% NH+4-N) were measured in the surface 10 cm of a transitional red earth at Yanco, N.S.W., and of a grey soil of heavy texture at Trangie, N.S.W. Measurements were made in Autumn (May), prior to planting crops of winter oats, at the time of harvest (October) and in December, using both cropped and continuously fallowed soils. At Trangie, additional measurements were made in September, near the beginning of rapid growth in spring. Despite differences in soil type, pH .and location, both sites showed: (i) S15N in extractable mineral nitrogen varied with time (decreasing from 18.7 to 6.0% in fallowed soil at Yanco, and increasing from 5.8 to 12.0%~ under oats at Trangie), and in cropped versus fallowed treatments (12.0 and 5.3% respectively in December at Trangie), and values were different from those of the total soil nitrogen, in which S15N remained virtually unchanged (over all times and sites, S15N = 8.2 � 0.2 at Trangie); (ii) after removal of the crop, S15N in increments of extractable mineral nitrogen were higher than in the total nitrogen of previously cropped soils, whilst in the continuously fallowed soils, S15N of extractable mineral nitrogen was lower than in the total nitrogen. In addition, at Trangie, S15N in the extractable mineral nitrogen was highest late in growth of the oat crop, and this was reflected in the values for S15N of nitrogen assimilated in the crop. Values of the S15N of plant nitrogen agreed well with the S15N of extractable mineral N when the former were determined in increments of plant N during fixed periods of growth and plotted appropriately (the mid-point between sampling times) in relation to the time courses of changes in the mineral N. These results are discussed in relation to the use of 15N natural abundance techniques for estimating nitrogen fixation by nodulated legumes and in the study of other aspects of soil nitrogen cycle processes.

Changes in soil mineral nitrogen, nitrogen leached, and surface pH under annual and perennial pasture species

2009 ◽  
Vol 60 (10) ◽  
pp. 975 ◽  
Author(s):  
B. S. Dear ◽  
J. M. Virgona ◽  
G. A. Sandral ◽  
A. D. Swan ◽  
S. Morris
Keyword(s):  
Soil Ph ◽  
Perennial Grass ◽  
Subterranean Clover ◽  
Soil N ◽  
Soil Mineral ◽  
Soil Mineral Nitrogen ◽  
Mineral N ◽  
Available N ◽  
Surface Ph ◽  
Ornithopus Compressus

Soil mineral nitrogen (N) profiles during the growing season and changes in total soil N and available N after 3–4 years were examined under 9 different pasture swards containing annual legumes, lucerne (Medicago sativa L.), or one of 4 perennial grasses at 2 sites representative of the low and medium rainfall belt of south-eastern Australia. The effect of the presence of phalaris (Phalaris aquatica L.) or lucerne on the spatial variation in surface pH was also measured. The 9 pastures were subterranean clover (Trifolium subterraneum L.), subterranean clover with annual weeds, yellow serradella (Ornithopus compressus L.), lucerne, phalaris, cocksfoot (Dactylis glomerata L.), lovegrass (Eragrostis curvula (Schrader) Nees), wallaby grass (Austrodanthonia richardsonii (Cashm.) H.P. Linder), and a mixture of lucerne, phalaris, and cocksfoot. All the perennial treatments were sown with subterranean clover. Available mineral N values in the surface 0.10 m of soil following summer rainfall were substantially higher in pure subterranean clover or serradella (Ornithopus compressus L.) swards (24–50 μg N/g) than those containing a mixture of subterranean clover and perennials (9–20 μg N/g). Apparent leaching of soil nitrate down the profile during winter was greatest in annual pasture treatments and least in swards containing perennials. Soil pH(CaCl2) at the 0–0.10 m depth varied with proximity to perennial plants and was significantly higher (+0.2–1.1 pH units) near the base of perennial plants than in gaps between the perennials or in annual-only swards. Available mineral N to 1.0 m before cropping at the end of the pasture phase was highest following subterranean clover (175–344 kg N/ha) and serradella (202–316 kg N/ha) at both sites. Available N was lowest (91–143 kg N/ha) following perennial grass–clover swards at the drier site where the annual legume content was lower, but perennial grass–clover swards produced larger soil N values (147–219 kg N/ha) at the higher rainfall site. Removal of the pasture in August–September compared with November in the year before cropping increased available N at the time of sowing by an average of 44% (51 kg N/ha) at the drier site and 43% (74 kg N/ha) at the wetter site. Incorporating perennial pasture species in swards was found to be advantageous in reducing nitrate leaching and preventing a decline in surface soil pH; however, available soil N to following crops could be lower if the annual legume content of perennial grass-based pastures declined due to competition from the perennial species.

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.

Subterranean clover pasture responses to lime application on the acid soils of southern New South Wales

1992 ◽  
Vol 32 (8) ◽  
pp. 1051 ◽  
Author(s):  
BJ Scott ◽  
BR Cullis
Keyword(s):  
Soil Ph ◽  
Soil Amendment ◽  
Dry Matter ◽  
Nitrogen Concentration ◽  
Acid Soils ◽  
Subterranean Clover ◽  
Plant Responses ◽  
Nitrogen And Phosphorus ◽  
Pasture Production ◽  
Phosphorus Application

The effects of soil amendment with shallow (0-10 cm) incorporated lime or dolomite were examined at 3 sites with acid soils over 6 years. Measurement was made of soil pH and exchangeable cations, and of subterranean clover dry matter production, seed set, and concentrations of calcium, magnesium, manganese, nitrogen and phosphorus. Application of lime or dolomite increased the production of dry matter, but not by the alleviation of molybdenum deficiency. Response in yield ranged from nil to 47%, with most responses in the range 20-35%. Such responses persisted for 5-6 seasons following lime or dolomite application. Differences in soil pH associated with liming were maintained for the 6 years of measurement, so that the benefits in pasture production from soil amendment are likely to accrue beyond the time span of this study. The analyses of plant dry matter indicated that manganese toxicity may have been a factor in the response to lime at 1 harvest, and that higher nitrogen concentration was associated with liming at another. Generally, the plant analyses did not indicate a clear mechanism for the plant responses to lime, although the soil analyses indicated the presence of exchangeable aluminium in the unamended plots at all 3 sites. The plant responses demonstrated that acidity constrained the yield of subterranean clover grown on these soils.

scholarly journals A comparison under grazing of pasture production, pasture N content and soil mineral N levels between granular urea and ONEsystem® on two contrasting dairy farms in New Zealand

2015 ◽  
Vol 77 ◽  
pp. 259-268
Author(s):  
B.F. Quin ◽  
A.G. Gillingham ◽  
D. Baird ◽  
S. Spilsbury ◽  
M. Gray
Keyword(s):  
N Uptake ◽  
Dairy Farms ◽  
Field Trials ◽  
Early Spring ◽  
Early Summer ◽  
Mineral N ◽  
Pasture Production ◽  
Total N ◽  
Prilled Urea ◽  
N Efficiency

Field trials under grazing on two contrasting dairy farms in mid-Canterbury (Site C) on a stony silt loam under irrigation, and in rain-fed central Waikato (Site W) on a volcanic ash-derived soil, compared standard granular urea (4-5 mm diameter granules) with ONEsystem®. This uses prilled urea (0.8-2.8 mm diameter prills), passed through a fine water spray (50 litres/ha) that contains the urease inhibitor nbpt (2 gm nbpt/kg N) during application. A nil N control and three rates of each fertiliser were applied to 12 × 25 m plots on four occasions after rotational grazing during spring/early summer 2014. ONEsystem® resulted in extra dry matter (EDM) to N applied compared with granular urea at Site C. At Site W, the initial advantage to ONEsystem® in Period 1 (early spring) was not maintained. To produce EDM of 1250 (±750) kg/ha required 120 and 126 kg N/ha as granular urea at Sites C and W, respectively (giving EDM factors of 10.4 and 9.9 (± 2) kgDM/ kgN applied respectively). This compares with 50 and 74 kg N/ha required with ONEsystem® for higher EDM factors of 24 and 17 (± 5) kg DM/ kg N. Pasture N concentrations were higher at Site C following ONEsystem® application, and total N uptake was increased 3-fold compared to granular urea. At Site W, increases in EDM with ONEsystem® only occurred in the first period. The results of this study have implications for both the economic and environmental efficiency of fertiliser urea use on grazed pastures. Keywords: ONEsystem®, prilled urea, nbpt, granular urea, N efficiency, pasture, N uptake

Assessment of the phosphorus and sulphur status of subterranean clover pastures. 1. Environmental factors and pasture responses

1969 ◽  
Vol 9 (38) ◽  
pp. 310 ◽  
Author(s):  
K Spencer ◽  
D Bouma ◽  
DV Moye ◽  
EJ Dowling
Keyword(s):  
Soil Ph ◽  
Field Experiments ◽  
Subterranean Clover ◽  
Strong Relationship ◽  
Phosphorus Addition ◽  
Pasture Production ◽  
Podzolic Soils ◽  
South Wales ◽  
Site Characteristics ◽  
Phosphorus Status

A series of 21 standardized field experiments was set out on established subterranean clover (Trifolium subterranem) pastures in south-eastern New South Wales in the autumn of 1963. Pasture growth at eleven of the 21 sites responded to phosphorus addition ; eight responded to sulphur addition. A dual deficiency existed at five sites. Seasonal pasture production was increased by up to 3,200 lb of dry matter an acre by phosphorus addition, and by up to 5,500 lb by sulphur addition. Clover was the component responsive to phosphorus and/or sulphur at most sites. To determine whether site characteristics can provide a basis for predicting the phosphorus or sulphur status of a pasture, several climatic and soil components of the environment were correlated with responses. Phosphorus status was not related to the rainfall, temperature or elevation at the site, nor to the kind of soil or soil pH. The more deficient pastures were younger, and, on the granitic soils only, present phosphorus status reflected the amount of superphosphate used in the past. Sulphur status was significantly related to rainfall for the podzolic soils only (r = 0.72) ; the driest sites tended to be the most sulphur deficient ones. Sulphur status showed a poor overall relationship with temperature, the trend being for the occurrence of more deficient soils at lower temperatures or higher elevations. Within the podzolic soils, the relationship with temperature was more definite (r = 0.69). There was no association with kind of soil or past superphosphate use, but there was a moderate to strong relationship (r = -0.78) with soil pH (the less acid, the more S deficient).

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