Use of in situ 15N-labelling to estimate the total below-ground nitrogen of pasture legumes in intact soil - plant systems

1997 ◽  
Vol 48 (3) ◽  
pp. 295 ◽  
Author(s):  
Ann M. McNeill ◽  
Chunya Zhu ◽  
Ian R. P. Fillery
Keyword(s):  
Subterranean Clover ◽  
Bulk Soil ◽  
Vegetative Stage ◽  
Residual Fraction ◽  
N Fixation ◽  
15N Labelling ◽  
Below Ground ◽  
Sampling Procedures ◽  
Intact Soil

A leaf-feeding technique for in situ 15N-labelling of intact soil–pasture plant systems was assessed, using subterranean clover (Trifolium subterraneum L.) and serradella (Ornithopus compressus L.) grown under glasshouse conditions. Total recoveries of fed 15N were 87–100% following leaf-feeding of plants at flowering but were lower (74–84%) following the feed at the vegetative stage. Below-ground recovery of fed 15N ranged from 7 to 26%, with serradella partitioning a greater proportion of labelled N below ground than subterranean clover. Additionally, plants of both species fed at the vegetative stage accumulated a greater proportion of the 15N label below ground than did those fed at flowering. Dry sampling procedures, which utilised freeze-drying, enabled fractionation of the below-ground portion of the system into ‘clean’ nodulated macro-roots with no adhering soil, residual uncleaned root, rhizosphere, and bulk soil. Calculated specific enrichment for the ‘clean’ roots at different depths demonstrated a relatively uniform distribution of 15N label in the subterranean clover roots, whereas the presence of large indeterminate nodules in the crown region of serradella roots contributed to apparent uneven distribution of label. Approximately half of the N in the residual fraction of both species consisted of labelled material, postulated to be mostly fine root. Additionally, 5–20% of the rhizosphere N and 0·5–3% of the N in bulk soil was legume root-derived, with some 15N detected in the extractable total soluble N and microbial N pools. Rhizodeposition of N represented approximately 10% of total plant N and 17–24% of total below-ground N for subterranean clover, whereas values for serradella were 20 and 34–37%, respectively. Estimated total below-ground N of subterranean clover reached a maximum value of 177 mg N/plant at 98 days after sowing, which corresponded with a peak shoot N of 243 mg N. Maximum below-ground N for serradella attained 196 mg N/plant 84 days after sowing with a corresponding shoot biomass of 225 mg N. There was a decline in the total below-ground N of serradella at maturity. Overall, recovered clean root N represented 30–62% of estimated total below-ground N, so it was concluded that standard root recovery procedures might be likely to underestimate severely the total below-ground N accretion and N turnover by legumes. The implications of these results for field estimation of total legume N yield, biological N fixation, and the N benefit from legumes in rotations are discussed.

A new approach to quantifying the N benefit from pasture legumes to succeeding wheat

1998 ◽  
Vol 49 (3) ◽  
pp. 427 ◽  
Author(s):  
Ann M. McNeill ◽  
Chunya Zhu ◽  
Ian R. P. Fillery
Keyword(s):  
Subterranean Clover ◽  
Bulk Soil ◽  
Residual Fraction ◽  
15N Tracer ◽  
Soil Columns ◽  
Total N ◽  
Plant Soil ◽  
Soil Systems ◽  
Peak Biomass ◽  
Below Ground

Vegetative subterranean clover (Trifolium subterraneum L.) and serradella (Ornithopus compressus L.), growing in 1-m soil columns under glasshouse conditions during 1994, were fed 15N tracer by immersion of individual leaves (5 per plant) in a 0·4% (w/w) solution of labelled urea (99·6 atom% 15N). Four replicate soil-plant systems were harvested in late October 1994 at legume peak biomass (41 days after labelling) and in early December 1994 at maturity (90 days after labelling). The shoots were removed and the soil columns fractionated into clean macro-root, residual (root/soil) fraction, and bulk soil; the shoots from the remaining replicates were also harvested at maturity leaving the labelled soil columns intact. These intact columns were kept dry for 5 months during the summer then rewetted and planted with wheat in June 1995. Four replicate soil-plant systems were harvested at planting, tillering, anthesis, and maturity of the wheat and fractionated as before. Mean recovery of fed 15N by the plant{soil systems was 42% for subterranean clover and 64% for serradella. Proportional distribution of the recovered 15N was similar for both plant-soil systems: 67-69% recovered above-ground and 31-33% recovered below-ground for subterranean clover compared with 71-75% above-ground and 25-29% below-ground for serradella. Uniform labelling of below-ground nitrogen (BG N) enabled estimation of total BG N accumulation, under undisturbed conditions, for the two pasture species. Less than 60% of the total legume BG N for both species was recovered as macro-root, with up to 17% recovered in the residual fraction and 33-51% in the bulk soil. Subterranean clover increased its total amount of BG N from 174 to 218 mg/plant between peak biomass and maturity with >65% of this located in the top 10 cm of the soil. Total BG N for serradella was similar at peak biomass (172 mg/plant) and not only decreased slightly by maturity (160 mg/plant) but was also redistributed to depth between the 2 sampling times. The ratio of shoot N to total BG N at peak biomass was 1 : 0·68 for subterranean clover and 1 : 0·60 for serradella. Recovery of labelled legume BG N at harvest by wheat following subterranean clover was 25% and after serradella was 18%. Root residues from subterranean clover appeared to decompose more rapidly than those from serradella, manifest by rapid uptake by the succeeding wheat so that 66% of the total N benefit had accrued by tillering, whereas only 44% of the N benefit from serradella roots had accrued by tillering and 72% by anthesis.

scholarly journals Use of 33P to trace in situ the fate of canola below-ground phosphorus, including wheat uptake in two contrasting soils

2016 ◽  
Vol 67 (7) ◽  
pp. 726 ◽  
Author(s):  
Foyjunnessa ◽  
Ann McNeill ◽  
Ashlea Doolette ◽  
Sean Mason ◽  
Mike J. McLaughlin
Keyword(s):  
Brassica Napus ◽  
Phosphoric Acid ◽  
P Uptake ◽  
Bulk Soil ◽  
P Pools ◽  
P Cycling ◽  
Below Ground ◽  
Crop Root

Our understanding of the contribution of crop root residues to phosphorus (P) cycling is mainly derived from studies using excavated roots re-introduced to soil. This study aims to quantify total below-ground P (BGP) of mature canola in situ and to estimate directly the proportion accessed by subsequent wheat. 33P-Labelled phosphoric acid was fed by stem wick to canola (Brassica napus) grown in sand or loam in pots. Shoots were removed from all plants at maturity. Half of the pots were destructively sampled. After a 3-week fallow, wheat was grown for 5 weeks in the remaining undisturbed pots. At canola maturity, 23–36% of the 33P was partitioned in recovered roots and 34–40% in the soil. More 33P was recovered in the loam than the sand. Within the soil, 6–10% of the fed 33P was present in resin P and 3–5% was in hexanol-released P pools. Ratios of shoot P : BGP (8 : 1 in sand and 15 : 1 in loam) were much narrower than those of shoot P : recovered root P (17 : 1 in sand and 39 : 1 in loam). A greater proportion and amount of the mature canola BG33P was recovered by wheat grown in the loam (26%, 2.6 mg/plant) than in the sand (21%, 1.5 mg/plant). The majority of canola BG33P remained in the bulk soil. Input of P below-ground by mature canola and subsequent P benefit to wheat was greater in loam than sand. The P from canola below-ground residues contributed up to 20% of P uptake in wheat during the first 5 weeks of growth. Longer term benefits of P from below-ground residues require investigation.

scholarly journals Study of Oak Ridge soils using BONCAT-FACS-Seq reveals that a large fraction of the soil microbiome is active

2018 ◽  
Author(s):  
Estelle Couradeau ◽  
Joelle Sasse ◽  
Danielle Goudeau ◽  
Nandita Nath ◽  
Terry C. Hazen ◽  
...  
Keyword(s):  
Soil Microbes ◽  
Sequence Similarity ◽  
Large Fraction ◽  
Amplicon Sequencing ◽  
Bulk Soil ◽  
Soil Microbiome ◽  
Active Fraction ◽  
Soil Microbial Diversity ◽  
Oak Ridge

AbstractThe ability to link soil microbial diversity to soil processes requires technologies that differentiate active subpopulations of microbes from so-called relic DNA and dormant cells. Measures of microbial activity based on various techniques including DNA labelling have suggested that most cells in soils are inactive, a fact that has been difficult to reconcile with observed high levels of bulk soil activities. We hypothesized that measures of in situ DNA synthesis may be missing the soil microbes that are metabolically active but not replicating, and we therefore applied BONCAT (Bioorthogonal Non Canonical Amino Acid Tagging) i.e. a proxy for activity that does not rely on cell division, to measure translationally active cells in soils. We compared the active population of two soil depths from Oak Ridge (TN) incubated under the same conditions for up to seven days. Depending on the soil, a maximum of 25 – 70% of the cells were active, accounting for 3-4 million cells per gram of soil type, which is an order of magnitude higher than previous estimates. The BONCAT positive cell fraction was recovered by fluorescence activated cell sorting (FACS) and identified by 16S rDNA amplicon sequencing. The diversity of the active fraction was a selected subset of the bulk soil community. Excitingly, some of the same members of the community were recruited at both depths independently from their abundance rank. On average, 86% of sequence reads recovered from the active community shared >97% sequence similarity with cultured isolates from the field site. Our observations are in line with a recent report that, of the few taxa that are both abundant and ubiquitous in soil, 45% are also cultured – and indeed some of these ubiquitous microorganisms were found to be translationally active. The use of BONCAT on soil microbiomes provides evidence that a large portion of the soil microbes can be active simultaneously. We conclude that BONCAT coupled to FACS and sequencing is effective for interrogating the active fraction of soil microbiomes in situ and provides new perspectives to link metabolic capacity to overall soil ecological traits and processes.

Estimating Wheat Shoot Nitrogen Content at Vegetative Stage from In Situ Hyperspectral Measurements

Crop Science ◽  
2013 ◽  
Vol 53 (5) ◽  
pp. 2063-2071 ◽  
Author(s):  
Yansong Bao ◽  
Kang Xu ◽  
Jinzhong Min ◽  
Jianjun Xu
Keyword(s):  
Nitrogen Content ◽  
Vegetative Stage ◽  
Wheat Shoot

Seed-setting in subterranean clover (Trifolium subterranean L.). III. The effect of plant density

1961 ◽  
Vol 12 (1) ◽  
pp. 10 ◽  
Author(s):  
JJ Yates
Keyword(s):  
Seed Production ◽  
Seed Weight ◽  
Plant Density ◽  
Plant Cover ◽  
General Pattern ◽  
Strain Differences ◽  
Subterranean Clover ◽  
Seed Setting ◽  
Below Ground ◽  
Australian Wheat

Various aspects of seed production in a number of strains of subterranean clover sown at fire seeding rates at two sites in the Western Australian wheat-belt were investigated. Dry matter yields and percentage leaf in the foliage were also recorded. Percentage leaf increased with plant density in the earlier-maturing, stemmy strains, so that differences amongst strains diminished as density increased. The differences amongst strains in number of inflorescences when grown as single plants were largely eliminated under dense sward conditions, so that the two main factors in seed production were number of seeds per inflorescence and mean seed weight. The proportion of burrs above and below ground varied widely amongst strains, and was influenced by plant density in some strains. It is postulated that the extent of burr burial depends on the interaction between strain, environment, and condition of the surface soil. Burr burial improved the efficiency of seed-setting, particularly in the more severe environment. Strain differences in seeds per inflorescence below ground were relatively small, but within each strain, values were higher in the more favorable environment. The efficiency of seed-setting above ground differed considerably amongst strains and between the two environments, and tended to increase with plant density particularly in the earlier-maturing strains. Correlations were established between seeds per inflorescence above ground and the amount of plant cover in these strains. An artificial covering of wood-wool also improved seed-setting above ground. Mean seed weight followed the same general pattern as seeds per inflorescence.

Nitrogen fixation by subterranean clover (Trifolium subterraneum L.) growing in pure culture and in mixtures with varying densities of lucerne (Medicago sativa L.) or phalaris (Phalaris aquatica L.)

1999 ◽  
Vol 50 (6) ◽  
pp. 1047 ◽  
Author(s):  
B. S. Dear ◽  
M. B. Peoples ◽  
P. S. Cocks ◽  
A. D. Swan ◽  
A. B. Smith
Keyword(s):  
Medicago Sativa ◽  
N2 Fixation ◽  
Pure Culture ◽  
Subterranean Clover ◽  
Trifolium Subterraneum ◽  
Shoot Biomass ◽  
N Fixation ◽  
Mineral N ◽  
Phalaris Aquatica ◽  
Medicago Sativa L

The proportions of biologically fixed (Pfix) plant nitrogen (N) and the total amounts of N2 fixed by subterranean clover (Trifolium subterraneum L.) growing in pure culture and in mixtures with different densities (5, 10, 20, or 40plants/m2) of newly sown phalaris (Phalaris aquatica L.) or lucerne (Medicago sativa L.) were followed over 3 years in a field study using the 15N natural abundance technique. The amount of fixed N in subterranean clover was linearly related to shoot biomass. Over the 3-year period, subterranean clover fixed 23–34 kg N/t shoot biomass compared with 17–29 kg N/t shoot biomass in lucerne. Based on above-ground biomass, pure subterranean clover fixed 314 kg N/ha over the 3 years compared with 420–510 kg N/ha by lucerne–clover mixtures and 143–177 kg N/ha by phalaris–clover mixtures. The superior N2 fixation by the lucerneŒsubterranean clover mixtures was due to the N fixed by the lucerne and the presence of a higher subterranean clover biomass relative to that occurring in the adjacent phalaris plots. In the first year, 92% of subterranean clover shoot N was derived from fixation compared with only 59% of lucerne. The reliance of clover upon fixed N2 remained high (73–95%) throughout the 3 years in all swards, except in pure subterranean clover and lucerne in August 1996 (56 and 64%, respectively). Subterranean clover usually fixed a higher proportion of its N when grown in mixtures with phalaris than with lucerne. The calculated Pfix values for lucerne (47–61% in 1995 and 39–52% in 1996) were consistently lower than in subterranean clover and tended to increase with lucerne density. Although lucerne derived a lower proportion of its N from fixation than subterranean clover, its tissue N concentration was consistently higher, indicating it was effective at scavenging soil mineral N. It was concluded that including lucerne in wheat-belt pastures will increase inputs of fixed N. Although lucerne decreased subterranean clover biomass, it maintained or raised Pfix values compared with pure subterranean clover swards. The presence of phalaris maintained a high dependence on N2 fixation by subterranean clover, but overall these swards fixed less N due to the lower clover herbage yields. Perennial and annual legumes appear compatible if sown in a mix and can contribute more N2 to the system than where the annual is sown alone or with a perennial grass. These findings suggest that increases in the amount of N2 fixed can be achieved through different legume combinations without interfering greatly with the N fixation process. Different combinations may also result in more efficient use of fixed N2 through reduced leaching. Further work looking at combinations of annuals possibly with different maturity times, different annual and perennial legume combinations, and pure combinations of perennial (e.g. lucerne) could be investigated with the aim of maximising N2 fixation and use. Grazing management to encourage clover production in mixtures with phalaris will be necessary before the potential of subterranean clover to contribute fixed N2 in these swards is fully realised.

Estimates of lupin below-ground biomass nitrogen, dry matter, and nitrogen turnover to wheat

1996 ◽  
Vol 47 (7) ◽  
pp. 1047 ◽  
Author(s):  
CA Russell ◽  
IRP Fillery
Keyword(s):  
Dry Matter ◽  
Soil Columns ◽  
Soil System ◽  
Wheat Growth ◽  
Ground Biomass ◽  
Plant Soil ◽  
Below Ground ◽  
3.0 T ◽  
Net Mineralisation

The amount of lupin below-ground biomass (BGB), BGB nitrogen (N) content, and utilization of BGB-N by subsequent wheat was estimated from lupins grown in soil columns. Lupin plants were enriched in situ with 15N-labelled urea through a cotton wick inserted through the stem. Of the applied 15N. 92% was recovered in the lupin plant-soil system at maturity: 87% of this 15N was in lupin aboveground biomass and 13% in the soil columns. Total mature lupin dry matter (DM) approximated 11 t/ha, with 3.0 t/ha (27%) of this DM below ground. Total mature lupin N approximated 321 kg/ha, of which 91 kg/ha (28%) resided below ground. In terms of N and DM, BGB was the largest lupin residue component even though only 35% of this was recoverable as root material. About 13% of the BGB-N was in inorganic form at maturity. The net mineralisation of lupin BGB-N after 2 consecutive years of wheat growth was 27%. and wheat assimilated about 74% of this N (i.e. 20% of BGB-N), with equal quantities assimilated in each year. The contribution of lupin BGB-N to the N in wheat tops ranged from 40% for soil columns receiving no fertiliser N to 15-20% for soil columns fertilised with 30 kg N/ha. The net mineralisation of BGB-N and the assimilation of BGB-N by wheat were unaffected by the application of fertiliser N.

scholarly journals The Interaction of Light and Temperature in Determining the Growth Rate of Subterranean Clover (Trifolium Subterraneum l.)

1955 ◽  
Vol 8 (3) ◽  
pp. 330 ◽  
Author(s):  
JN Black
Keyword(s):  
Growth Rate ◽  
Growth Rates ◽  
Agricultural Research ◽  
South Australia ◽  
Subterranean Clover ◽  
Trifolium Subterraneum ◽  
Vegetative Stage ◽  
Agricultural Research Institute ◽  
Waite Agricultural Research Institute ◽  
Pot Culture

An experiment is described in which the growth of subterranean clover (Trifolium subterraneum L.) in the early vegetative stage was measured over 52 consecutive weekly periods. To eliminate possible trends of growth rates with age, plants of comparable morphological stage were used for each period. The variety Bacchus Marsh was grown in pot culture in the open at the Waite Agricultural Research Institute, Adelaide, South Australia.

Variation in nutritive value of plant parts of subterranean clover (Trifolium subterraneum L.)

2000 ◽  
Vol 40 (3) ◽  
pp. 397 ◽  
Author(s):  
Y. J. Ru ◽  
J. A. Fortune
Keyword(s):  
Nutritive Value ◽  
Nitrogen Concentration ◽  
Subterranean Clover ◽  
Trifolium Subterraneum ◽  
Vegetative Stage ◽  
Field Station ◽  
Leaf Petiole ◽  
Plant Parts ◽  
Dry Matter Digestibility ◽  
Lack Of Information

While it has been reported that leaves of subterranean clover are less digestible than stems, there is a lack of information on the variability of nutritive value of plant parts of subterranean clover. To determine the variation in nutritive value of leaf, petiole, stem and burr, an experiment with 26 cultivars of subterranean clover was conducted at Shenton Park Field Station, Perth, Western Australia. The cultivars were divided into 3 maturity groups according to flowering time and each cultivar was sown in blocks comprising 4 replicates. The plots were grazed by sheep at 2-weekly intervals. Plants were sampled at the vegetative stage before grazing and after the cessation of flowering. Dry matter digestibility (DMD) and nitrogen concentration of leaves, petioles, stems and burrs were determined. At the vegetative stage, there was no difference in DMD (P>0.05) among plant parts for most cultivars, and leaf had the highest (P<0.05) nitrogen concentration (4.8–5.4%). After the cessation of flowering, leaf had the highest DMD and nitrogen concentration (P<0.05). The DMD of plant parts differed significantly among cultivars (P<0.05). There was a slight decrease in DMD over time for leaves and a significant decrease in DMD for stems and petioles. These results suggest the main objective of grazing management of subterranean clover swards should be to increase the proportion of leaf material in the swards and that selection of leafy varieties by breeding could improve the late season digestibility of subterranean clover. Such management and breeding strategies would have value when the cultivars are in mixed pastures or used with supplements in summer.

Sign in / Sign up

Export Citation Format

Share Document