Differential rhizobial colonisation of the roots of sown and volunteer annual species of Medicago in an acid soil

1994 ◽  
Vol 34 (6) ◽  
pp. 745 ◽  
Author(s):  
RM Barclay ◽  
DM Hebb ◽  
J Brockwell
Keyword(s):  
Rhizobium Meliloti ◽  
Acid Soil ◽  
Arid Environment ◽  
Plant Infection ◽  
South Wales ◽  
Large Populations ◽  
Specific Strain ◽  
Acid Tolerant ◽  
Red Earth ◽  
Annual Medics

Two annual medics, Medicago murex and M. truncatula, were inoculated with specific strains of Rhizobium meliloti, WSM540 and CC169, respectively, and sown into a mildly acid red earth in a semi-arid environment at Cobar, New South Wales. A third medic, M. laciniata, volunteered abundantly at the experimental site and large populations of its specific strain(s) of R. meliloti were naturalised in the soil. Serial dilution, plant infection tests, using 3 test plants in parallel, were employed to count the populations of each of the 3 types of R. meliloti that colonised the roots (rhizospheres) of the 3 medics. The size of the rhizosphere populations was regarded as an index of nodulation potential. Large populations of the naturalised rhizobia (about 45000lplant) developed in the rhizospheres of M. laciniata; these rhizobia also colonised the root surfaces of the sown medics but in much lower numbers (< 80/plant). Strain WSM540 colonised the rhizospheres of M. murex in sufficient numbers (1121 rhizobia/plant) to indicate that an effective nitrogen-fixing symbiosis would have established had seasonal conditions permitted. By contrast, the colonisation of M. truncatula rhizospheres by CC169 was significantly lower (64 rhizobia/plant; P<0.05) and the likelihood of nodulation was uncertain. Both WSM540 and M. murex are known to be acid tolerant whereas both CC169 and M. truncatula are acid sensitive. There was very little colonisation of the rhizospheres of the sown medics by non-specific inoculant strains. Nor was there evidence that the large naturalised population of rhizobia for M. laciniata competed with the specific inoculant strains for colonisation of the roots of the sown medics or interfered with their potential nodulation.

Persistence, productivity and seed yield of Medicago murex, M. truncatula, M. aculeata and Trifolium subterraneum on an acid red earth soil in the wheat belt of eastern Australia

1992 ◽  
Vol 32 (3) ◽  
pp. 319 ◽  
Author(s):  
BS Dear ◽  
L Jenkins
Keyword(s):  
Seed Yield ◽  
Trifolium Subterraneum ◽  
Hard Seed ◽  
South Wales ◽  
Eastern Australia ◽  
Large Populations ◽  
Acid Tolerant ◽  
Seed Reserves ◽  
Red Earth ◽  
Alternative Species

The persistence, productivity, and seed yield of 4 annual legume species, Trifolium subterraneum L. var. subterraneum, Medicago murex Willd, M. truncatula Gaertn var. truncatula, and M. aculeata, were compared on an acid red earth soil at Temora. New South Wales. All species persisted for 4 years but there were significant differences in herbage yields and seed reserves between species, and between cultivars and lines within species. The recently released T. subterraneum cultivar, Junee, produced superior seedling densities in 2 of the 3 regenerative years and maintained similar summer seed reserves, but carried over a higher proportion of seed (hard seed) through each winter and was as productive as the older cultivar, Woogenellup, except in late spring. The 6 M. murex lines persisted and remained well nodulated on the moderately acid [pH(CaCl2) 4.81 soil when grown with a new acid-tolerant Rhizobium strain, WSM 419. Medicago murex demonstrated potential as an alternative species to T. subterraneum for the eastern wheat belt; it maintained high seed reserves and was more hardseeded than T. subterraneum cultivars, but this did not reduce its ability to produce large populations of seedlings in autumn. While the M. aceuleata and M. truncatula lines demonstrated that they could persist and regenerate adequately over the 4-year period, neither proved to be superior to either the T. subterraneum or M. murex lines in any of the parameters.

Influence of soil pH on the development of symbiosis in field-grown acid-sensitive and acid-tolerant annual medics

1992 ◽  
Vol 32 (2) ◽  
pp. 167 ◽  
Author(s):  
RR Young ◽  
J Brockwell
Keyword(s):  
Soil Ph ◽  
Rhizobium Meliloti ◽  
New South ◽  
Annual Species ◽  
Resident Population ◽  
Growing Period ◽  
South Wales ◽  
Normal Expression ◽  
Acid Tolerant ◽  
Annual Medics

Relationships between soil pH, resident population of Rhizobium meliloti in the soil, rhizobial colonisation of the rhizosphere, and nodulation of annual species of Medicago were examined. Established swards of M. truncatula (acid-sensitive) and of M. murex and M. polymorpha (acid-tolerant) growing at 6 different locations in central and western New South Wales were sampled to measure soil pH, to enumerate the populations of R. meliloti resident in the soil and colonising plant rhizospheres, and to assess the extent of nodulation. Soil pH (0.01 mol CaCl2/L) varied from 4.70 to 7.25, soil populations from 3 to 100000 rhizobialg, and rhizosphere populations from 10 to >1 x 106 rhizobia/plant. Nodulation varied from poor to good, depending on growing period and location, but was consistently poorer on M. truncatula than on M. murex or M. polymorpha. Regression analysis showed a consistent and significant (P<0.01) relationship between rhizobial colonisation of the rhizosphere and extent of nodulation. There was also a significant (P<0.001) correlation over all 44 sampling sites between soil pH and the population of R. meliloti resident in the soil. The relationships between soil pH and rhizosphere colonisation, and between soil pH and nodulation, were significant for M. truncatula (P<0.01, P<0.02, respectively) but not for either M. murex or M. polymorpha. These data suggest that the range of soil pH at which M. truncatula was growing (4.80-7.25, but mainly 4.8-5.6) spanned the threshold at which unfavourable soil pH began to obstruct normal expression of its symbiosis, whereas, the critical soil pH levels for symbiotic development of M. murex and M. polymorpha were below this range.

Rhizobium as a factor in the re-establishment of legume-based pastures on clay soils of the wheat belt of north-western New South Wales

1998 ◽  
Vol 38 (6) ◽  
pp. 555 ◽  
Author(s):  
A. M. Bowman ◽  
D. M. Hebb ◽  
D. J. Munnich ◽  
J. Brockwell
Keyword(s):  
Nitrogen Fixation ◽  
Rhizobium Meliloti ◽  
New South ◽  
New South Wales ◽  
Clay Soils ◽  
Natural Fertility ◽  
Fixed Nitrogen ◽  
South Wales ◽  
Annual Medics ◽  
North Western

Summary. Populations of Rhizobium meliloti in self-mulching clay soils (Vertisols) at 48 sites on 27 properties in north-western New South Wales were classified according to number and ability to fix nitrogen with several species of Medicago. Rhizobia were counted using serial dilution, nodulation frequency, plant infection tests. Abilities of the soil populations to fix nitrogen were determined in the laboratory with whole-soil inoculation of Medicago seedlings in test tubes with shoots exposed to the atmosphere and roots within the tubes under bacteriological control, and in the field using a technique based on the natural abundance of 15N in the soil. The majority of soils contained >1000 cells of R. meliloti per gram. The major component of those populations fixed nitrogen with lucerne (Medicago sativa) and some components of some soils also fixed nitrogen with M. polymorpha, M. scutellata, M. littoralis, M. tornata, M. laciniata and Trigonella suavissima. However, a number of soils were located which contained few if any rhizobia effective in nitrogen fixation with M. polymorpha. Overall, the effectiveness of nitrogen fixation of the naturally occurring populations of R. meliloti in association with M. polymorpha, M. scutellata, M. littoralis and M. tornata was only 46% of the effectiveness of standard strains. At one particular site, where 10 lines of annual Medicago spp. were growing experimentally, fixed nitrogen as a proportion of shoot nitrogen averaged only 28%. At that site, there were no effective rhizobia for M. scutellata and it was wholly dependent on the soil as the source of its nitrogen. The results are discussed in relation to the need for a substantial input of legume nitrogen for restoring the natural fertility of self-mulching clay soils in degraded wheat lands of north-western New South Wales. It is suggested that lucerne, or perhaps other perennial Medicago spp., might fill this role better than annual medics such as M. polymorpha and M. scutellata that are more dependent than lucerne on specific strains of R. meliloti to meet their requirements for symbiotic nitrogen fixation.

Acid tolerance in the Rhizobium meliloti - Medicago symbiosis

1986 ◽  
Vol 37 (1) ◽  
pp. 55 ◽  
Author(s):  
JG Howieson ◽  
MA Ewing
Keyword(s):  
Rhizobium Meliloti ◽  
Acid Soil ◽  
Acid Soils ◽  
Acid Tolerance ◽  
Loamy Sand ◽  
Alkaline Soils ◽  
Regenerative Growth ◽  
Commercial Inoculant ◽  
Acid Tolerant ◽  
Second Year

Several strains of Rhizobium meliloti that originated from acid soils in Sardinia, Italy, were markedly superior in colonizing a moderately acid loamy sand (pH 5.0 in 1:5 0.01 M CaCl2) than two Australian commercial inoculant strains (U45 and CC169), and a group of strains that originated from alkaline soils in Syria and Iraq. Six Medicago hosts also varied greatly in their ability to achieve nodulation in this soil. M. polymorpha and M. murex were far superior in this respect to M. littoralis, M. truncatula and M. tornata. The most acid-tolerant strains of R. meliloti, WSM419 and WSM413, were able to nodulate a high proportion of plants of M. polymorpha and M. murex sown in the second year between 11 and 20 cm from the point of introduction of the rhizobia into the soil the previous year. It is suggested that these more saprophytically competent isolates of R. meliloti, combined with the species of Medicago more able to nodulate readily in acid soil, will extend the range of soils suitable for successful regenerative growth of these species.

Nodulation and growth of Medicago truncatula on acid soils. I. Effect of calcium carbonate and inoculation level on the nodulation of Medicago truncatula on a moderately acid soil

1970 ◽  
Vol 21 (3) ◽  
pp. 427 ◽  
Author(s):  
AD Robson ◽  
JF Loneragan
Keyword(s):  
Calcium Carbonate ◽  
Medicago Truncatula ◽  
Soil Ph ◽  
Soil Acidity ◽  
Rhizobium Meliloti ◽  
Acid Soil ◽  
Acid Soils ◽  
Acid Tolerant ◽  
Annual Medicago ◽  
Medicago Species

On a moderately acid soil (pH 4.6 in 115 suspension of soil in 0.01M calcium chloride), nodulation of Medicago truncatula cv. Cyprus responded markedly to increasing applications of calcium carbonate, which increased soil pH. Since the effect of increasing soil pH on the percentage nodulation could be replaced to a large extent by increasing the inoculation level, it appeared that nodulation was restricted by the inability of Rhizobium meliloti to survive or multiply in the acid soil. The growth of R, meliloti appeared more sensitive to soil acidity than growth of the host plant of annual Medicago species. It is suggested that more acid-tolerant strains of R. meliloti would permit annual Medicago species to be grown successfully on moderately acid soils, thus extending the range of soils suitable for the growth of these species.

Grain protein responses to nitrogen applied to wheat growing on a red earth

1991 ◽  
Vol 42 (5) ◽  
pp. 735 ◽  
Author(s):  
JF Angus ◽  
RA Fischer
Keyword(s):  
Ammonium Nitrate ◽  
Theoretical Background ◽  
Yield Response ◽  
Grain Protein ◽  
Fertilizer N ◽  
South Wales ◽  
Eastern Australia ◽  
Red Earth ◽  
Subsequent Crop ◽  
Urea Ammonium Nitrate

Dryland wheat was fertilized with ammonium nitrate or liquid urea-ammonium nitrate at the time of sowing or about 3 months later (generally at the terminal-spikelet stage) on a well-drained site near Harden on the south-west slopes of New South Wales. The experiments continued from the second to the fifth year (1981-1984) of the cropping phase of a crop-pasture rotation. The maximum agronomic efficiencies for yield in the four consecutive years were 19, 4, 23 and 25 kg grain per kg of applied nitrogen (N). The three large responses were obtained in wetter than average seasons and the small response was obtained during drought. In the last three years of the study the yield response to nitrogen at the terminal-spikelet stage was found to be close to but slightly less than that for N applied at sowing. In those years the agronomic efficiencies for the late-applied N were 0, 22 and 22. The apparent recovery of fertilizer N in the above-ground parts of the crop at maturity was up to 70% of the fertilizer applied in the year of sowing, and, after the drought during which there was little uptake of fertilizer N, up to 62% by the subsequent crop. The fertilizer efficiencies in the non-drought years were higher than generally reported in south-eastern Australia, and indicate potential for profitable delayed application of N fertilizer to wheat. Grain-protein responses were variable from year to year and are discussed against a simple theoretical background of the amount of N applied and grain-yield response.

Evaluation of pasture legumes sown into a prepared seedbed at Tamworth, New South Wales. 2. Seed production and seed reserves

1993 ◽  
Vol 33 (3) ◽  
pp. 299 ◽  
Author(s):  
GM Lodge
Keyword(s):  
Seed Production ◽  
New South ◽  
New South Wales ◽  
Pasture Legumes ◽  
South Wales ◽  
Medicago Scutellata ◽  
Seed Reserves ◽  
Annual Medics ◽  
Perennial Legumes ◽  
Seed Yields

Plots sown in 1983 were used to examine the seed production and reserves (residual hardseeds) of 15 annual legumes over 5 years at Tamworth in northern New South Wales. Seed production characteristics were measured in 1983 for these annuals, and for 6 perennial legumes. After the annuals had set seed in 1983, an area of the plots was sprayed to prevent flowering in subsequent years, and the rates of decline in seed reserves were compared with those from areas that seeded annually. Seed yields of the perennials were often significantly lower than those of the annuals except Trifolium glomeratum. Seed yields of T. subterraneum var. subterraneum cvv. Seaton Park and Woogenellup were significantly higher than those of cv. Nungarin and T. subterrarzeum var. brachycalycinum cv. Clare. Seed numbers were lowest for Medicago scutellata cv. Sava among the annual medics, and for Nungarin among subterranean clovers. There was little relationship between the mean number of seeds produced from 1983-86 and maturity grading, and between seed numbers and relative dry matter yield. Seed reserves decreased over 5 years by more than 90% in the sprayed treatments of all species. This decrease was not continuous, with the largest declines occurring from December 1983 to August 1984. In the sprayed treatments of Seaton Park, Woogenellup, and Clare, and in both treatments of Astragalus hamosus cv. Ioman, Vicia dasycarpa var. villosa cv. Namoi, and T. hirtum cv. Hykon, none of the original 1983 seed was recovered in 1987. For the annual medics and Nungarin, the number of residual hardseeds in the sprayed treatments in 1987 was about 3-5% of the seed produced in 1983. From 1983 to 1987, seed numbers in the unsprayed treatments declined by 7040% for the annual medics and by 85-95% for Seaton Park, Woogenellup, and Clare. Long-term persistence of annual medics and Nungarin depended on seed production in most years and the maintenance of a high number of residual hardseeds in the soil. In contrast, the mid- and late-maturing subterranean clovers Woogenellup and Clare had low seed reserves and were dependent on seed production in most years for their continued regeneration.

Acidification of soils on a transect from plains to slopes, south western New-South-Wales

Soil Research ◽  
1990 ◽  
Vol 28 (4) ◽  
pp. 539 ◽  
Author(s):  
CJ Chartres ◽  
RW Cumming ◽  
JA Beattie ◽  
GM Bowman ◽  
JT Wood
Keyword(s):  
Cation Exchange ◽  
Soil Acidification ◽  
Cation Exchange Capacity ◽  
Management Practices ◽  
New South ◽  
Exchange Capacity ◽  
Soil Types ◽  
The West ◽  
South Wales ◽  
Red Earth

Samples were collected from unimproved road reserves and adjacent paddocks on a 90 km transect crossing red-brown earth soils in the west and red earth soils in the east. Measurements of pH in water and CaCl2 indicated that the red earths have been acidified by approximately 0.5 pH units over the last 30-40 years. Small increases in CaCl2-extractable A1 were also recorded for the acidified red earths. The red-brown earths do not appear to have been markedly affected by soil acidification to date. Clay mineralogical data and measurements of cation exchange capacity of the <2 �m fraction indicate that red-brown earths are better buffered against acidification than red earths. However, small differences in management practices and rainfall along the transect may also be partially responsible for differences in acidification between soil types.

Effects of fenced seed production areas and restoration treatments on the size and composition of the native grass seedbanks in moderately degraded rangelands in semiarid Australia

2016 ◽  
Vol 38 (1) ◽  
pp. 47
Author(s):  
Judith M. Bean ◽  
Gavin J. Melville ◽  
Ronald B. Hacker ◽  
Sharon Anderson ◽  
Alicia Whittington ◽  
...  
Keyword(s):  
Seed Production ◽  
Positive Influence ◽  
Native Grass ◽  
North West ◽  
South Wales ◽  
Red Earth ◽  
Preferred Species ◽  
Study Sites ◽  
Production Areas ◽  
And Control

Seed production areas containing populations of native grasses were fenced on topographically high areas at two study sites in the semiarid rangelands of north-west New South Wales, Australia. The surrounding slopes were initially almost bare of pastorally preferred grasses. Three restoration treatments (control, mechanical pitting, and contour-aligned branch piles) were established on these surrounding slopes and the size and composition of the native grass seedbanks determined. A positive influence of the seed production areas mostly occurred within 15 m of the fence and was probably insignificant beyond 33 m at both sites. On a hard-setting red earth site, the size of the native grass seedbank in all three treatments increased over 2 years with the greatest increase under the piles of branches and smaller increases in the pitting and control treatments. The piles of branches preferentially incorporated seed of the pastorally preferred species Monachather paradoxus Steud into the seedbank whereas pits preferentially incorporated seed of the pastorally unpreferred species Aristida jerichoensis (Domin) Henrad. Evidence generally pointed to incoming seed rain rather than the seedbank as the main source of new seedlings. On a medium-textured lithosol site neither the pits nor the branches treatment was effective in enhancing either the size or composition of the seedbank; in fact the piles of branches resulted in a decrease in its size.

Long-term benefits of limestone applications to soil properties and to cereal crop yields in southern and central New South Wales

2003 ◽  
Vol 43 (1) ◽  
pp. 71 ◽  
Author(s):  
M. K. Conyers ◽  
C. L. Mullen ◽  
B. J. Scott ◽  
G. J. Poile ◽  
B. D. Braysher
Keyword(s):  
Grain Yield ◽  
New South ◽  
New South Wales ◽  
Commercial Application ◽  
South Wales ◽  
Cereal Grain ◽  
Subsurface Soil ◽  
Acid Tolerant ◽  
The Cost

The cost of buying, carting and spreading limestone, relative to the value of broadacre crops, makes investment in liming a questionable proposition for many farmers. The longer the beneficial effects of limestone persist, however, the more the investment in liming becomes economically favourable. We re-established previous lime trials with the aim of measuring the long-term effects of limestone on surface acidity (pH run-down), subsurface acidity (lime movement) and grain yield. The study made use of experiments where there was adequate early data on soil chemical properties and cereal yields. We report data from 6 trials located at 4 sites between Dubbo and Albury in New South Wales. The rate of surface soil (0–10 cm) pH decline after liming was proportional to the pH attained 1 year after liming. That is, the higher the pH achieved, the more rapid the rate of subsequent pH decline. Since yields (product removal) and nitrification (also acid producing) may both vary with pH, the post-liming pH acts as a surrogate for the productivity and acid-generating rate of the soil–plant system. The apparent lime loss rate of the surface soils ranged from the equivalent of nearly 500 kg limestone/ha.year at pH approaching 7, to almost zero at pH approaching 4. At commercial application rates of 2–2.5 t/ha, the movement of alkali below the layer of application was restricted. However, significant calcium (Ca) movement sometimes occurred to below 20 cm depth. At rates of limestone application exceeding the typical commercial rate of 2.5 t/ha, or at surface pH greater than about 5.5, alkali and Ca movement into acidic subsurface soil was clearly observed. It is therefore technically feasible to ameliorate subsurface soil acidity by applying heavy rates of limestone to the soil surface. However, the cost and risks of this option should be weighed against the use of acid-tolerant cultivars in combination with more moderate limestone rates worked into the surface soil.There was a positive residual benefit of limestone on cereal grain yield (either barley, wheat, triticale, or oats) at all sites in both the 1992 and 1993 seasons. While acid-tolerant cultivars were less lime responsive than acid-sensitive ones, the best yields were generally obtained using a combination of liming and acid-tolerant cultivars.The long-term residual benefits of limestone were shown to extend for beyond 8–12 years and indicate that liming should be profitable in the long term.

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