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

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.


2006 ◽  
Vol 285 (1-2) ◽  
pp. 245-255 ◽  
Author(s):  
M. T. McHenry ◽  
B. R. Wilson ◽  
J. M. Lemon ◽  
D. E. Donnelly ◽  
I. G. Growns


1993 ◽  
Vol 33 (3) ◽  
pp. 299 ◽  
Author(s):  
GM Lodge

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.



1971 ◽  
Vol 16 (1) ◽  
pp. 29 ◽  
Author(s):  
PT Bailey ◽  
PN Martensz ◽  
RD Barker


1981 ◽  
Vol 8 (2) ◽  
pp. 255 ◽  
Author(s):  
NC Shepherd

Over 7 weeks a group of five dingoes killed 83 red kangaroos within 150 m of a watering point in north-western New South Wales. All except three of these kangaroos were juveniles. Detailed autopsies were performed on 17 of the dead kangaroos: primary predation was the only significant gross pathological finding; the dingoes had eaten portions from about half the kangaroos killed. The daily rate of killing was estimated to be about 0.38 kg prey per kg predator. The rate of killing and the selection for juvenile kangaroos suggested that dingoes could have a direct effect on kangaroo densities by limiting rate of increase. The significance of this finding is discussed with reference to the difference in abundance of kangaroos between the New South Wales and Queensland sides of the border fence.



1992 ◽  
Vol 14 (2) ◽  
pp. 128 ◽  
Author(s):  
MT Maher ◽  
LW Braithwaite

The significance of inland wetlands to Australian waterbirds has been overlooked until recently. One important area identified from regular aerial survey centres on the Paroo River in north-western New South Wales. Between April 1983 and December 1985, a period covering a major flood, waterbird populations were estimated on five wetland systems associated with the Paroo during 14 trips. Fifty- three waterbird species were recorded with the anatids, Anas gibberifrons and Malacorhynchus membranaceus, accounting for 75 per cent of total estimated populations. Most breeding events were observed in those wetlands dominated by Muehlenbeckia florulenta (lignum). Breeding accounted for shifts in waterbird populations between wetland systems. A model of waterbird usage of the five wetland systems in relation to a complete flood event is described. The importance for waterbird conservation of wetlands used for breeding and maintenance of populations between flood events, and threats to the integrity of these wetlands are discussed.



2000 ◽  
Vol 27 (5) ◽  
pp. 531 ◽  
Author(s):  
Peter J. S. Fleming ◽  
David Choquenot ◽  
Richard J. Mason

An experiment that held the density of feral pigs constant while varying the effective density of aerially distributed baits was conducted at three sites in north-western New South Wales. Meat baits, containing one of the biomarkers iophenoxic acid, tetracycline or rhodamine B, were distributed at different intensities over each site, and a sample of pigs was shot from a helicopter at each site to determine bait uptake. Serum and tissue samples taken from each pig were analysed for the occurrence of the biomarkers; the proportions of pigs exhibiting biomarkers represented the proportions of the feral pig populations that had consumed baits at different baiting intensities (expressed as baits per unit of pig density). The maximum percentage of sampled pigs that had eaten baits varied from 31% to 72% across the three sites. Bait uptake was regressed against baiting intensity. For two of the trials, the quantity of bait hypothetically required to eliminate a population of feral pigs was extrapolated to be 1577 baits per unit of pig density, while for the third trial 1874 baits per unit of pig density would have been required. Bait-uptake by non-target animals was substantial, posing potential hazards to birds and reducing the availability of baits to feral pigs. Most likely, seasonal conditions affected bait-uptake by feral pigs. We discuss the implications of these results for exotic disease contingency planning.



2005 ◽  
Vol 45 (3) ◽  
pp. 269 ◽  
Author(s):  
D. F. Herridge ◽  
M. J. Robertson ◽  
B. Cocks ◽  
M. B. Peoples ◽  
J. F. Holland ◽  
...  

Apparent nodulation failures and associated low grain yields have been reported for commercial mungbean (Vigna radiata) crops in southern Queensland and northern New South Wales. We therefore conducted on-farm surveys of 40 commercial mungbean crops in the region in which symbiotic traits, i.e. nodulation and nitrogen fixation, and biomass and grain yield were monitored. Effects of bradyrhizobial inoculation and inoculation methods on mungbean and soybean (Glycine max) symbiosis and yield were determined in experiments at 3 sites in northern New South Wales. Thirty-four of the 35 mungbean crops assessed for nodulation were nodulated. The relationship between soil nitrate to a depth of 90 cm at sowing and mungbean nodulation was not significant. However, at low-to-moderate soil nitrate levels (<100 kg N/ha), the mean nodule score was 1.6, compared with 0.5 at high (>100 kg N/ha) soil nitrate levels. Soil nitrate had a negative effect on the percentage of mungbean nitrogen derived from nitrogen fixation (%Ndfa). Mean %Ndfa values for soil nitrate levels <50, >50–100 and >100 kg N/ha were 35, 22 and 19% respectively. Grain yields of the surveyed mungbean crops varied from 0.3 to 2.1 t/ha, and were correlated with shoot dry matter. Grain yield was not significantly correlated either with sowing soil nitrate, nodule score or %Ndfa. In the inoculation experiments, mungbean did not nodulate as well as soybean, producing about one-third the number of nodules. Both species responded to inoculation with increased nodulation, although data from one of the sites suggested that responses during early growth of mungbean were not maintained during pod-fill. Effects of inoculation on mungbean %Ndfa were marginal. Average increases were 9%, based on natural 15N abundance, and 6%, based on the ureide method. Soybean %Ndfa, on the other hand, responded strongly to inoculation, with increases of 56 (15N) and 77% (ureide). Inoculation increased mungbean crop N by an average of 10% and grain yield by 6%, compared with responses to fertiliser nitrogen of 31% (crop N) and 10% (grain yield). For soybean, inoculation increased crop nitrogen by 43% and grain yield by 7%, similar to responses to fertiliser nitrogen of 45 (crop N) and 5% (grain yield). These results suggest that inoculated mungbean was N-limited and that inoculation of mungbean using current technology may be somewhat ineffectual. We concluded that low nodulation and nitrogen fixation of commercial mungbean most likely results from the suppressive effects of nitrate and/or insufficient numbers of bradyrhizobia in the soil. When low symbiosis and low soil nitrate are combined, N is likely to limit crop growth, and potentially grain yield. Suggested strategies for improving mungbean nodulation and nitrogen fixation in the northern grains belt include selection of more symbiotically competent plant and bradyrhizobial genotypes and more effective utilisation of established soil populations of mungbean bradyrhizobia.





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