Soils In South Australia Research Articles

Persistence of diverse lucerne (Medicago sativa sspp.) germplasm under farmer management across a range of soil types in southern Australia

The persistence of a diverse group of lucerne (Medicago sativa sspp.) germplasm was evaluated under farmer management across a range of acidic and neutral-alkaline soils at 8 sites in South and Western Australia. Dryland field trials were sown in parallel with commercial lucerne paddocks being grown in rotation with cereal crops, remaining unfenced and under management by the farmer for the life of the stand. The combined differences in soil type, grazing management, and low rainfall contributed to large differences in average lucerne persistence between sites in South Australia and Western Australia. After 3 years, plant frequency (a measure of plant density used to monitor persistence) averaged 17% (at least 17 plants/m2) on the strongly acidic soils in Western Australia and 30% on the neutral-alkaline soils in South Australia (at least 30 plants/m2). Differences in persistence were attributed to the combined stresses of soil pH, drought conditions, and grazing management. Genetic correlation analyses between sites failed to show any clear patterns in the performance of entries at each site, except for a high correlation between 2 South Australian sites in close proximity. Highly winter-active germplasm was less persistent than other winter activity groups, but was higher yielding when assessed in an additional trial at Katanning, WA. Highly winter-active lucerne (class 9–10) should continue to be recommended for short (2–4 year) phases in rotation with cereals, and winter-active groups (6–8) should be recommend for longer (4–7 year) phases in rotations. The results of this evaluation are also being used to identify broadly adapted, elite genotypes in the breeding of new lucerne cultivars for the southern Australian cropping districts.

Genetic diversity and biological control activity of novel species of closely related pseudomonads isolated from wheat field soils in South Australia.

Rhizobacteria closely related to two recently described species of pseudomonads, Pseudomonas brassicacearum and Pseudomonas thivervalensis, were isolated from two geographically distinct wheat field soils in South Australia. Isolation was undertaken by either selective plating or immunotrapping utilizing a polyclonal antibody raised against P. brassicacearum. A subset of 42 isolates were characterized by amplified 16S ribosomal DNA restriction analysis (ARDRA), BIOLOG analysis, and gas chromatography-fatty acid methyl ester (GC-FAME) analysis and separated into closely related phenetic groups. More than 75% of isolates tested by ARDRA were found to have >95% similarity to either Pseudomonas corrugata or P. brassicacearum-P. thivervalensis type strains, and all isolates had >90% similarity to either type strain. BIOLOG and GC-FAME clustering showed a >70% match to ARDRA profiles. Strains representing different ARDRA groups were tested in two soil types for biological control activity against the soilborne plant pathogen Gaeumannomyces graminis var. tritici, the causative agent of take-all of wheat and barley. Three isolates out of 11 significantly reduced take-all-induced root lesions on wheat plants grown in a red-brown earth soil. Only one strain, K208, was consistent in reducing disease symptoms in both the acidic red-brown earth and a calcareous sandy loam. Results from this study indicate that P. brassicacearum and P. thivervalensis are present in Australian soils and that a level of genetic diversity exists within these two novel species but that this diversity does not appear to be related to geographic distribution. The result of the glasshouse pot trial suggests that some isolates of these species may have potential as biological control agents for plant disease.

Distribution, abundance and symbiotic effectiveness of Rhizobium leguminosarum bv. trifolii from alkaline pasture soils in South Australia

The current dissatisfaction with low productivity of annual medic (Medicago spp.) pastures has highlighted the need to seek alternative legumes to provide efficient N2 fixation in low rainfall, alkaline soil environments of southern Australia. Clover species adapted to these environments will have limited N2 fixation if effective rhizobia are not present in sufficient quantities. A survey of 61 sites was conducted across South Australia to determine the size, distribution and effectiveness of Rhizobium leguminosarum bv. trifolii (clover rhizobia) populations resident in these low rainfall, alkaline soil environments. Clover rhizobia were detected at 56 of the sites, with a median density of 230–920 rhizobia/g soil. Most rhizobial populations were poor in their capacity to fix nitrogen. Rhizobial populations from fields provided 11–89% and 10–85% of the shoot biomass of commercial reference strains when inoculated onto host legumes T. purpureum (purple clover) and T. resupinatum (persian clover), respectively. Rhizobial population size was correlated negatively to pH and the percentage of CaCO3 in the soil, and was significantly increased in the rhizospheres of naturalised clover, found at 17 sites. Management options for rhizobial populations to improve legume diversity and productivity are discussed in terms of rhizobial population dynamics and likely soil constraints to successful rhizobial colonisation.

Earthworms as indicators of sustainable production in dryland cropping in southern Australia

Crop-monitoring by farmer groups has been established to identify agronomic and soil factors limiting crop yields and to promote the adoption of sustainable farming practices in South Australia. The use of earthworms as a potential indicator of sustainability has been investigated with a survey of 95 paddocks sown to wheat, barley or peas, within an area of about 3500 km 2. Mean annual rainfall ranged from less than 350 mm to more than 500 mm, and soils varied from coarse sands through lighter loams to heavy clays. The dryland cropping soils in South Australia have been colonized by four immigrant earthworm species, Aporrectodea rosea (Savigny), Aporrectodea trapezoides (Duges), Microscolex dubius (Fletcher) and Microscolex phosphoreus (Duges); populations are generally dominated by A. rosea. Population differences, such as the higher numbers of A. rosea recorded under barley than peas and more juveniles under peas than wheat, and the occasional abundance of other species in some paddocks may be used to indicate changes in soil conditions associated with management. Conservation tillage, retaining plant-residues and reducing cultivation, is being promoted as desirable in developing sustainable farming systems and the inverse relationship between earthworm abundance and intensity of tillage (r = −0.69 ∗∗∗) provides support for earthworms as a potential indicator of sustainability. Earthworm abundance showed a small but significant correlation between earthworm activity and grain yields (r = 0.44 ∗∗∗) and grain protein content (r = 0.52 ∗∗∗). A positive correlation between nitrogen fertilizer levels and earthworm numbers (r = 0.48 ∗∗∗) and biomass (r = 0.43 ∗∗∗) may be related to increased soil organic matter, derived from increased plant growth. The distribution and abundance of earthworms is dependent not only on management related to crop production, but also on local soil and climatic factors. Density and biomass were significantly higher in paddocks with higher annual rainfall and inversely correlated with levels of coarse sand. The soils, crops, climate, management and history of a region of the geographic scale surveyed here is probably too diverse to provide simple relationships between earthworms and plant productivity. It is important to distinguish the broad concept of sustainable productivity on a regional basis from the reality of productivity and sustainability on the spatial and temporal scales of activity of the organisms studied and the production and management processes involved. At an appropriate scale, ecological data on both the species composition and on functional groups within earthworm communities, may be useful indicators of crop production and its sustainability.

Biology and control of Reseda lutea L. 1. Seed biology and seedling growth

Reseda lutea L. is a major perennial weed of alkaline cropping soils in South Australia. Seed biology and early seedling growth of R. lutea were studied in field and laboratory experiments to gain information needed for effective control strategies. Recovery of intact seeds buried for 4 years in the field at 50 and 150 mm was 77–96%. Germination of this seed was 33–63% (50 mm) and 0% (150 mm). Germination patterns differed markedly between seed collected from 2 populations. Seed germinated at all constant and fluctuating temperatures between 10 and 35° C with the maximum (88%) at 25°C constant. Mean temperature, rather than constancy or fluctuation, determined the germination rate. Light strongly inhibited germination. Seedling shoot growth was slow but tap root growth was rapid, reaching 350 mm within 28 days of emergence. Secondary roots arose 3–7 days after emergence and shoot buds formed on the roots within 28 days. R. lutea was found to be well adapted for persistence in cultivated fields with a temperate climate.

Sodicity in South Australia - a review

The current knowledge of the nature and distribution of sodic soils in South Australia is reviewed. The agriculturally developed area of South Australia lies south of latitude 32-degrees-S. and is mainly used for low intensity grazing and dry land cereal/sheep production. A high proportion of the State, including much of the high rainfall area, has soils which are sodic (>6% ESP) through a significant proportion of the profile but information on the precise nature of sodicity in these soils is limited. Where exchangeable cation data axe available, the analytical techniques used often did not precisely delineate between soluble salts in the soil and ions on exchange sites. Therefore, many of the datasets have major weaknesses and may be unreliable. Since many soils with ESP <6 also show dispersive characteristics typical of sodic soils, there is an urgent need for new sodicity studies relating to distribution and the criteria (ESP) used to identify dispersive soils. Information on the effect of sodicity on nutrient requirements of plants, especially the modern varieties, is scarce both locally and internationally, making development of management strategies for economically sustainable crop production difficult. Further, many different grades of gypsum are available in South Australia. Preliminary studies show the presence of impurities drastically influences gypsum dissolution characteristics. More effort is needed to assess the quality and reactivity of South Australian gypsum. Some effort has been directed by land managers towards reclamation and management of sodic soils by using both gypsum and lime either separately or as mixtures. However, there is neither a scientific basis for the application of gypsum-lime mixtures nor crop production data to support such management strategies.

Natural radionuclides in tidal saltmarsh soils in South Australia—An unusual distribution?

Sediments collected from tidal saltmarsh areas in South Australia have been analysed for natural radionuclides from the uranium and thorium decay series. The concentrations observed indicate a significant enhancement of some nuclides in comparison to inland soils, consistent with the recent incorporation of uranium, thorium and actinium into the sediments. The probable source of the nuclides is sea-water. It has been experimentally established that the organic residues from the decay of vegetable matter play a major role in this process.

Silvicultural research for sustained wood production and biosphere conservation in the pine plantations and native eucalypt forests of south-eastern Australia

Summary In the last decade, greatly increased public and political awareness of the need for biosphere conservation has placed strict controls on the productive use of Australia's already limited forest resource. The challenge is considerable. Ultimately, it could mean that much of Australia's native forests will no longer be available for wood production either directly or indirectly through conversion to plantations of pine of eucalyptus. This paper describes how the Department of Conservation and Environment in the State of Victoria is meeting this challenge for forested public land. Specifically, it addresses silvicultural research: to sustain wood production in second and subsequent rotations of pine plantations; and to balance sustained wood production and ecosystem conservation in native forests. From a review of field trials and fundamental studies motivated by reports of a “2R-decline” in wood production on sandy soils in South Australia, it is concluded that a serious irreversible decline is unlikely to be caused by pines in themselves. It is more likely to be caused by silvicultural practices that compact the soil and, especially in the case of sandy soils, deplete soil organic matter. A reversible decline is most likely to be due to a water X nutrient interaction related to water consumption by weeds and nutrient losses from practices such as slash burning. In native forests, Victoria has embarked upon a silvicultural investigation of a magnitude and complexity never before attempted in Australia. The main issues are the use of the clearfelling silvicultural system, and harvesting of residual wood mainly for wood chipping and conversion to pulp and paper products. Organisational arrangements for planning, managing and monitoring the research, with strong community involvement, are described together with the research studies which are based on three main systems; namely: the forest ecosystem; the forest management system; and the socio-economic system. It is concluded that success will require the achievement of high scientific objectivity and strong community involvement.

Variability in characteristics of some acidic pasture soils in South Australia and implications for lime application

The variability of soil pH (0.01 M CaCI2), aluminium and manganese (extractable in 0.01 M CaCl2), total carbon and some soil morphological factors have been investigated in the surface and subsoil at seven pasture sites in the southern Mount Lofty Ranges and Kangaroo Island, South Australia. The coefficients of variation of the factors measured were found to be of a similar order, except for soil pH which, being a logarithmic transformation, is much lower. Relationships between pH and soil aluminium, manganese and carbon are used to predict the effects of further acidification, especially with respect to the development of increased extractable aluminium, and to assess the likelihood of problems in selecting appropriate rates of lime application.

Pectic enzyme patterns of Rhizoctonia solani isolates from agricultural soils in South Australia

Pectic enzymes produced by isolates of Rhizoctonia solani from many hosts and localities within South Australia were subjected to electrophoresis in pectin acrylamide gels. Seven different zymogram groups (ZG) were detected with the majority of isolates being ZG1-1, ZG1–2, ZG1–3 or ZG2. Representatives of these zymogram groups were found in all localities sampled. Of isolates from cereals and legumes, 92% were ZG1-1, ZG1–2, ZG1–3 or ZG2; in contrast, only 23% of isolates from soil were from these zymogram groups. Isolates in ZG1-1, ZG1–2, ZG1–3 and ZG2 were all anastomosis group AG-8, ZG5 were AG-2-1, ZG7 were AG-3 and ZG8 were AG-4. Pectic zymogram patterns are proposed as a fast and reliable method of determining anastomosis group.

Anastomosis grouping of some isolates of Thanatephorus cucumeris from agricultural soils in South Australia

The ‘crucifer’, ‘solanaceous’ and ‘stem’ strains of T. cucumeris in South Australia were identified as belonging to AG-2 type 1, AG-3 and AG-4 respectively. A new group, AG-8, is proposed for the most common strain pathogenic to cereals, the ‘root’ strain which did not anastomose with any of groups AG-1-7. AG-2 type 1, AG-3, AG-4 and AG-8 are the only anastomosis groups yet found in agricultural soils in South Australia.

Nitrogen fertilisers in establishingPinus radiataplantations on sandy soils: an evaluation of their use

Summary Results from experiments with Pinus radiata (D. Don) at several locations raise serious doubts about the benefits of current nitrogen fertilisation practices on sandy soils in South Australia and western Victoria. Intensive silvicultural practices appear to exert a major influence on the rate of nitrogen supply to young trees and until the mechanisms involved are clearly understood, the benefits of nitrogen fertiliser will remain uncertain. The control of weeds and the organic matter left after site preparation seem to be the two most important factors determining nitrogen availability, and hence the responses of trees to applied nitrogen. Methods of applying fertilisers should take account of potential leaching losses and the root distribution of the young pines.

Moisture characteristics of irrigated Mallee soils in South Australia

The soil moisture characteristics of undisturbed samples of Mallee soils, taken from typical profiles of the Riverland district neat Berri in South Australia, were determined. Samples were grouped according to texture and bulk density and, for each group, the moisture storage between matric potentials was derived. Over the usual range of soil moisture tensions (-0 to 40kPa) these showed only small variation between soil groups since, while moisture storage at field capacity and at wilting point does vary with texture; 50 to 60 mm/m is available between field capacity (-7 kPa) and the re-irrigation point (-30 to 40kPa) in all soils.

Plant Parasitic Nematodes Occurring in Bushland Soils in South Australia.

Plant Parasitic Nematodes Occurring in Bushland Soils in South Australia.

Soil water changes under fallow-crop treatments in relation to soil type, rainfall and yield of wheat

Soil water changes under fallow (initial cultivation in spring), grassland (initial cultivation in autumn) and the succeeding wheat crops were recorded at two to three weekly intervals in three consecutive seasons in three soil types representing the range of wheat-growing soils in South Australia. Differences in water content between the two treatments developed soon after the start of fallowing due to the greater loss of water from grassland in spring. Rainfall during the fallow period contributed little to soil water storage except in one year when heavy spring rains were recorded. In some instances the water content in the fallowed soils at seeding was less than at the start of fallowing, but the fallowed soils consistently retained more water than the grassland soils. Soil water contents decreased after August of the crop year (end of tillering) and by harvest the wheat crops had commonly dried the soil to a depth of 150 cm. Fallow crops used more water and produced significantly higher wheat yields with a greater efficiency of water use in all trials.

Abundance of Pythium Species in Nursery Soils in South Australia

The abundance of Pythium propagules and frequency of 11 Pythium species were estimated in 16 soil plots in South Australian forest nurseries, in one ornamental nursery. and in one pine forest. A soil-plating technique Was utilized and a medium developed which was highly selective for these species and allowed their identification directly on the plates. The number of Pythium propagules in a unit volume of soil varied greatly. being lowest (24 per cubic centimetre) in the forest and highest (226 per cubic centimetre) in an alkaline loamy nursery soil. Loams had significantly more Pythium propagules than sandy soils. The immediately previous usage and soil amendments usually made no great difference to the total number of Pythium propagules. It is concluded that the abundance of pathogenic Pythium spp. in these nurseries is not the main factor governing the great variation found in the disease incidence of conifer seedlings. P. irregulare Buisman was frequent in all plots except the forest, and P. mamillatum Meurs in most sandy nurseries. The frequencies of P. ultimum Trow, P. paroecandrum Drechsler, P. rostratum Butler, P. iwayamai Ito, P. oligandrum Drechsler, P. acanthicum Drechsler, and P. echinulatum Matthews varied inconsistently between the plots. A new species, coded as P. col, was rare but occurred in eight plots. Another new species (P. dis) occurred only in one plot but frequently in this. This was a nursery freshly established on grassland pasture which differed from the others also in the frequencies of several other species.

The residual effect of superphosphate in soils cultivated for wheat in South Australia.

This paper presents further results of a study of phosphorus in the red-brown earths and solonized brown soils of South Australia. The investigation involved both field and pot-culture experiments in which different amounts of superphosphate were applied to soils which had received previous superphosphate applications ranging from 0 to nearly 30 cwt. per acre. Only a small part of the phosphorus applied has been removed in crops and the residual phosphorus has remained in the soil in fairly readily available inorganic forms. Where previous applications of superphosphate exceeded 15 cwt. per acre, little if any response in yield of wheat grain was obtained with current superphosphate dressings, although yields of straw were sometimes increased. The phosphorus content of wheat grown under South Australian conditions is lower than that of overseas crops and is dependent on the phosphorus status of the soil. It is only slightly increased by moderate applications of superphosphate. Evidence is presented of a relationship between response to superphosphate and the nitrogen status of the soil which suggests that no appreciable response to applied phosphate is likely with stubble-sown crops other than legumes on soils of improved phosphorus status.