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Potato cropping in southern Australia can involve up to 30 passes with a tractor, with up to 15 cultivations and multiple applications of fertilisers, fungicides, herbicides and insecticides. This was expected to significantly affect earthworm activity. Earthworms from four pasture sites were compared with those from adjacent potato paddocks. In the year following potatoes, earthworm numbers were about half in the paddocks which had been cropped. When the same sites were again sampled in the following year, populations had recovered and, on one field, were significantly higher in the second year after potatoes than in the adjacent pasture. This relatively rapid recovery, following substantial soil disturbance, may have been associated with the increased pH with lime added to the cropped paddocks.

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.

Earthworms were surveyed in 113 pasture soils in the Mount Lofty Ranges, Fleurieu Peninsula, South Australia, in a region where annual rainfall is 600–1200 mm and the climate is mediterranean. The soils within these pastures included a variety of profile forms (e.g. sandy soils with yellow, brown or red clays in the B horizon; uniform coarse textured sands). The most widespread earthworm species were Aporrectodea trapezoides (found at 95% of sites), Microscolex dubius (61%), Aporrectodea rosea (38%) and Aporrectodea caliginosa (36%). These are all introduced species. The total densities of earthworms varied from 0 to 608 m −2 (mean = 169.2). At most sites (66%), densities were −2 . Native earthworms were present at 40 sites but their total densities exceeded 100 m −2 at only 7 sites. The species richness and diversity of the earthworm communities were low; never more than 5 species were found in any one pasture (mean = 3.1). The abundance of the introduced species (all species combined) varied between soil profile forms, being least in the uniform sands. No such variation was found for native species. Several significant, but weak, correlations were obtained between the numbers and weights of earthworms and other environmental variables (e.g. rainfall, depth of A horizon, % sand, clay. nitrogen and carbon). Stepwise multiple regression of the numbers and weights of introduced species against these environmental variables suggested that % clay was the most important regressor. The potential for increasing the abundance and diversity of earthworms in Australian soils is discussed.

The seasonal abundance of earthworms and their vertical distribution were studied in two adjacent fields, sown annually in an alternating cereal-legume rotation, with minimal cultivation and stubble-mulching. The introduced species Aporrectodea trapezoides, Microscolex dubius and M. phosphoreus were concentrated in the upper 10cm of soil for 90–150 days following the onset of autumn rains, but were not active in the top 60 cm after the rainfall declined in spring and throughout the dry summer. Densities of up to 430 worms m−2 with a biomass of 111 g m−2 were recorded in the wetter months. M. dubius was the dominant species in both fields in both years. Differences in abundance, biomass and age-structure are discussed in relation to soil moisture, pH, carbonate, organic C and N, and to the phase of the crop rotation. The two fields have similar soils, similar cropping history and productivity, but one field had consistently higher earthworm numbers and biomass throughout 1988 and 1989. In each field the average size and total biomass were higher, growth rate higher and adults relatively more abundant under cereal than under the alternate legume phase.

The introduced earthworms, Aporrectodea trapezoides and Aporrectodea caliginosa, are common in agricultural soils in southern Australia. The seasonal abundances of these species were monitored in five pastures in the Mount Lofty Ranges, South Australia. Highest numbers occurred from winter to early spring: densities of up to 407 and 446 m−2 were recorded for A. trapezoides and A. caliginosa, respectively. Adults were restricted to winter and spring, when breeding occurred. Subadults and juveniles survived summer. Aporrectodea trapezoides and A. caliginosa were abundant in the surface layers of the soil (0–10 cm depth) for between 3 and 7 months (autumn to spring), when soils were moistest. During summer, most individuals were found > 20 cm below the surface where they were inactive, coiled tightly within sperical chambers. The abundance of A. trapezoides and A. caliginosa varied within and between pastures. Numbers were lowest where the clay content of the soil was low. A dipteran parasite attacked a small proportion of A. trapezoides at one site in spring.

The earthworm fauna of soils used for pasture-cereal rotations in south-eastern Australia was surveyed in 1990–91 (126 sites). Numbers were generally low (0–366 m-2, mean = 41.9 m-2 for all species combined). The fauna was dominated by introduced species. Aporrectodea rosea (Lumbricidae) was the most common species (mean = 31.4 m-2) followed by A. trapezoides (5.0 m-2). A. rosea and A. trapezoides were found at 45 and 29% of sites, respectively. There was no obvious relationship between earthworm abundance and soil pH.

The effects of tillage and stubble management on the population distribution of earthworms were examined under wheat on a red-earth soil at Harden and under canola on a red-brown earth at Temora in the wheatbelt of southern New South Wales. At Harden, a five-year pasture had been followed by a conventionally cultivated oat crop in the year before the experiment. At Temora, a six-year pasture immediately preceded the experiment. Tillage treatments at Temora, and tillage and stubble treatments at Harden, were established during February-May 1990 and earthworm populations were measured in September. A number of earthworm species (Aporrectodea trapezoides, Microscolex dubius and M. phosphoreus) were present at both localities, but the introduced species A. trapezoides made up 97-99% of the earthworms collected. Earthworms were substantially more abundant at Temora (425 m-2) than at Harden (122 m-2). At Temora there was no effect of the intensity of tillage (4, 1 or 0 passes prior to sowing) on earthworm numbers. Earthworm densities were reduced in waterlogged soil. At Harden the direct-drill (DD) plots had a greater population density and biomass of earthworms and cocoons than the tilled plots. The size (mean weight) of adult earthworms, and the number of cocoons per adult, were also greater in the DD plots. However, no differences in earthworm populations were detected between minimum tillage (one cultivation prior to sowing) and stubble incorporation (three cultivations prior to sowing). On DD plots, burning stubble resulted in significantly smaller adult earthworms, a lower density of cocoons and a lower mean number of cocoons per adult than in the unburnt plots, but the differences in numerical abundance and in biomass were not statistically significant. Similarly, plots which had standing stubble contained fewer and smaller adults than those in which stubble was bashed and in close contact with the soil. There was a strong positive correlation between earthworm biomass and the amount of stubble present on the surface of the plots at the beginning of the winter (r2 = 0.64, P < 0 01). The contrasting effects of tillage at the two sites and the impact of stubble management on earthworms are discussed in terms of the effects of recent paddock history and management practices on the amount, quality and distribution of suitable organic food for earthworms. The influence of these factors is reflected in the number, biomass and reproductive performance of the earthworms.

The abundances of the introduced earthworms, Aporrectodea rosea, A. trapezoides, Microscolex dubius and M. phosphoreus were monitored monthly in the top 30 cm of soil at three farms used for cereal and lucerne production in South Australia. The farms had approximately 500 mm annual rainfall. Total earthworm densities of up to 303 m-2 were recorded, with the Aporrectodea spp. far more abundant than the Microscolex spp. Highest numbers were found in winter and early spring, when the soils were wettest (water suction potential < approx. 150 kPa) and the majority of worms were present in the top 10 cm of soil. During the drier months of the year, most worms were found below 10 cm depth. Adults with mature clitella were restricted to winter and spring. Juveniles and adults (with regressed clitella) of Aporrectodea spp. survived summer.

The termite Nasutitermes exitiosus (Hill) was fed natural and synthetic [14C]labelled lignins and related compounds, and the respired CO2 collected. All the compounds were partially degraded to CO2, from an average of 7% of the added 14C for ring-labelled phenate to 63% for methoxyl-labelled maize lignin and 64% for ring-labelled ferulic acid, during periods of 6–69 days. The breakdown commenced immediately and was linear until the food was consumed. Thereafter a slow release continued for some time. Termite bodies assayed at the end of the experiments contained only a small proportion of the added radioactivity. When live termites were separated from their faeces, it became apparent that most of the decomposition of lignin had taken place in the termites and not externally in the voided faeces. An estimate of respiration rates of N. exitiosus indicates a significant release of C as respired CO2, and this species of termite would appear to return a considerable proportion of the C in litter lignin directly to the atmosphere.

Two long-term field trials in South Australia were used to detect and characterise changes in soil biological properties that were a consequence of different agricultural management. The properties examined were total bacteria, fungi, and actinomycetes; total pseudomonads; cellulolytic bacteria and fungi; mycorrhizal fungi; plant root pathogens (Gaeumannomyces graminis var. tritici, Rhizoctonia solani, Pythium irregulare); bacterial-feeding protozoa; soil mesofauna (collembola and acari); earthworms; microbial biomass; C and N mineralisation; in situ CO2 respiration; cellulose decomposition; and soil enzyme activity (peptidase, phosphatase, sulfatase). The sensitivity of these biological properties was assessed to tillage (no-tillage v. conventional cultivation), stubble management (stubble retained v. stubble harvested), crop rotation (continuous wheat v. wheat-sown pasture), and N fertilisation (nil v. 80 kg N/ha applied during the crop phase). Tillage, stubble management, crop rotation, and N fertilisation significantly (P