This CRDC-funded project is studying the effect of repeated wet/dry cycles, with drying by rotation crops, on the structure repair of a black, cracking clay. The cotton industry knows that the majority of its soils (cracking clays) respond to wet/dry cycles, to repair structure. Past studies succeeded in showing soil structure repair of the topsoil by repeated wetting/drying where the drying was solely by evaporation. Other field studies have examined the role of rotation crops in drying the soil profile to prevent compaction in subsequent cultivation

The diet incorporation technique has been used to detennine the variability in the baseline susceptible response to Bt in a number of field populations of both Helicoverpa armigera & Helicoverpa punctigera. The commercial Bacillus thuringiensis subspecies kurstaki formulation DiPel 2X (32,000 IU/mg) was incorporated into the standard soyflour/ wheat germ/ agar artificial diet. Newly moulted early third instar larvae were confined on the treated diet in 24 well tissue culture trays for up to 8 days at 25 degrees C. The criterion for assessing mo1tality was the same as for conventional insecticides: no co-ordinated movement when prodded. LCSOs are expressed in mg DiPel 2X per ml of diet.

There have been claims that the addition of lime to irrigated heavy textured clays have improved soil conditions and yields. For soils that already have high levels of free natural lime or high pH there exists theoretical grounds that the practice should be rejected. This project was initiated to record the effects such a practice could have on soil properties, plant growth and yield and to establish if this practice has merit for soils of this nature

Host plant resistance has long been a focus of the CSIRO cotton breeding program. Over the past 8 years we have compared the levels of pest resistance in a variety of cotton cul ti vars which bear either morphological (okra leaf, frego bract), or biochemical factors (high gossypol) for resistance to insects. Some of this work was reported at the last cotton conference (Pitt et al 1992) and elsewhere (Thomson 1987, Wilson and Fitt 1987). As a result of that work, which focussed on resistance to Helicoverpa and mites, several promising lines have been introduced into the CSIRO breeding program. Conventional breeding for pest resistance makes small incremental improvements in the tolerance of varieties to insect feeding. With the advent of genetically engineered cotton the stage is set for quantum leaps in pest resistance, through for example the introduction of the Bt toxin genes. However, this does not mean conventional approaches are no longer useful. Any change which can be made to the plant to make it less atttracti.ve to pests or more tolerant to damage will only enhance the value of genetically engineered traits by providing a stronger, more stable basis on which to manage those genes

The distinctive dark glands covering most of the aelial parts of the cotton plant are well known to growers. These glands contain an oil rich in insecticidal terpenoid compounds and as a consequence are associated with host plant resistance. The glands are a general characteristic of the tribe Gossypiae which, in addition to the cultivated species, includes many wild cottons of no commercial importance. Approximately sixteen wild cottons occur in Australia, probably the best known being Sturt's Desert Rose (Gossypium sturtianum), the floral emblem of the Northern Te1Titory. Whilst this species has been studied in some detail, in particular with respect to its potentially useful glanded plant/glandless seed trait, detailed studies of the chemistry of Australian wild cottons generally, have not been reported. Anecdotal evidence suggests that many of the native species are relatively free of insect infestation in the wild. In association with other work assessing the pest resistance of G. hirsutum varieties, a small plot of wild cottons was grown at Nai.Tabri over the 1993/94 season. The plot was unsprayed and plants were used in bioassays which measured the growth and survival of Helicoverpa larvae throughout the season. Preliminary results of these bioassays are presented here.

In 1993 a series of experiments were established in the Namoi and Macquarie valleys to study the effects and benefits of rotation crops for subsequent cotton crops. The results presented here, are the effects of 4 different rotations on soil moisture, in the Macquarie valley, during the 1993 season.

The aim of this research is to define the best rotation/management combination whereby yields and quality of subsequent cotton crops can be maximized and sustained over the long-term.

Competition for scarce water resources in northern inland New South Wales has raised concerns among irrigations about the specification of water property rights and the efficiency of use of water resources within and between sectors of the water industry. Recent severe drought conditions, questions concerning the extent to which water allocations are required for environmental management purposes, and speculation about long term urban and industrial demands for water, have fuelled these concerns.

The first Australian cloud seeding experiment was conducted by the Commonwealth Scientific and Industrial Research Organisation (CSIRO) in February 1947. In a spectacular demonstration near Bathurst in New South Wales, a single cumulus cloud seeded with 225 kg of dry ice produced an average of 13 mm of rain over an area of about 130 Ian2 while neighbouring clouds produced none. The Hydro-Electric Commission of Tasmania (HECT) first became involved with cloud seeding in 1964, jointly sponsoring a 5-year experiment with CSIRO which resulted in a statistically significant rainfall increase of about 23%. Recent discoveries In the field of atmospheric physics have prompted a re-analysis of CSIRO's early cloud seeding experiments with startling results. Some of their efforts including the New England Experiment, appear to have been far more successful at putting extra rain on the ground than at first thought Three separate cloud seeding projects sponsored by HECT in Tasmania spanning 14 years, have contributed further to our understanding and have confirmed that cloud seeding can routinely enhance runoff into Tasmanian storages by 10 - 20%.

Transgenic cottons expressing the crystal protein toxin genes from the bacterium, Bacillus thuringiensis (Bt) have progressed to the field testing stage and may soon become part of the Australian cotton production scene. Bt cottons offer the potential for highly efficacious use of the Bt proteins and for significant reductions in the requirement for pesticides to control Lepidopterous pests like Helicoverpa. These reductions should reduce environmental concerns associated with cotton growing, and from the viewpoint of IPM will allow the implementation of other novel management strategies which are not compatible with pesticide use (eg. food sprays, pheromones, various parasites and predators). In future these other methods may help in management of pests other than Helicoverpa. Bt cottons are thus compatible with many other IPM tools and will provide a new platform on which IPM systems can be based