Ripping (deep soil working ) can give conflicting responses. Sometimes it i ncreases cotton yields and other times it de creases cotton yields. The aim of this paper is to summarize t he position on ripping and to draw basic principles from the information we have. Some basic principles are discussed below as 'rules for ripping'.

In addressing this topic I have been asked to consider the development of management strategies for farmers faced with a shortage of irrigation water, a situation that appears endemic in the Gwydir Valley. Ten years ago Greg Constable and I showed in an analysis of our experimental data that 8 Ml per planted ha are needed for maximum yields in the driest years, while 7 Ml/ha gives the greatest remrns per Ml on average by allowing a larger area to be planted with a given allocation. When the allocation is reduced, greatest returns would be obtain on average when the crop area was reduced to allow 6 to 7 Ml for each planted ha. With less than 6 Ml per ha the risks of obtaining yields below the breakeven point were very great and there was no advantage in delaying the first irrigation or increasing the interval between irrigation

Having outlined the complexity of this topic, I now intend to summarise the soil and plant mineral relations during waterlogging, followed by a brief review of the scientific principles to improve understanding of the problem and to point to methods of dealing with it. Key references are listed to enable those who wish to delve further into the scientific literature.

Proper nutrition is one of the many factors necessary in achieving the high yield and quality standards we have set for our cotton crop. Laboratory testing can reveal situations where more or new nutrients should be added to a crop. Unfortunately there have been bad experiences with predicting fertiliser use based on laboratory tests, but these experiences, plus research and new equipment should be used to our advantage. Most cotton growing soils are relatively fertile. However there are three categories of deficiency where fertiliser use is necessary for maximum production:

Nematodes are regarded as a major pest of cotton in many parts of the world. It has been claimed that "nematodes cause economic losses to cotton everywhere it is grown" (Watkins. 1981). Apart from yield reductions resulting from nematode activity alone, nematodes are often involved in interactions with other plant pathogens. The interaction between fusarium wilt and the root knot nematode is well documented. Nematodes usually are favoured by well drained light-textured soils. In recent years plant parasitic nematodes have been found in wheat growing on the heavy textured soils of north-west NSW.

This review of the literature referring to A. macrospora indicates the extent of current knowledge about the pathogen and the disease it causes.

Currently in Australia there are approximately 700 cotton germplasm accessions located with CSIRO, QDPI and a few private seed companies. My job during 88/89 season will be to obtain samples of all these accessions and to grow then in the field for seed increase and evaluation of morphological and fibre characteristics. Good quality seed will be harvested, dried to 6% moisture content, and stored in alfoil packets at -20oC. Seed stored under these conditions will remain viable for 20-50 years. Data collected on morphological and fibre characteristics together with passport data (pedigree, origin. etc) will be entered on our computer database.

The objective of the cotton breeding programme is to breed cultivars which are adapted to central Queensland environments. Specific objectives include t.he development of cultivars having high yield, with stability of yield over years, a superior fibre quality (especially high fibre strength) bacterial blight resistance, and resistance to Heliothis and pinkspotted bollworm (obtained by selecting for okra leaf, smooth leaf, frego bract and nectarilessness).

Four cotton breeding programs have been operating in Australia, three i n New South Wales and one in Queensland . This is based on previous experience and limited evidence that cultivar s different from those in the Namoi are required on the Darling Downs and central Queens land. In orde r to efficiently pursue all aspects of cotton cultivar improvement in eastern Australia, a J critical examination is required of the adaptation patterns of cultivars and the effectiveness of locations to evaluate cultivar differences .

It is now two years since we advi sed the previous conference on the progress of the trials so will take this opportunity for a further update. The 1986/87 trial comprised sixteen entries and results were obtained for the following ten sites: Warren, Breeza, Narrabri, Bourke, Moree, Boggabilla, St George, Darling Downs, Biloela and Emerald. Results for that season have been printed in the Australian Cotton Grower (Nov. 1987). This season thirty entries were tested at twelve sites, the ten just cited, plus Theodore and Merah North. No yield results were able to be obtained from Merah North, effectively limiting the trial to eleven sites.