Water is the major factor limiting cotton production in Australia, with 70-90% of the cotton production area usually managed under an irrigated system. The Cotton Catchment Communities Cooperative Research Centre (Cotton CRC) placed a major emphasis on improving water use efficiency and productivity of irrigated cotton farming systems in Australia. This paper reviews the research and trends in the water use efficiency and productivity of irrigated cotton.

Cotton CRC research from 2006 – 2012 focused on promoting measurement of water use efficiency, optimising the performance of surface irrigation systems, investigating alternatives irrigation systems to the conventional furrow irrigation systems, understanding the movement of water through the soil and the potential of deep drainage, reducing water losses from on farm storages and better understanding of plant water relations

Surface irrigation systems are used on 80% of the irrigated Australian cotton crop and utilise 6-7 ML/ha depending on the amount of seasonal rain received. Over the past decade water use efficiency by Australian cotton growers has improved by 3-4% per annum, or by 40% increase in the water use productivity. This has been achieved by both yield production increases and more efficient use of applied irrigation water. The whole farm irrigation efficiency has improved from 57% - 70%, while crop water use index is above 3 kg/mm/ha and is high by international standards. The seasonal evapotranspiration of surface irrigated crops averages 729 mm over the last 20 years

Yield increases over the last decade can be attributed to plant breeding advances, the adoption of genetically modified varieties, and other agronomic research. There has been an increased use of irrigation scheduling tools and furrow irrigation system optimisation evaluations. This has reduced in field deep drainage losses. The largest losses of water on cotton farms is from evaporation from on farm water storages. Application efficiencies of over 90 per cent are achievable under well managed furrow irrigation. The greatest initial gains in water use efficiency can be achieved by improving the management of existing surface irrigation systems through this site specific optimisation. Growers are also making changes to alternative systems such as centre pivots and lateral move systems and it is expected there will be increasing numbers of these machines in the future. These systems achieve labour and water savings (30%), but have significantly higher energy costs associated with water pumping and machine operation.

The standardisation of water use efficiency measures and improved water measurement tools for surface irrigation have been important research outcomes to enable irrigation benchmarks to be established. While the Cotton CRC achieved important new research outcomes, its major effort was related to water extension projects, training of growers and advisers, capacity building, technology demonstrations and information packaging. The industry benchmarks indicate that Australian cotton irrigators should be producing >1.1 bales per ML water (total water, ie irrigation water applied, rainfall and soil moisture used) with surface irrigation systems and 1.3 bales/ML with centre pivots and lateral move machines.

Water use management performance is highly variable and site specific between cotton growers, farming fields and across regions. Therefore, site specific measurement is important. The range in the presented data sets indicates there remains potential for further improvement in water use efficiency and productivity.

The Back Paddock Company has become one of the leading soil nutrition consultants in the cotton industry. The objective of the project is to better educate CGA member growers about soil nutrition by completing two Back Paddock nutrition courses.

The CGA has highlighted that soil nutrition is a key area where growers can improve their business. Soil and crop nutrition was also an issue highlighted by growers at a R&D Thank Tank facilitated by Ingrid Roth. As a result of these discussions a grower focus group has been established in the Macintyre Valley with the objective of increasing yields and increasing Fertiliser Use Efficiencies. The group is being facilitated by our local CottonInfo team Regional Development Officer, Sally Dickinson. The group recently met with the CRDC as part of its soil research review. It was highlighted that growers are making decisions from previous year’s crop and not on soil test data. It was also highlighted that growers rely on consultants to decide what fertiliser rates they are going to use on their farm. Increasing yields has also resulted in growers applying increased fertiliser rates. There are a number of questions involving critical levels, namely where to apply fertiliser? What fertiliser type to use? How to apply the fertiliser? And the timing of fertiliser application?

Growers that undertake the workshop will learn to make better management decisions when applying fertilisers. It will enable growers to understand and interpret soil tests and allow them to communicate and design a fertiliser program best suited to their business.

The cotton industry will benefit from this project as it will increase fertiliser use efficiency on farms through increased capacity of the growers who have participated in the course and the focus group. Growers will increase productivity on their farms by improving fertiliser use efficiency.

This project will also consider key industry research in the Macintyre Valley, including the CottonInfo team's Nitrogen Use Efficiency trial.

The Walgett CGA wanted to increase their knowledge about weather patterns and forecasts. By increasing the number of weather stations in their area then learning how to use them and the numerous forecasts available they will be better able to predict rainfall events but also wind changes which will reduce issues surrounding spray drift. Ultimately though this is a way to better mitigate risks inherent in farming.

To develop their knowledge of weather patterns- a meeting was held at the completion of installation and 12 growers and advisors attended. Jon Welsh went through the models and based on qualitative feedback, knowledge has been increased.

Fill in the weather gaps- 4 Next Gen weather stations have now been installed which fills a large gap in the information available to growers in the Walgett area.

Increase the use of wind speed and direction in decision making - Many growers were not aware of the detailed wind direction and strength models available on the BOM website and so Jon was able to increase awareness to better use these tools to minimise drift.

Findings at a glance

Water availability and the related subject of climate change is the primary issue facing the

community. It has jumped ahead of all other issues - the economy, terrorism, education, health - with

surprising rapidity. The full implications of this rapid rise are yet to be seen.

For the overwhelming majority of participants cotton is not on the radar as an issue.

Overall, respondents had mildly negative to neutral perceptions of the cotton industry. They know

little about cotton. Their default position veers towards negative because of the perceived excessive

use of water, but they are not negative towards the cotton industry itself.

Perceptions of the cotton industry are based on very little knowledge - so are lightly held

Once they are given more information about cotton, nearly all respondents became more positive

The strongest messages supporting cotton relate to job creation, contribution to the economy

world's best practice and improved water efficiencies and reduced chemical usage.

There is a widespread view that cotton farming has a long term future in Australia. However,

people do want to see evidence of more efficient use of water and investigation into new drought

resistant strains of cotton.

Most respondents support some kind of public education campaign to help combat negative

perceptions.

However, the research as a whole shows that this is risky as most people automatically turn

negative when they hear that cotton uses a lot of water and it takes focused reading and

discussion to educate most of them back to a positive standpoint. In the real world this would

be a formidable and very costly task given the complexity of the issue.

I was invited to speak in a symposium on monitoring for resistance to Bt at the 2006 combined Meetings of the Society of Invertebrate Pathology and VIII International Conference on Bacillus thuringiensis (ICBt). These meetings were held in Wuhan, China from 27th August until 1st September 2006. The major output from the trip was to disseminate my latest research results to my peers by presenting a talk in the symposium entitled "Monitoring and managing for Bt-resistance in Australia: The challenges for the next decade". The talks in the symposium gave an International overview of the latest developments in Bt resistance monitoring in terms of current methodologies and up-to-date findings. Our approach to monitoring in Australia was well received and there was considerable interest in my reports of a higher than anticipated frequency of alleles conferring resistance to Cry2Ab in H. armigera. All of the talks in the symposium were presented as written papers in a special edition of the Journal of Invertebrate Pathology in Volume 95 (see below). I established contact with key international researchers in my field of Bt resistance monitoring including Saku Sivasupramaniam from Monsanto, who has subsequently visited ACRI, and Carlos Blanco from the USDA, whom I have been in regular contact with since the meeting. In particular, Carlos and I discussed approaches to studies of sperm precedence and I have since reviewed several of his papers on this topic. I also established an important link with Ryan Kurtz, a research entomologist with Syngenta, and met face-to-face with a collaborator David Heckle, from the Max Plank Institute in Germany and the University of Melbourne, and discussed progress on the CRDC funded project on isolating the Cry2Ab resistance gene in Helicoverpa armigera. Attending the meetings increased my breadth of knowledge by attending talks outside my direct area of interest that focused on microbial control, mechanisms of resistance, and Bt-performance enhancement.

This pilot study involved the processing of five bales of cotton, representing

three varieties i.e. Sicala 3508, Sicala 60BR and Sicot 289BR, into ringspun

carded and combed yarns to determine their textile processing performance.

The results indicate that the yarns and fabrics produced from Sicala 350B

were better then those produced from Sicala 60BR and superior to those

produced from Sicot 289BR. The study did highlight that agronomic and

ginning variables should be controlled as they have a large impact on each

variety's fibre properties and processing performance.

Cotton Bunchy Top is a disease of cotton that was first reported in the 1998-99 cotton season. Symptoms of the disease include shortening of internodes and petioles, . CBT affected plants also have a reduced photosynthetic rate, and reduced cotton lint and seed yields. Research in this project aimed to (i) identify the causal agent of CBT and develop a probe to detect it (ii) identify the vector(s) of the disease and investigate its transmission characteristics and alternative hosts and (iii) Assist in selection of resistance to CBT in elite cotton germplasm. These are discussed below;

• Identification of the causal agent. Despite exhaustive efforts the agent causing CBT remains unidentified. Tests looked for viruses (common RNA virus, circular DNA Geminivirus and nanovirus, double stranded RNA viruses and a range of virus specific ELISA test including Barley Yellow Dwarf Virus), viroids, phytoplasmas and endoparasitic fungus hyphae. Testing also employed subtractive hybridisation, which did not reveal any non-cotton genes, and cDNA microarrays, which did reveal three clones (genes) that did not match the cotton genome. Unfortunately the project ended before these genes could be characterised.

• The disease is vectored by Aphis gossypii (cotton aphid) and attempts to transmit it using Myzus persicae (green peach aphid) or Aphis craccivora (cowpea aphid) failed. Cotton aphid transmits CBT semi-persistently, meaning they can transmit the disease to multiple plants over several days. Aphids can acquire CBT after feeding on CBT affected plants for five minutes and can inoculate a healthy plant after feeding for one hour. As few as one aphid can transmit the disease though more aphids do it more effectively. Cotton plants infected with CBT are capable of infecting aphids with the disease after a period of about 16-17 days, about 2 weeks before symptoms were obvious in the plants.

• Gossypium barbademse cv Pima S7 is a symptomless host of CBT, while the resistant variety DeltaOpal did not host the disease.

• Two alternative hosts of the disease have been identified, both from the family Malvacae. These are Malva parviflora and Malvastrum americanum..

• Over the past four seasons we have screened cotton varieties in the field and glasshouse for resistance to CBT. This has lead to selection of CBT resistance in several elite lines for commercial release of the first variety in 2005-06.

This project has provided the basic information to begin to understand the field epidemiology of this disease. It is likely that it is acquired by aphids feeding on an alternative host. Aphids transmit the disease semi-persistently, so they are infective for days after leaving alternative hosts and entering cotton crops. Cotton plants can become infected by the feeding of a single aphid, though more aphids results in higher transmission rates. Cotton plants colonised by aphids become new CBT sources after about 17 days and show clear symptoms after 3 – 5 weeks. Initial spread of the disease is slow as aphids are in the apterous form but as populations build alates begin to appear and secondary transmission to other parts of the field can occur.

CBT continues to threaten the industry both due to yield reductions and due changes in growers and consultants perceptions of aphids – resulting in lower thresholds, increase spraying and selection for insecticide resistance in aphids. Potential problems due to CBT have been hidden in recent years due to drought reducing over winter survival of aphids. There is a need for continued research to select for CBT resistance in elite germ plasm, to identify the agent so that a probe can be developed to facilitate understanding field epidemiology and breeding and there is a need to further study the field epidemiology so that outbreaks of CBT can be predicted and managed.

Regular disease surveys have highlighted the changing status of cotton diseases over time and

provided valuable insights into the factors affecting their distribution and severity.

• Seedling mortality was low during the 1990’s but increased dramatically in 2000, 2001

and 2002, largely due to cool wet conditions during spring.

• The risk of seedling disease increases with increasing latitude; the southern regions of

NSW are particularly prone with up to 60% seedling loss observed in some fields.

• NSW is currently experiencing an epidemic of black root rot of cotton. Black root rot was

observed on all of the farms surveyed regularly in the Macintyre, Gwydir, Namoi and

Macquarie Valleys, and in 78% of fields and 39% of plants within those farms. The

disease was detected in the Murrumbidgee Valley for the first time in 2003.

• The distribution of continued to increase. Fusarium wilt has been reported

on a total of 75 farms in NSW and was observed on 30% of the farms surveyed regularly

by NSW Department of Primary Industries.

• In NSW, adoption of less-susceptible varieties is ahead of the incidence of Fusarium wilt

• Transects of an infested field in the Macquarie Valley suggested that Fusarium wilt may

progress much more quickly in cooler cotton growing regions.

• Verticillium wilt was observed at very low levels, although its incidence has increased in

the Namoi Valley, probably due to a period of declining use of resistant varieties.

• Many farms do not have black root rot, Fusarium wilt or Verticillium wilt and farm

hygiene should be practiced to minimise further spread.

Experiments were conducted to develop and/or evaluate control strategies for control of

seedling disease, black root rot and Fusarium wilt:

• Delaying the date of sowing as late as possible within the planting window can avoid

conditions that favour seedling disease and black root rot.

• Planting should be timed to coincide with the onset of periods in which the mean soil

temperature will be 16°C during the first week from sowing and delayed after preirrigation

until soil water content is at the lower end of the range that is adequate for

seedling establishment, in a given soil

• Different seedling pathogens vary in dominance from field to field and year to year; the

fungicide treatment DynastyTM consistently performing as well as the standard fungicides.

• Seed treatment with acibenzolar-S-methyl consistently activated resistance against

Fusarium wilt of cotton but not Verticillium wilt.

• A practical method for application of acibenzolar-S-methyl to cotton seed was developed,

using 6 mg/kg seed incorporated in the standard seed treatment fungicides, with no

phytotoxic effects and an extended, active shelf life.

• Vetch, mustard and canola were increased the severity of Fusarium wilt and should not be

used as biofumigation crops on farms with Fusarium wilt

• The peak activity of the black root rot pathogen and seedling pathogens are mutually

exclusive, providing further evidence that T. basicola does not kill cotton seedlings

• Mycorrhizal fungi survived in substantial numbers after long bare fallows of 28 and 35

months in fields at Bourke and after a bare fallow of four years at Narrabri

Results of these experiments and observational studies have been incorporated in strategies

for integrated disease management and disseminated to the cotton industry by way of

publications, media releases, field days and meetings with growers and consultants.

Indonesia has a large spinning capacity of about 7.5 million spindles. About 45-50% of the spindles are on cotton and cotton blends. On an average about 500,000 metric tons of raw cotton are imported per year from all over the world. Australian cotton has a significant share of this for the production of medium count ring spun cotton yarns and blends.

Small laboratory gins are a vital piece of equipment in cotton research at the plant breeding and other subjects where small plots are used. CSIRO’s plant breeding program has more than 30,000 small plots for ginning. Since the instance of Fusarium wilt, sites with that disease have not been sampled for ginning and fibre quality. This reduces the available information on fibre quality. One solution is to have a gin located at Goondiwindi or Moree for ginning samples from breeding or other plots, so fibre can be tested at a contract testing line in the same valley.

The gin has been successfully purchased, delivered and modified to appropriate operating safety standards. The gin ensures better and more comprehensive data from all sites and thus assists with better decisions on breeding line selection.