Project Summaries from Postgraduate Visit

McKinnon, Buchanan, Delaney, Dodd, Humphries, Ivkovic, Lightfoot, Lowor, Machado, Najar, Speirs, Vanags, Werth, Whiffen and White

At a July 2004 meeting of the CHCG&IA Research and Technical Subcommittee it was resolved that DPI&F research staff develop a strategy to meet the regional R&D needs of the Emerald area, as identified in a discussion paper by Mr. Hamish Millar.

Following discussions with local industry, staff and researchers from the Cotton CRC (Mr. Guy Roth, Drs. Greg constable and Ian Rochester), CSD (Mr. John Marshall) and other QDPI staff, general agreement was reached that a practical way of addressing the regional R&D needs, as identified above, is to begin with a preliminary assessment of cotton phenology and yield response in the form of a one-season pilot planting-time trial.

Cotton R&D Corporation funds for the project entitled ‘Operational Costs for Cotton Experiments’ were used to fund cotton experimental trials at the Australian Cotton Research Institute (ACRI). The management of cotton growing for cotton trial experimentation is dependent on the aims of the specific trial. However cotton growing at ACRI is undertaken to industry standards with the intention of maintaining the long-term productive capacity of the land. The ACRI has recently received Cotton Australia BMP accreditation. Over the three years of the project an average of 50Ha of experimental cotton was grown at ACRI on behalf of NSW Department of Primary Industries researchers. Cotton was successfully grown at ACRI over the three year period under a broad array of experimental criteria. The successful growing of cotton in this context is intended to meet the needs for cotton experimentation in agronomy, entomology, farming systems and pathology.

Five sites representing the main cotton growing soil types in the Lower Macquarie Valley were selected and soil sampled in late October and May 2004. Field selection was based on being a representative irrigated cotton soil of the Macquarie Valley as well as irrigation water source. One of the sites sources irrigation water from a moderately brackish (1.0 dS/m) bore. Three sites are supplied by schemes and the other by a river pump.

The pattern of measured is consistent with previous reports, the lighter red soils have significant higher deep drainage rates than the heavier grey soils. The increased drainage under the site irrigated with the saline bore (Bw) may be due to an electrolytical effect in which high EC water partially flocculates the soil and increases deep drainage (Beecher 1992).

The upper 50 cm of the meander plain soil (Bw ) became sodic (ESP greater than 5%) after irrigation compared to the pre irrigated samples. There was no significant change in the Na content the back plain soils due to the 2003-04 irrigation season (Ya, Dr). This result suggests that irrigation during the 2003-04 season on the lighter meander plain soils increased the risk of sodicification of these soils while there was no such effect on the heavier back plain soils.

The change in soil salt stored was calculated and the results show that all sites increased the salt store over the observation period (Fig. 6). The biggest increase occurred on the meander plain soils irrigated with the bore. At this site an additional 3.5 t/ha of salt was stored in the top 2.1 m. This estimate does not account for any effect of leaching by winter rainfall. Previous studies (Friend 2000) showed that winter rainfall has a significant effect on the amount of deep drainage and hence leaching of salts. Again it would be difficult to draw too many conclusions without undertaking additional post winter sampling.

Long term farm soil and water data has been collected and collated for one site. Some historical yield data has also been collected. The yield data was used to pinpoint areas of high and low yield. Initial analysis of the soil data in conjunction with yield maps suggests that areas of low yield also have high sub soil nitrates present after harvest. This suggests that the plant did not or could not access the nutrients. The finding has enabled the grower to eliminate nutrition as a factor in yield. The grower has identified these areas of low yield and high sub soil nitrates as areas of restricted infiltration.

The objective of development of a detailed research proposal that meets alternative funding bodies priorities was not achieved. The original plan was to approach the CW CMA and CRC IF for additional funding. The CW CMA is still being established and the investment plan has yet to be finalised, while the CRC IF will only fund post graduate studies. It is hoped that the CMA will be operational in the later part of 2004 or early part of 2005 and this will allow negotiation of a research agreement

Correct identification of the species of aphid present is a critical step in determining a management strategy. Many winged forms of nonpest aphid species will settle on cotton and test feed, then move on when they find it unsuitable.

Fleabane has become one of the most difficult-to-control weeds in dryland cropping systems in recent years, The weed problem is thought to have resulted from recent changes in farming practices toward greater use of zero tillage, and possibly from recent seasonal conditions that have favoured fleabane growth. Some preliminary studies on fleabane biology indicated that the seed emerged only on or near the soil surface, and that seed persistence was relatively short. The weed seemed to emerge throughout the year, but peak emergence was during spring, particularly under wet conditions. One mature plant can produce an average of 11 0,000 seeds.

The National Centre for Engineering in Agriculture (NCEA) is seeking feedback from growers about the incorporation of the John Deere 7760 On Board Module Builder (JD7760) into farming systems.

Bladder ketmia (Hibiscus trionum) is an increasingly problematic weed in the Australian cotton industry. Two varieties of the weed exist, narrow leaf bladder ketmia that can emerge, grow and produce seeds throughout the year, and wide leaf bladder ketmia that only grows throughout the cotton season, producing seeds in summer and autumn. Successive seedling flushes of the weed produce seeds within 46-62 days respectively, depending on the type. Between 2500 and 5000 seeds are produced on medium sized plants.

There are a number of minor weeds that occur throughout the Australian cotton industry that have considerable potential to spread and become increasing problems. Two of these are anoda weed (Anoda cristata) and velvetleaf (Abutilon theophrasti). Research has been focussed on these weeds in an effort to better understand the biology and lifecycle of these weeds to prevent further spread and to lead to increased management success. This paper briefly outlines that best management of these species can be achieved by controlling successive flushes of seedlings, preventing weed seed set and by rigorous farm hygiene practises. While these practises need to be part of an Integrated Weed Management (IWM) package, the limited suite of herbicides that are currently registered to control anoda weed, and lack of any herbicide registrations for velvetleaf is likely to hamper future management. This paper calls for further herbicide screening and registration of herbicides for both weeds in the Australian cotton industry. At present, one of the best means of management is the maintenance of rigorous standards of farm hygiene, akin to the Collie Clean Go Clean campaign used to prevent the spread of cotton pathogens

The weed management costs incurred by Australian cotton growers represent a significant and often under estimated loss to cotton cropping gross margins. Although there are likely to be a number of weeds present in cotton cropping fields at any one time, some species are more problematic than others' For example, weeds in the family Malvaceae (those related to cotton) are causing increasing problems in many areas, in particular bladder ketmia (Hibiscus trionum), Anoda weed (Anoda cristata) and velvetleaf (Abutilon theophrasti). This paper examines the costs of weed control between fields with and without bladder ketmia, anoda weed and velvetleaf