Ground Cover North : Ground Cover 051 August-September 2004 - North
By DAVID EAST Despite the introduction of conservation tillage, minimum tillage, direct drilling and no-till, the initially popular disc tillage and seeding machines looked like fading from the Australian scene. These alternative tillage and planting practices, hailed as the path to more sustainable production, triggered other concerns that, in some cases, have become just as serious as those caused by conventional tillage. The new practices rely on chemical weed control, which unless monitored closely can lead to herbicide resistance. Another concern is the control of some soil-borne and plant root diseases. However, continuing research and development suggests these worries are not insurmountable. After a lull of several years, there is now an upsurge in farmer interest in discs. A new generation of disc machines are much bigger than their predecessors of a decade ago. They are wider, stronger and heavier with improved flotat ion, hydraulic depth control and folding capabilities, and are better suited to the bigger- powered tractors found on most grain properties. They can be used as cultivators to break the cycle of ground- working to help overcome soil disease problems and they can be used with air seeders. Disc machines have also become popular in some areas for green manuring -- 'ploughing in' green and growing crops to help tackle herbicide-resistance problems or to arrest signs of declining productivity. In other areas, disc machines are popular because they 'ride over' rocks and stones, in contrast to the pulling affect of tined machines. Researcher Jack Desbiolles at the University of South Australia's Agricultural Machinery Research And Design Centre (AMRDC) believes the rising interest in disc seeders is being driven by their low soil disturbance, which minimises weed seed germination, soil layer mixing, stubble incorporation and evaporation. Mr Desbiolles says zero-till disc openers can be classified into three design categories -- coulter disc, angled disc and undercut disc types. 1. Coulter disc. Flat or fluted, continuous or scalloped cutting edge, free swivelling or rigid in the vertical plane and running parallel to the travel direction. Soil disturbance and soil throw are a function of the disc attributes (smooth, bubble, ripple or wavy) and settings (cutting depth and operating speed). Common disc diameters range between 430 millimetres (17 inches) and 508mm (20in.) and no side forces are generated. Coulter disc applications include deep soil disturbance, residue cutting, and seed and fertiliser banding (sometimes in association with tine and point openers). 2. Angled disc. Single disc unit, mostly flat and smooth, set vertically, but running at a small angle of sweep (5 to 8 degrees) to the travel direction. The sweep angle allows seed/fertiliser delivery boot(s) to be located in the 'shadow' of the disc (passive side). Soil disturbance is the function of the sweep angle, cutting depth and disc diameter. Side forces must be balanced between the implement's left and right gangs. Common disc diameters range between 430mm (17in.) and 609mm (24in.). 3. Undercut disc. A similar flat, smooth disc tilted sideways from vertical up to 20 degrees. Undercut discs are often paired in opposition (closed in at the front as in twin coulter disc seeders), as a way to cancel side forces. Closed-in paired disc configurations can, however, present the higher risks of soil smearing and furrow compaction in heavier soils, and are best used behind deeper working coulters (for example, triple coulter set-up) to minimise down pressure requirements and compaction damage. On disc draft requirements, Dr Desbiolles says that a coulter disc can be compared to a narrow point inclined at a backward rake angle, where the additional rotating motion imparts a slightly different balance in soil/ tool force reactions. "The draft force reaction of a coulter disc is typically proportional to the weight required to keep the disc at the desired cutting depth, which in turn is proportional to disc diameter," he says. Mr Desbiolles says disc thickness and wedge angle are also factors influencing disc- operating forces. "While thin discs and small wedge angles minimise draft and vertical force reactions, they are subject to shorter wear life, lower strength and poorer durability. "As discs develop a blunt cutting edge, both the vertical and draft force reactions significantly increase, while at the same time reducing the ability to cut through residues." For more information: Dr Jack Desbiolles, 08 8302 3946, fax 08 8302 3380, jacky.desbiolles@unisa. edu.au For a copy of the article, Mechanics and Features of Disc Openers in Zero-Till Applications, contact Jack Desbiolles. MACHINERY 24 AUGUST 2004 The Grains Research and Development Corporation (GRDC) invests in research and development on behalf of the Australian grains industry and the Federal Government. APPLICATIONS FOR CONFERENCE SPONSORSHIP 2004-05 The GRDC invites and assesses Conference Sponsorship Applications twice a year. Conference Sponsorship Applications are being considered for the period January to June 2005 and must be submitted by Friday, 24 September 2004. Applications must be submitted at least three months prior to the conference. These applications should not be included as a part of any other GRDC research project or attached to other GRDC applications. Applicants interested in preparing Conference Sponsorship Applications are required to use the GRDC's Word 6 template (see details below). INDUSTRY DEVELOPMENT AWARDS (IDA) APPLICATIONS This award is aimed at developing the skills and knowledge required to achieve growers and GRDC's objectives. There are several Industry Development Awards available to growers, processors and others in the grains industry not engaged in R&D activities, who are seeking to enhance their experience and potential to contribute to the work of the Australian grains industry. The awards may be for study tours within Australia or overseas, or for other purposes approved by the GRDC. Support will be for up to six months and will not exceed $15,000. HOW TO APPLY Applicants are required to use the GRDC's Word 6 templates. These documents can be opened and completed on any computer that has Microsoft Word 6 (or a later version), or any word processing software that converts from Word 6. The GRDC requires six (6) A4 paper copies, double-sided and stapled to be submitted. These should be addressed to: Mrs Katie Poidomani Program Coordinator Product and Service Delivery Grains R&D Corporation PO Box 5367 KINGSTON ACT 2604 In addition to the 'hard' copies, an electronic copy should also be emailed to firstname.lastname@example.org. The name of the word document should incorporate the applicant's name and the award, for example, smith IDA.doc These Word templates can be found at the 'Applying and Reporting' section on our website: http://www.grdc.com.au/researchers/forms.htm Applications close on 24 September 2004. No late applications will be accepted. TRAVEL/CONFERENCE ATTENDANCE APPLICATIONS The GRDC invites and assesses Travel/Conference Attendance applications twice a year. The next two closing dates for travel applications are 24 September 2004 (for travel from January 2005 to June 2005) and 25 March 2005 (for travel from July 2005 to December 2005). The GRDC's usual preference is for travel requests to be incorporated into project applications wherever possible. Applications for financial support for travel or conference attendance not forming an element within a research project, may be made on the Travel/Conference Attendance Application form (see details below). Disc's reputation on the mend KEY POINTS n Sales of disc machines on the rise n New-generation discs suited to direct drilling n Discs do not pull up stones n Disc performance influenced by both soil and stubble conditions. Angled disc openers: develop side forces and are associated with a side wheel. Paddock conditions: strongly affect the performance of modern direct-seeding disc technology. Undercut disc openers: offer superior penetration ability in hard ground.
Ground Cover 052 October-November 2004 - North
Ground Cover 050 June-July 2004 - North