Stubble Management – A Burning Issue!
By Rohan Wardle
Research and Extension Agronomist
Please note that this is text only. To view the figures, photos and diagrams you will need to download the full document. (.pdf 110kb)
It is intended that in conjunction with today’s overview, that you are able to help SFS direct important ‘National Landcare Program’ funding into critical and specific local stubble management research.
Introduction
With many southern crop producers now returning in excess of 5-7t/ha cereal yields, a real concern is evolving as to what else can be done with the heavy straw residues. Burning has been the ‘non preferred’ practice (see Figure 1) for many farmers who incur severe slug, weed or disease burdens (or those who just cannot manage the trash via mechanical limitations).
What so ever, a poor portrayal of land stewardship and the increased potential of erosion and off-site nutrient or pesticide leakage are demanding change to this tradition.
This now presents farmers with an enormous opportunity to use stubbles in a more economical and environmentally sustainable way, whilst also addressing major crop productivity concerns.
Fig.1. Typical Autumn ‘stubble burning’ scenario within close proximity to Geelong. Our aim over the next four years is to achieve a conversion from the approximate 99% burning of cereal stubbles within the region (in particular wheat), to far less than 80% via on farm research and extension.
NLP & SFS Stubble Management Research
With funding from the National Landcare Program, SFS has embarked on this extensive research agenda with soil management as the major concern. The introduction of organic matter (as stubble) into the topsoil not only helps increase hydroconductivity, resulting in additional moisture and nutrient availability during the critical grainfill periods, but also attains subsoil benefits by decreasing other localized hostilities (Kirkby; 2001).
Paddock scale demonstration trials have been established across South West Victoria at four sites (Inverleigh, Lismore, Lake Bolac and Hamilton) that involve a number of treatments addressing both the stubble and subsoil issues. Mulching, burial of ‘other’ organic substances and skip row seeding are some of the alternative treatments aimed at lessening the destruction of our fragile native habitat and enhancing the benefits of biodiversity across the region.
At the Hamilton ‘Stubble Bash’ field day in February, both Clive Kirkby and Tom Dunstan were enthusiastic to relay the message that there are alternatives to burning stubbles that are not only less stressful to conduct, but also help soil organisms in their function to recycle nutrients and benefit the cropping rotation (but it does take time and effort).
Let us not forget however, that burning at present is still an important tool for many to use when it comes to managing heavy wheat stubbles about the district. We do not want to be seen to be promoting its demise to the regulatory bodies overnight.
We hope over the next four years to provide detailed solutions on how to handle such high volume loads and with the continuing facilitation of trials and ideas that this will bring us closer to the required site specific outcomes. Our proactive approach as an industry in trialing new stubble management alternatives will not only help increase the size of our management toolbox, but be seen by our members as a way of linking the environment into the way we do business, making us even more successful in land and profit management.
Mechanical means of Residue Management
With sowing of the NLP Stubble Management trials occurring across the south west in early June of this year, strong interest was directed toward toolbar design and its residue handling capabilities. The residue management tools which were used throughout these trials showed signs of increased flexibility when it came to heavier stubble loads and within paddocks that had been intensively grazed.
These unique additions to the sowing operation (Figure 2 & 3), aid in helping push enough fallen residue aside to minimize the ‘vinegar affect’ on the emerging crop, whilst maintaining optimal ground cover for moisture retention and weed suppression (Figure 4).
Fig.2.(left) Yetta twin stars, Fig.3.(middle) Gessner residue management system (foreground), Dawn management system (background), Fig.4.(right) Result of seeding pass using three types of mechanical residue management systems.
The so called ‘ideal’ is to promote soil contact with the stubble as close to the harvest operation as possible. This begins degradation and results in beneficial soil biology and eventual increases to the potential of the following crop (Unfortunately with the 2005 experience, the lack of rainfall was critical to the overall success of this practice). The compromise with these techniques is that grazing value may also be reduced; so knowing what is in your best interest needs to be determined when the crop is about to be harvested.
In addition to non grazed scenarios, grazing of stubbles has offered many challenges to the seeding operation, however, in combination with feed additives and energy supplements for stock during this period, then this allows for further pulverization and loss into the atmosphere, lightening the overall bulk load of the stubble and decreasing the chance of blockages during seeding.
Our overall aims of the stubble project has been to use differing approaches from post harvest onwards, including the basic single pass of the harvester, through to application of cellulose digesters, to multiple passes with off-set discs. Future plans will be to sow alternate rows each year (with GPS), to help minimize the effects of blockages and toxicities. Variety choice and delayed nitrogen timing are other critical tools that can greatly reduce stubble loading at the end of the season and can also benefit nitrogen efficiency.
From current research, the breakdown of stubble is most difficult in the highly lignified red wheats and becomes somewhat easier with white wheats and then barley stubbles, which appear to be far more palatable to grazing stock, are somewhat easiest to manage.
Southern Farming Systems is about innovation, entrepreneurialship and designing the future of our industry. If you have any further interest in the topic of stubble management, call myself on 0438 343079, or you can visit our webpage: www.sfs.org.au for progress of the project from crop establishment through to harvest across all sites.
I do suspect that many growers already have localized answers to this general dilemma and would appreciate your contribution to this project!
Acknowledgements: Kirkby, C. (2001) Early incorporation helps manage heavy stubbles. Farming Ahead, No.118, pp.38-39.
