Bentleg furrow opener research throws up potential benefits
Date: 08 Sep 2015
Research into the use of bentleg furrow openers at seeding has underlined their potential benefits for no-till farming systems.
University of South Australia PhD student James Barr says bentleg openers, which can reduce soil throw and maximise furrow backfill, represent a new opportunity for optimising the performance of tine seeders.
The devices offer an “unprecedented ability for high-speed, low soil throw, no-till tine seeding”, according to Mr Barr, whose work is being funded by the Grains Research and Development Corporation (GRDC), the South Australian Grain Industry Trust (SAGIT) and the University of SA.
Speaking at recent GRDC grains research Updates in the southern cropping region, Mr Barr said soil disturbance caused by tine openers could affect the success of no-till seeding operations.
“Furrow moisture loss, weed seed germination, seeding depth variability across seed rows, crop safety and pre-emergent herbicide efficacy are issues that can be influenced by the amount of soil disturbance by tine openers.
“Excessive soil throw limits the furrow backfill, reducing soil cover over the seed, and creates ridging between adjacent seed rows, resulting in additional soil cover which increases seeding depth and potentially induces crop damage from herbicides,” Mr Barr said.
In September last year, the University conducted a trial in clay-loam soil at Roseworthy (SA) to validate in a field situation previous findings from laboratory soil bin trials, and to investigate the potential for higher speed seeding.
A selection of straight and bentleg openers were tested, measuring draft, vertical and side forces, lateral soil throw and furrow backfill, at 8, 12 and 16 kilometres/hour and at 120 millimetre operating depth.
The two straight openers used reflected the range of rake angles displayed in narrow knife points, and the two bentleg openers featured a beveled edge and differed in their shank offset values (45 mm and 95 mm).
Both bentleg openers reduced soil throw compared with the blunt face straight openers at 8 km/h, virtually cancelling soil spill out of the furrow boundary.
At the higher speeds, the 95 mm offset bentleg opener retained its very low soil throw benefits, while the 45 mm offset bentleg design showed a sensitivity to speed, reaching similar levels of soil throw to the 53 degree rake angle opener.
Furrow backfill data showed the ability of the 95 mm offset bentleg opener to maintain maximum furrow backfill regardless of speed, while the straight openers, from a comparative baseline of 8 km/h, significantly emptied the furrows with faster speed.
The “furrow-emptying” feature of straight openers was strongest with the 53 degree rake angle opener. The 45 mm offset bentleg achieved significantly lower backfill at 16 km/h only.
Overall, the 95 mm offset bentleg design was able to maintain its baseline lateral soil throw at twice the sowing speed while maintaining 100 per cent furrow backfill, according to Mr Barr.
Draft force measurements indicated that the vertical knife opener required about 50 pc more pull than the 53 degree rake angle opener, demonstrating the known beneficial effect of low rake angle on draft. This was also about twice that of bentleg openers, which were able to minimise the pulling requirement due to their 45 degree rake angle leading foot.
Under the dry conditions, the draft requirement increased with speed for all openers, with the least effect measured with the vertical knife opener.
“The field data acquired to date confirms the great potential benefits of bentleg opener designs, both in controlling soil throw (and associated crop safety), seeding depth accuracy and in minimising draft forces, compared with the existing knife and spear point technologies,” Mr Barr said.
“Bentleg openers represent a new opportunity for optimising the performance of tine seeders and in particular, enabling high-speed sowing operations, on a par with disc seeders.
“Further, the soil handling features of the bentleg opener may achieve specific benefits of low weed germination, low moisture loss and increased residue cover which will need to be validated in further dedicated field studies.”
Mr Barr said dedicated research was required to refine the bentleg opener design and opportunities existed to further scale down the design (currently sized to operate at 120 mm depth), to suit shallow soils and further minimise power requirements.
Current postgraduate studies will seek to further validate – and optimise via modeling – the bentleg opener concept and recommend solutions for the design of an integrated seeding system.
“The benefits of a scaled-down and integrated seeding system would broaden the scope for widespread adoption of this technology,” Mr Barr said.
James Barr, University of SA
Sharon Watt, Porter Novelli
Caption: University of SA PhD student James Barr (left) shows a bentleg furrow opener prototype to Mallala (SA) grain grower and former GRDC Southern Regional Panel member Richard Konzag, at a GRDC grains research Update at Kadina.