Grains Research and Development

Date: 01.06.1996

Right equipment = big yield increases. Results from two studies on soil-levelling devices and seeding equipment. Narrowing in on narrow points.

Update your seeding equipment and methods — increase yields by up to 0.33 t/ha.

That's the dynamic link which researcher Rohan Rainbow has found in 23 field trials over the past four years in South Australia, supported by growers through the GRDC.

"Improved seeding technology is one of the very few areas where we can not only significantly improve crop emergence but crop growth rates and hence total grain yield," said Mr Rainbow, of the SA Research and Development Institute.

The yield boosts were obtained when Mr Rainbow compared results from:

  • the standard seeder with 125-mm-wide cultivation and seeding shares and a trash finger tine harrow following the seeder, against:
  • row aligned deep cultivations from a knife or lucerne chisel type point combined with accurate seed placement derived from a spear-type point on a separate tine and press wheels as the covering device.

"The ability to direct drill field crops is limited only by the seeder's ability to handle trash and provide good soil tilth for the emerging seedling," he said.

The work, which was conducted with the University of South Australia's Agricultural Machinery and Design Centre, highlighted the need to select drill points in combination with the seed tube and to use points which maintained their integrity during seeding. It was important that seed placement did not change as the seeding point wore.

Poor placement could cause yield losses of up to 4.6 per cent. As well, seed placement should not be compromised by the seeder performing other functions such as deep tillage below the seedbed and weed control.

Key findings:

seeder points

  • soil smear caused by blunt leading or cutting edges can reduce emergence and subsequently reduce yields by up to 20 per cent in cold, wet conditions on heavier soils,
  • spear-type points with a positive angle of entry, combined with adequate tungsten carbide protection and an integrated seed delivery tube, have produced better emergence and hence crop yield than many other narrow points. Inverted T-type seeding points are effective in soils which require more tilth from the seeder point at seeding, particularly if they have a slightly deeper front blade, and
  • too much tilth or a soft seedbed from too much tillage reduces seed to soil contact even with press wheels. The rule is to approach extra cultivation at depth below the seed zone with caution. It is better to deep cultivate less than to be too aggressive.

covering devices

  • on all soil types, press wheels resulted in yield increases of more than 8.5 per cent on average over the four years, compared with rotary prickle chains and finger tine harrows. Even higher yields can be expected on soils that crust and surface seal when there is dry weather after seeding, because the press wheels facilitate moisture conservation. While press wheel use will also boost yields in field peas, surface rolling post-seeding is still necessary to level the soil and reduce dirt contamination at harvest, and
  • there is no difference in the performance of prickle chains and trash finger tine harrows when stubble trash is not present. When it is at high levels, prickle chains improve crop emergence and grain yields more than the harrows.

Subprogram 3.4.2 Contact: Mr Rohan Rainbow 08 8842 3900