SEEDING SYSTEMS FOR STONY SOILS

A trial, funded by the National Landcare Program was set up at Colton, north of Elliston to test different seeding systems on stony soils.   A range of seeding systems spring and hydraulic tynes one disc opener were tested. 

The K-Hart disc system left the soil surface in a similar state as it was pre-sowing.  Small stones were flicked out in the seeding pass, however the surface was largely undisturbed. 

Shallow working with tynes was also favourable and brought little stone to the surface.  However this was offset by poor seeding depth which resulted in reduced crop establishment in most treatments.  This may be a small price to pay to reduce damage to seeding equipment in areas with a lot of stone. 

The new rock hopper point was evaluated alongside the standard 12mm Agmaster point.  The rock hopper point has a unique design allowing it to ride up over buried stone rather than loosen and lift it as conventional point can.  The rock hopper relies on welded tacker for wear resistance, which wears more rapidly than conventional tungsten tipped points.  The rock hopper point also required a reasonable amount of tyne breakout pressure to achieve a similar working depth to the Agmaster point, however brought less stone to the surface with the seeding pass. 

Throughout the trial, increased working depth resulted in greater crop establishment as it placed more seed in the soil rather than on the surface, despite tynes breaking out.  This result confirms work by Dr Jack Desbiolles in the Mallee, that despite tynes breaking out over stone, deeper working is favourable for crop establishment.  Machine maintenance and longevity are a totally different scenario, which would favour less tyne tripping and shallower working depth.

Seeding systems which provide seed placement independent of the tyne position such as the Conservapak and DBS systems gave consistent seeding depth through the trial.  Parallelogram type systems may result in increased maintenance in the long term if large areas of stony soil is sown. 

Adequate seeding depth was critical for successful crop establishment and was exacerbated by the late seeding date (6th June), which led to dry conditions post sowing.  The trial was sown over a stony rise and down in to a flat, allowing the seeding systems to be compared over a range of conditions.  A constant seeding speed of 6 km/h was used throughout the trial, with a contrast speed of 8 km/h used in specific treatments.  The increased speed didn’t increase the amount of rock bought to the surface.  Crop establishment was reduced with increased speed in the tyne systems, however was unaffected in the K-Hart disc system. 

Reducing sowing speed is a cheap and effective method of reducing machinery damage and increasing crop establishment, however is offset by the reduced seeding capacity and trifluralin incorporation. 

The final results of this work will be published in the SANTFA Newsletter and the Eyre Peninsula Farming Systems Book, due out in March 2008. 

CONTACT: Michael Bennet, SARDI Livstock Systems, Minnipa Agricultural Centre on 0428 103 792.