The trial is part of a Grains Research and Development Corporation (GRDC) research project, focusing on maintaining profitable farming systems with retained stubbles in Victoria and Tasmania.
This replicated trial was sown on April 12, into dry conditions, at Streatham in south-west Victoria.
The disc seeder sowed canola into 30cm high stubble from a 2015 wheat crop. This year a machine with 25cm row spaces was used, which had some challenges, as the 2015 crop was sown using 30cm row spaces.
The tine seeder was sown into 15cm high stubble using 30cm row spaces in both 2015 and 2016. This year the canola was direct drilled, inter-row.
Initial germinations have highlighted potential dangers of dry sowing with disc seeders.
There were far less plants on average in the disc sown plots.
Germination and establishment were also higher in the burnt areas than in the stubble retained. There may be more viable seeds in the soil that will germinate once it rains but the establishment in the tine sown plots has been reasonable in the dry sowing conditions.
The target canola plant population is 35 plants per square metre and sown with 80kg/ha MAP. Data shows the disc has not established because of fertiliser toxicity or lower soil to seed contact than the tine.
Urea was also applied at sowing, 60kg/ha in half of the plots for each seeder and this has had a detrimental impact on emergence, as evidenced by the differences in treated and untreated plots where stubble was burnt.
The Equalizer uses a twin tube setup, which separates seed and fertiliser and this failed to prevent seed damage. Strangely where stubble was retained there was no difference in the plus or minus urea at sowing treatments
This data has not yet been analysed but the average plants per square metre indicate that there will be a statistically significant difference between some treatments. SFS projects coordinator Paul Breust said they will monitor the emergence after decent rain to see if any more seeds germinate.
Past experience has led to the belief that the disc is more reliable at establishing crops in low moisture seed beds but the data from this trial shows otherwise. It is commonly known that fertiliser toxicity can be a problem in dry seed beds with disc seeders, especially with canola. The data certainly supports this and the current very low plant numbers in both burnt and stubble retained treatments for the disc may require re-sowing.
Soil moisture was also measured in the seed furrow for all treatments. A common perception is that tine seeders dry out the furrow more than the disc. This is supported by the data but there was no subsequent increase in germination, thought to be due to increased fertiliser toxicity in the disc furrow.
Keep up to date with the progress of this trial throughout the season at www.sfs.org.au