Background

Successful establishment of crops in paddocks with high cereal stubble loads continues to be an issue for stubble retention in no till. Good stubble management involves harvesting as low as practical straw chopping/spreading and slashing. Despite these measures burning stubbles (mainly wheat) remains a last resort for many farmers when sowing equipment simply can't handle the amount of straw. Efficacy of soil applied herbicides (Dual Diuron Treflan Lexone Simazine Avadex) is also a problem with stubble particularly given the heavy reliance of these herbicides in no-till. The advent of 2 cm auto steer systems could potentially solve this stubble problem by leaving most of the stubble standing and sowing between the rows next year. Less soil borne fungal disease on the inter-row e.g. take-all crown rot could result in increased yield for cereal on cereal. SARDI researcher John Heap has found 2 to 5 times less soil borne disease can exist on the inter-row compared to in-row of last years stubble.

2004 trials

ACC in conjunction with YP Alkaline Soil Group conducted an inter-row sowing trial to investigate the benefits of inter-row sowing with funding from Landcare SANTFA and GPS-Ag. Four stubble treatments (standing slashed removed late burn) were established on existing wheat stubble sown with 2 cm auto steer in 2003. Two crops (wheat canola) were sown on 5 th June under two sowing treatments (inter-row and in-row of last year's stubble) across these stubble treatments. Plots were sown with a 2 cm AutoFarm™ supplied by GPS-Ag and a plot seeder with knife points and press wheels on 9" spacings supplied by UniSA. Measurements included plant establishment disease levels and crop yield.

Results

Plant establishment

For wheat sowing on the inter-row significantly improved plant establishment for both standing and slashed stubble treatments (Table 1). There were no significant differences in canola establishment (Table 2) probably due in part to poor seed quality (60% germination).

Disease

At seeding large differences in take-all between inter-row and in-row at this site were evident from the Predicta-B soil test (Table 3). A number of dead heads appeared at this site from early October. Plant samples were taken and it was confirmed by SARDI that this was due to take-all and differences in the level of disease were evident inter-row compared to in-row (Figure 1). Stubble standing inter-row had a significantly lower number of dead heads compared to in-row treatments (slashed burnt removed) and burnt inter-row (Table 4). In general the trend was for less disease inter-row compared to in-row although the reverse trend was evident in the burnt treatment. Burning is known to reduce levels of take-all inoculum.

Yield

For wheat (Table 5) no significant interaction between stubble and row treatment occurred but there was a significant difference in yield for row treatment alone (but not stubble). Yield was 6% higher for the inter-row compared to in-row. Why? The impact of higher levels of take-all in-row compared to inter-row is the likely reason for this result overall across all treatments. This is despite the reverse trend of take-all inter-row vs in-row in the burnt treatment. Due to large variation in crop yields no significant differences were observed in canola.

Future trials for 2005

Inter-row sowing has created a lot of interest especially amongst no-till farmers. In 2005

Ag Consulting Co. in conjunction with the YP Alkaline Soils Group plan to continue to explore and quantify the agronomic benefits of 2 cm auto steer.

Planned projects include

• Efficacy of soil applied herbicides with inter-row sowing
• Investigating the 'trellising effect' that standing stubble may provide for lentils crops that could lead to improved harvestability and yield.
• What to sow in Year 3 of inter-row sowing? Will the standing stubble from Year 1 break down in time for Year 3 crops?

GPS requirements for inter-row sowing

There are some fundamental rules to follow if you want to inter-row sow.

These include

• Your auto-steer must be a 2 cm RTK system equipped with a base station.
• The base station must remain at the same location for a particular paddock year-in year-out.
• Your auto-steer must have the ability to store and recall an AB line for a particular paddock.
• Your auto-steer must have a 'nudge' feature in order to move the required distance to go inter-row e.g. nudge over 5" in Year 2 if you are on 10" spacings
• You must keep the same row spacing year-in year-out
• It is preferable to sow in the same direction each year for each run because sowing rigs will crab but hopefully crab in the same pattern as the previous year.

Take Home Messages

• Inter-row sowing can increase plant establishment by 15-20% and yield of wheat on wheat by 6%.
• This yield increase will be of particular interest to farmers in low rainfall regions who are more likely to have intensive cereal rotations due to a lack of profitable break crops.
• Farmers in higher rainfall regions will achieve more from the stubble handling benefits of 2 cm Auto-steer e.g. crop establishment efficacy of soil applied herbicides.

Acknowledgements

Funding by National Landcare Innovation Grant SANTFA and GPS-Ag.
Mattschoss Family Sandilands
Bill Long Aaron Long Danny Le Ferve and Nathan Rennie.