By Emma Leonard
Retaining stubble is known to protect the soil and potentially improve yield.But for many growers it is still a headache at seeding, prompting the WA No-till Farming Association (WANTFA) to take a closer look at managing high-residue loads in a no-till system.
WANTFA"s Mike Collins says harvest is the first stubble management operation, and the study has found headers differ considerably in their ability to spread stubble. The degree of spread is also affected by cutting height and harvesting pattern.
Three cutting heights have been tested according to different grower situations. In one trial, low was 20cm, medium 43cm and high 60cm.
Low resulted in the most uneven spread, with up to 12 tonnes per hectare of standing and chopped stubble behind the header and as little as 2t/ha at the edge of the spread pattern.
The highest cut gave the best spread, with between 5 to 6t/ha of loose and standing residue across the 11-metre spreader width. The medium height resulted in a similar spread pattern to the high cut, but still resulted in up to 9t/ha of stubble in the header row.
In the experiment, spreading was consistently greater at the centre of the swath and sometimes to one side of centre.
Mr Collins says that such a bias, resulting in an accumulation of material, comes from harvesting up-and- back. In the long term this would cause nutrients to build up in these areas.
Starting alternate harvests half a header width in from the edge of the paddock would help reduce this annual concentration of stubble and, eventually, nutrients.
Mr Collins has also looked at the impact of clumping and how this can be overcome. He has found:
Some WA growers are experimenting with slashing stubble but these results are variable. It has been found that slashers work better on hot days (bringing a fire risk) because the residue is brittle and the material also spreads more evenly. However, slashers need to have the wheels at the back to reduce the amount that is rolled down.
For more information:
Mike Collins, 08 9622 3390, firstname.lastname@example.org
GRDC Research Code: WAN 00003, program 4
North, South, West