Test of tramline designs for weed control and wheat value by Paul Blackwell, Bindi Webb and Darshan Sharma, WA Department of Agriculture

Figure 1: Percentage of weeds counted in or out of (alongside) the three different styles of tramlines in November. Figure 2: Percentage of grain yield loss or gain in the tramline zone (tramline width and both edge rows) for the three designs of tramline and the four varieties of wheat.

Take home messages

  • Seed set of weeds, especially radish, was well controlled with fuzzy or shallow-sown tramlines compared with bare tramlines in those tramlines not used for spraying.
  • Estimated effects of non-spraying tramlines on paddock yield and grain quality were small.
  • WyalkatchemPBR logo was generally a poorly adapted wheat variety and CalingiriPBR logo generally better adapted to tramlines.
  • The best choices of tramline design will depend more on convenience, weed competition and the need for any early tramline smoothing. Any yield benefits and tramline smoothing from shallow sown tramlines may help compensate for early costs of adoption and rough running.

Use of tramlines can reduce soil compaction between the tramlines and improve paddock yield by 5-15 per cent. In a recent trial, we aimed to optimise the value of tramlines not used for in-crop operations. Bare tramlines not used for spraying or spreading can present weed and erosion problems as well as a possible sacrifice of yield if there is little compensation from edge rows in the tramline zone.

Using bare, fuzzy or shallow-sown tramline designs in wheat after lupins on a sandy soil, we sought to quantify:

  • the relative infestation of weeds that set seed in each tramline design, and
  • the grain yield and quality penalties or benefits of each design, each with four wheat varieties.

How the trial was done

The 2002 trial was undertaken on a sandy to sandy loam soil near Mullewa in the northern agricultural region of WA. The area receives an average of 337 mm of rainfall each year. In 2002 the annual total was 152.4 mm, with 148 mm from May to October.

The tramlines were 900 mm wide between edge rows to allow a wide range of wheel width and wheel track options. All treatments were sown in early June 2002. The different tramline designs were made as follows.

  • Bare: Two tines were removed for each tramline and the seed from the missing tines sent into the edge rows (the fertiliser was on a separate system and spread across all rows).
  • Fuzzy: Tines modified as for 'Bare', but the seed and fertiliser from the missing rows was sprayed into the tramlines from the hoses strapped to the airseeder frame above the tramline. The seed was covered by rubber belting dragged in the tramline and rolled by the wheels of the following airseeder cart.
  • Sown: The tines were replaced and shallow digging (50 mm) points used instead of 125 mm digging points. Seed and fertiliser were supplied to the rows as normal. The tramlines were made with a 7.5 m wide airseeder sowing on a 300 mm row spacing with knife-points and 100 mm wide press wheels.

Plots were un-ripped or ripped to 300 mm before seeding with 450 mm spaced ripper tines. None of the tramlines were ripped. Weeds were controlled using a pre-seeding knock-down, followed at the trial site by 500 ml of MCPA with 5 g/ha Logran® and 4 g/ha Ally. In moist conditions plots were 0.2 per cent wetter on 3 July.

Results were analysed using normalisation to the weeds in the adjacent crop or the yield of the crop between the spraying and spreading tramlines. The plots had no post-seeding traffic on the tramlines and there were two plots between each airseeder run which made bare tramlines for spraying and spreading using CarnamahPBR logo wheat, sown on the same day.

Weeds counted in November mainly occurred where the crop residue fell from the header when the lupins were harvested in 2001.

RESULTS

More weeds in the bare tramlines

Bare tramlines had six times more weeds that set seeds than the main crop; fuzzy or sown tramlines had no more than the crop. Figure 1 emphasises how well the fuzzy or sown tramlines controlled weeds, although the very low grass populations are partly a result of the densities in Figure 1 being averaged over the whole plot length.

There was more radish than grass in the bare tramlines, but it could have been controlled with a second, selective spray.

Yields and wheat quality variable

  • Yields in the bare tramline zone (tramline and both edge rows) were lower than in the sown tramline zone, except for the longer season wheat variety CalingiriPBR logo. This variety yielded 25 per cent more grain (350 kg/ha) in the tramline zone with 50 per cent less screenings than the crop outside the tramline zone.
  • Fuzzy tramlines had the poorest yield in the tramline zone, especially WyalkatchemPBR logo wheat with a 900 kg/ha penalty. CarnamahPBR logo and CalingiriPBR logo seemed best adapted to fuzzy tramline design.
  • Shallow-sown tramlines had the most consistent yield benefit in the tramline zone, especially about 400 kg/ha in WestoniaPBR logo wheat. Rows of crop in the tramline offer no on-ground guidance. This can come from auto-steer options or central broad rows and wheel marks from tow-behind airseeders. Further benefit of sown instead of fuzzy tramlines is the levelling of rough running when the seeding direction is changed from racetrack to parallel.
  • Most differences in grain quality were too small to change quality over a whole header width - the other rows would easily dilute the effect. But screenings in the grain from the edge rows of bare tramlines in CalingiriPBR logo wheat were about 50 per cent less than the crop outside the tramline zone. This could have a beneficial reduction of whole crop screenings for narrow-width seeders such as combines with wide tramlines and seed diversion to the edge rows.
  • The effect of design on bulk yield from the whole airseeder width of 12 m shows that, if sown tramlines (instead of fuzzy) are chosen to control weeds, a net yield benefit of about 70 kg/ha or 5 per cent of the main crop yield may be possible with WestoniaPBR logo.

Program 4 Contact: Dr Paul Blackwell 08 9956 8555 email pblackwell@agric.wa.gov.au