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Narrow spacing boosts yield in northern trial

Grain growers in medium and high-rainfall areas have much to gain by narrowing the row spacings used in their seeding programs.

That is the advice from weeds researcher Peter Newman, who coordinated a GRDC-funded trial in the northern wheatbelt in 2013 that showed reduced row spacing (using paired row seeding where a single seeding boot creates paired crop rows – usually 75 to 100mm apart) produced higher wheat yields.

He said narrow row spacing could also potentially help crops to outcompete weeds and this was an increasingly important non-herbicide weed control tactic.

Mr Newman, the communications leader with the Australian Herbicide Resistance Initiative and based at Planfarm in Geraldton, says wide row spacings remain common across WA’s wheatbelt.

He says this is due to the practicalities of continuous cropping, seeders needing to handle increased stubble loads, a need to harvest water in a bigger furrows, chemical safety, cheaper seeding bars, less horsepower required for pulling fewer tynes and perceptions that yields are not penalised.

However, new machinery innovations are making it possible to shift to narrower row systems, for example, harvesters that cut stubble shorter and seeders with well-spaced tyne ranks and no wheels in the frame of the seeder bar.

These machines can handle higher amounts of stubble and ensure good herbicide safety.

“All of the research from around Australia is pointing to significant and incremental yield benefits for every one-centimetre reduction in row spacing when wheat yield potential is higher than 1.5 tonnes/hectare,” Mr Newman says.

Yield benefits

Yield benefits were assessed in a GRDC and Department of Agriculture and Food, WA (DAFWA) 2013 northern crop competition trial that was hosted by Mingenew grower Peter Horwood. It compared:

  • single row, paired row and ribbon seeding systems;
  • row spacings of 15cm, 22cm and 30cm; and
  • seeding rates of 60, 90 and 120kg/ha.

The paired row plots were treated with a deep working knife point and Stiletto winged boot that created paired seeding rows 75mm apart – effectively doubling the length of the crop row.

The ribbon sowing involved planting seed evenly across an entire band (ribbon).

As expected, based on national historical research, the narrow row spacing plots (at 15cm) out-yielded the wider row spacings (at 22cm and 30cm) by an average of 240 kg/ha.

This is the equivalent of 16 kg/cm of row spacing and is consistent with findings from a recent GRDC-funded review of 50 years of national row spacing trial data. These findings were published in Row spacing of winter crops in broad scale agriculture in southern Australia.

Mr Newman says the preliminary data appears to show there is no difference in wheat yield between the single row, paired row and ribbon seeding systems at the Mingenew 2013 trial. “We didn’t really achieve a good paired row with the seeding gear we used in the trial, so unfortunately we didn’t see much yield difference between the seeding systems,” he says.

“There also appears to be little wheat yield variation in plots with different seeding rates – as was expected in this weed-free trial.

“But previous research has demonstrated that narrow row spacing in combination with high seeding rates has a big effect on weed seed set and yield through extra competition.”

Weed competition

Paired row seeding using 30.5cm tyne spacing and a winged boot effectively produced the same length of crop row in a paddock as using 15cm single row spacing.

This provided even seed distribution across the paddock and created a similar potential for crop plant density.

Mr Newman says the trials showed narrow row spacing using high seeding rates increased plant density per square metre, suppressing weed numbers and weed seed-set.

He says this supported previous local research that showed increasing seeding rates by 40kg/ha halved seed-set in annual ryegrass populations.

Narrow row spacing economics

Mr Newman recommends growers aim to use the narrowest row spacings that are practical for their area and this should be a consideration when upgrading machinery.

He says a lot of research has been conducted into row spacing and growers could access results when planning their cropping programs.

Mr Newman will be presenting a full analysis of results from the northern crop competition trial at the GRDC-DAFWA Agribusiness Crop Updates in Perth on 24 and 25 February.

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