What's all the row about row spacings?

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Growers considering changes to row spacing and row placement need to weigh up all the benefits and risks to limit the impact on crop yields and the weed population.

 

Fast fact

Wider row spacings make it easier to sow into retained stubble systems but can come at the cost of reduced yield and higher weed populations.

Photo: Mark Kentish checks emergence of inter-row-sown wheat at Piangil, Victoria, in 2017. (By BCG)

It is well known that the key benefits of stubble retention are increased infiltration and storage of soil moisture and reduced soil erosion. Unfortunately, with heavy stubble loads these benefits can come at the cost of blockages of seeding equipment and poor seed-to-soil contact, leading many growers to experiment with wider row spacings and inter-row sowing to overcome these challenges.

Through the GRDC’s Stubble Initiative farming systems groups across the southern and northern regions, including Birchip Cropping Group (BCG), have worked with grain growers to help them navigate the implications of changes to sowing placement.

Row spacing

The ideal row spacing for stubble-retained systems will vary depending on the farming system. Wider rows make it easier to use inter-row sowing and avoid blockages, but the rainfall zone and yield potential are particularly important.

Widening of row spacings above the traditional seven inches (17.5 centimetres) will generally result in a yield penalty in cereal crops (about 0.5 t/ha in the low to medium-rainfall zones). However, growers have experimented with the use of wider rows in stubble-retained systems to improve the ease of stubble management at sowing.

Yet the need to increase the ability of crops to compete with weeds has encouraged growers in lower-rainfall environments to reconsider narrower row spacings. BCG research in 2015, through the GRDC’s ‘Overdependence on Agrochemicals’ project in the Southern Mallee, found faster weed establishment and higher weed populations in Mace wheat sown on wider row spacings. In the trial there were 35 weeds per square metre at the 22.5cm row spacing, compared with 44 weeds/m2 at the 30.5cm spacing and 48 weeds/m2 at the 38cm row spacing.

Inter-row spacing

With the technological advances in GPS accuracy many growers have effectively implemented inter-row sowing. The potential to improve stubble flow and reduce seeder blockages are driving this adoption, increasing the ease of stubble management in a retained-stubble system. In heavy stubble loads a wider row spacing (30cm and higher) makes inter-row sowing easier to implement.

As part of the GRDC’s Stubble Initiative, Yeruga Crop Research compared the impact of different seed placement with respect to previous crop stubble rows on barley production at Bute, South Australia, in 2017. There was little difference in yield and plant establishment from inter-row sowing, although tiller numbers appeared to increase when sown offset alongside the row (Table 1).

Although the yield did not significantly increase, other benefits may include improved sowing efficiency and stubble flow and reduced seeder blockages. Soil-borne disease levels of take-all, crown rot, common root rot and root lesion nematodes have also been shown to be consistently lower in the inter-row when compared with on-row.

Inter-row sowing is not suitable for all situations. In non-wetting sands, on or near-row sowing provides better access to soil moisture.

Growers considering their options for row spacing and inter-row sowing should consult Stubble Initiative guidelines. See more information below.

Table 1. Impact of seed placement with respect to previous stubble rows on barley at Bute, SA, 2017.

TreatmentOffset Plants/m2 Tillers/m2 Yield (t/ha)
On row 0cm 105 a 270 b 2.33
Alongside row 5cm 95 a 315 a 2.43
1/3 inter-row 8cm 91 a 268 b 2.50
1/2 inter-row 12cm 88 a 285 ab 2.54
LSD - 20 34 NS

Numbers followed by the same letters are not significantly different.

SOURCE: Yeruga Crop Research

GRDC Research Codes BWD00024, YCR00003, CWF00020, UNF00002, EPF00001

More information:

Claire Browne, BCG
03 5492 2787
claire@bcg.org.au

The Stubble Project Victoria and Tasmania