Row spacing and stubble retention on irrigation

Guideline for growersICC Logo with Slogan

  • Increasing row spacing beyond the traditional 7” (17.5cm) results in yield loss in high yielding cereals.
  • Broadleaf crops are more forgiving of wider row spacings.

Irrigation is associated with high yielding crops which equates to high stubble loads that have to be managed. Pressure to reduce burning and the belief that the advantages of stubble retention outweigh the negatives has seen many changes to crop management.

As an aid to manage stubble loads, the practice of widening row spacing has been adopted, allowing sowing machinery to handle more stubble. Unfortunately in high yielding environments, widening row spacing does lead to yield reduction, although the severity is dependent on the crop type and the increase in width (Figure 1).

Figure 1. The relationship between grain yield at 18cm row spacing and the rate of change in grain yield with row widening for 89 experiments on wheat in Australia (Scott et al., 2013).

Figure 1. The relationship between grain yield at 18cm row spacing and the rate of change in grain yield with row widening for 89 experiments on wheat in Australia (Scott et al., 2013).

Many irrigators use sowing equipment with row spacings greater than 17.5cm (7”) but this is often because they want the flexibility to sow both irrigated and dryland winter crops, and summer crops typically on wide row spacings.

Finding the optimum row spacing

For irrigators, the benefits of row spacings greater than 18cm are related to the ease of stubble management rather than yield and profitability.

Summer crops are generally grown on wider spacings than winter crops. Maize, for example, is commonly sown on 55 to 75cm row spacings.

In an effort to retain the summer crop stubble, the winter crop row spacing is usually a multiple of the summer row spacing so the winter rows avoid the summer stubble.

Nevertheless, seeking opportunities to increase the practice of stubble retention by irrigators, the impact of row spacings has been examined by Irrigated Cropping Council (ICC) with research trials at Kerang in 2013 and 2015.

In general broadleaf crops sown on row spacings above 25cm will suffer a yield penalty. Conversely, trials at Kerang have shown no statistical reduction in canola yield by widening from 17.5cm to 35cm, however further widening to 70cm did result in yield loss (Table 1).

Table 1. Yield results from SFS canola row spacing x sowing rate trial.

Row spacing

Yield (t/ha)
7″

3.23

14″

3.05
28″

2.82

P

0.018

LSD

0.26

CV%

6.7

* Published in the ICC 2013 Trial Results compendium, pp. 20.

Similar research carried out for faba beans has produced mixed results. In 2015 a yield reduction of five per cent was suffered when row spacing was increased from 17.5cm to 35cm, but in 2013 only a small, but not statistically valid, yield reduction was a consequence of going from 17.5cm to 35cm, and widening rows to 70cm resulted in a 20 per cent yield reduction (Table 2).

Table 2. Results from SFS 2013 faba bean row spacing x sowing rate trial.

Row spacing (“) x Population (plants/m2)

Yield
(t/ha)

Bean size
(g/100 seeds)

7″ x 25 pl/m2

4.96a

70.1 g/100 seeds

7″ x 35 pl/m2

4.84a

71.9 g/100 seeds

14″ x 35 pl/m2

4.66ab

67.3 g/100 seeds

14″ x 25 pl/m2

4.46abc

68.8 g/100 seeds

28″ x 30 pl/m2

4.09bcd

68.6 g/100 seeds

28″ x 20 pl/m2

3.8cd

72.2 g/100 seeds

28″ x 10 pl/m2

3.53d

71.5 g/100 seeds

P

0.008

LSD

0.734

CV%

9.5

* Published in the ICC 2013 Trial Results compendium, pp. 21.

In 2013 there was no yield difference between the 7” (17.5cm) and 14” (35cm) row spacings, but there was between the 7” and 28” (71cm) spacings. However, plant population had an influence with yields from plots sown on 28” spacings not significantly different from their 14” counterparts, so long as the plant population was at 30 plants/m2.

Yields did not respond when the plant population was increased from 25 to 35 plants/m2 at either 7” or 14” row spacings.

However, results from row spacing research carried out by ICC in 2015 (Table 3) indicated reduced yields were a consequence of wider row spacing (17 v 35cm).

Table 3. Results from 2015 SFS faba bean, row spacing, plant population and PGR trial (full report available in the 2015 SFS Trial Results compendium).

Spacing (cm)

Yield (t/ha)

17

6.44
35

6.09

P

0.003

LSD

0.224

CV%

5.3

For irrigators, the major hurdle to increased row spacing is yield reduction.

In low yielding seasons the adoption of wider rows has had minimal consequence with no significant yield penalty. However a study into stubble retention systems and adoption by The Graham Centre (Scott BJ. et al. 2013) concluded that lower yields were a consequence of irrigators sowing crops on wider rows. The study, which combined results of many studies into a predictive relationship between the estimated losses by widening row space over a range of cereal yield potentials, suggested that by sowing with the ‘narrow’ spacing of 17.5cm, irrigators targeting crop yields greater than 8t/ha were already forgoing yield.

Therefore, any move to wider spacing is likely to be at the expense of yield.

References

Scott BJ, Martin P, Riethmuller GP, 2013. Graham Centre Monograph No. 3: Row spacing of winter crops in broad scale agriculture in southern Australia. Eds T Nugent and C Nicholls.

NSW Department of Primary Industries, Orange. Accessed at: www.grahamcentre.net

Scott BJ, Podmore CM, Burns HM, Bowden PI, McMaster CL, 2013 Developments in stubble retention in cropping systems in southern Australia. Report to GRDC on Project DAN 00170. (Ed. C

Nicholls and EC (Ted) Wolfe). Department of Primary Industries, Orange NSW pp 103. Available at: www.grahamcentre.net

By Damian Jones
ICC trials manager
damian.jones@irrigatedcroppingcouncil.com.au

GRDCLogoStacked_TM_CMYKThis research is being conducted by BCG as part of the GRDC Maintaining profitable farming systems with retained stubble initiative (project BWD00024 ‘Maintaining profitable farming systems with retained stubble in Victoria and Tasmania’).

Disclaimer: Any recommendations, suggestions or opinions contained in this publication do not necessarily represent the policy or views of the Birchip Cropping Group (BCG) or the Grains Research and Development Corporation (GRDC). No person should act on the basis of the contents of this publication without first obtaining specific, independent professional advice. BCG and GRDC and contributors to these guidelines may identify products by proprietary or trade names to help readers identify particular types of products. We do not endorse or recommend the products of any manufacturer referred to. Other products may perform as well as or better than those specifically referred to. BCG and GRDC will not be liable for any loss, damage, cost or expense incurred or arising by reason of any person using or relying on the information in this publication. 
Stubble project overview: This guideline has been developed for BCG Farming Systems Group as part of the Maintaining Profitable Farming Systems with Retained Stubble initiative, funded by the Grains Research and Development Corporation (GRDC). The initiative involves farming systems groups in Victoria, South Australia, southern and central New South Wales and Tasmania collaborating with research organisation’s and agribusiness to explore and address issues for growers that impact the profitability of cropping systems with stubble, including pests, diseases, weeds, nutrition and the physical aspects of sowing and establishing crops in heavy residues.
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About BCG

Birchip Cropping Group Inc. (BCG) is a not-for-profit agricultural research and extension organisation led by farmers in the Victorian Wimmera and Mallee.
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One Response to Row spacing and stubble retention on irrigation

  1. Pingback: Row spacings in a retained stubble system | The stubble project: Victoria and Tasmania

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