Impact of narrow row spacing on grain yield, seed quality and weed competitiveness in sorghum

Author: Trevor Philp (Pacific Seeds) | Date: 23 Jul 2018

Key message

In a tough season sorghum grown in narrow rows didn’t not reduce the yield or increase lodging, narrow row sorghum did reduce weed populations and has potential to increase fallow efficiency.

Introduction

Grain sorghum is currently grown in three main row widths in the north eastern Australian grain belt, 150cm, 100cm and 75cm. Broadly the higher the yield potential and the more reliable the environment the narrower the row spacing.

There has been a renewed interest in narrow rows in field crops due to two main factors

  1. Weeds with resistance to one or more herbicide mode of action group.
  2. Improving ground cover to drive improvement in the efficiency of subsequent fallows.

Little data is available for Australia on the effect of narrow row spacing in grain sorghum on yield, grain quality, suppression of weeds and improvement in fallow efficiency. There is also no data on narrow row sorghum planted with precision planters.

Summary

In the 2017-18 season nine grain sorghum trials were conducted to measure the effect of row spacing on yield grain quality and weed populations. Six trials compared 50cm, 75cm and 100cm rows, one trial compared 50cm and 100cm rows and two trials compared 50cm, 75cm and 150cm rows.

All configurations were sown at the same plant density using a single hybrid. Only eight trials were harvested, with the trial at Felton abandoned due to lodging. The Felton site was assessed for weed competition and was the only site that had significant weed populations to assess.

No grain quality data is available at this stage.

A significant difference in grain yield was measured at two of the eight sites, one at Tamworth and one at Goondiwindi, no significant difference between the row configurations was measured at any of the other sites.

Row width had a significant effect on weed population at the Felton Site, with weed population reducing with row width.

An across site analysis of the five sites comparing 100cm, 75 cm and 50 cm was conducted. No difference in grain yield was measured between row configurations.

The 2017-18 sorghum season was below average for yield, with grain size also reduced. Most spring planted crops suffered high levels of stress in the grain fill period, due to no rainfall in January.

Trial analysis description

The trait of yield (kg/ha) was analysed in two ways, firstly with row width included as a fixed effect (model 1: Best linear unbiased estimate BLUE) otherwise known as least square mean. This gives an estimate of the mean yield of the each of the treatments.

And secondly with row width included as a random effect (model 2: Best linear unbiased prediction BLUP). The BLUP value is used to estimate/predict the difference between row widths.

Only the BLUPS are reported.

Results

Table 1. Locations, row widths compared and sowing rate by site

Location

State

Row widths compared

Plant density/ha

Clifton

QLD

100, 75, 50 cm

85,000

Felton

QLD

100, 75, 50 cm

75,000

Brookstead

QLD

100, 75, 50 cm

85,000

Pampas

QLD

100, 75, 50 cm

85,000

Yelarbon

QLD

150, 75, 50 cm

65,000

Goondiwindi

QLD

150, 75, 50 cm

65,000

Yallaroi

NSW

100, 75, 50 cm

85,000

Tamworth

NSW

100, 75, 50 cm

75,000

Premer

NSW

100, 50 cm

85,000

Table 2. Individual trial results, grain yield by row width

Location

Row width

BLUP kg/ha

RANK

Rel mean %

se

Rep number

CV%

h2

P.value

Goondiwindi

50CM

3262

1

132.9

58

2

3.37

0.99

0.16

Goondiwindi

75CM

2214

2

90.2

58

2

- - -

Goondiwindi

150CM

1886

3

76.9

58

2

- - -

Premer

50CM

7462

1

100.0

70

3

NA

NA

NA

Premer

100CM

7462

1

100.0

70

3

- - -

Pampas

50CM

3655

1

108.2

263

3

30.22

0.24

0.28

Pampas

75CM

3173

3

94.0

263

3

- - -

Pampas

100CM

3303

2

97.8

260

3

- - -

Brookstead

50CM

3075

1

103.2

186

3

20.01

0.22

0.32

Brookstead

75CM

3039

2

102.0

186

3

- - -

Brookstead

100CM

2828

3

94.9

181

3

- - -

Yelarbon

50CM

1947

2

94.8

177

3

15.52

0.89

0.19

Yelarbon

75CM

1626

3

79.2

177

3

- - -

Yelarbon

150CM

2588

1

126.0

177

3

- - -

Tamworth

50CM

6469

3

97.0

52

2

1.12

0.95

0.18

Tamworth

75CM

6770

2

101.5

42

3

- - -

Tamworth

100CM

6771

1

101.5

42

3

- - -

Yallaroi

50CM

4480

1

101.8

139

3

9.39

0.15

0.34

Yallaroi

75CM

4321

3

98.2

149

2

- - -

Yallaroi

100CM

4396

2

99.9

144

2

- - -

Clifton

50CM

2972

3

100.0

26

2

0.23

0.03

0.04

Clifton

75CM

2972

1

100.0

26

4

- - -

Clifton

100CM

2972

2

100.0

26

3

- - -

Table 3. Across site result, Clifton, Pampas, Brookstead, Yallaroi, Tamworth, and Premer

Treatment

est_blup

rank_blup

rel_blup

se_blup

100CM

4627

1

100

0

75CM

4627

1

100

0

50CM

4627

1

100

0

Table 4. Weed population by row spacing at harvest, Felton Site 2018

Row width

Subscript

Weed count blup

Rank blup

Rel %

se_blup

 

100CM

a

49.8

1

175.6

3.2

CV%

19.861

75CM

b

23.5

2

82.8

3.2

h2

0.974

50CM

b

11.8

3

41.6

3.2

P.value

0.166

Discussion

Overall these trials demonstrated no consistent significant difference in yield by row width, although only one hybrid was tested at a single planting rate.

Two sites showed significant difference in row spacing, Goondiwindi showed a clear advantage in the 50cm rows against the commercial standard row spacing of 150cm. This advantage was created due to less lodging in the 50cm, the 50cm rows appeared to create more biomass early and ran into stress earlier than the 150cm rows. The earlier stress resulted in less yield potential, and reduced height, no rainfall occurred in the grain fill period which resulted in the higher yield potential treatment to lodge.

The Tamworth trial had a similar environment but stressed earlier and then was relieved by late rain, which favoured the 100cm rows over the 75 and 50cm rows.

In all sites row canopy closure occurred much earlier in the 50cm row configuration, providing better ground cover. Water use and water use rate wasn’t measured in these trials, but the 50cm rows may use soil water at a faster rate in the vegetative phase and potentially increase the chance of stress prior to flowering.

The combination of an appropriate hybrid and plant density and the 50cm row spacing has the potential to improve the sorghum crops competition against weeds, reducing weed seed set and improving yields. This system has potential to improve the fallow efficiency of the overall system, as well as lifting the sorghum yield and reliability in most seasons.

Further work to assess the impact on yield and quality is needed and work is needed to assess the effect on the fallow efficiency after the sorghum crop. Detailed economic analysis is needed to determine the cost benefit of purchasing a narrow row precision planter.

Contact details

Trevor Philp
Summer Grains Agronomist
Pacific Seeds
Mb: 0427 568 517
Email: trevor.philp@advantaseeds.com