Planting date row spacing and plant population impacts in wheat

Author: Mick Brosnan & Jo Weier | Date: 25 Feb 2016

Take home message

Yield penalties become increased with delayed planting dates so when faced with the decision to replant, a plant density of low populations can be more successful than replanting. Moisture seeking to plant on time achieves better results than waiting for a rain fall event and planting later than ideal.  Narrow row spacing did not make any difference to yield so wide rows are fine if yield expectations don't exceed 3t/ha and provided you can control weeds.

Background & aims

In order to answer questions relating to optimum plant population and planting dates for wheat Mungindi Cropping Group &  DAFF initiated a trial comparing various plant populations and row spacings over 2 planting dates. The trial was run over 3 years from 2012 to 2014.

Potential interactions between genotype, maturity, row spacing and planting dates were also looked at.

Trial setup

A series of trials were conducted in 2012, 2013 and 2014, on grey vertosol soils at Bullawarrie, North West of Mungindi.  In 2014 an additional trial was conducted at another location south of Mungindi (Greentree). The aim of the trials was to determine timing, row spacing and plant population combinations that achieved the best yield outcome in two standard wheat varieties. Trials comprised four replicates of each treatment combination.

The following are the four treatment groups.

2 X Planting dates

  • First week of May and first week of June.

2 X Cultivars (varieties) 

  • Gregory, main variety in area, long season but can shorten up.
  • Baxter 2012, Suntop 2013/2014.  Common varieties for area.  Good disease package.  Slightly shorter season.

2 X Row spacings

  • 25cm (10”) and 50cm (20”)

5 X Plant populations

  • 7, 15, 30, 50, & 80 plants per meter. (no 7 in 2012)

Results

Figure 1. Full set of analysed means from the across sites analysis of Bullawarrie 2013, Bullawarrie 2014 and Greentree 2014 data.  Analysed means of Bullawarrie 2012 are from individual trial analysis, note Baxter cultivar planted in 2012 not Suntop.

Figure 1. Full set of analysed means from the across sites analysis of Bullawarrie 2013, Bullawarrie 2014 and Greentree 2014 data.  Analysed means of Bullawarrie 2012 are from individual trial analysis, note Baxter cultivar planted in 2012 not Suntop.

* (only have early planting data for 2012 analysed)


In 2012 results indicate the higher densities of plant population showed significantly higher yields than the lower plant populations.  The density of 80 plants/m was not significantly higher yielding than 50 plants/m, and 50 plants/m was not significantly higher than 30 plants/m, but all three of these densities showed significantly higher yields than the lowest density of 15 plants/m. The row spacing by cultivar interaction shows that the effect of row spacing is not consistent across the two cultivars.  The difference in yields between the 25cm and 50cm row spacing of Baxter showed a greater difference in yield than what was displayed in Gregory.

Site by planting time by plant population interaction

Figure 2. Analysed means from the site x planting time by plant population interaction

Figure 2. Analysed means from the site x planting time by plant population interaction

This interaction shows significantly higher yields in the May planting at the Bullawarrie 2013 and Greentree 2014 trials. Bullawarrie 2014 trial the yield benefit is not as evident. 

Within each planting time, there was a significant gain in planting at higher densities as opposed to lower densities.  The exception to this was in the early planting at the Bullawarrie 2014 trial, where the highest yield was achieved from the mid-range density (30 plants/m), but it was not significantly different to the lowest (7 plants/m) or highest (80 plants/m) density.

Site by cultivar by plant population interaction

Figure 3. Analysed means from the site x cultivar by plant population interaction

Figure 3. Analysed means from the site x cultivar by plant population interaction

This interaction shows that planting higher densities provided significantly higher yields across cultivars and sites, with the exception of Gregory in the Bullawarrie 2014 trial.  For this cultivar at this site the yield at 30 plants/m was significantly higher than the yield at 15 plants/m, other than this, Gregory at Bullawarrie 2014 showed no significant difference in yield across the range of densities.

Cultivar by planting time by plant population by row spacing interaction

Figure 4. Analysed means from the cultivar by planting time by plant population by row spacing interaction

Figure 4. Analysed means from the cultivar by planting time by plant population by row spacing interaction

Results suggest that in an early planting of Suntop with low density, the 25cm row spacing would provide a higher yield than the 50cm spacing.  The cultivar Gregory  did not show the same effect.   Apart from this difference in Suntop, there was no significant difference in yield between the 25cm and 50cm row spacings. 

Results again suggest the maximum yield would be achieved in high density planting early in the season.   Planting later in the season indicated lower yields than early season planting, however, within the later plating time the best gain to be made was still in planting high populations.

Acknowledgements

The research undertaken as part of this project is made possible by the significant contributions of growers through both trial cooperation and the support of the GRDC, the author would like to thank them for their continued support.

Contact details

Jo Weier
Mungindi Cropping Group
Mb: 0428 532 256
Email: joweier@bigpond.com

Michael Brosnan
B & W Rural
Mb: 0428 532 143
Email: mbrosnan@elders.com

 Varieties displaying this symbol beside them are protected under the Plant Breeders Rights Act 1994

Data was analysed using a linear mixed model method.

GRDC Project code: DAQ00162