Contribution of leaves to the yield of sunflowers - Willow Tree

2016 - 2017

Research organisaton
Funding sources

Trial details

Researcher(s) Loretta Serafin, Mark Hellyer and James Filby (NSW DPI)
Year(s) 2016 - 2017
Contributor Department of Primary Industries NSW
Trial location(s) Willow Tree, NSW
Further information View external link
Related trials
Contribution of leaves to the yield of sunflowers - Willow Tree locations

To quantify the contribution of different sunflower leaves to yield and oil quality by applying 12 leaf defoliation treatments.

Sunflowers are generally considered a minor crop in the northern grains region. However, they play an important role in providing a broadleaf summer crop rotation option. An individual sunflower plant produces on average 2000–6,000 cm2 of leaf area, which drives yield and oil content.

Identifying which leaves contribute most towards yield and oil content helps inform decisions around disease, pest and general crop management in sunflower crops. Whether it is because the crop is infected with a disease such as powdery mildew, or has insect damage e.g. loopers, the end result is a need for growers and advisors to know where and when to spend money in crop protection to achieve the best economic return on investment through maintaining green leaf area.

Key messages
  • Sunflower yields were greatly affected by the various defoliation treatments, ranging from 0.12 t/ha to 0.97 t/ha.
  • Reductions in yield, of between 55% and 82% compared with the control resulted from total leaf removal at all three of the targeted growth stages (budding, start of flowering and flowering completion) as well as removing two-thirds of the leaves at budding.
  • There was no negative effect on grain yield from removing the bottom third of leaves at budding or the start of flowering. Removing the bottom third of leaves at the start of flowering actually provided a slight yield advantage over the control treatment. The largest effect on plant height, head diameter and head arc length were caused by removing all leaves at the budding stage.
Lead research organisation Department of Primary Industries NSW
Host research organisation N/A
Trial funding source GRDC DAN00197
Trial funding source DPI NSW DAN00197
Related program Tactical agronomy for selected crops in the northern region (safflower, linseed, sunflower)

This experiment was part of the project Tactical agronomy for selected crops in the northern region (safflower, linseed, sunflower) (DAN00197), with joint investment by NSW DPI and GRDC. Thanks to Nuseed and Neil Weier for the supplying seed for the experiment. Technical assistance provided by Delphi Ramsden, Alice Bowler, Max Cloake and Jim Perfrement (NSW DPI) is gratefully acknowledged. Thanks to Joe Fleming, ‘Parraweena’, Willow Tree for hosting the experiment. Thanks to Neroli Graham for assistance with the statistical analysis.

Other trial partners Joe Fleming, ‘Parraweena’, Willow Tree
Download the trial report to view additional trial information


Crop type Sunflower
Treatment type(s)
  • Crop
Trial type Experimental
Trial design Replicated

Willow Tree 2016

Sow date 9 October 2016
Harvest date 24 February 2017
Plot size Not specified
Plot replication Not specified
  • 150 kg/ha Gold N pre-sowing
  • 10 L/ha Amps Kickstart plus Petrik applied at sowing
Other trial notes

Crop type: Sunflower (Hybrid: Ausigold 62)

Willow Tree 2017

Sow date Not specified
Harvest date Not specified
Plot size Not specified
Plot replication Not specified
Fertiliser Not specified
Other trial notes

Crop type: Sunflower (Hybrid: Ausigold 62)

Download the trial report to view additional method/treatment information

Download results

Trial results Impact of defoliation treatments on sunflower plant structures

# Treatment 1
Plant height (cm) Head arc length (cm) Head diameter (cm)
1 Control - no leaves removed (0/3) 144.7 21.4 19.1
2 Budding - remove all leaves (3/3) 117.5 3.2 3.6
3 Budding - remove top 10 leaves (1/3) 146.8 17.6 18.1
4 Budding - remove top 20 leaves (2/3) 137.6 7.7 9.8
5 Budding - remove bottom 10 leaves (1/3) 152.5 22.2 19.6
6 Start of flowering - remove top 10 leaves (1/3) 146.6 19.4 18.1
7 Start of flowering - remove top 20 leaves (2/3) 132.9 16.9 17.1
8 Start of flowering - remove all leaves (3/3) 139.4 10.4 11.6
9 Start of flowering - remove bottom 10 leaves (1/3) 146.3 21.2 19.2
10 Flowering complete - remove top 10 leaves (1/3) 139.4 19.6 18.1
11 Flowering complete - remove top 20 leaves (2/3) 157.3 20.6 19.6
12 Flowering complete - remove all leaves (3/3) 138.9 17.6 17.5

Head arc length cm


Head diameter cm


Plant height cm


Trial results Impact of defoliation treatments on grain yield

# Treatment 1
Grain yield (t/ha)
1 R5.1 bottom 1/3 0.97
2 Bud bottom 1/3 0.85
3 R6 1/3 0.83
4 R6 2/3 0.78
5 R5.1 1/3 0.76
6 Bud 1/3 0.74
7 Control 0.66
8 R5.1 2/3 0.61
9 Bud 2/3 0.3
10 R6 Total 0.27
11 Bud Total 0.16
12 R5.1 Total 0.12

Grain yield t/ha

Observed trial site soil information
Trial site soil testing
Site Depth Type pH EC P K N A OC CAT
Willow Tree, NSW 0 - 10cm 6.40 37.00 1.58
Willow Tree, NSW 10 - 30cm 6.70 9.00 1.00
Willow Tree, NSW 30 - 60cm 7.00 4.00 0.80
Willow Tree, NSW 60 - 90cm 7.80 10.00 0.64
Willow Tree, NSW 90 - 120cm 8.10 25.00 0.46
Soil conditions
Trial site Soil texture
Willow Tree, NSW Not specified
Derived trial site soil information
Australian Soil Classification Source: ASRIS
Trial site Soil order
Willow Tree, NSW Anthroposol
Soil Moisture Source: BOM/ANU
Average amount of water stored in the soil profile during the year, estimated by the OzWALD model-data fusion system.
Year Willow Tree NSW
2017 476.0mm
2016 504.6mm
2015 531.9mm
2014 497.3mm
2013 488.8mm
2012 483.1mm
2011 489.0mm
2010 528.5mm
2009 492.5mm
2008 516.1mm
2007 564.0mm
2006 563.4mm
2005 570.8mm
2004 576.0mm
2003 604.6mm
2002 546.9mm
2001 553.3mm
2000 603.9mm
National soil grid Source: CSIRO/TERN
NOTE: National Soil Grid data is aggregated information for background information on the wider area
Actual soil values can vary significantly in a small area and the trial soil tests are the most relevant data where available

Soil properties



Willow Tree NSW 2016

Observed climate information

Rainfall avg ann (mm) 668.9mm
Rainfall trial gsr (mm) 639mm

Derived climate information

Willow Tree NSW

NOTE: Exact trial site locality unknown - Climate data may not be accurate

Some data on this site is sourced from the Bureau of Meteorology

SILO weather estimates sourced from
Jeffrey, S.J., Carter, J.O., Moodie, K.B. and Beswick, A.R. (2001). Using spatial interpolation to construct a comprehensive archive of Australian climate data , Environmental Modelling and Software, Vol 16/4, pp 309-330. DOI: 10.1016/S1364-8152(01)00008-1.

Trial report and links

2016 trial report

Trial last modified: 17-07-2019 12:08pm AEST