Contribution of leaves to the yield of sunflowers - Pine Ridge 2015-16


Research organisaton
Funding sources

Trial details

Researcher(s) Loretta Serafin, Mark Hellyer and Peter Perfrement (NSW DPI)
Year(s) 2015
Contributor Department of Primary Industries NSW
Trial location(s) Site 3, Pine Ridge, NSW
Further information View external link
Related trials
Contribution of leaves to the yield of sunflowers - Pine Ridge 2015-16 locations

To quantify the contribution of sunflower leaves to yield and oil quality through the application of twelve leaf defoliation treatments.

Sunflowers are generally considered a minor crop in the NSW northern grains region.
However, they play an important role in providing a broadleaf summer crop rotation option.
An individual sunflower plant produces on average between 2000–6,000 cm2 of leaf area, which drives yield and oil content.
Identifying which leaves contribute most towards yield and oil content helps growers make
decisions about 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 of maintaining
green leaf area.
This experiment was one of three sunflower leaf-loss sites conducted in the 2015–16 season, with the other sites being located at Gurley and Willow Tree.

Key messages
  • Sunflower grain yield averaged 1.07 t/ha at this site with the highest yields obtained from the control and the treatments where only the bottom one third (1/3) of leaves were removed.
  • The total leaf removal treatments had the largest effect on yield, at worst yielding only 0.16 t/ha.
  • Removing all leaves at budding or at the start of the flowering growth stages had the largest effect on plant structures.
  • Total leaf removal at the end of flowering had the largest effect on 1000 grain weight and test weight.
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 supply of experiment seed. Technical assistance provided by Delphi Ramsden (NSW DPI), Angus Hombsch, Alice Bowler and Bronwyn Brennan (formerly NSW DPI) is gratefully acknowledged. Thanks also to Neroli Graham, NSW DPI for assisting with data analysis. Thanks to Peter Winton, ‘Windy Station’, Pine Ridge for hosting the experiment.

Other trial partners Peter Winton, ‘Windy Station’, Pine Ridge
Download the trial report to view additional trial information


Crop type Oilseed: Sunflower
Treatment type(s)
  • Crop
Trial type Experimental
Trial design Unknown
Sow rate or Target density Not specified
Sowing machinery Not specified
Sow date 18 September 2015
Harvest date 17 February 2016
Plot size Not specified
Plot replication Not specified
Plot blocking Not specified
Plot randomisation Not specified
Paddock history Not specified

42 kg/ha Granulock Z applied at sowing


Defoliation applied prior to harvest

Insecticide Not specified
Fungicide Not specified
Pesticide Not specified
Soil amelioration Not specified
Seed treatment Not specified
Inoculant Not specified
Tillage Not specified
Other trial notes

Crop type: Sunflower (Hybrid: Ausigold 62)

Starting soil water and rainfall

The site was soil cored before sowing and found to have 270 mm of plant available water (PAW) to 1.2 m deep. A total of 157.5 mm of in-crop rainfall was recorded at the experiment site 


Plant height

Five plants in each plot were measured for physiological maturity – taken from ground level up to the point of attachment at the back of the head. The average plant height in the experiment was 131.7 cm. No defoliation treatment affected plant height.

Head diameter and arc length:

Five plants in each plot had had head diameter and arc length measured at physiological maturity. Head diameter was measured across the back of the head and arc length across the front face of the head. The average head diameter was 14.1 cm. There were significant treatment differences based on defoliation . The smallest head diameters were recorded from removing all leaves at either budding or the start of flowering at 6.9 cm and 8.8 cm, respectively. There was very little difference statistically between many of the treatments.

The average arc length was 21.2 cm and there were significant differences based on the treatments. Removing all leaves at budding and the start of flowering had the largest impact on arc length reducing it to 9.7 cm and 16.2 cm respectively. The remaining defoliation treatments had no significant impact on arc length compared with the non-defoliated control 

Grain yield

The average yield was quite low at the site in 2015–16 compared with that normally expected for sunflower crops on the Liverpool Plains, with an experiment average of 1.05 t/ha. There was, however, a large range in the yields as a result of the treatments. Removing the bottom 1/3 of leaves at budding had the highest yield at 2.07 t/ha, however, there was no significant difference in the top four yielding treatments. The lowest yields were obtained from the total leaf removal treatments at 0.16 t/ha.

Grain quality

Sub samples from each plot were collected at harvest and analysed for 1000 grain weight and test weight. Oil contents were not available at the time of publication.

The average 1000 grain weight in the experiment was 47.1 grams. The largest effects on grain weights were obtained in treatments were all leaves were removed, while the smallest impact on grain weight was obtained when only the top 10 leaves were removed (data not shown).

The average hectolitre weight in the experiment was 39.2 kg/hL, which is well above the receival standard of 32 kg/hL. The largest reduction in test weight resulted from removing all leaves at the end of flowering (data not shown).

Download the trial report to view additional method/treatment information

Trial results Impact of defoliation treatments on plant structures

# Treatment 1
Plant height (cm) Head arc length (cm) Head diameter (cm)
1 Control - no leaves removed (0/3) 130.6 23.5 16.3
2 Budding - remove all leaves (3/3) 121.7 9.7 6.9
3 Budding - remove top 10 leaves (1/3) 132.1 24.1 17.7
4 Budding - remove top 20 leaves (2/3) 133.5 18.8 13.1
5 Budding - remove bottom 10 leaves (1/3) 136.5 24.3 15.7
6 Start of flowering - remove top 10 leaves (1/3) 135.1 24.5 17.1
7 Start of flowering - remove top 20 leaves (2/3) 128.7 19 15.6
8 Start of flowering - remove all leaves (3/3) 128.7 16.2 8.8
9 Start of flowering - remove bottom 10 leaves (1/3) 136.1 25.7 17.1
10 Flowering complete - remove top 10 leaves (1/3) 134.3 24.3 16.1
11 Flowering complete - remove top 20 leaves (2/3) 134 22.1 15.1
12 Flowering complete - remove all leaves (3/3) 129.1 22.5 13.1
LSD (P=0.05): n.s. (P=0.05): 4.11 (P=0.05): 3.88

Head arc length cm


Head diameter cm


Plant height cm

Observed trial site soil information
Trial site soil testing
Site Depth Type pH EC P K N A OC CAT
Site 3, Pine Ridge, NSW 0 - 10cm 7.49 53.00 2.33
Site 3, Pine Ridge, NSW 10 - 30cm 7.85 14.80 2.03
Site 3, Pine Ridge, NSW 30 - 60cm 8.11 23.90 1.92
Site 3, Pine Ridge, NSW 60 - 90cm 8.29 38.20 1.89
Site 3, Pine Ridge, NSW 90 - 120cm 9.07 48.70 1.80
Soil conditions
Trial site Soil texture
Site 3, Pine Ridge, NSW Not specified
Derived trial site soil information
Australian Soil Classification Source
Trial site Soil order
Site 3, Pine Ridge, NSW Anthroposol
National soil grid Source
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



Site 3, Pine Ridge NSW 2015

Observed climate information
Rainfall avg ann (mm) 668.9mm
Rainfall trial gsr (mm) 157mm
Derived climate information
NOTE: Exact trial site locality unknown - Climate data may not be accurate
BOM Data source PINE RIDGE (BILLABONG) [11285] 5km proximity to trial site location


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

2015 trial report