Grain & Graze Trial Results from 2006
Effect of Grazing on the Grain Yield and Quality of Seven Cereals - Inverleigh, Vic.
Location:
Inverleigh Trial Site, Victoria
Researchers:
Cam Nicholson, Grain & Graze
Stacey Alexander, SFS
Author:
Cam Nicholson, G&G
Funding:
Grain and Graze, National Landcare Program (NLP)
Acknowledgements:
Rohan Wardle and the SFS field staff for sowing and post emergent crop management.
Background/Objectives:
Grazing cereal offers a benefit to the farm system if it can be achieved with minimal or no impact to the grain yield of the crop. Previous trialling would indicate grain yield is reduced if grazing occurs around or after GS 31. Yet grazing the crop later increases the amount of drymatter on offer. The ability to identify the ideal growth stage to graze is complicated because of the different times varieties reach the commencement of stem elongation.
To achieve the maximum benefit for both the grazing and cropping enterprises, there is a need to maximise drymatter production available for grazing but also refine the point where grazing must cease otherwise grain yield will be reduced.
This trial is designed to quantify the drymatter potential of seven long season cereal crops before stem elongation is reached and to determine the impact on grain yield if heavy grazing occurs at GS 31.
Rainfall (mm): 235mm
Trial Input and Design
Seven long season cereal varieties (4 x wheat, 2 x barley & 1 x triticale) were sown in three replicates on 11th May 2006. One wheat variety with a shorter growing season was chosen as a marker to provide forewarning of the onset of GS 31. The varieties were:
- Wheat – Mackellar, Amarok, Marombi, Brennan
- Barley – Yerong, Gairdner (used as a marker)
- Triticale – Monstress
Pre-emergent:
Sprayseed @ 2.0 l/ha, Triflur @ 1.2 l/ha
Post-emergent:
Dual Gold @ 250 ml/ha, Diuron @ 500 ml/ha
Tigrex – 1.0 l/ha on July 14th
Urea @ 50kg/ha on September 24th
Tilt Xtra @ 250ml/ha on ungrazed plots on September 25th
Tilt Xtra @ 250ml/ha on grazed plots on October 13th
Each plot was 16m x 2m, with 8 m buffer strips. Each variety was monitored for growth stage and grazing commenced when GS 30 was reached. Six cuts of 0.1 m2 were taken from each variety immediately before grazing to determine drymatter on offer.
Exclusion areas were erected to prevent grazing on half of each of the plots. Plots were grazed with 10 month old merino wethers for between one and four days (until all drymatter was removed).
Harvest Date: 13th December 2006
Summary Of Findings
Intensive grazing at GS 30 – GS 31 (start of stem elongation) reduced grain yield compared to no grazing by an average of 37%. The greatest yield loss of 57% occurred with Monstress triticale and the lowest yield loss occurred with Amarok wheat (18%). Up to 2.1 t/ha of drymatter was available for grazing before stem elongation was reached. Yerong barley yielded the greatest drymatter pre grazing, with Brennan wheat the lowest drymatter yielding at 1.5 t/ha.
Trial Results
Grazing of the Gairdner barley commenced on August 7, 81 days after sowing. The last grazing of Amarok wheat occurred 14 days later on August 21. The amount of drymatter present and the growth stage at grazing is presented (Table 8‑3).
Table 8-3: Days From Sowing To Grazing, Growth Stage At Grazing And Available Dry Matter
|
Variety |
Date grazing commenced |
Growth Stage |
Days grazed |
Days from sowing to grazing |
Feed on offer (kg/ha) |
|---|---|---|---|---|---|
|
Yerong barley |
11/08 |
GS 30 - GS 31 |
3 |
88 |
2190 |
|
Monstress triticale |
11/08 |
GS 30 - GS 31 |
3 |
95 |
2120 |
|
Amarok wheat |
21/08 |
GS 30 |
1 |
85 |
2020 |
|
Gairdner barley |
07/08 |
GS 31 - GS 32 |
2 |
88 |
1920 |
|
Mackellar wheat |
14/08 |
GS30 - GS31 |
4 |
81 |
1730 |
|
Marombi wheat |
14/08 |
GS 30 |
4 |
85 |
1490 |
|
Brennan wheat |
14/08 |
GS 30 |
4 |
88 |
1480 |
|
LSD (0.05) |
700 |
||||
Grazing resulted in a significant reduction in grain yield, from an average 4.1 t/ha to 2.6 t/ha. However the yield reduction varied between varieties, with Yerong barley and Brennan wheat showing no statistical significance in yield loss despite declines of 1.5 t/ha and 1.3 t/ha respectively (Table 8‑4).
Table 8-4: Impact Of Grazing On Grain Yield
|
Variety |
Growth Stage |
Yield (ungrazed) (t/ha) |
Yield (grazed) (t/ha) |
Difference in yield due to grazing (t/ha) |
Statistical significance (p=0.05) |
|---|---|---|---|---|---|
|
Gairdner barley |
GS 31 - GS 32 |
4.9 |
3.2 |
- 1.7 |
Sig (1.6) |
|
Yerong Barley |
GS 30 - GS 31 |
4.4 |
2.9 |
-1.5 |
NS (1.5) |
|
Monstress triticale |
GS 30 - GS 31 |
4.1 |
1.8 |
-2.3 |
Sig (1.6) |
|
Marombi wheat |
GS 30 |
4.1 |
2.5 |
-1.6 |
Sig (1.3) |
|
Mackellar wheat |
GS30 - GS31 |
4.0 |
2.7 |
-1.3 |
Sig (0.2) |
|
Amarok wheat |
GS 30 |
3.8 |
3.1 |
-0.7 |
Sig (0.1) |
|
Brennan wheat |
GS30 |
3.1 |
1.9 |
- 1.2 |
NS (1.4) |
Grain quality was also affected by grazing (Table 8‑5 and Table 8‑6).
Table 8-5: Impact Of Grazing On Grain Protein
|
Variety |
Growth Stage |
Protein (ungrazed) (%) |
Protein (grazed) (%) |
Difference in protein due to grazing |
Statistical significance (p=0.05) |
|---|---|---|---|---|---|
|
Gairdner barley |
GS 31 - GS 32 |
11.9 |
11.3 |
- 0.6 |
NS (2.6) |
|
Yerong Barley |
GS 30 - GS 31 |
12.0 |
11.4 |
- 0.6 |
NS (1.3) |
|
Monstress triticale |
GS 30 - GS 31 |
11.0 |
10.8 |
- 0.2 |
NS (2.2) |
|
Marombi wheat |
GS 30 |
11.2 |
10.6 |
- 0.6 |
NS (2.3) |
|
Mackellar wheat |
GS30 - GS31 |
11.2 |
9.6 |
- 1.6 |
Sig (0.9) |
|
Amarok wheat |
GS 30 |
11.4 |
9.8 |
- 1.6 |
Sig (0.1) |
|
Brennan wheat |
GS30 |
12.3 |
11.8 |
- 0.5 |
NS (1.3) |
Table 8-6: Impact Of Grazing On Thousand Grain Weight
|
Variety |
Growth Stage |
TGW (ungrazed) |
TGW (grazed) |
Difference in TGW due to grazing |
Statistical significance (p=0.05) |
|---|---|---|---|---|---|
|
Gairdner barley |
GS 31 - GS 32 |
32.2 |
34.3 |
+ 2.1 |
NS (6.4) |
|
Yerong Barley |
GS 30 - GS 31 |
33.8 |
36.8 |
+ 3.0 |
NS (6.5) |
|
Monstress triticale |
GS 30 - GS 31 |
37.8 |
28.2 |
- 9.6 |
Sig (8.3) |
|
Marombi wheat |
GS 30 |
33.5 |
27.6 |
- 5.9 |
Sig (2.4) |
|
Mackellar wheat |
GS30 - GS31 |
27.5 |
25.1 |
- 2.4 |
Sig (1.6) |
|
Amarok wheat |
GS 30 |
35.4 |
30.3 |
- 5.1 |
Sig (3.0) |
|
Brennan wheat |
GS30 |
34.8 |
29.6 |
- 5.2 |
Sig (4.6) |
Trial Observations
The amount of drymatter on offer varied between varieties. The two barley varieties, Yerong and Gairdner, Monstress triticale and Amarok wheat produced around 2 tonnes of drymatter by GS 30 – GS 31. However the time from sowing to reach GS 31 varied, with Gairdner barley reaching stem elongation 14 bays before Amarok wheat. The other wheat varieties tested produced closer to 1.5 t/ha before reaching GS 31.
Although there is a difference between the total amount of drymatter produced, even the lower drymatter yielding wheat varieties (Brennan, Mackellar, Marombi) still produced a valuable quantity of high quality feed at a time of year when pasture is often in short supply.
The time to reach GS 31 varied by up to two weeks, even though all varieties except for Gairdner are considered dual purpose cereals. This is useful information when determining the time of grazing.
Grazing at GS 30 – GS 31 reduced grain yield compared to no grazing by an average of 37%. The greatest yield loss of 57% occurred with Monstress triticale and the lowest yield loss occurred with Amarok wheat (18%).
Despite the yield loss, the ability for the cereals to recover given the timing and intensity of grazing was surprising. Physical examination of the plants showed a difference in growth stage between tillers on any individual plant. An average was taken to determine the growth stage for this experiment, however some tillers had already commenced stem elongation.
Given the intensity the plots were grazed it is highly likely some embryonic ears were removed, reducing yield. This is especially so for triticale where a minimum grazing height of 5 to 7 cm is suggested. Lighter grazing that left some drymatter behind may have lessened the grain yield loss.
No measurements were taken to determine if the yield loss was due to a loss of ears per plant or loss of grains per ear. The size of the grains per ear measured as thousand grain weight (TGW) was significantly lower in all the wheat varieties tested and the triticale. The average reduction in TGW was 16% due to grazing, which accounts for approximately 40% of the average grain loss in the wheat and triticale.
Surprisingly the TGW of the two barley varieties increased by 8% despite the barley yields being reduced by 35% due to grazing. This difference in response from the wheat and barley is difficult to explain, as the removal of leaf area at stem elongation would have been expected to conserve soil moisture, thus allowing increased grain size.
The impact of grazing would suggest a reduction in grain protein over the no grazed cereal. All varieties exhibited a decline in grain protein, however the reduction was only statistically significant with two varieties (Mackellar and Amarok wheat). The decline in grain protein due to grazing is consistent with observations from other trials and is thought to be a consequence of reducing the nitrogen available for grain fill when the leaves are eaten.
