| Researcher(s) |
Linda Bailey |
|---|---|
| Year(s) | 2021 |
| Contributor | Northern Grower Alliance |
| Trial location(s) |
Springvale, QLD
|
To evaluate the impact of split application of herbicides for grass control pre-plant and in-crop
This was a complex trial to evaluate the impact of split or sequential residual herbicide applications for feathertop Rhodes grass (FTR) management both prior to and in sorghum. Dual Gold, Atragranz or Valor were applied at the end of July or in early September. These treatments either remained as stand-alone or were topped-up with Dual Gold at 1 L/ha, at sorghum planting or in-crop. The in-crop application was delayed till ~6 weeks after planting due to flooding not allowing trial access. Reference treatments were an untreated and Dual Gold rates applied at planting or in-crop
Levels of rainfall of <5 mm occurred in the week following application at the end of July, early September or the in-crop application. Monthly rainfall totals of <10 mm were recorded in both August and September. The trial received ~72 mm between 3 and 7 days after the at-planting application.
MR Taurus sorghum was sown on 1 m rows into sorghum stubble (~30% ground cover) at the beginning of November. No emergence counts were possible due to the inability to access the trial until mid-December.
The first weed assessment was conducted 1 week prior to planting, following ~60 mm of rainfall in the previous fortnight. FTR counts in the untreated were ~1.2/m2. Both Dual Gold and Valor provided effective control with no product or timing difference. Atragranz performed poorly at both application timings and was not significantly different to the untreated. A commercial application of glyphosate was applied across the trial at planting.
A second assessment was conducted ~7 weeks later in December, after ~270 mm of rainfall. FTR counts were very low with only ~0.2/m2 found in the untreated. Factorial analysis showed Valor continued to provide effective residual FTR control with significantly higher FTR counts where Dual Gold or Atragranz had been applied. There was no clear impact of timing or the Dual Gold application at planting.
Awnless barnyard grass and button grass counts were also conducted with untreated populations of 0.4 and 0.7/m2 respectively. Dual Gold and Valor had significantly lower counts of both weeds than Atrangranz with Valor more effective than Dual Gold on button grass. There was no clear impact from application timing but there was a clear impact of sequential application. Treatments topped-up with Dual Gold 1 L/ha at planting providing significantly improved control of both weeds.
Trace levels of broadleaf weeds were also assessed. Valor provided almost complete control of red pigweed and common sowthistle. Dual Gold and Atragranz had significantly increased counts of both weeds with no apparent difference between products and no clear impact of from the Dual Gold applied at planting.
A final weed assessment was conducted in late January with no indication of new weed emergence.
This trial highlights the importance of residual herbicide application prior to FTR emergence. Despite very low levels of incorporating rainfall, applications of either Dual Gold or Valor ~9-13 weeks prior to planting provided effective levels of control of a low density FTR emergence ~ 3 weeks prior to planting. In this trial there was a clear indication that Valor provided improved FTR control than Dual Gold when assessed in mid-December following large rainfall totals in November and early December. In this situation there was no clear impact of the sequential application of Dual Gold 1 L/ha at planting on FTR control. In this situation Valor provided superior control of low populations of a range of grass and broadleaf weed species.
Useful data on the length of in-crop efficacy from the sequential treatments was not possible as effective knockdown control of emerged seedlings at planting could not be achieved.
| Lead research organisation |
Northern Grower Alliance |
|---|---|
| Host research organisation | N/A |
| Trial funding source | GRDC NGA2009-002RTX |
| Related program | N/A |
| Acknowledgments | N/A |
| Other trial partners | Not specified |
| Crop type | Cereal (Grain): Sorghum |
|---|---|
| Treatment type(s) |
|
| Trial type | Experimental |
| Trial design | Replicated |
| Sow date | Not specified |
|---|---|
| Harvest date | Not specified |
| Plot size | Not specified |
| Plot replication | Not specified |
SILO weather estimates sourced from https://www.longpaddock.qld.gov.au/silo/
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.
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