| Researcher(s) |
Linda Bailey |
|---|---|
| Year(s) | 2021 |
| Contributor | Northern Grower Alliance |
| Trial location(s) |
Nandi , 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 end of August. These treatments either remained as stand-alone or were topped-up with Dual Gold at 1 L/ha, at sorghum planting or early in-crop. 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 the application timings at the end of July, end of August or at-planting. Monthly rainfall totals of <10 mm were recorded in both August and September.
The site was sown to MR Buster sorghum on the 17th October. The untreated had a population of ~6.4 plants/m row. All treatments were crop safe with no impact on emergence counts at 10 days after planting or any visual crop effect evident.
Rainfall totalling over 60 mm occurred during the 12th-14th of October with FTR seedlings already apparent at planting. The 1st assessment count was conducted four days later with >150 FTR/m2 in the untreated. All Dual Gold or Valor treatments reduced FTR populations to <5/m2 with no significant difference between products or application timing. Atragranz provided poor levels of FTR suppression and was not significantly different to the untreated. A ‘clean-up’ application of glyphosate was applied after this assessment but only resulted in FTR suppression.
A second assessment was conducted ~2 weeks later. Although there was no significant difference between Dual Gold and Valor, there was a trend to improved FTR control from Valor. There was also a trend to improved control where initial applications of Dual Gold were ‘topped-up’ with Dual Gold 1 L/ha shortly after planting. There was no obvious benefit where Valor was ‘topped-up’ with the at-planting treatment. Dual Gold applied at the end of July, without the at-planting ‘top-up’, trended to poorer control than either timing of Valor or where Dual Gold was applied at the end of August. Applications of Dual Gold alone at-planting provided poor FTR control and were not significantly different to the untreated. The at-planting treatment of Dual Gold 2 L/ha was significantly poorer than all Valor or early Dual Gold treatments except where Dual Gold was only applied in July.
A final weed assessment was conducted in mid-December. Rainfall totals of ~300 mm were recorded between the 2nd and final assessment. Similar patterns were apparent to the 2nd assessment. Dual Gold applications alone at planting or in-crop were not significantly different to the untreated and poorer than 11 of the 12 treatments with July or August herbicide application. It is expected that the poor performance of Dual Gold at planting or in-crop was due to the majority of weeds being already emerged at application combined with the poor knockdown efficacy provided by glyphosate.
Low levels of flaxleaf fleabane were present at the final assessment with <0.2/m2 in the untreated. Factorial analysis showed Atragranz provided improved control compared to Dual Gold or Valor.
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 ~7-11 weeks prior to planting provided very effective levels of control. In contrast, ineffective FTR control was achieved from all Dual Gold treatments applied only at-planting or in-crop. Improved FTR efficacy from sequential application was most apparent from the July application of Dual Gold with the at-planting ’topped-up’.
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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