Maintaining profitable farming systems with retained stubble in Victoria & Tasmania

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1 GRDC Stubble project BWD00024 Maintaining profitable farming systems with retained stubble in Victoria & Tasmania Impacts on herbicide efficacy from different stubble management practices. Introduction: One of the major concerns with stubble retention systems is the impact on herbicide efficacy. Standing or prostrate stubble intercepts herbicide preventing it from being placed on the soil surface that it is targeted for. In this study herbicide efficacy was tested in 3 stubble management practices; 1. Retained & direct drilled 2. Stubble incorporated with Topdown 3. Stubble burnt. SFS gratefully appreciate and acknowledge the contributions of Myles Read and family and Swayne & McCabe in the running of this trial. Authors: Paul Breust & Megan Beveridge SFS Seasonal conditions 2014 was a Decile 1 year. Average annual rainfall in Westmere is 530mm but the trial site received only 370mm. Growing season rainfall (GSR) was a Decile 2, with Westmere receiving only 300mm from April to November compared to a long term average GSR of 400mm. Below average rainfall was recorded in every month except April and June. Key messages: No significant differences in phyto-toxicity and weed counts from stubble treatment or seeder used. Disc seeder establishment was significantly better and produced higher NDVI than tyne seeder establishment. No significant difference in establishment between burn, incorporate and retained treatments. Burn treated plots had significantly higher NDVI (read dry matter) than incorporated & retained.

2 Retained stubble treatments were lowest for NDVI, even with similar establishment numbers, indicating lower crop vigour. Yield and grain weights for the disc seeder treatment were significantly lower than the tyne seeder at this sight despite better establishment and dry matter production early in the growing season. We are unsure of the reason why. Pictures 1, 2 & 3: 1. Tyne + Burn v Disc + burn. 2. Tyne + Incorporation v Disc + Incorporation. 3. Tyne + retained stubble v Disc + retained stubble Agronomic information: Operation Date Product rates Crop 5/6/14 Beaufort wheat Seed treatment 4/6/14 Jockey Sowing rate kg/ha 70kg/ha Target plants/m 2 160/m 2 Fertilizer 5/6/14 MAP 100kg/ha + 4ml Impact Fertilizer 13/7/14 Urea 70kg/ha Fertilizer 20/7/14 UAN 139/ha Herbicide 3/6/14 Gramoxone 2l/ha PE Herbicide Sakura 118g/ha PE Herbicide 5/6/14 Avadex 1.6l/ha PE Herbicide 5/9/14 Axial 0.6l/ha Post E Herbicide 5/9/14 Velocity 0.65l/ha Surfactant 5/9/14 Adigor 1% Molluscicide 25/6/14 Meta 7kg/ha Molluscicide 7/7/14 Meterex 10kg/ha Table 1: Agronomy for 14 GRDC STUB WHT MR in Tyne seeder on 20cm spaces, Disc on 18.5cm Tyne seeder used was Southern seeder with knife points on 20cm spacing. Disc seeder used was Vaderstaad Rapid on 17.5cm spacing. Disc seeder engaged cultivation disc s in front of seeding disc s which gave a high level of incorporation for the stubble retained plots. Stubble from wheat crop in 2013 was on 30cm spacing and was measured at 3.8t/ha dry matter.

3 Design: Burn Incorporate Retain Retain Incorporate Burn Incorporate Burn Retain DISC TYNE TYNE DISC DISC TYNE TYNE DISC DISC TYNE TYNE DISC DISC TYNE TYNE DISC DISC TYNE REPLICATE 1 REPLICATE 2 REPLICATE 3 Figure 1: Trial plan 14 GRDC STUB 13 WHT MR Results: Seeder Est. Sig NDVI Sig Yield Sig Weight Sig Disc a 0.24 a 1.75 b 65.0 b Tyne 90 b 0.23 b 2.49 a 71.2 a Table 2: Establishment, NDVI, yield & grain weight results for 14 GRDC STUB WHT MR in Data followed by the same letter are not significant. Stubble TRT Est. Sig NDVI Sig Yield Sig Burnt stubble 130 a 26 a 1.9 a Incorporated stubble 120 a 23 b 2 a Retained stubble 131 a 21 c 2.4 a Table 3: Establishment, NDVI & yield results for stubble treatments in 14 GRDC STUB WHT MR. Data followed by the same letter are not significant. Pictures 4 & 5: 4. Tyne + Incorporation 5. Disc + Incorporation.

4 Pictures 6 & 7: 6. Tyne + Retained stubble 7. Disc + retained stubble. Note high level of incorporation from Vaderstaad Rapid disc. Pictures 8 & 9: 8. Tyne + Burn 9. Disc + Burn Discussion: The level of stubble, 3.8t/ha, is considered lower than regional levels in normal seasons and this would have reduced impact on herbicide efficacy. The aggressive incorporation provided by the Vaderstaad Rapid disc setup would have provided a higher degree of incorporation than normally experienced with a single disc opener. This may have increased phyto-toxicity impacts on the crop in all disc treatments but conversely increased herbicide efficacy and weed control. Evaluation of phyto-toxicity and weed control found no significant differences between seeders or stubble treatments. There were however positive significant differences in establishment & NDVI for the disc treatments. NDVI is a good indicator of dry matter production when measured before canopy closure. The differences did not contribute to higher yields for the disc treatments, in fact it had the opposite effect and the yields for the disc treatment were significantly lower than the tyne. This may have been a result of haying off at grain fill as a result of higher plant numbers using greater amounts of moisture during the season combined with poor spring rainfall. Over all weed control was considered good. For this trial area there were very few grass weeds present as the Sakura & Avadex did a good job. The trial received a post emergent application of Axial only because it was beside another trial area that had significant grass weed issues and it was more efficient to apply to both trials. Velocity was used to control minor infestations of broadleaves. No solid conclusions could be drawn for herbicide

5 efficacy impacts of stubble management or seeder type. However it is clear retained stubble had no significant impact on establishment compared to burning and incorporating. Retaining stubble however did negatively impact on early dry matter production as evidenced by significantly lower NDVI scores at growth stage 21. Past research supports this data but as also evidenced here there is minor impact on grain yields in a stubble retained system. Further experimental work with commercial seeders will be conducted in 2015 to provide further evidence to support or refute impacts of stubble retention.