Maintaining profitable HRZ farming systems with retained stubble systems.

Transcription

1 GRDC stubble project BDW Maintaining profitable HRZ farming systems with retained stubble systems. Retaining the large stubble loads common in the Southern region HRZ while maintaining profitability presents many challenges. High among these is the problem of stubble intercepting knockdown & pre-emergent herbicides and thus reducing its effectiveness. SFS ran a demonstration site in a range of stubble treatments in early 2017 to determine if it could be done better. Aim Test different boom spray nozzle setups for efficacy in different stubble management situations. Treatments; Stubble 3 treatments (grazed, burnt & retained) x 3 stubble heights; 1. 80cm stubble harvested by stripper front cm stubble normal front 3. 23cm stubble normal front Teejet AIXR nozzle setups a) 50cm spaces with flat fan 02 size b) 25cm spaces with flat fan 02 size c) 25cm spaces with flat fan on extensions for inter-row spraying 02 size d) 25cm spaces with 80 0 flat fan on extensions for inter-row spraying 015 size 9m 9m 9m 9m 9m 9m 9m 9m 9m 9m 9m 9m 9m Retained Retained Burnt Burnt Grazed Grazed Stripper front 30cm harvest 15cm harvest 50cm noz 25cm noz 25cm noz 25cm noz 50cm noz 25cm noz 25cm noz 25cm noz 50cm noz 25cm noz 25cm noz 25cm noz boom extended 80 0 fan boom extended 80 0 fan boom extended 80 0 fan Figure 1: Paddock demonstration layout, SFS spraying in stubble program. Spray pressures for each setup were held constant at 3bar and speeds were adjusted to provide 100l/ha water rates for each nozzle setup. Heights were adjusted to suit each stubble height and application method.

2 Figure 2: Stubble heights grazed & retained standing at site. Monitoring Summer knockdown efficacy 7 & 14 DAT, water sensitive paper coverage using Snap card. (before grazing & burning treatments were applied) (Scale 1-9 European weed death scale. 1 = complete kill. 9 = no effect.) Table 1: Volunteer crop & weed death scores 7 and 14 days after knockdown treatment was applied in standing 80, 40 and 23cm stubble using 4 different nozzle setups. Plant death 7DAT x nozzle type 80cm high (stripper) Av all nozzles 80cm cm high Av all nozzles 40cm cm high Av all nozzles 23cm 2.8 Plant death 14DAT x nozzle type 80cm high (stripper) Av all nozzles 80cm cm high Av all nozzles 40cm cm high Av all nozzles 23cm 1.3 Summer knockdown spray coverage percentage using Snapcard app. 7.7% 7.8% 7.4% 7.4% 9.7% 10.2% 7.8% 10.7% 20% 14.8% 14% 18.9% Figure 3: Water sensitive spray coverage in 80cm, 40cm and 23cm stubble using 4 different nozzle setups..

3 From the tables and water sensitive paper we concluded that the 25cm spaces improved spray coverage slightly as did the shorter stubble heights. If you went a step further and used 80 degree fans on 25cm extensions to drop the nozzle down into the inter row this also gave a slight increase in spray coverage percentage as determined by the app Snapcard. Grazing and burning treatments were applied in early Autumn and a second knockdown, combined with a preemergent herbicide, application done before sowing on the 20 th April. Volunteer wheat & weed deaths were recorded 8 and 15 days after treatment. Spray coverage was again recorded using water sensitive paper and the Snapcard app. Table 2: Volunteer crop & weed death scores 8 and 15 days after pre-em plus knockdown treatment was applied in standing 80cm, 40cm and 23cm stubble using 4 different nozzle setups. Standing stubble pre-emergent spray plant death 8DAT x nozzle type 80cm high (stripper) Av all nozzles 80cm cm high Av all nozzles 40cm 4 23cm high Av all nozzles 23cm 4.7 Standing stubble pre -emergent spray plant death 15DAT x nozzle type 80cm high (stripper) Av all nozzles 80cm cm high Av all nozzles 40cm cm high Av all nozzles 23cm % 9.3% 11.6% 11.9% 9.4% 9.3% 6.8% 15.% 8.5% 23.2% 26.6% 25.5% Figure 4: Water sensitive spray coverage in 80cm, 40cm and 23cm standing stubble using 4 different nozzle setups. In the standing stubble 8DAT plant death scores were not as expected. Death scores in the 80cm stubble were marginally better than the shorter stubble heights of 40cm & 23cm, averaging 1.2 compared to 1.6 & 1.8 respectively. The trend of slightly improved plant death observed in the first knockdown using the 80 degree fan pattern nozzles on extensions was consistent in the pre-em + knockdown application. This trend was evident in the water sensitive paper coverage percentages with the 80 degree fan nozzles giving a noticeable increase in coverage. The demonstration appears to have confirmed the grower s assumption that more droplets applied on less angle would improve standing stubble penetration. We cannot be conclusive as the work was not replicated but it may have highlighted an area where more work could be done to investigate the hypothesis. Below we have compared the same nozzle setups in grazed stubble treatments with similar results.

4 Table 2: Volunteer crop & weed death scores 8 and 15 days after pre-em plus knockdown treatment was applied in grazed 80cm, 40cm and 23cm stubble using 4 different nozzle setups. Grazed stubble pre-emergent spray plant death 8DAT x nozzle type 80cm high (stripper) Av all nozzles 80cm cm high Av all nozzles 40cm cm high Av all nozzles 23cm 4.1 Grazed stubble pre-emergent spray plant death 15DAT x nozzle type 80cm high (stripper) Av all nozzles 80cm cm high Av all nozzles 40cm cm high Av all nozzles 23cm % 11% 11.5% 13.8% 13.9% 7.6% 13.6% 15.6% 14% 44.9% 40.2% 35.9% Figure 5: Water sensitive spray coverage in 80cm, 40cm and 23cm stubble using 4 different nozzle setups in grazed stubble. There was no discernible difference between retained and grazed stubbles for plant death or spray coverage. As shown in figure 1 there was a noticeable difference in the stubble architecture between these treatments. There are also no definable differences in either measurement attributable to stubble height in the second spray application. On the contrary there is a slight decrease in efficacy and coverage for the shorter 23cm stubble. I was unable to conclude why this occurred and it leaves some doubt on the accuracy of the work. Conclusions. This demonstration was designed to test several theories being considered and practiced locally; 1. 25cm nozzle spacings provide better coverage than the traditional 50cm spaces. 2. Shorter stubble improves herbicide efficacy 3. Standing stubble increases spray droplet penetration fan patterns increase spray droplet penetration 5. Inter-row spraying using extended nozzles might improve droplet penetration The demonstration was able to provide no statistical information. It did however indicate that the narrower 80 0 fan pattern may increase coverage in the conditions tested. There are a huge number of variables that can t be accounted for in this demonstration. Lower harvest heights spread greater amounts of trash on the ground which effectively prevent spray droplets hitting the soil. This is critical when aiming to maximise pre-emergent herbicide

5 efficacy in stubble retention systems. Herbicide solubility, strength of bonds to organic matter, boom spray height, nozzle size, design and speed play a critical role in droplet penetration and herbicide efficacy. Current wide spread adoption of auto steer guidance systems will assist greatly in the development and success of new application methods. The demonstration has raised questions on whether herbicides can be more effectively applied in stubble retained systems using specific nozzle patterns, placement in the canopy and nozzle spaces. Much more detailed work is required to determine the best fit equipment and setups to provide the best efficacy in a range of paddock situations. SFS will encourage GRDC to utilize grower levees to pursue this work. Paul Breust, Project Co-ordinator, Southern Farming Systems. Acknowledgements; Neville, Grant & Troy Keating. Tim Pilkington - Southern Ag Management Mark Slatter Nufarm Jim Caldwell & Hugh Burbury SFS staff References; GRDC Spray application tips and tactics Bill Gordon Nufarm Australia Limited Klein R, Golus J and Kruger G, Evaluation of Soybean (Glycine max) Canopy Penetration with Several Nozzle Types and Pressures. Evaluation_of_soybean_glycine_max_canopy_penetration_with_several_nozzle_types_and_pressures.pdf