Farm Table says:
What is the problem?
Disc-based zero-till seeding systems are being adopted by an increasing number of no-till farmers.
Herbicide safety at sowing in no-till is largely dependent on creating a physical separation between germinating crop and herbicide. The level of incorporation can vary greatly with different disc seeders and configurations, and this can affect the efficacy of volatile pre-emergence herbicides such as trifluralin and pendimethalin.
This field study was done to evaluate the effect of three pre-emergence herbicides on annual ryegrass control and crop phytotoxicity in four different disc seeding systems.
What did the research involve?
The study was undertaken in 2012 at Roseworthy, SouthAustralia, to evaluate the effect of four different disc seeding systems on the control of annual ryegrass with pre-emergence herbicides and their effect on wheat.
All disc systems were operated according to manufacturer specifications and sowing seeds.
– single discs: John Deere (90 series), NDF (650 series)
– triple discs: Bertini and KHart
Herbicide treatments used in the study were:
– trifluralin 720 g ha−1 (Triflur X®), recommended rate of prosulfocarb 2000 g ha−1 + S-metolachlor 300 g ha−1 (Boxer Gold®)
– double the recommended rate of prosulfocarb 4000 g ha−1 + S-metolachlor 600 g ha−1, and pyroxasulfone 100 g ha−1 (Sakura®).
What were the key findings?
– Highersoil disturbance in triple discs (Bertini and KHart) was the likely cause of greater ryegrass establishment in triple discs than single discs (JD and NDF).
– Trifluralin and prosulfocarb + S-metolachlor caused significant damage to wheat in the single discs but not in triple discs.
– Removal of herbicide treated soil from the furrow in the triple discs (Bertini and KHart) appears to be responsible for low herbicide damage in these systems.
– The single discs (JD and NDF) appear to leave herbicide treated soil in the furrow where it damages wheat seedlings.
– Herbicide damage was significantly reduced by the residue managers fitted in front of the single disc modules
Seedling recruitment of annual ryegrass tends to increase substantially in high soil disturbance seeding systems. With no crop damage observed with pyroxasulfone, it appears to be the safest herbicide option for use in wheats own with low soil disturbance single disc seeding systems.