With pre-emergence sprays there is only one target – the ground. An even distribution of the spray liquid is the aim. Patchy weed control most usually comes from patchy application, due to the wrong choice of nozzle and drift.
Fine sprays are important for retention on difficult to wet grass weed leaves such as wild oats and black-grass. For a given volume of liquid, when the drop size is halved, the number of drops produced goes up by a factor of eight, and the coverage of a flat area of leaf or ground may be up to four times greater. So where the target is very small, a fine spray will greatly increase the chances of hitting it.
Cereals present a tall, thin target. Bigger spray droplets penetrate better into the canopy than fine mist, which is either dragged in by turbulence or drifts away. Typically, a standard fan-jet puts half the spray on the crop at GS30/31, the other half is available for weed control, or is wasted to the ground. Nozzles can be selected to suit different application targets.
Low drift nozzles have proven very effective and good results from air induction nozzles can be expected. The AMISTAR nozzle has been specifically designed to achieve the best results with fungicide applications – providing the ideal spectrum of droplet sizes. Syngenta cereal fungicides are robust and work well when applied as coarse sprays and at reduced volumes.
|Timing||Water volume (l/ha)||Forward speed||Best nozzle||Reduced drift option|
|Pre-em herbicides||100-200 l/ha||12-14 km/h||DEFY 3D nozzle alternating forwards and back||AMISTAR nozzle|
|Post-em herbicides||100 and above||12-14 km/h||DEFY 3D nozzle all forwards or alternating forwards and back||DEFY 3D nozzle (worst case AMISTAR nozzle)|
|Spring wild oats||100 and above||12-14 km/h (slow down to 12 km/h for later season wild oats)||Standard Flat Fan or AMISTAR nozzles (keep to 50 cmboom height)||AMISTAR nozzle|
|Fungicides T0||100||12-14 km/h||DEFY 3D nozzles||AMISTAR nozzle|
|Fungicides T1-T2||100||12-14 km/h||AMISTAR nozzles||AMISTAR nozzle|
|Fungicides T3||100||12-14 km/h||DEFY 3D nozzle alternating forwards and back||AMISTAR nozzle|
Best application = best wild oat control
AMISTAR nozzles at 100 l/ha and 12 km/h with 0.5 m boom height is the best way to control oats. Low drift and high efficacy.
Grain £100/t; 10 t/ha yield; 5 plants/m2 = 5% yield reduction; untreated plots had 30 plants/m2