Pre-emergence spraying of maize: after sowing, before emergence
Pre-emergence spraying of maize means applying a soil-acting herbicide after sowing and before emergence, while the soil is moist. It is first and foremost a job for a tractor. We apply herbicide by drone only when rain keeps the tractor out of the field and the surrounding fields carry the same crop.
By Nikola Mojsa, MSc in Agricultural Engineering
What pre-emergence spraying means
A pre-emergence spray is a soil-acting herbicide that, after sowing, kills germinating weed seeds on the surface and in the top 10 cm of soil before they emerge (Agromarket, in Serbian). The active ingredient terbuthylazine forms a herbicide film that stops germination, and it is also taken up through the leaves of weeds that have already emerged. Protection lasts several weeks.
The reason is simple: maize is least able to tolerate weeds at the start of the season, so BASF advises controlling weeds in the first 3 to 5 weeks after emergence (BASF). Agromarket adds that the post-sowing treatment is an important step in a strategy against weed resistance.
When to spray maize pre-emergence
A herbicide applied to moist soil is activated very quickly, and 10 to 20 mm of rain after application is enough (Savacoop). In a dry spring it works somewhat less well, but according to the same source still well enough.
The window is measured by emergence, not by the calendar. The soil surface must be well prepared, because even application depends on it (Agro Info Net, S. Miletaković), and the same source advises spraying in the evening, in calm weather with no wind.
Pre-emergence spraying: tractor or drone
A tractor does the job in the early stages, right up to emergence: the herbicide needs to land as close as possible to the soil and the weeds, so the weeds get a proper soaking. A drone applies the product over the whole leaf mass, and at pre-emergence there is no leaf mass yet.
We apply herbicide by drone only as an exception, and only under conditions that protect neighbouring fields:
| Situation | What we do |
|---|---|
| The field is passable | Tractor: your own or a contractor's. If you have a sprayer, there is no reason to pay for a drone |
| Rain is keeping the tractor out of the field, and the surrounding fields carry the same crop as yours | A drone is possible: after rain, only the access to the field needs to dry |
| The maize is next to sunflower, vegetables or an orchard | We don't apply herbicide by drone, because of drift |
Drift is exactly why herbicides come last on our list: fungicides, insecticides and foliar feeding take priority. We explain how wind and flight height affect it in Drift in drone spraying.
What if it rains after sowing
Rain works in the herbicide's favour, but a waterlogged field can keep the tractor out precisely in the days between sowing and emergence. That is when a drone becomes an option, under the conditions in the table.
How much water per hectare for a soil-acting herbicide
A soil-acting herbicide is usually sprayed in 300 to 600 litres of water per hectare: less on lighter soils and more on heavier ones, with the water serving only to spread the product evenly (Agro Info Net). On field crops a drone sprays 15 to 20 litres per hectare, 15 to 40 times less.
Whether the product may be applied in that much less water is stated on the label; if it may not, the soil-acting herbicide goes on by tractor.
What if the maize has already emerged
Once maize has emerged it is too late for a pre-emergence spray, but there are options: post-emergence herbicides, up to 8 or 10 leaves. Some soil-acting products can, according to their labels, also be applied after emergence, up to the 3rd leaf (Agrosava), and terbuthylazine, according to Agromarket, can be applied even later. Check the timing for your product on the label; there is an overview in Herbicides for maize up to the 10th leaf.
We apply a late herbicide by drone under the same conditions as a pre-emergence spray.
Drone spraying maize: price per hectare
Drone spraying costs €25, €22 or €20 per hectare, for areas up to 20 ha, from 20 to 100 ha and over 100 ha, and the price is the same for herbicide, fungicide and insecticide. You supply the product and the water, and travel within 50 km of Opovo is free. Contract tractor spraying in Banat costs about €30 per hectare, but for pre-emergence spraying a tractor does the job even when the service costs more than a drone. Check the price for your field in the calculator.
Frequently asked questions
After sowing and before the maize emerges, on moist soil. The window is measured by emergence: once the maize breaks through the soil, it is too late for a soil treatment. The exact timing for your product is on the label.
Yes: 10 to 20 mm of rain is enough to activate the herbicide. The problem is that a waterlogged field can keep the tractor out. A drone only needs a dry road to the field, but we apply herbicide by drone only when the surrounding fields carry the same crop.
Then you switch to post-emergence herbicides, up to 8 or 10 leaves, according to the label. Some soil-acting products can, according to their labels, be applied up to the 3rd leaf of maize.
Only as an exception. A tractor does the job in the early stages, because the product needs to land close to the weeds. We use the drone when rain keeps the tractor out of the field and the surrounding fields carry the same crop.
- First hectare free
- Free travel up to 50 km
Book your pre-emergence spray
Tell us how many hectares of maize you are sowing, where, and which herbicide you plan to use, and we will tell you whether a drone or a tractor is the better choice for that field.