Soybean desiccation: when, why and how by drone
Soybean is desiccated strictly at harvest maturity: the leaves on most plants turn yellow and start to drop, and seed moisture falls to about 30 to 40%. Going in any earlier cuts seed filling short, which means lower quality and lost yield. Depending on the product and the state of the crop, harvest can start 4 to 14 days after spraying; the exact safe interval is always set by the label.
By Nikola Mojsa, MSc in Agricultural Engineering
What soybean desiccation is and why it is done
Desiccation is a crop management practice that uses chemical products to dry the green leaf mass of soybean, and any weeds left in the field, quickly and evenly (agromedia). Agronomists stress that glyphosate is not recommended for this purpose in soybean.
In practice, our agronomist Nikola recommends desiccation mainly because of the heavy leaf mass that keeps seed moisture high at delivery: the leaves (especially at the top of the stem) often stay fully or partly green even when the pods and seed are already ripe. This is more marked in wet years, when the crop ripens unevenly. If that green mass goes into the combine, harvesting is harder, the sieves clog and the seed moisture measured at the weighbridge comes out high (agromedia).
The second, equally important reason is the sowing date for the next crop. Desiccating on time (as advisory services such as PSS Zrenjanin recommend) gets the soybean off the field promptly and leaves enough time to sow winter cereals at the best autumn date.
How to recognise the right moment for soybean desiccation
The right moment is when the crop reaches harvest maturity: the leaves on most plants turn clearly yellow and start to drop from the stem, and seed moisture falls to 30 to 40% (agromedia). Some advisory services recommend starting the treatment exactly when moisture reaches 40% (PSS Zrenjanin).
| What to check in the field | Advisory threshold for desiccation | Source |
|---|---|---|
| Leaves | On most plants they turn yellow and start to drop from the stem | agromedia |
| Seed moisture | 30 to 40%; treatment can start once it reaches 40% | agromedia; PSS Zrenjanin |
| When not to desiccate | As long as the seed is still filling | agromedia |
| Product | Must be registered for use as a desiccant | agromedia |
Seed moisture is always measured directly in the field, and your agronomist sets the exact application day from that reading.
How long after desiccation soybean harvest can start
Depending on the product used and the state of the crop, the combine can go into the field 4 to 14 days after spraying (agromedia). The most precise figure, though, is always the pre-harvest interval on the product label: the legal minimum interval between spraying and harvest, set to protect consumers' health.
That is why planning always works backwards: the agronomist first checks the pre-harvest interval of the product you plan to use, then sets the spraying date from the planned harvest day. For a detailed explanation of what the pre-harvest interval means and how it differs from the re-entry interval, read pre-harvest and re-entry intervals.
Why we desiccate soybean by drone
Just before harvest, soybean is very dense and full of tangled leaf mass. The drone applies the product vertically from above, covering the whole leaf mass, without any mechanical damage to the plants. A tractor driven into a crop like this, on the other hand, permanently flattens and destroys about 5 to 6% of the plants.
A tractor sprayer needs 300 to 600 litres of water per hectare for desiccation (agromedia); the drone does the same job with only 15 to 20 litres. Nikola mixes the product on site, in our tank on the trailer, and we top up the water together. After rain the drone doesn't have to wait for the mud in the field to dry: a dry access road is enough. If a tarmac road leads to the field, we work the same day after rain.
Desiccants can seriously damage neighbouring crops that are still green if the wind carries them. So, following the guidance in the DJI Agras T70P manual, we apply these products only in winds below 3 m/s. If the wind picks up while we are working, we stop flying until conditions settle. More on this in drift in drone spraying. For how we offer this service on other crops, see desiccation by drone.
What soybean desiccation by drone costs
Soybean desiccation costs €25 per hectare up to 20 ha, €22 from 20 to 100 ha and €20 over 100 ha. You supply the product and the water. We don't charge for travel within 50 km of Opovo, and new clients get the first hectare free on a first order of at least 10 ha.
Worked example: 25 ha near Debeljača (16 km from Opovo), a first order. 25 ha × €22 = €550; minus €22 for the first hectare = €528 (no travel charge). If you book a package of three treatments on the same field in a season, you get 5% off. Check the price for your location and area in the calculator.
Frequently asked questions
Only at harvest maturity: when the leaves on most plants turn yellow and start to drop, and seed moisture falls to about 30 to 40%. Going in earlier cuts seed filling short and costs yield. Your agronomist sets the exact day by measuring moisture in the field.
In practice, 4 to 14 days on average, depending on the product and the state of the plants. The shortest permitted interval (the pre-harvest interval) is always set by the label of the product you choose.
€25/ha (up to 20 ha), €22/ha (up to 100 ha) and €20/ha (over 100 ha). Product and water are not included. Travel within 50 km of Opovo is free, and on a first order of at least 10 ha the first hectare is free.
- First hectare free
- Free travel up to 50 km
Book desiccation before the soybean turns yellow
Send us the location, the number of hectares and the name of the product your agronomist recommended. We will fix the exact spraying day by tracking how fast seed moisture falls, the pre-harvest interval and the weather forecast.