Best weather to spray soybeans
The weather window for spraying soybeans — Delta T, humidity, wind, inversion and rain — plus canopy coverage, drift near sensitive crops and preset values.
Soybeans are sprayed several times a season — herbicides early, then fungicides and insecticides as the canopy develops, and in some regions a desiccant before harvest. The weather window is the same for all of them, but the crop's changing canopy and the products used change how much margin you need.
The weather window
- Delta T: 2–8 °C. Above 8, fine droplets evaporate before they reach the lower canopy; below 2, check for an inversion. See Delta T.
- Humidity: avoid very dry afternoons, and wet foliage where the label advises against it. See humidity and dew point.
- Wind: a light, steady breeze within the label's range, blowing away from sensitive areas. See wind speed for spraying.
- Inversion: do not spray under one — particularly important with herbicides. See thermal inversion.
- Rain: leave the product's rainfast period clear. See rain and spraying.
Crop-specific considerations
Canopy and coverage. Once the rows close, the lower canopy is hard to reach. Many soybean diseases start low in the plant, so fungicide applications after canopy closure depend on good penetration: the right droplet class and water volume, and a Delta T that lets droplets survive the trip down. Hot, dry afternoons are a poor choice for these applications.
Herbicide drift. Soybeans are grown next to many other crops, and some herbicides used in soybeans — especially growth-regulator products in tolerant varieties — can injure susceptible neighbouring crops, gardens and trees through droplet or vapour drift. Their labels are often strict about wind, droplet size, buffers, temperature and inversions. Conventional soybeans are themselves sensitive to drift from those products.
Growth stage. Label timing depends on the crop's growth stage and pre-harvest interval, and weeds are best controlled small and actively growing.
Desiccation. Where pre-harvest desiccation is used, uniform coverage of the whole plant matters, and the usual drift precautions apply to neighbouring crops that are still green.
Typical applications
Herbicides (pre- and post-emergence), fungicides, insecticides and, in some systems, pre-harvest desiccants. Follow the label for each.
Setting it up in PulveCast
Choose the Soybean preset. It sets Delta T to 2–8 °C, humidity to 55–95 % and Medium as the ideal droplet class; in automatic mode the app suggests a coarser class when the wind requires it. Crop presets are part of Pro — with the free Custom preset you can enter the same values yourself. Adjust the wind ceiling to your label and equipment, or pick your drone model.
Other crops
- Best weather to spray corn (maize)
- Best weather to spray sugarcane
- Best weather to spray cotton
- Best weather to spray wheat
- Best weather to spray coffee
- Best weather to spray rice
- Best weather to spray citrus
- Best weather to spray vineyards
- Best weather to spray potatoes
- Best weather to spray pastures
Frequently asked questions
What is the best Delta T for spraying soybeans?
The general guideline of 2 to 8 °C applies. For fungicides that need to reach the lower canopy, avoid the upper end on hot, dry days, as fine droplets evaporate before they get there.
When is the best time to spray soybean fungicide?
Timing depends on the disease, the product and the growth stage on the label. On the weather side, choose a window with Delta T in range, a light steady wind, no inversion and no rain within the rainfast period.