Optimum humidity is 60-80%. When treating in lower humidity conditions, use plant safe preparations (e.g. chelates or amino chelates instead of simple salts).
High relative humidity promotes longer persistence of the liquid on the plant surface, which allows more efficient penetration of the preparation into the plant and improves the effectiveness of the applied preparations.
The optimum air temperature is 12-20°C (acceptable lower temperature from 4°C, acceptable upper temperature up to 25°C).
Foliar fertilizers are most often used together with pesticides. Therefore, it is important that the label indicates the air temperature at which the pesticide is effective. This information refers not only to the temperature range at which the active ingredient is effective, but also to the temperature at which the treatment can be safely applied to plants.
Temperatures below the optimum will slow the uptake of ingredients from the solution and reduce the effectiveness of the applied product. At temperatures above 25°C, there is an increased risk of plant tissue damage due to rapid evaporation of water from the solution applied to the leaves. In addition, when treatments (especially fine droplets) are applied at high temperatures and low humidity, a significant amount of the applied liquid will not reach the plants due to evaporation.
It is recommended to spray plants during periods of limited sunlight (cloudy weather, late afternoon, etc.). Strong sunlight during application may cause crop damage.
Do not spray in winds that cause droplets to drift (follow regulations for acceptable wind speed for crop protection treatments). Optimum water temperature for solution preparation 12-20°C.
This parameter is particularly important for proper solution preparation (e.g. dissolving solid products, homogenizing the solution).
In hot weather, the best time to spray crops with agrochemicals is in the late afternoon or in the evening and night hours – until a heavy dew forms. In addition, pollinating insects have completed their flight in the evening, the wind tends to die down, and there is no spray drift.