(Air) humidity

The plant must always be dry when administering granular fertilisers and liquid fertilisers. So please wait a few hours before spreading after it has rained. Spreading/spraying fertilisers can cause leaf burn. The image shows leaf burn caused by spraying urea.

The fertiliser becomes sticky when you spread fertiliser with high humidity or during (light) rain. This can cause clod formation, resulting in blockages in the spreader. This can have a significant influence on the spreading pattern. Therefore, ensure the fertiliser spreader is covered with tarpaulin when high humidity.
Prilled fertilisers, in particular, are sensitive to humidity during storage and handling. The grains stick together at high humidity, with a high chance of cloud formation. When applying liquid fertilisers, the crop must be dry.

Sources:
Bemesting, 2013.
Bouma, Agrometeorologisch specialist bij Agrometeorologisch Adviesbureau Erno Bouma, 2014.
PPO