After spreading

Clean the fertiliser spreader thoroughly immediately after use, especially around the dispenser opening. Artificial fertilisers consist largely of salts, which can cause unprotected metals (and unprotected concrete) to corrode. Never leave fertiliser stored in the spreader after spreading. Storing fertilisers in the spreader for long periods can cause serious damage to the spreader.
The best way to protect a fertiliser spreader is to clean it with soap and water after use. In addition, the spreader should be stored moisture-free.
When winterising the fertiliser spreader, re-lubricate everything thoroughly with the grease pump. Parts prone to rust should be sprayed or lubricated with vegetable oil. Put the fertiliser spreader away with cylinders retracted to protect the cylinder rod from rust. Please refer to your spreader manual for information on the correct maintenance of your spreader.

Source:
Turenhout, 2014