A more thorough explanation:

Definition: To work on something using your hands.

Examples:

• He manured the garden by digging and planting the seeds.
• The farmer manured the field by spreading cow dung with his hands.

The examples show how manure means to work on something manually. In the first example, the person is working on the garden by digging and planting seeds with their hands. In the second example, the farmer is spreading cow dung on the field using his hands. Both examples illustrate the definition of manure as performing manual labor on something.