How to update just a field

[Jaisol]

Hi,

I've added one document to my db.

# cat file.json
{
   "docs": [
      {
         "_id": "prod",
         "sysAdmins": [
            "admin",
            "sys_admin"
         ],
         "webDeploy": {
            "source": "server1.domain.com",
            "username": "myUser",
            "password": "xxxxxx",
            "websites": {
               "site1.domain.com": {
                  "path": "d:\\websites\\site1.domain.com",
                  "appPoolIdentity": "domain\\sys_site1"
               },
               "site2.domain.com": {
                  "path": "d:\\websites\\site2.domain.com",
                  "appPoolIdentity": "domain\\sys_site2"
               }
            }
         }
      }
   ]
}

#curl -d @file.json -X POST http://localhost/mydb/_bulk_docs -H "Content-Type: 
application/json"
[{"id":"prod","rev":"1-a4f83f088384ea39ad593e4b4c2f7018"}]


I'm so new on this.
I've read the HTTP API and I still don't figure out how to update or delete 
just 
one field.
1. Update the webDeploy field ?
2. Delete the sysAdmins field ?

Sorry to bother you with a newbie question.

Any advice is greatly appreciated. Thanks!