Not able to send POST request with raw JSON as request body

I am trying to POST request using Postman with raw JSON as body, but it is failing by throwing Error 400 bad request.But same working fine and getting response token when I select body as x-www-form-urlencoded. Could someone help me here.

Below is headers and my JSON content:

Content-Type : application/JSON
Accept = application/JSON

{    
"grant_type":"password",    
"username":"kumaran",    
"password":"test123" 
}

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