No it doesn't happen automatically. You ahve to apply for an adsense account. And it can be approved or rejected based on content of the posts posted by you, form where are you applying for adsense. Here is some helpful article, that will help you. First of all, you should know How to apply for adsense and get it aproved. After you have got your adsense acount approved then, you must look for incresing your adsense revenue and for that you can read How to increase you adsense revenue.
If you still have any doubts, feel free to ask.
Thanks a lot for your response. Hoping to get this type of cooperation in future also.