Google Adsense through Wordpress Blog

I am maintaining a blog from last 5 to 6 months, at now i want to apply for google ads through my blog. i have tried for google ads from my forum many times but google refused it and say insufficient content i dont know what wrong because my forum is almost 3 years old. anyways my blog have all unique content so i want to apply for google ads. please someone tell me what should i can do?

Poster :
Zee Leo