What is the effect of adding adsense to nonenglish pages? Is it allowed? Does it affect smart pricing?
I have AdSense on two Danish Language websites and that works just great. One of my sites is in Danish on one domain and in English on another, and both are treated very well by AdSense.
I suggest you see the list of supported languages in Adsense and only place your ads in the supported languages. Other than that, I would say not to ... it is risky.
It is indeed allowed to have AdSense ads in non-English websites but I would suggest you to check beforehand if there are ads to be showed in your language for your main keywords.
I have a Dutch blog (not made for adsense, just for fun) that runs Dutch ads without any problems. I picked a bad keyword (for my audience anyway) up in a blog post so my CTR crashed, but it was great. So running any non english ads shouldn't be any problem. Depending on what language ofcourse.
I'm using AdSense on Turkish and German pages. It's not a problem but CTR is lower and earnings are consequently lower than English pages, ie; I can earn 1 USD with 1 click from English page but could't have 1 USD with 10 clicks from other pages (Turkish and German), also it depends where visitor coming and click from (country).