traveling south america with two passports diffrent countries,is it possible to use a diffrent one in middle?

to change in the middle of my traveling between them and use my second one.

I doubt it. They look for that stamp which tells them when you entered their country. If the passport you show doesn't have that, they'll really question you about it and I'm sure you'll get into some sort of trouble.

It could be a problem as you cross the border - the officials will often look for the departure stamp of the previous country.