What else other than carrots can dogs eat?

My dog went for neutering 3 days ago and for his convenience this is what i fed him. Avoderm kibbles + Cesar wet food + carrots. After eating this two meals a day, i realise that his poopy is really smooth but still it smells! But it's good that it came out smoothly. I want to introduce more vegetables to him other than carrots. What vegetables do you reccomend for dogs? A nutritious one. Can i add potatoes into his kibbles as well? Thanks all. I want him to eat a well balanced meal. FYI, he's five years old now. :)