What are all those yellow flowers?

LOL, they are canola! Cooking oil is made from the little round seeds when they mature. They are a major crop here on the prairie (and this movie was filmed in Alberta, Canada). Years ago it was called "rapeseed" but for obvious reasons that name was changed! (Ha ha.) BTW, it is a very healthy cooking oil. My father used to grow it on our farm!

Those are the Mustard plant. Its black/brown seeds are widely used in Indian subcontinent for cooking before frying anything with the hot oil in a pan.

You better know what you want to do before somebody knows it for you -The Astronaut Farmer