Question

Why Are there "Agricultural belt "
in the USA

Answer 1

because there is very fertile sol

Answer 2

The belt regions of the United States are portions of the country that share certain characteristics. The "belt" terminology was first applied to growing regions for various crops, which often follow lines of latitude because those are more likely to have similar climates. The allusion was to a long clothing belt, as seen on a map.[citation needed]

The usage has expanded to other climatic, economic, and cultural concentrations. These regions are not formally defined; they frequently overlap and have vague borders. The terminology is also used outside the U.S.