Nope. There is a huge difference between "tope" and "udongo". The former is translated as mud, whereas the later means soil. A good example is "udongo mfinyanzi" of which translates as "clay soil"
I don't know how it is with this noun, but in genera a lot of words for liquids and substances act as mass nouns, and often take the plural, like maji and maziwa (both ma- class), and also some abstracts like matata. I do think however that matope and tope both are used and means mud, but I don't know what pluralisation gives to the meaning of the word.