Question

Why is soil erosion worse on farm lands than in forests

Answer 1

Well it is part of nature and the forest is nature
in farm lands farmers hate it because it will ruin the crops

Answer 2

In a forest, tree roots hold the land together, and they also soak up water,
and they get wider and deeper every year.

On farm land, there's no long-term network of roots.  They grow for maybe six
months, they don't get any deeper, and the land is bare naked the rest of the year.