User blog comment:HalointheSkye/Volume 3 Chapter 12 - End of the Beginning/@comment-10390252-20160215111615/@comment-15586611-20160215124956

Don't forget though, all the volcanic ash left parts of Mordor as really fertile farmland. It's how sauron could feed his armies. Of course, such information was hidden in Tolkien's notes and the vast appendices, which is why it's not well known.