Real problem with my east side yams this year after years of eating pleasure from there...they often have corky discolored areas inside, and no matter how I cook them there is a very unpleasant "squeaky" rubbery texture and an odd sweetish yet acrid taste. The chickens are eating fried yams often these days. An "African Yellow" yam in my south bed (where Muscovy ducks also lived for nearly a year) that for years gave me tons of delicious tubers to fry now also has an unpleasant taste and squeaky rubbery texture.....is Muscovy duck poop the culprit here and in the center east bed? I'd think it'd be great for plants. Just a coincidence? I looked into if my poor tasting yams could be diseased...seems very unlikely...only real theory at this point is a year of Muscovy duck poop in both beds. Next I will dig up and cook yams from parts of the yard where there have never been ducks. I've been growing the true yams since 2001....first time ever that I have had ANY problem.