Reporting
A dry potato can be due to

A dry potato can be due to variety (such as russets vs. more waxy types), or cultural/environmental disorders or disease problems. If your potatoes showed any discoloration inside, or sunken or hollow areas, you might look into a disease such as fusarium dry rot, or a cultural or environmental problem. For more information, see:

 

http://vegetablemdonline.ppath.cornell.edu/factsheets/Potato_Fusarium.htm

 

http://vegetablemdonline.ppath.cornell.edu/factsheets/Potato_Detection.htm

 

http://cropwatch.unl.edu/web/potato/physiological_disorders

 

Check your soil to make sure it has the nutrients that potatoes need (not too much/not too little), and be sure that the crop has the proper amount of water, consistently. Consider environmental factors that might be coming into play, such as chemical damage from nearby areas, heat or cold stress, etc.