Cornell: 4.8 to 5.5 Cornell University: Growing Guide -- Potatoes Cornell University: Potatoes Cornell University: Potatoes http://www.gardening.cornell.edu/homega ... ec6be.html Cornell University Growing Guide: Potatoes Cornell University: Potatoes Cornell University: Potatoes http://www.gardening.cornell.edu/homega ... ec6be.html Cornell University: Potatoes Cornell University Extension: Potatoes