Using Gypsum to Increase Yield and Reduce Tuber Rot for White Potatoes in the Mid-Atlantic.

Calcium (Ca) and sulfur (S) may significantly impact white potato (Solanum tuberosum) tuber quality and yield in the Mid-Atlantic. A field trial was initiated on a Bojac sandy loam using ‘Superior’ white potatoes in summer 2010. Gypsum was applied at 1120, 2240, 3360, and 4480 kg ha^-1, giving effective S application rates of 188, 376, 564, and 753 kg S ha^-1 and Ca application rates of 252, 504, 756, and 1008 kg Ca ha^-1. Sulfur rates comparable to the gypsum application were also applied using elemental sulfur along with separate treatments of 0, 28, 56, and 112 kg S ha^-1. Soft rot (Erwinia carotovora ss. carotovora) and Pythium leak (Pythium sp.) occurred naturally in this trial causing tuber rots in the field. Potato tubers were harvested using a mechanized potato harvester and graded for marketability.  Gypsum applications reduced tuber rot in 2010 and 2011 and increased total marketable yield. Sulfur applications alone did not impact total yield, but S applications via gypsum did reduce tuber rot in 2011. This study will be repeated summer 2012 to determine if S and Ca fertilization will increase tuber yields and reduce tuber rots for potatoes grown in Mid-Atlantic sandy loam soils.