Factors Affecting Specific Gravity of Potatoes

Nitrogen

Chlorides

Some work has shown an association between chloride (Cl) application and decreased specific gravity. However, other literature indicates that potatoes are more sensitive than many crops to shortages of chloride. Producers who suspect that excessive chlorides may be a problem should consider using potassium sulfate vs. potassium chloride for K2O.

Water

Excess or insufficient soil moisture can lower specific gravity. Optimum moisture availability as tubers approach maturity can increase specific gravity.

Harvest

Vine kill at peak physiological maturity increases specific gravity, and killing vines slowly with chemicals increases specific gravity compared to a quick kill by physical means.

Planting Date

Short day lengths during tuber formation contribute to higher specific gravity, so adjusting planting dates to take advantage of this can be beneficial.

Calcium

While high levels of available Calcium (Ca) has not been proven to directly affect the specific gravity of potatoes, it has been shown to play a major role in improving several other "quality" factors in potatoes. Calcium is a structural component of cell walls. Adequate Ca, therefore, contributes to the structural integrity of plant cells. Potatoes low in Ca will have an increased susceptibility to internal brown spot and soft rot disease in tubers. In the studies where additional Ca reduced these problems, gypsum was applied at rates of 500 and 750 lb./acre in the root zone. High levels of available Ca has also been shown to improve potato skin-set.