Nitrogen
- Excess N or high tissue N, in relation to other nutrients (out of balance) c
an lower specific gravity.
- High available soil N at, or just prior to tuber set, can lower specific gravity
Chlorides
Some work has shown an association between chloride (Cl) application and decreas
ed specific gravity. However, other literature indicates that potatoes are more
sensitive than many crops to shortages of chloride. Producers who suspect that e
xcessive chlorides may be a problem should consider using potassium sulfate vs.
potassium chloride for K
2O.
Water
Excess or insufficient soil moisture can lower specific gravity. Optimum moistur
e 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 affe
ct the specific gravity of potatoes, it has been shown to play a major role in i
mproving several other "quality" factors in potatoes. Calcium is a structural co
mponent of cell walls. Adequate Ca, therefore, contributes to the structural int
egrity 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 addi
tional 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 impro
ve potato skin-set.
