Mawk,
That would make sense, but....
Consequences just don't foster such logic.
Potato sprouts take a lot of energy out the seed piece. The result is a weaker plant. You want to use just enough of the energy of the seed piece to get the early emergence. Then the balance of the tuber juxtapositions with energy produced from the leaf/root complexes. Deep planting when the soil is cold will slow down the emergence of the potato plant. Weeds then get the jump. The idea is to plant it fairly shallow in the soil horizon where the soil temps are higher. The quick emergence and timely cultivation eliminates many weeds as they germinate and grow. The hilling up process after emergence allows the stolons and eventual tubers to form in cooler soil as the season warms up.
Planting too deep puts the tuber development in soil that hardens as time goes on. The idea is to have friable soil to tuberize in where there is ample oxygen to avoid swollen lenticels, etc., on the potato skin.
It is harder to dig potatoes when they are planted too deeply. You truly want a ridge or hill to dig from. That comes after one, two, or even three hillings. The tubers are not as liable to be mis-shapened as they would be in hard, cracked, or water-logged soil.
Potatoes that have to grow sprouts from 12 "(they can do it) have long distances between the nodes and the tubers will be produced up and down that long distance. The yields and timing of the potato maturities are not desirable. You want the potato to grow fast, develop the root system and have the stolons produced in a fairly tight area. Covering up these stolon shoots will force the synchronized tuberization and proper depth to provide the perfect horizon to mature them off, without worry of greening from being too shallow or rot from being too deep.
I could explain this much better if I had the time to organize my thoughts, but I hope you get part of the picture.
Tom Wagner
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