Earthing up potatoes causes formation considerable quantity of root runners. Root runners are underground stalks on which new potato tubers develop. Along with it at Earthing up the soil crust collapses, the air flow to roots amplifies.
It is necessary to mean, that earthing up only then will benefit, when the soil is damp (after watering or a rain). Otherwise this procedure does to potato plants harm. To condense soil at earthing up does not follow.
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