Potatoes make their best growth when they are planted in a deep, well-prepared, mellow type of seedbed. Good potatoes seedbed preparation reduces weed growth and assures good stands. Inasmuch as potatoes usually follow sod or green-manure crops, plowing is necessary as the first step in seedbed preparation for potatoes. Deep plowing is usually practiced. Plowing 6 to 7 inches deep is common; and at times the deeper, heavier soils are plowed to a depth of 10 inches. Fall plowing is generally practiced on heavier types of soil or when green-manure crops or residues of hay or pasture crops are being plowed under. Plowing at the time provides more time for the organic matter to decay and for the nutrients which it contains to become available for use by the potatoes. On the lighter soils or on soils that are subject to erosion, spring plowing is common. Spring plowing should be done two or three weeks or more before planting seed potatoes, to allow as much time as possible for the organic matter to decay.
With tough hay or pasture sods, it is often good practice to work the field first with a field cultivator or other tillage implements. This practice is effective in destroying perennial weeds such as quack grass, and in assuring easier and better tillage later on. Such treatment is particularly desirable if a dense, heavy sod is plowed in the spring. Another procedure that is effective with tough sods is to plow both In the fall, a depth of 3 inches being common. This practice, which is called crowning, is often used on alfalfa sods in some of the irrigated areas of the western states. The land is the worked shallowly in the late fall or early spring to destroy existing plants and replowed at normal depths sufficiently early in the spring to provide enough time for the other tillage operations that are required to prepare a good potatoes seedbed.
In the spring, the soil should be worked sufficiently well to destroy as many weeds as possible and to provide a deep, moderately firm, mellow potato seedbed. This is usually accomplished by disking first and then following with a spring tooth harrow or field cultivator. If the soil remains lumpy, a cultipacker or spike tooth harrow should be used before planting.