to grow upon a spot of ground where only one grew before,
would deserve better of mankind and do more essertial
service to his country than the whole race of politicians together.
--Anonymous
Potatoes do best in deep, well-drained soils ranging in texture from silt loams through sands. Loose, coarse soils are desirable for potatoes not only because of yield advantages but also because of improved quality. Tubers of some varieties, such as Russet Burbank, are highly susceptible to deformation because of mechanical restrictions in heavy or rocky soils. Good drainage is especially desirable for potatoes because of high tuber susceptibility to disease-causing bacteria and fungi. Bacterial soft rot and pink water rot ( Pest Management; UC IPM Home Page ; Online Guide to Plant Disease Control (Oregon)) can lead to high losses in wet conditions.
Potatoes do not require an extremely smooth seed bed. In fact, over-preparing the soil is far more damaging than underpreparation. Loss of soil structure through repeated tillage can lead to severe crusting after heavy rains. Crusting tends to maintain high soil moisture at the expense of oxygen. Potato seedpieces tend to suffocate under such low-oxygen conditions while bacteria thrive. Seedpiece decay can be rampant and stand losses can exceed 50%. A loose, relatively coarse surface is recommended wherever wet conditions are probable.
Field preparation for planting may involve application of fertilizers, herbicides, insecticides or fumigants depending on local needs and customs. Materials for control of wireworms (Lorsban, Dyfonate, Mocap, Diazinon) and other soil insects are typically applied pre-plant ( see pest management sections of this web page). Further descriptions for these practices will be provided under pertinent headings below.
Potatoes benefit considerably from long rotations and the use of cover crops to improve soil tilth. The soilborne fungus Verticillium (see Verticillium wilt) builds up in direct proportion to the frequency of cropping with susceptible species, especially potatoes. It can eventually reduce yields by as much as 25% in susceptible varieties such as Russet Norkotah. To reduce damage from Verticillium and other problems, a rotation involving three years of resistant species between potato crops is recommended. Most legumes, cereals and grasses and some crucifers make excellent rotation/cover crops for potatoes (Pest Management). By the same token, eggplant, tomato, pepper, strawberry, and cane berries are not desirable in a potato rotation. See the following links for additional information on common potato cover/rotation crops.
Field
Preparation
Fertilization
and Liming
Weed
Control
Production
Organic
Farming
Potatoes,
General
In Oregon, seedpiece spacing ranges from 9 to 12 inches in 34-inch rows. Ideal plant spacing depends on a number of factors including variety, local growing conditions, and even seed physiological age. Because physiologically old seed has less apical dominance, it tends to produce more stems and tubers but smaller average tuber size. To compensate for this tendency, "old" seed should be planted farther apart to reduce the stem and tuber population. Likewise, varieties which tend to produce small tubers benefit from wider spacing. Single-drop seed (small, uncut tubers) typically produce more stems and tubers than an average seedpiece and should be planted at lower populations. Single-drop tubers typically are extremely resistant to bacterial decay, further increasing stem and tuber counts and the need for wide spacing.
Planting depth varies from 2 to 6 inches below the surrounding soil level. Shallow planting favors early emergence but also causes tubers to set relatively shallow and be more susceptible to sungreening (and late blight tuber decay?). Some growers achieve early emergence by covering seedpieces shallowly in deep furrows. The furrows are then gradually filled in during tillage and hilling operations to maintain good tuber depth.
Deep planting, or even shallow planting in deep furrows, can be hazardous on heavy, wet soils. Rapid emergence is the best guarantee of plant survival in most wet situations. Plant survival is sometimes viewed as a race between seedpiece decay and sprout growth and emergence. An emerged plant typically has sufficient root and foliage reserves to survive without the seedpiece. However, bacterial decay organisms can move from the seedpiece into the base of the plant causing weakness and possibly even death.
As noted earlier, potatoes are planted from early March through mid June in Oregon. Low elevation, coarse soil texture, and low spring rainfall all favor early planting. Consequently, earliest plantings typically occur in the Columbia Basin while long delays are frequently experienced in areas such as the Klamath basin because of low temperatures and in the Willamette Valley due to prolonged spring rains and heavy soils. Early planting is especially desirable for early fresh market and from-the-field processing of chips and frozen fries. Crops harvested in early July in the Columbia Basin, and on some sandy sites in the Willamette Valley, are typically planted in March or very early April.