Apply 55 Ibs/A N along with recommended P
by either broadcast preplant incorporated or one half broadcast
and one half with the planter in bands placed 3 inches to 4
inches to each side and 1 inch to 2 inches below the seed
piece. Top dress or irrigate additional N when tubers begin
to form. Two top dress applications of nitrogen at 75 lbs. per
acre, then 70 Ibs. per acre each may be needed. Too much
nitrogen can be detrimental and decrease tuber quality, grade,
yield and slow down maturity. Soils having a high amount of
nitrate-N from previous fertilization, green-manure crops or
livestock manure will require less N fertilizer. Potassium sulfate
is preferred to potassium chloride as the potassium source
since skin color and speciﬁc gravity may be adversely affected
by potassium chloride.
Good water penetration and aeration are musts for
proper growth and tuber formation. Excessive tillage and land
preparation cause compaction and should be avoided. To be
effective, the soil should be plowed below any compacted
layer within the normal root zone, then disk harrowed before
planting. Spike-tooth harrowing to break up clods and level
the soil may be needed just prior to planting.
Seed and Planting
Use only certiﬁed seed tubers. Potato production costs
are too great to risk using non-certiﬁed seed. Certiﬁed seed
of good quality grown in the northern U.S. normally produces
the largest yields, the highest quality tubers and the fewest
disease problems. Pieces of large seed tubers are used for
planting. Small whole tubers can be used with equal results.
Seed pieces should be 1
ounces to 2 ounces in size. Using
smaller seed pieces usually results in lower yields. Cut seed
pieces can be suberized (healed over) before planting, but
planting fresh cut seed is a normal practice, since growers
usually lack the time and space to store large quantities of cut
seed before planting. Treatment of seed pieces with fungicides
may not always be necessary, as research has shown that
such applications are likely to increase yield only when the
cut seed pieces must be stored three or more days prior to
planting. Seed required to plant an acre depends upon seed
piece size and seed spacing (Table 3). Distance between rows
is commonly 36 inches.
Planting should begin in early March in central Oklaho-
ma and mid-March in northern Oklahoma to promote early
crop development and avoid extreme summer temperatures.
There are several types of planters available that place the
seed pieces in the soil and apply fertilizer and systemic in-
secticides in one operation. Seed depth should be about 4
inches below the top of the planted bed. Soil is ridged over
the row by throwing soil to the plants during early cultivation,
so about 6 inches of soil cover the seed piece when tuber
formation occurs. Depth for hilling differs among varieties.
Potatoes develop larger and more extensive root systems
in response to proper cultivation. Loose, friable soil improves
tuber set and development of smooth, well-shaped and
even-colored potatoes. Cultivation may be necessary to control
weeds, keep soil hilled-up, and aid water penetration and soil
aeration. Cultivate only when needed. Deep cultivation should
be avoided since many roots are damaged. Extra cultivations
are expensive, increase soil compaction and reduce yield.
Cultivation should be completed by the time plants reach full
Weeds must be controlled in potato ﬁelds, since they
compete with the crop for water, nutrients and light, and are
hosts for insects and diseases. Weed control can include
systems that utilize cultivation only, herbicides or a combina-
tion of cultivation and herbicides. An effective weed control
program takes into account problem weed species in the
ﬁeld. Fields containing perennial weeds should be avoided.
Herbicide selection will involve becoming familiar with labeled
herbicides for potato, understanding ﬁeld weed pressure and
what weed species the potential herbicide will need to control.
In addition, growers should understand how the herbicide will
be applied (i.e., pre-plant incorporated (PPI), preemergence
following planting (PRE), postemergence (POST), and after
crop emergence at drag-off or as a lay-by application). As
with all pesticide applications, make certain to read and
follow label instructions to ensure effectiveness, crop health
and applicator safety. Various herbicides can be applied by
ground rig or through the sprinkler irrigation system. For her-
bicide recommendations consult the most recent edition of
OSU Extension Agents’ Handbook of Insect, Plant Disease,
and Weed Control (E-832).
Soil moisture is probably the most important factor de-
termining potato yield and quality. Twenty or more inches of
water is required to produce a potato crop in central Oklahoma.
When irrigation is practiced to supplement rainfall, it should
be applied in frequent, but light amounts. Secondary growth
and growth cracks occur when irrigation or rainfall occurs
after moisture stress. Potato can be successfully grown using
several types of irrigation including overhead sprinkler, furrow
and drip irrigation systems. The soil should be kept uniformly
moist until tubers have reached full size. Considerations for
irrigation management decisions include: the effective rooting
depth of potatoes is 2 feet; soil should not be allowed to dry
below 65 percent of ﬁeld capacity; moisture levels above ﬁeld
capacity will seriously affect yield and quality of potato. On
extremely sandy soils, it is nearly impossible to prevent the
soil from drying below 65 percent of ﬁeld capacity, due to the
low water-holding capacity of sandy soil.
Potatoes should never be planted in ﬁelds that have been
in sod or grass the previous year. By avoiding this situation,
Table 3. Seed potatoes needed per acre.
Spacing for seed pieces Average seed piece weight
for 36 inch row centers 1 ½ oz 1 ¾ oz 2 oz
needed per acre)
8 inches between seed pieces 20.4 23.8 27.2
10 inches between seed pieces 16.3 19.0 21.8
12 inches between seed pieces 13.5 15.8 18.1