(Revised August 1936)
The Fall Crop of Irish Potatoes
THE fall crop 
of Irish potatoes 
is more difficult 
to grow than
the spring crop, and yields are generally much lower. There
are also certain factors operating to make the fall crop less
certain than the spring crop. It is more difficult to obtain stands
from summer-planted than from spring-planted potatoes; tem-
peratures and rainfall during the growing period are often un-
satisfactory; and many soils are not moist enough in late summer
and fall to produce a good yield. There are, however, many
farms where seed potatoes are available from thespring crop,
where a small area of moist, well-drained bottom land is avail-
able, and where there is sufficient straw to permit mulching of
the crop. On such farms, a fall crop of potatoes may be planted
each year with a reasonable assurance of a yield sufficient to
justify planting. With a good stand and favorable seasons, high
yields may be obtained. On farms where seed potatoes must
be bought, where only dry upland soil is available, and where
mulching cannot be practiced, the growing of a fall crop of
potatoes is too uncertain to be generally recommended. There
are many farms between these two extremes where the advis-
ability of attempting to grow a fall potato crop will depend upon
the individual circumstances. It is of fundamental importance
that the potatoes used as seed be ready to sprout when planted
and that they be placed in a soil which is cool and moist enough
to insure favorable conditions for sprouting of the potatoes and
growth of the young plants.
WHY POTATOES FAIL TO SPROUT
To be certain that the potatoes, or the tubers, are in condition
to sprout when planted, it is necessary to understand something
about their characteristics. Potato tubers after maturity always
pass through what is called a "rest period". This rest period is
nature's provision for making certain that the potato will per-
petuate itself through future years. Until the rest period is
broken, the tubers will not sprout. In nature a crop of pota-
toes is produced one year, the tubers pass the winter in a resting
or dormant condition, and sprout in the spring. So fixed is this
cycle that a tuber is not easily induced to behave differently.
However, there are conditions or treatments which affect the
the length of the rest period. Cold, heat, wounds, and certain
AGRICULTURAL EXPERIMENT STATION
OF THE
ALABAMA POLYTECHNIC INSTITUTE
M. J. FUNCHESS, Director
AUBURN
LEAFLET No.11 OCTOBER 1934
chemicals have been known to shorten the rest period. Nature
makes use of cold or low temperatures to break the dormancy of
the potato; winter does this in a natural way. It has been known
for some time that the rest period of potatoes may be artificially
broken by placing them in a temperature of 320 F for about one
month. Various chemicals, such as potassium thiocyanate, ether,
and ethylene chlorhydrin have been used to break the rest period
and hasten sprouting. Some of these treatments are being used
in a practical way on many farms today. Cutting potatoes into
pieces, or removing a portion of the peel, materially hastens sprout-
ing.
There are several ways of handling the spring crop to shorten
the rest period and hasten sprouting. Satisfactory results have
been obtained at Auburn by placing potatoes in cold storage at
350 to 400 F. for about one month and then storing them in a
ground cellar until planting time. Potatoes may be stored in a
damp cellar or under the house for about one month, and later
placed for one month in an attic, where the temperature at noon
reaches about 1000 to 1100 F. In the central and southern part
of the state, certain varieties stored on straw in the shade of trees
have generally completed their rest period by planting time and
are ready to sprout without further treatment. In the northern
part of the state, where there is only a short period between the
harvest of the spring crop and planting of the fall crop, potatoes
have been cut into seed pieces, dipped for one minute in an ethy-
lene chlorhydrin solution (1 pint ethylene chlorhydrin to4 gal-
lons of water), placed in a tightly closed container in a cool place
for 24 hours, or in some instances overnight only, and then planted.
This treatment in some cases has been satisfactory in the northern
part of the state. In the central and southern parts of Alabama a
poorer stand and lower yields have consistently resulted from the
use of the ethylene chlorhydrin treatment.
VARIETIES AND SOURCES OF SEED
Four sources of seed for the fall crop have been used in Ala-
bama. They are: first, the northern-grown main crop which has
been carried in cold storage until planting time;-second, the f all-
grown crop of Virginia, also carried over in cold storage; third,
the early Florida, or South Alabama, spring-grown crop; and
fourth, the local-grown spring crop. Certain seed-dealers are
prepared to supply Cobblers, Triumphs, and Green Mountains
from the northern-grown main-crop and also Triumphs from
the Virginia fall-grown crop. Many seed potatoes in Alabama
have been purchased from the Florida early spring crop, the
Rose No. 4 being the variety most generally used. Local-grown
spring seed, however, constitutes the largest source of seed for
the fall crop. This is logical since many small potatoes are
available from the spring crop, and since more potatoes are often
produced in the spring than will be consumed before sprouting
3
occurs in the fall. Fall-grown potatoes can, therefore, be plant-
ed from the spring-grown crop without cost of purchased seed.
The larger part of the spring-grown potatoes in Alabama con-
sists of the Triumph and Cobbler varieties. Of these two va-
rieties, the Triumph has a shorter rest period, will generally give
a better stand when planted during the summer, and also will
produce a higher yield of fall potatoes than the Cobbler.
Results of experiments comparing each of the different sources
of potatoes mentioned above have shown that local spring-grown
Triumphs are as satisfactory as any other potato; this suggests
that they should be used for the fall crop if available. Besides
Triumphs fair yields have been obtained at Auburn from the fol-
lowing varieties and sources of seed potatoes: Florida spring-
grown Rose No. 4, local spring-grown Green Mountain, Virginia
fall-grown Triumphs, and northern-grown Green Mountain.
PLANTING DATE
There is nothing to be gained by planting potatoes so early
that the growing plants are subjected to the high temperatures
of summer or early fall. Favorable soil moisture and cool weather
make for high yields of potatoes. If tubers are being formed
during periods of drouth and during periods of high temperature,
low yields will generally follow. The seed should be planted so
that the plants are up to a stand approximately 8 to 10 weeks
before frost.
Potatoes should be planted in North Alabama from 15th of
July to the first of August and in middle and South Alabama from
1st to 15th of August.
SITE, CULTURE, AND FERTILIZER
A moist, but well drained, bottom land is ideal for fall pota-
toes. Mulching with three or four inches of straw keeps the soil
cool, helps maintain a favorable level of soil moisture, and greatly
increases the yield. To obtain the best results with the fall crop
of potatoes, especially in the central and southern portions of the
state, a well-drained, moist bottom land should be selected and
the area mulched with straw. It is not as necessary to mulch in
North Alabama nor is it as necessary to plant on bottom land in
this section of the state, as it is in the other sections. Failures
with the fall crop of potatoes are less frequent in North Alabama
than in other sections, due apparently to more favorable climatic
conditions.
If the spring crop which preceded the fall potato crop re-
ceived 800 to 1,000 pounds per acre of a complete fertilizer, it is
not necessary to add more potash or superphosphate; an applica-
tion of 150 pounds per acre of ammonium sulphate, should, how-
ever, be applied at planting time. If no fertilizers have been
added during the spring, then 800 pounds of a fertilizer analyzing
4
approximately 4-10-7 should be carefully worked into the soil, or
applied in two bands about two or three inches to the side of the
seed, and the soil so turned in covering the potatoes that there
is a minimum amount of contact of fertilizer with the seed.
EXPERIMENTAL RESULTS
In Table 1 are given the yields by years of fall potatoes from
spring-grown seed stored in different ways. It should be espe-
cially noted what wide differences in yields have been obtained in
different years; this shows to what extent favorable seasons af-
fect yields. Moist conditions during part of the storage period
seem necessary for good sprouting. Sprouting has been satis-
factory with potatoes stored from harvest to planting time in a
cool moist cellar or with potatoes stored 6 weeks in a moist cel-
lar and 3 to 4 weeks in a warm attic. Potatoes dug less than 8
weeks before planting time will be benefited by 3 weeks storage
at 35 degrees. Sprouting has been poor where potatoes have been
stored continuously from harvest to planting time under warm,
dry conditions.
TABLE 1.-Yield of Fall Potatoes from Seed Stored in Different Ways.
Storage condition 
Yield in bushels 
per acre by 
years*
1932 1933 1934 1935
Cellar 238 26 212 61
Under greenhouse bench 39 229 61
Cellar 6 weeks-attic 1 month 34 252
Barn -- 30
*Potatoes planted approximately August 10 on moist bottom land and mulched.
In Table 2 are given the yields of potatoes in 1932 from cer-
tain treatments. It may be seen that ethylene chlorhydrin reduced
the yield on mulched plots located on bottom land 94 bushels per
acre; it may also be seen, with untreated seed, that mulching
gave an increased yield of 107 bushels on bottom land, and that
the yield of potatoes was 66 bushels higher on bottom land than
on upland.
TABLE 2.-Yield of Potatoes from Local-Grown Triumph Potatoes-1932.
Location 
Cultural 
treatment 
Yields in 
bushels per 
acre
Treated* Untreated
Mulched 144 238
Bottom land Unmulched 113 131
Upland Unmulched 26 65
*Potatoes cut and dipped in solution containing 1 pint of ethylene chlorhydrin to 4 gal-
lons of water and then stored 24 hours in a closed container.
DEPARTMENT OF HORTICULTURE AND FORESTRY