Bulletin 504 October 1952
UNIVERSITY OF FLORIDA
AGRICULTURAL EXPERIMENT STATIONS
WILLARD M. FIFIELD, Director
Effect of Liming and Fertilization on
Yield and the Correction of Nutritional
Leaf Roll of Irish Potatoes
G. M. VOLK and NATHAN GAMMON, JR.
Fig. 1.-A potato plant showing typical nutritional leaf roll.
Single copies free to Florida residents on request to
AGRICULTURAL EXPERIMENT STATION
BOARD OF CONTROL P. T. Dix Arnold, M.S.A., Asst. Dairy Husb.2
Leon Mull, Ph.D., Asso. Dairy Tech.
RH. H. Wilkowske, Ph.D., Asst. Dairy Tech.
Frank M. Harris, Chairman, St. Petersburg James M. Wing, M.S., Asst. Dairy Husb.
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Eli H. Fink, Jacksonville EDITORIAL
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EXECUTIVE STAFF ENTOMOLOGY
J. Hillis Miller, Ph.D., President3
J. Wayne Reitz, Ph.D., Provost for Agr.3 A. N. Tissot, Ph.D., Entomologist
Willard M. Fifield, M.S., Director L. C. Kuitert, Ph.D., Associate
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L. 0. Gratz, Ph.D., Assistant Director F. A. Robinson, M.S., Asst. Apiculturist
Rogers L. Bartley, B.S., Admin. Mgr.3 R. E. Waites, Ph.D., Asst. Entomologist
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Ouida D. Abbott, Ph.D., Home Econ.1
MAIN STATION, GAINESVILLE R. B. French, Ph.D., Biochemist
AGRICULTURAL ECONOMICS G. H. Blackmon, M.S.A., Horticulturist
H. G. Hamilton, Ph.D., Agr. Economist 3 F. S. Jamison, Ph.D., Horticulturist 3 4
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Zach Savage, M.S.A., Associate R. A. Dennison, Ph.D., Asso. Hort.
A. H. Spurlock, M.S.A., Associate R. H. Sharpe, M.S., Asso. Horticulturist
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M. R. Godwin, Ph.D., Associates R. D. Dickey, M.S.A., Asso. Hort.
H. W. Little, M.S., Assistant L. H. Halsey, M.S.A., Asst. Hort.
W. K. McPherson, M.S., Economist C. B. Hall, Ph.D., Asst. Horticulturist
Eric Thor, M.S., Asso. Agr. Economist Austin Griffiths, Jr., B.S., Asst. Hort.
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Orlando, Florida (Cooperative USDA) LIBRARY
G. Norman Rose, B.S., Asso. Agri. Economist Ida Keeling Cresap, Librarian
J. C. Townsend, Jr., B.S.A., Agricultural
Statistician 2 PLANT PATHOLOGY
J. B. Owens, B.S.A., Agr. Statistician
J. K. Lankford, B.S., Agr. Statistician W. B. Tisdale, Ph.D.. Plant Pathologist s
Phares Decker, Ph.D., Plant Pathologist
AGRICULTURAL ENGINEERING Erdman West, M.S., Mycologist and Botanist
Frazier Rogers, M.S.A., Agr. Engineer' Robert W. Earhart, Ph.D., Plant Path.2
Frazier Rogers, .S.A.., Agr. Engineer 1 Howard N. Miller, Ph.D., Asso. Plant Path.
J. M. Myers, B.S., Asso. Agr. Engineer Lillian E. Arnold, M.S., Asst. Botanist
J. S. Norto, M.S., Assot. Agr. Eng.neer C W. Anderson, Ph.D., Asst. Plant Path.
AGRONOMY N. R. Mehrhof, M.Agr., Poultry Husb.' S
Fred H. Hull, Ph.D., Agronomist 1 J. C. Driggers, Ph.D., Asso. Poultry Husb.
G. B. Killinger, Ph.D., Agronomist
H. C. Harris, Ph.D., Agronomist SOILS
R. W. Bledsoe, Ph.D., Agronomist F. B. Smith, Ph.D., Microbiologist 1
W. A. Carver, Ph.D., Associate Gaylord M. Volk, Ph.D., Soils Chemist
Darrel D. Morey, Ph.D., Associate 2 J. R. Neller, Ph.D., Soils Chemist
Fred A. Clark, M.S., Assistant2 Nathan Gammon, Jr., Ph.D., Soils Chemist
Myron C. Grennell, B.S.A.E., Assistant4 Ralph G. Leighty. B.S., Asst. Soil Surveyor'
E. S. Horner, Ph.D., Assistant G. D. Thornton, Ph.D., Asso. Microbiologist3
A. T. Wallace, Ph.D., Assistant 3 Charles F. Eno, Ph.D., Asst. Soils Micro-
D. E. McCloud, Ph.D., Assistant 3 biologist 4
H. E. Buckley, B.S.A., Assistant H. W. Winsor, B.S A., Assistant Chemist
E. C. Nutter, Ph.D., Asst. Agronomist R. E. Caldwell, M.S.A., Asst. Chemist 3
V. W. Carlisle, B.S., Asst. Soil Surveyor
ANIMAL HUSBANDRY AND NUTRITION J. H. Walker, M.S.A., Asst. Soil Surveyor
T. J. Cunha, Ph.D., An. Husb.1 S. N. Edson, M. S Asst. Soil Surveyor 3
G. K. Davis, Ph.D., Animal Nutritions William K. Robertson, Ph.D., Asst. Chemist
S. John Folks, Jr., M.., Asst. An. Hus. 0. E. Cruz, B.S.A., Asst. Soil Surveyor
. Katherine Bon, Jr., .S., Asst. CAnh W. G. Blue, Ph.D., Asst. Biochemist
A. M. Pearson, Ph.D., Asso. An. Hus. J. G. A. Fiskel, Ph.D., Asst. Biochemist
John P. easter, Ph.D. Asst. An. Nutri. H. F. Ross, B.S., Soils Microbiologist
H. D. Wallace, Ph.D., Asst. An. Husb. L. C. Hammond, Ph.D., Asst. Soil Physicist
M. Koger, Ph.. ..D., An. usad H L. Breland, Ph.D.. Asst. Soils Chem.
E. F. Johnston, M.S.. Asst. An. Husbandman VETERINARY SCIENCE
J. F. Hentges, Jr., Ph.D., Asst. An. Husb. D. A. Sanders, D.V.M., Veterinarian
M. W. Emmel, D'.V.M., Veterinarian 3
DAIRY SCIENCE C. F. Simpson, D.V.M., Asso. Veterinarian
E. L. Fouts, Ph.D, Dairy Tech.13 L. E. Swanson, D.V.M., Parasitologist
R. B. Becker, Ph.D., Dairy Husb.3 Glenn Van Ness, D.V.M., Asso. Poultry
S. P. Marshall, Ph.D., Asso. Dairy Husb.3 Pathologist
W. A. Krienke. M.S., Asso. Dairy Tech.3 W. R. Dennis. D.V.M.. Asst. Parasitologist
BRANCH STATIONS SUB-TROPICAL STATION, HOMESTEAD
Geo. D. Ruehle, Ph.D., Vice-Dir. in Charge
NORTH FLORIDA STATION, QUINCY D. Wolfenbarger, Ph.D., Entomologist
W. C. Rhoades, Jr., M.S., Entomologist in Francis B. Lincoln, Ph.D., Horticulturist
Charge Robert A. Conover, Ph.D.. Plant Path.
R. R. Kincaid, Ph.D., Plant Pathologist John L. Malcolm, Ph.D., Asso. Soils Chemist
L. G. Thompson, Jr., Ph.D., Soils Chemist R. W. Harkness, Ph.D., Asst. Chemist
W. H. Chapman, M.S., Asso. Agronomist R. Bruce Ledin, Ph.D., Asst. Hort.
Frank S. Baker, Jr., B.S., Asst. An. Hush. J. C. Noonan, M.S., Asst. Hort.
T. E. Webb, B.S.A., Asst. Agronomist M. H. Gallatin, B.S., Soil Conservationist
Frank E. Guthrie, Ph.D., Asst. Entomologist
Mobile Unit, Monticello WEST CENTRAL FLORIDA STATION,
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R. L. Smith, M.S., Associate Agronomist RANGE CATTLE STATION, ONA
Mobile Unit, Chipley
J. B. White, B.S.A., Associate Agronomist W. G. Kirk, Ph.D., Vice-Director in Charge
E. M. Hodges, Ph.D., Agronomist
CITRUS STATION, LAKE ALFRED D. W. Jones, M.S., Asst. Soil Technologist
A. F. Camp, Ph.D., Vice-Director in Charge
W. L. Thompson, B.S., Entomologist CENTRAL FLORIDA STATION, SANFORD
R. F. Suit, Ph.., Plant Pathologist R. W. Ruprecht, Ph.D., Vice-Dir. in Charge
E. P. Ducharme, Ph.D., Asso. Plant Path. J. W. Wilson, Sc.D., Entomologist
C. R. Stearns, Jr., B.S.A., Asso. Chemist P. J. Westgate, Ph.D., Asso. Hort.
J. W. Sites, Ph.D., Horticulturist Ben. Whiter, Jr., B.S.A., Asst. Short.
H. 0. Sterling, B.S., Asst. Horticulturist Geo. Swank, Jr., Ph.D., Asst. Plant Path.
H. J. Reitz, Ph.D., Horticulturist
Francine Fisher, M.S., Asst. Plant Path.
I. W. Wander, Ph.D., Soils Chemist WEST FLORIDA STATION, JAY
J. W. Kesterson, M.S., Asso. Chemist
R. Hendrickson, B.S., Asst. Chemist C. E. Hutton, Ph.D., Vice-Director in Charge
Ivan Stewart, Ph.D., Asst. Biochemist H. W. Lundy, B.S.A., Associate Agronomist
D. S. Prosser, Jr., B.S., Asst. Horticulturist W. R. Langford, Ph.D., Asst. Agronomist
R. W. Olsen, B.S., Biochemist
F. W. Wenzel, Jr., Ph.D., Chemist
Alvin H. Rouse, M.S., Asso. Chemist SUWANNEE VALLEY STATION,
H. W. Ford, Ph.D., Asst. Horticulturist LIVE OAK
L. C. Knorr, Ph.D., Asso. Histologist 4
R. M. Pratt, Ph.D., Asso. Ent.-Pathologist G. E. Ritchey, M.S., Agronomist in Charge
J. W. Davis, B.S.A., Asst. in Ent.-Path.
W. A. Simanton, Ph.D., Entomologist
E. J. Deszyck, Ph.D., Asso. Horticulturist GULF COAST STATION, BRADENTON
C. D. Leonard, Ph.D., Asso. Horticulturist
W. T. Long, M.S., Asst. Horticulturist E. L. Spencer, Ph.D., Soils Chemist in Charge
M. H. Muma, Ph.D., Asso. Entomologist E. G Kelsheimer, Ph.D., Entomologist
F. J. Reynolds, Ph.D., Asso. Hort. David G. A. Kelbert, Asso. Horticulturist
W. F. Spencer, Ph.D., Asst. Chem. Robert O. Magie, Ph.D., Plant Pathologist
I. H. Holtsberg, B.S.A., Asst. Ento.-Path. J. M. Walter, Ph.D., Plant Pathologist
K. G. Townsend, B.S.A., Asst. Ento.-Path. Donald S. Burgis, M.S.A., Asst. Hort.
J. B. Weeks, B.S., Asst. Entomologist C. M. Geraldson, Ph.D., Asst. Horticulturist
R. B. Johnson, M.S., Asst. Entomologist Amegda Jack, M.S., Asst. Soils Chemist
W. F. Newhall, Ph.D., Asst. Biochem.
W. F'. Grierson-Jackson, Ph.D., Asst. Chem.
Marion F. Oberbacher, Ph.D., Asst. Plant FIELD LABORATORIES
Evert J. Elvin, B.S., Asst. Horticulturist Watermelon, Grape, Pasture-Leesburg
Roger Patrick, Ph.D., Bacteriologist
Roger Patrick, Ph.D., Bacteriologist C. C. Helms, Jr., B.S., Asst. Agronomist
EVERGLADES STATION, BELLE GLADE L. H. Stover, Assistant in Horticulture
W. T. Forsee, Jr., Ph.D., Chemist Acting in Strawberry-Plant City
R. V. Allison, Ph.D., Fiber Technologist A. N. Brooks, Ph.D., Plant Pathologist
Thomas Bregger, Ph.D., Physiologist
J. W. Randolph, M.S., Agricultural Engr. Vegetables-Hastings
R. W. Kidder, M.S., Asso. Animal Husb. A. H. Eddins, Ph.D., Plant Path. in Charge
C. C. Seale, Associate Agronomist E. N. McCubbin, Ph.D., Horticulturist
N. Hayslip, B.S.A., Asso. Entomologist T. M. Dobrovsky, Ph.D., Asst. Entomologist
E. A. Wolf, M.S., Asst. Horticulturist
W. H. Thames, M.S., Asst. Entomologist Pecans-Monticello
W. N. S'oner, Ph.D., Asst. Plant Path.
W. A. Hills, M.S., Asso. Horticulturist A. M. Phillips, B.S., Asso. Entomologist 2
W. G. Genung, B.S.A., Asst. Entomologist John R. Large, M.S., Asso. Plant Path.
Frank V. Stevenson, M.S., Asso. Plant Path.
Robert J. Allen, Ph.D., Asst. Agronomist Frost Forecasting-Lakeland
V. E. Green, Ph.D., Asst. Agronomist
J. F. Darby, Ph.D., Asst. Plant Path. Warren O. Johnson, B.S., Meteorologist 2
H. L. Chapman, Jr., M.S.A., Asst. An. Husb.
Thos. G. Bowery, Ph.D., Asst. Entomologist
V. L. Guzman, Ph.D., Asst. Hort. 1 Head of Department
M. R. Bedsole, M.S.A.. Asst. Chem. 2 In cooperation with U. S.
J. C. Stephens. B.S., Drainage Engineer -
A. E. Kretschmer, Jr., Ph.D., Asst. Soils Cooperative, other divisions, U. of F.
Chem. 4 On leave
Fig. 2.-Potato plants suffering severe nutritional leaf roll usually have the
tubers set close to the stem.
Effect of Liming and Fertilization on
Yield and the Correction of Nutritional
Leaf Roll of Irish Potatoes
G. M. VOLK and NATHAN GAMMON, JR.1
A type of leaf roll of potatoes has occurred under certain
conditions in the Hastings area for the past several years. More
recently it has been noted in other areas of similar soils. Since
no disease producing entity has been found in connection with
this condition, it 'has become known as "nutritional leaf roll."
It should not be confused with the virus disease commonly knoin
as leaf roll.
Fig. 3.-A field showing severe nutritional leaf roll on old land.
1A. H. Eddins, Plant Pathologist in Charge, Potato Investigations
Laboratory, first brought this problem to the attention of the authors in
March of 1949, at which time he stated that the trouble was not due to a
fungus, bacterium or virus. Figures 1 and 3 were taken for the authors
by Dr. Eddins. The authors are indebted to the personnel of the Potato
Investigations Laboratory for valuable assistance throughout the work.
6 Florida Agricultural Experiment Stations
The major symptom of the trouble was a rolling upward and
inward of leaf sides toward the midrib (Fig. 1). Under very
severe conditions it sometimes appeared as cupping of the first
thick round leaves of the young plants and purpling of stems
and leaf veins, but usually the roll became most apparent about
blossom time (Fig. 3). Up to this time the field might have
appeared to be making normal growth. Severe leaf roll usually
was accompanied by a close setting of tubers on the stem (Fig.
2) and an abnormally low yield.
Examination of the soils on which the leaf roll occurred
showed that they were holding ammonia nitrogen abnormally
long after fertilization. This suggested that the soils were
limited in their ability to carry on nitrification, the process of
converting ammonia nitrogen to nitrate nitrogen. Laboratory
tests of nitrification rates verified this assumption. The soils
on which the leaf roll was severe were found to be very acid,
and either lighter than average or relatively new land. The
fertilizers being used where the trouble occurred usually con-
tained less than 1 percent nitrate nitrogen. At first it was
thought that high ammonia nitrogen in the soil was the major
cause of the leaf roll,2 but lowering the rate of application of
high ammonia fertilizer did not reduce the leaf roll. Increasing
the amount of nitrate nitrogen in the fertilizer did reduce or
eliminate the leaf roll. This indicated that an unbalance be-
tween ammonia and nitrate nitrogen available to the plant was
the probable cause of the trouble.
There are two ways in which this balance could be improved:
first by reducing soil acidity by liming, which in turn would
increase the rate of nitrification, and second by increasing the
proportion of nitrate nitrogen from the fertilizer. In order to
obtain data on this problem, field plot tests were conducted in
which the value of lime and nitrate nitrogen in preventing leaf
roll and increasing the yield of potatoes could be determined.
A certain amount of nitrogen in the form of Cyanamid, usually
2 A type of leaf roll has been observed in Florida also on two other
solonaceous crops, tomatoes and tobacco. This was observed by Fred Clark
and co-workers on tobacco in 1941, where high ammonia fertilizers had
been used, and on tomatoes following soil fumigation in 1948 by F. S.
Jamison and co-workers; but the significance of low nitrate nitrogen was
overlooked until March of 1950, when soil and plant tissue analyses in con-
nection with the study of leaf roll of potatoes showed a definite inverse
correlation between leaf roll and nitrate nitrogen content of the plant, but
no correlation with ammonia nitrogen. Correlations of leaf roll of tomatoes,
tobacco, peppers and eggplant with low nitrate nitrogen supply have been
reported by the senior author.
Correction of Nutritional Leaf Roll of Irish Potatoes 7
200 to 300 pounds, was being used in the area by plowing it
under with the cover crop, apparently with some beneficial re-
sults. Cyanamid contains both nitrogen and lime. Therefore
tests of the effect of plowing under nitrogen and lime separately
and in combination were included with the other studies in an
attempt to determine which portion of the Cyanamid was giving
the response and its relation to the leaf roll problem.
Field plots tests were made in the Bunnell and Hastings areas
for two seasons, 1950 and 1951, using 2,500 pounds of fertilizer
per acre. The fertilizer was made up to carry various propor-
tions of nitrate nitrogen and was applied to soils of different
pH values with and without liming.
There was a significant response to increases in nitrate nitro-
gen in the fertilizer on soils requiring lime. Table 1 presents
data from a 1950 test at Bunnell in which the south end of a
set of beds 1,100 feet long was strongly acid and had shown leaf
roll dn potatoes in 1949, while the north end was less acid and
had shown no leaf roll. This was relatively new land, first crop-
ped in 1948. The soil is St. Johns fine sand, well supplied with
organic matter, and potentially a very good soil for potatoes in
TABLE 1.-EFFECT OF SOIL PH ON RESPONSE OF POTATOES TO NITRATE
NITROGEN APPLIED IN 2,500 POUNDS OF FERTILIZER PER ACRE.
Source Yield in Bushels per
Pounds I Acre. pH Values Are
Treatment Nitrate | Approximate and
No. Nitrogen [ Units Relative
Applied Formula Nitrate pH 4.4 pH 4.9
Nitrogen (South) (North)
1 0 5-6-6 0.00 165 313
2* 19 6-8-8 .75 214 312
3 50 5-6-6 2.00 241 292
3-S** 50 5-6-6 2.00 241 331
"** Split application, 1,600 lbs. in drill and 900 lbs. at 59 days.
S All data were obtained on plots in which the drill application of fertil-
izer was the same for the length of the field for a given four-row plot.
Certain broadcast treatments were banded across a series of drill treat-
ments. For this reason some responses may appear only by combining
subtreatments, for example, the overall effect of lime. In no instance were
non-random subplots compared to each other.
8 Florida Agricultural Experiment Stations
Where the highest acidity existed (pH 4.4) the yields from
Treatments 2, 3 and 3-S were significantly 4 higher than from
Treatment 1, but yields in the south end were all much less than
where less acidity existed in the north end of the field (pH 4.9).
No significant differences between treatments existed at this
higher pH. Leaf roll was very obvious with Treatment 1 and
to some extent with Treatment 2 where the pH was 4.4, but
no leaf roll appeared in Treatments 3 or 3-S at pH 4.4 or in any
treatments at pH 4.9. It is of interest to note the difference in
yield where Treatment 3 was all applied at planting as compared
to the split application, 3-S, on soil at pH 4.9. Excessive leach-
ing of nitrate when all of the fertilizer was applied at time of
planting was the probable reason for the increase when part
of the fertilizer was withheld and applied later."
Certain of these treatments were repeated on this area in
1951. The soil pH apparently was rising with increasing age
under cultivation. It measured approximately 5.0 for the south
area which previously had been pH 4.4. Yields for the north
and south areas were approximately equal at over 400 bushels
per acre, regardless of nitrogen source, and no leaf roll was
present. There was no consistent increase in yield due to addi-
tion of dolomite, hydrated lime or "plow-under" Cyanamid or
Uramon where the pH was 5.0 or above and the full 2,500 pounds
of 5-6-6 fertilizer had been used.
Further evidence of the benefit of nitrate nitrogen on new
land was brought out by a grower's demonstration. A yield
check by the writers showed approximately 150 bushels per acre
for a high ammonia fertilizer, but 240 bushels where nitrate
was used to replace about half of the ammonia in a high ammonia
fertilizer. The potential of this soil, indicated by the adjoining
old land, was about 350 bushels, a condition similar in certain
respects to that already cited for the Bunnell tests. Leaf roll
was extreme and plants died very early where high ammonia
fertilizer was used on new land, but no leaf roll was present
and plants held up much longer where the nitrate nitrogen was
used (Fig. 4). Other extreme examples have been noted in
which severe leaf roll occurred on new land but not on old land
in the same field. Leaf roll has been noted also in land rebroken
after having been in meadow for several years.
L.S.D.-39 bushels at 5 percent point.
5 While it appears inconsistent that a similar difference did not show
up at pH 4.4, it has been noted in other tests, also, that potatoes under
poor fertility may mature too early to benefit from side-dressings applied
as in these tests.
Correction of Nutritional Leaf Roll of Irish Potatoes 9
Fig. 4.-Potatoes on new land. Left: Fifty percent of the nitrogen
from nitrate sources. Right: Ninety-four percent of the nitrogen from
ammonium sulfate. Background: Transverse band of lime.
Certain tests were made on old land in the vicinity of Hast-
ings. One series was on a highly variable area in the center
of which was a Leon fine sand white cap of pH 5.0, locally known
as a "sand soak" area. Such spots are relatively unproductive
because they consist of a sand very low in organic matter in
which it is difficult to maintain fertility or to irrigate properly.
Their occurrence is such that it may not be practical to avoid
them in planting, but returns from seed and fertilizer so used
are small. It is on these areas and on the type of soil usually
associated with them that leaf roll generally first appears and is
most severe in the Hastings area.
The 1950 tests showed that leaf roll was severe where no
nitrate was used in the 5-6-6 fertilizer, but where two-fifths of
10 Florida Agricultural Experiment Stations
the nitrogen was supplied as nitrate the leaf roll did not develop,
except to a limited extent on the very lightest of the soils
(Fig. 5). Soil analysis showed that nitrates were rapidly leached
from these light soils and indicated that side-dressings might
have been beneficial.
In the 1951 tests on this area part of the nitrate and potash
were withheld from the drill mixture and applied 50 days after
planting as 125 pounds of 13-0-44 nitrate of potash. Splitting
the fertilizer had no differential effect on leaf roll but gave a
yield of 225 bushels per acre, which was significantly more than
the 153 bushels obtained when all of the fertilizer was used at
planting. While these yields are very low, they do represent a
72 bushel increase obtained at an additional cost for side-dressing
alone, since other costs were already fixed by planting over the
area, regardless of productivity.
Fig. 5.-Left: 5-6-6 fertilizer with no nitrate nitrogen. Right: 5-6-6
fertilizer with two units of nitrogen from nitrate sources.
Correction of Nutritional Leaf Roll of Irish Potatoes 11
A similar light sandy area with an average pH of 5.3 was used
in 1952 to test various side-dressings on two different amounts
of fertilizer in the drill. Data are given in Table 2.
TABLE 2.-EFFECT OF SIDE-DRESSING ON YIELD OF POTATOES. 1952 TESTS.
I_______ Fertilization Yield
Treatment Pounds of Bushels
No. 5-7-5 at Pounds Side-Dressing per Acre
Planting* at 42 Days**
1 2,500 270, 13-0-44 Nitrate of Potash 321
2 1,800 270, 13-0-44 Nitrate of Potash 305
3 1,800 700, 5-7-5t ... .......... ..-- 283
4 2,500 80, Nugreen (urea) ...........- 271
5 2,500 None ........---- -.... ..... ...... -261
6 1,800 1 None .------------ -------------- 259
1.0%o nitrate nitrogen.
** 35 pounds of nitrogen applied in these side dressings.
SThis makes 2,500 pounds total 5-7-5 to this treatment.
Treatment 1 is significantly greater than 4 or 5.
Overall effect of nitrate of potash in Treatments 1 and 2, as compared
to 5 and 6, significant at odds of 1 to 99.
Side-dressing with 270 pounds of 13-0-44 nitrate of potash
gave an increase of 60 bushels per acre when following a 2,500-
pound application at planting. An equal nitrogen application
in the form of Nugreen (urea) did not produce any material
increase in yield. These data further substantiate the need for
side-dressing potatoes on light sandy soils for maximum yield.
No appreciable amount of leaf roll was apparent, probably be-
cause of a combination of favorable pH range and the 1 percent
nitrate nitrogen in the fertilizer used at planting. The economy
of side-dressing very light soils would, of course, depend on the
actual severity of the soil condition, the number of leaching
rains and the ability to supply moisture by irrigation during
A comprehensive set of tests was made in 1951 on another
field in the vicinity of Hastings on which the soil varied from
Bladen fine sand to Leon fine sand. The original soil pH aver-
aged 4.75. Various ratios of nitrate nitrogen to non-nitrate
nitrogen were used in a formula of 5-6-6 fertilizer at 2,500
pounds per acre on both limed and unlimed plots. Lime was
12 Florida Agricultural Experiment Stations
applied as hydrate at 650 pounds per acre. Leaf roll appeared
on the lightest soil of the test area only where a low nitrate
nitrogen fertilizer was used without lime.
The average yield increases due to increasing nitrate nitrogen
in the drill application were most marked where followed by
side-dressing. Apparently the higher nitrate in the drill gave
the plants a better start, but to show the real effect on yield it
was necessary to maintain growth with side-dressing. Yields
are given in Table 3.
TABLE 3.-EFFECT OF INCREASING PERCENTAGE OF NITRATE NITROGEN ON
YIELD OF POTATOES.*
With 125 lbs. of
Drill Percent Without 13-0-44 Nitrate
Treatment Nitrate Nitrogen Side-Dressing of Potash
in Fertilizer Side-Dressing
2,500 lbs. 0.48 335 bu. 339**
1.43 345 bu. 366**
1.92 355 bu. 383**
These data are average of limed and unlimed plots.
** Significant increase by regression on percentage of nitrate.
A general comparison of limed plots with unlimed plots showed
a significant increase of 37 bushels due to lime. There was a
significant increase of 32 bushels due to side-dressing if lime
was first applied.
In one comparison the high nitrate treatment was split to
put 1,900 pounds in the drill and 600 pounds on the side 58 days
after planting. The 1,900 pounds produced 307 bushels, but the
1,900 pounds plus 600 pounds of side-dressing of the same ma-
terial produced 384 bushels, showing that 1,900 pounds was not
sufficient fertilizer and that later application of the withheld
portion produced a marked increase over the 1,900 pounds in
The preceding data and general observations made during the
study bring out several important factors regarding the problem
of nutritional leaf roll.
1. Nutritional leaf roll apparently results when there is too
"There was some evidence in all areas that splitting the application
increased yields over putting all at time of planting, but data were not
sufficiently conclusive to justify changing present practices.
Correction of Nutritional Leaf Roll of Irish Potatoes 13
little nitrate nitrogen available to produce a healthy potato
2. New soils of the area in general, and older soils that are
strongly acid and lighter than average in texture, are inhibited
in their ability to produce nitrates from ammonia.
3. Liming strongly acid soils will increase nitrification and
help overcome leaf roll.
4. Lack of nitrate production from ammonia by the soil can
be partially offset by increasing the amount of nitrate nitrogen
applied to the crop:
5. Supplying about one-fifth of the fertilizer nitrogen from
nitrate sources apparently is adequate for good soil at the proper
pH value, if over three years under cultivation.
6. Very light soils may develop leaf roll even when the pH
is favorable and a high nitrate drill fertilizer used. Part of the
cause of low productivity of very light soils is their inability to
hold fertilizer elements, especially nitrate nitrogen.
It follows that nutritional Jeaf roll is a problem only on rela-
tively abnormal or marginal soils, i.e. sandy soils, very acid
soils, new lands and reclaimed meadows; and that the condition
can be readily corrected in all but very light sands simply by
proper liming and the use of increased amounts of nitrate nitro-
gen during the corrective period.' The use of high analysis fertil-
izers which usually cannot be made physiologically neutral s will
require added attention to soil pH, and periodic liming as indi-
cated by pH., Average fertilizers 'will develop enough acidity
to require Trom 200 to 300 pounds of ground limestone per year
unless this is offset by adding dolomite to the mixture, as is
possible with lower analysis materials. It is estimated that
1,000 pounds of lime would be needed every three to five years
to maintain soil pH under potato production.
General observations of the tests indicate that dolomite is
satisfactory for adjusting soil pH where it is not too far out of
line, but that a more active material such as high calcic lime or
hydrated lime should be used if nutritional leaf roll has been
present and rapid adjustment is desired.
SAnalysis of leaves from rolled and healthy plants for Ca, Mg, K, P, Na,
and Fe did not indicate that these elements were involved in the malnutri-
tion, but the possibility of significant interaction with NOs was not com-
pletely explored. Leaf roll appeared in the absence of chlorides, but
chlorides probably enhance the trouble when present in high quantity.
8 The potential acidity of the fertilizer is offset by addition of the proper
amount of dolomite filler.
14 Florida Agricultural Experiment Stations
A very significant characteristic of leaf roll is that plants in
a field so affected die much earlier than normal plants. Side-
dressing was not effective in the tests unless initial corrective
steps were taken, such as liming and using a high nitrate nitro-
gen fertilizer to establish a healthy plant. Low yields, on po-
tentially good soils carrying crops showing leaf roll, appeared
to be more the result of abnormally early maturity.
It should not be implied from the preceding tests that more
fertilizer in the drill would be beneficial. There is some evi-
dence that fertilizer injury would result in unfavorable years
if more than 2,500 pounds of 5-6-6 fertilizer or its equivalent
of other formulas is used in the drill, but soil analysis indicated
that residual accumulation of soluble salts from year to year
was not a factor.
Soil pH Determinations.-For old lands where leaf roll has
not been prevalent the soil pH should be determined in the fall
as soon as the summer cover crop is turned under. If nutri-
tional leaf roll has been prevalent or if new land is being cleared
determine the pH as soon as the spring crop is off or when the
new land is broken, and lime as soon as possible. Each type of
soil should be sampled separately by taking several plugs of
the surface six inches over the area and mixing them together
to make one sample. Several samples should be taken from
each field so as to be able to tell how much variation in pH exists.
Liming.-Maintain soil pH between 5.0 and 5.5. For average
soils of the Hastings and Bunnell areas use approximately 1,000
pounds of dolomite or high calcic limestone or 600 pounds of
hydrated lime if the pH is between 4.5 and 5.0. For pH values
below 4.5 use double these amounts. Proportionate amounts of
lime may be used on the basis of 200 pounds of ground limestone
or 120 pounds of hydrated lime for each 0.1 pH below 5.5.
pH values determined immediately following removal of the
crop in the spring maybe from 0.2 to 0.5 pH lower than those
determined in the fall, but the larger amount of lime indicated
as necessary by spring values should be beneficial where nutri-
tional leaf roll has been observed. For rapid pH adjustment on
new land, or where leaf roll has been observed, high calcic lime
or hydrated lime is recommended because of the faster reaction
with the soil. Otherwise dolomite is preferred because of the
magnesium it carries.
Correction of Nutritional Leaf Roll of Irish Potatoes 15
Nitrogen Fertilization.-For normal conditions where old land
has been in potatoes and no leaf roll was apparent on the pre-
vious crop, approximately one-fifth of the nitrogen should be
from nitrate sources. This should be adequate protection against
a dry year or cold season when nitrification in the soil may be
For all new lands which have carried less than three crops;
for any area showing nutritional leaf roll the previous year; and
for any land of pH 4.5 or below with unknown leaf roll history;
it is recommended that one-third of the nitrogen be from nitrate
and that the crop be side-dressed with approximately 120 pounds
of nitrate of soda or its equivalent per acre when blossom buds
appear, or in the period 40 to 60 days after planting, depending
on how much heavy leaching rainfall has occurred.
The writers wish to thank the following who furnished in part the
facilities for research on nutritional leaf roll of potatoes: Miles Potato
Corporation; Hastings Potato Growers Association; and Michael Steflik,
Bunnell. Many valuable suggestions based on practical experience were
made by J. B. McCallum, Hastings. The authors are indebted to S. M.
Burrell, laboratory assistant, Potato Investigations Laboratory; P. R.
McMullen, St. Johns County Agricultural Agent; and H. E. Maltby, Putnam
County Agricultural Agent; for general field observations and the collection
of soil samples which helped to determine the extent of the problem; and
to the various fertilizer companies who gave the authors the benefit of
their observations and made the special formulas required in the study.