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 Introduction
 Conditions common to the two...
 The phosphate experiment
 The potash experiment
 Extension of experiments
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Group Title: Bulletin - University of Florida. Agricultural Experiment Station ; 158
Title: Fertilizing the Irish potato crop
CITATION THUMBNAILS PAGE IMAGE ZOOMABLE
Full Citation
STANDARD VIEW MARC VIEW
Permanent Link: http://ufdc.ufl.edu/UF00027427/00001
 Material Information
Title: Fertilizing the Irish potato crop
Series Title: Bulletin University of Florida. Agricultural Experiment Station
Physical Description: 28 p. : ; 23 cm.
Language: English
Creator: Floyd, B. F ( Bayard F )
Ruprecht, R. W ( Rudolf William ), b. 1889
Publisher: University of Florida Agricultural Experiment Station
Place of Publication: Gainesville Fla
Publication Date: 1920
 Subjects
Subject: Potatoes -- Fertilizers -- Florida   ( lcsh )
Genre: government publication (state, provincial, terriorial, dependent)   ( marcgt )
non-fiction   ( marcgt )
 Notes
Statement of Responsibility: by Bayard F. Floyd and R.W. Ruprecht.
General Note: Cover title.
 Record Information
Bibliographic ID: UF00027427
Volume ID: VID00001
Source Institution: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: aleph - 000922789
oclc - 18171104
notis - AEN3298

Table of Contents
    Title Page
        Page 1
    Table of Contents
        Page 2
    Introduction
        Page 3
        Page 4
    Conditions common to the two experiments
        Page 5
        Page 6
        Page 7
        Page 8
    The phosphate experiment
        Page 9
        Page 10
        Page 11
        Page 12
        Page 13
        Page 14
    The potash experiment
        Page 15
        Page 16
        Page 17
        Page 18
        Page 19
        Page 20
        Page 21
    Extension of experiments
        Page 22
        Page 23
        Page 24
        Page 25
        Page 26
    Resume
        Page 27
        Page 28
Full Text

November, 1920


UNIVERSITY OF FLORIDA

Agricultural Experiment Station




FERTILIZING THE IRISH POTATO

CROP

By
BAYARD F. FLOYD and R. W. RUPRECHT


Fig. 1.-No phosphate in foreground, acid phosphate in background.
See page 14.


Bulletins will be sent free upon application to Experiment Station,
GAINESVILLE, FLORIDA


Bulletin 158

















CONTENTS
PAGE
* INTRODUCTION ................... ..... ............. 3

CONDITIONS COMMON TO THE TWO EXPERIMENTS............................................ 5
Weather Conditions ......--............- ---.--------- ...... 6
Harvesting and Grading........................ ----------.... --- 7
Fertilizers U sed ............................................................ ... 8
Manner of Applying Fertilizers.............................----------- 8
P lots ............................................. 8

THE PHOSPHATE EXPERIMENT-----..................... ------------------------- 9
Results in 1918, 1919, 1920..--------....................---------......... 9
Growth of the Plants............................................................... 12
Influence of Fertilizers on Succeeding Crops-.......-.................-........... 14

THE POTASH EXPERIMENT....................---............................---------- 15
R results ..................................... .. .... ........... 19
Influence Upon Growth of Tops.......................------------------ 19
Symptoms of Potash Starvation..... ..............----------------- 20
Succeeding Crops ............................................................. 21
Greenhouse Experiments ........................................ .................. .. 21

EXTENSION OF EXPERIMENTS......................... ------ -------. 22
Extension of Phosphate Experiments--................ .................... 22
R results ................................................................ 24
Extension of Potash Experiments................................ .....------. 25
Influence of Residual Potash on 1919 and 1920 Crops.................. 27

RESUME ....... --.............--------------------................... 27
Conclusions .................------------------------- 28









FERTILIZING THE IRISH POTATO CROP
By BAYARD F. FLOYD and R. W. RUPRECHT
Florida is peculiar in that it grows a wide variety of crops,
and in that each of these is grown largely around certain centers
where they form the chief cash crops for those communities.
The conditions governing the locations are, character of soil and
subsoil, presence of flowing artesian water, freedom from cold,
and others.
The Irish or white potato is grown largely in the Hastings
section, which includes adjoining parts of St. Johns and Putnam
Counties. The acreage in this section varies from year to year.
In 1918 the total potato area in the state was about 35,000 acres,
of which approximately 13,000 acres were included in the Hast-
ings district. Other important potato centers are near Kissim-
mee, Moore Haven, Miami and Plant City. Small plantings are
made thruout the state.
Outside the section bordering Lake Okeechobee, the potatoes
are planted largely upon sandy loam soil of the type known
locally as flatwoods soil. In the Hastings district the soil is
underlain at an average depth of one to three feet by a rather
heavy sandy clay subsoil.
This subsoil affords a particular advantage in that it allows
a cheap form of sub-irrigation. At times, when the crops are in
need of moisture, the water from artesian wells is run onto the
land. In most of the district these wells are easily obtainable at
a depth of 200 feet or more. The water spreads from the ditches,
covering the top of the subsoil from whence it rises by capillary
attraction to the loamy soils above.
The sandy loam soils in the Hastings section and other sec-
tions are lacking in humus and particularly in the elements of
fertility, ammonia, phosphoric acid and potash. The following
is an analysis of a sample collected in part of the experimental
field receiving no fertilizer. The sample was collected in a low
area and is probably more fertile than the higher soils.
Ammonia ..-......-...................-........ .107 percent
Phosphoric acid ............-------............ .027 percent
Potash .............................-........-- .048 percent

(Note:-The experiments herein reported were planned and conducted
by B. F. Floyd until May 1, 1920, when R. W. Ruprecht took charge.)





Florida Agricultural Experiment Station


For the successful growing of potatoes on a commercial
scale, long practice has proven it necessary to' increase the
amounts of these plant food elements in the soil by the application
of commercial fertilizers. While this is a well established fact,
there is much difference of opinion and a lack of exact informa-
tion concerning what sources of these elements to use in making
up the fertilizers, what formulas to use, and what elements to
apply for the most profitable crop production.
Before the World War sources of potash fertilizers were
plentiful and cheap, and they were used more or less liberally.
But after the beginning of the war, when they became scarce and
expensive, there was much questioning of the profitableness of
their use. Many growers and farmers omitted them entirely
from their fertilizers; others used them sparingly; and no one
used them liberally.
During the first year of the scarcity there was much specu-
lation concerning the effects of the omission or reduction of pot-
ash in the fertilizers. At the end of the year when no detri-
mental effects were seen, many were of the opinion that it was
present in the soil in sufficient quantities for good crop produc-
tion and doubted the profitableness of using potash in their
fertilizers. Later, however, differences in yield and carrying
qualities of the crops caused some to question this conclusion.
Logically, the farmers and fruit growers of Florida looked
to their agricultural experiment station for answers to the many
questions concerning this situation. Unfortunately it had not
been possible to carry out experiments to obtain this infor-
mation.
In the fall of 1917, thru the efforts of the late J. A.
Stevens of DeLand, a cooperative arrangement was perfected
between F. M. Leonard & Co. of Boston, Mass., and the Florida
Agricultural Experiment Station to carry out some fertilizer
experiments with Irish potatoes on the plantation of the former
at Hastings, Florida, to obtain information that would answer
some of these questions.
Two experiments were outlined in the spring of 1918. The
purpose of one was to study the results to be obtained from the
use of raw Florida phosphate and of acid phosphate as sources
of phosphoric acid in fertilizers for Irish potatoes, as compared
with those obtained where no phosphate was used. The purpose
of the otherwas to study the results to be obtained from the use
of fertilizers containing various percentages of potash in com-






Bulletin 158, Fertilizing the Irish Potato Crop


prison with those obtained where no potash was used. Both
experiments were to be carried out on virgin land that had never
received any fertilizer.

NS IN s 1/7. 37.K 51, IT511. ?A

t S -N R S N 33 /f 57,H7oI 3// 7o/ 57.o1/

N A S iN A o5%K 1%H 57 57. K 1f7K

5 N A s H 37K/< 5 7.K n 371%K

: N A f IS N 73%o 5 %/ //A 37.1o 57.o/

Fig. 2.-Plan of Experiment Plots
A=Acid Phosphate 1%K=1% Potash
S=Soft Phosphate 3%K=3% Potash
N=Pebble Phosphate 5%K=5% Potash
Blank Left Side=No Phosphate Blank Right Side=No Potash

CONDITIONS COMMON TO THE TWO EXPERIMENTS
The experiments were carried out on the Leonard plantation
at Hastings, Florida, on a 10-acre tract, forming part of a 60-
acre field, all of which was planted in potatoes. Figure 2 shows
the arrangement of the plots. At the beginning of the experi-
ment in the spring of 1918, the land was virgin and newly cleared,
never having received any fertilizer. The soil was a sandy loam
underlain at a depth of from one to three feet by a sandy clay.
The lay of the land was practically level. There were, how-
ever, sufficient variations to cause some scattering low spots in
the field where the plants were sufficiently injured during heavy
rains to reduce the yield. This injury, however, was kept at a
minimum by the digging of shallow ditches to drain these areas
when necessary.
The potatoes were planted in east and west rows or mounds
on the beds. There were ten rows on each bed during the sea-
son of 1918, and nine during 1919. The number of rows to each
bed was reduced in 1919 in order to make higher mounds.
This was made necessary on account of heavy rains at the
beginning of the season.
The beds were separated by shallow ditches that connected
on the west end of the field with an irrigation ditch and at the
east end of the field with a drainage ditch.






Florida Agricultural Experiment Station


An artesian well was located on the west side of the field
and provided irrigation water when necessary.
Spaulding Rose No. 4 potatoes obtained from Maine were
used for planting. The following table shows the time of fer-
tilizing, planting and harvesting during the respective seasons:

TABLE 1.-TIME OF FERTILIZING, PLANTING AND HARVESTING IN
1918, 1919, AND 1920
Practice Acre Rate 1918 1919 1920
Soft Phosphate
applied.................... 1,570 lbs. Dec. 6, 1917 Jan 1, 1918 Dec. 22, 1919
Pebble Phosphate
applied.................... 1,275 lbs. Dec. 6, 1917 Jan 1, 1918 Dec. 22, 1919
Mixed Fertilizer
applied........... 1,530*lbs. Feb. 1, 1918 Jan. 10, 1919 Jan. 13, 1920
Potatoes planted ........................ Feb. 18, 1918 Jan. 28, 1919 Jan.23, 1920t
Potatoes harvested........................ May 27, 1918 May 16, 1919 June 10, 1920
*In 1918 fertilizer was applied at tle rate of 1,700 pounds an acre.
tDue to flooding of field potatoes replanted February 20, 1920.

The labor of caring for the experimental field formed part
of the regular routine of the Leonard plantation. Therefore, the
land was prepared and the crop planted, cultivated and sprayed
in exactly the same manner as the other fields on the planta-
tion.
The plants were sprayed at regular intervals with bordeaux
mixture to prevent blight. The spraying proved particularly
helpful during 1919 when both early blight and late blight of
potatoes was very prevalent in nearby unsprayed fields.
WEATHER CONDITIONS
Weather conditions varied greatly in 1918, 1919 and 1920.
There was a drought during the early half of 1918, making it
necessary to irrigate the fields; while in March, April and May
there were heavy rains that flooded the fields, doing some dam-
age. In 1919 the conditions were somewhat the reverse. There
was plenty of moisture in the soil early in the season, but
drought conditions prevailed during the latter part of the year.
In 1920 about one week after the potatoes were planted, a
heavy three-day rain flooded the fields, making replanting neces-
sary. As it was thought the heavy rains probably washed out
most of the soluble ammonia, all the plots were top dressed on
March 19, 1920, with nitrate of soda at the rate of 180 pounds
to the acre. The weather during the harvesting season was very
wet and digging was delayed several weeks.







SBulletin 158, Fertilizing the Irish Potato Crop 7

HARVESTING AND GRADING
The potatoes were dug with a digging machine, gathered by
hand, placed in crates, and taken to the packing shed where they
were graded by machine. Four different grades were made. On
the basis of weight, the different grades averaged as follows:
No. 1, 6 potatoes to the pound; No. 2, 11 to the pound; No. 3, 19
to the pound, and No. 4, 35 to the pound.
TABLE 2.-ANALYSIS OF FERTILIZER USED ON PLOTS CONTAINING NO
PHOSPHORIC ACID

A NA POTASH Av. PHOS. TOTAL
AMMONIA POTASH ACID PHOS. ACID


200 Sulphate of
Ammonia .... 25.24% 2.52% ...........
200 Fine Gr. To-
bacco stenis.. 2.79 .28 7.30%
200 High Grade
Tankage ...... 10.84 1.08 ............
400 Bright Cot-
tonseed Meall 7.19 1.44 1.82
100 Nebraska
Potash ........ ............ ..........28.00
900 Sand Filler ............ ..... .......
2,000 1 I| ............ 5.32 | ............|


.73%



.36

1.40

2.49


2.45% .24%

2.37 .47


............ ..........
............ 1.71 1


TABLE 3.-ANALYSIS OF FERTILIZER USED ON PLOTS CONTAINING
ACID PHOSPHATE


I



200 Sulphate of
Ammonia .... 25.24%
200 Fine Gr. To-
bacco stems.. 2.79'
200 High Grade
Tankage ...... 10.84
400 Bright Cot-
tonseed Meal 7.19
100 Nebraska
Potash ....... ...........
860 Acid
Phosphate .. ............
40 Sand Filler ............


ONIA


POTASH


S S

Sj. -
S.
S F
02l d


be
S.
S.
S
02


2.52% ............ .......... ........... ..........

.28 7.30% .73% ....................

1.08 .................... 2.45% .24%

1.44 1.82 .36 2.37 .47

.......... 28.00 1.40 ................

.......... ........... ..........17.57 7.52
.I...... ...........I....... .....


I ............15.32 I ............12.49 | ............18.23 1 ............8.81


tb IM Mibe
U ho t U U bo
4! II
;4 ;. >


4.80%

2.55


.48%

.51



.99


Av. PHOS. TOTAL
ACID PHOS. ACID


S.f
S.


4.80% .48%

2.55 .51



18.20 7.82


P4a
~1~~FV2


~ '


2,00011





Florida Agricultural Experiment Station


FERTILIZERS USED
The constitution of the mixed fertilizers used in this ex-
periment is shown in tables 2 and 3. The fertilizers were mixed
by machinery at the factory and applied by hand in the field. A
sand filler was used in mixing them so that equivalent weight
would carry the same amounts of a particular plant food. The
different mixtures were used at the rate of. 1,700 pounds an acre
during 1918, and 1,530 pounds during 1919 and 1920.
The raw phosphates, soft phosphates and finely ground
pebble phosphate, were applied in amounts carrying total phos-
phoric acid equivalent to three times the available phosphoric
acid in the mixtures where acid phosphate was the source of
phosphoric acid. On this basis the soft phosphate was used at
the rate of 1,570 pounds an acre, and the pebble phosphate at
the rate of 1,275 pounds an acre.

MANNER OF APPLYING FERTILIZER
Table 1 shows the time of application of the fertilizer used
in the two experiments. In 1918 the raw phosphates were mixed
with the soil in the rows or mounds. At the end of the season
the mounds over the whole field were leveled. In 1919 and 1920
the raw phosphates were broadcasted before the land was broken
in preparation for the crop.
The mixed fertilizers were applied by hand and mixed with
soil in the row.
PLOTS
The experimental field consisted of 10 beds extending en-
tirely across the field from east to west. Approximately one
acre was included in each bed. During 1918 only the first seven
beds on the south were included in the experiment.
In 1919 the three beds on the north side, adjoining the seven
beds used in the experiments in 1918, were plotted and added to
the experiments. Since the sequence of the fertilizer treatment
of these three beds were different from the remainder of the field,
the results obtained on them will be discussed separately under
the heading "Extension of Experiments."
Ten one-tenth acre plots were measured off on each bed. By
this division there were 70 one-tenth acre plots in the experiment
field in 1918 and 100 in 1919 and 1920.
A north and south line was established dividing the field
into halves. This line was coincident with the line between the
fifth and sixth plots on each bed. That part of the field west of






Bulletin 158, Fertilizing the Irish Potato Crop


this line was included in the phosphate experiment, that part
east in the potash experiment.
In 1919 and 1920, excepting the plots in the extension ex-
periments, the fertilizer treatment given each plot in the two
experiments was exactly the same as in 1918. The plan of the
experiments contemplates this repetition for a period of at least
five years. This bulletin is, therefore, only a progress report of
the two experiments.

THE PHOSPHATE EXPERIMENT
The purpose of this experiment, as stated, was to study the
results to be obtained from the use of raw Florida phosphates
and of acid phosphate as sources of phosphoric acid in fertilizers
for Irish potatoes planted on virgin land never before receiving
any fertilizer, as compared with those where practically no phos-
phate at all was included in the fertilizer used.
In that part of the field included in this experiment and be-
ginning on the south, all of the plots on the odd beds received a
fertilizer containing about 5 percent ammonia and 21/2 percent
potash, but practically no phosphoric acid. Owing to the fact
that the tankage and the cottonseed meal contained some phos-
phoric acid, the mixture was not entirely free from phosphoric
acid but carried between one-half and one percent of this element.
(See table 2.)
The plots on the even beds received mixtures containing 5
percent ammonia, 21/2 percent potash and 8 percent available
phosphoric acid where acid phosphate was used as the source
of phosphoric acid; or 24 percent total phosphoric acid where
either of the raw phosphates were used. The plots on the even
beds were so arranged that each particular mixture was used
five times at regular intervals in the field. Thus each plot,
receiving a fertilizer mixture containing phosphoric acid, was
flanked on either side by plots receiving mixtures without phos-
phoric acid. Tables 2 and 3 show the analyses of the fertilizer
mixtures used.
RESULTS IN 1918, 1919, 1920
Tables 4, 5 and 6 show the yields in pounds and by grades
for tenth-acre plots, and the treatment of the different plots.
Tables 7, 8 and 9 show the average yield calculated to barrels an
acre using 165 pounds as equivalent to one barrel.






Florida Agricultural Experiment Station


TABLE 4.-YIELDS IN POUNDS AND BY GRADES OF THE PHOSPHATE
AND NO PHOSPHATE TENTH-ACRE PLOTS, 1918


No Phosphate
Grades ....1 I 2 I 3 (4
361 36 23 33
118 67 29 13
Pounds 113 58 17 18
46 47 33 30
39 34 25 26
Total ........ 352 242 127 120
Average .. 70 481 251 24
Average of the two No Phosphal


No Phosphate
Grades .... 11 2 [ 3 | 4
118 73 36 23
162 83 31 20
Pounds 66 48 32 34
25 32 25 25
65 33 211 20
Total ........ 436 269 145 122
Average .. 871 541 29 24
Average of the two No Phosphat


Acid Phosphate
1 1 2 3 I 4
94 591 351 30
3871 93 361 21
2501 93 33 16
2581 91 40 21
155 73 40 8
1144 409 1841 96
2291 821 371 .19
e plots.................


Pebble Phosphate
11213 | 4
157 88! 47 35
225 87 40 23
173 83 49 36
101 65 40 32
66 51 34 28
722 3741 210 154
1441 751 42! 31
e plots......................


No Phosphate Soft Phosphate
Grades .... 1 2 3 4 1 2 I 3 I 4
68 47 32 30 116 67 37 29
10 21 19 26 99 62 46 34
Pounds 88 54 40 23 144 62 33 25
34 40 28 25 89 64 39 30
65 46 25 18 70 53 39 26
Total ........I 2651 208 144 122 518 1 308 194 144
Average .. 57 42 29 24 104T 621 391 29
Average of the two No Phosphate plots......................


No Phosphate
1121 3 4
101 211 19 26
88 541 40 23
65 461 25 18
341 40! 28 25
221 24! 12 28
219 18 1 1 1241 120
S44 371 25! 24
571 431 251 24


No Phosphate
_1 2 [ 3 1 4
461 471 33 30
113 58 17 18
39 34 25 26
28 39 33 36
61 11 15 18
232[ 189 .123 128
46 38 25 26
67 46 27 25
No Phosphate
1 1 2 1 3 1 4
66 481 32. 34
25 321 25 25
65 33 21 20
61 50! 32 27
21 311 33 21
238 194 143 127
48 39 29 26
51 40 29 25


TABLE 5.-YIELD IN POUNDS AND BY GRADES OF PHOSPHATE AND
ADJACENT NO PHOSPHATE TENTH-ACRE PLOTS DURING 1919
No Phosphate Acid Phosphate No Phosphate
Grades .... 1 2 I 3 1 4 1 2 1 3 1 4 1 2 3 4
172 170 80 38 411 186 60 27 152 176 86 48
179 154 56 26 319 192 56 23 153 159 72 27
Pounds 170 173 74 28 436 166 49 19 163 133 49 28
78 113 59 34 220 127 42 22 120 112 37 37
208 165 68 40 381 154 51 24 178 141 57 38
Total ........ 8071 775 1337 166 1767 825 258 115 766 721 301 178
Average .. 161 1551 67 33 353 1651 52 23 1531 144 60 36
Average of the two No Phosphate plots.................... 157 150 64 35
No Phosphate Soft Phosphate No Phosphate
Grades .... 1 | 2 3 j 4 1 1 2 I 3 i 4 1 1 2 1 3 | 4
157 165 77 42 319 200 69 41 235 183 72 34
152 176 86 48 228 183 64 30 223 1701 67 29
Pounds 153 159 72 27 259 179 59 29 158 150 79 42
163 133 49 28 251 166 57 25 1471 122 53 27
120 112 37 37 2221 1731 65 35 1411 1281 65 32
Total ........ 745 745 321 182 1279! 9011 314 160 9041 753 I 336 164
Average 1491 1491 64 36 256 1801 63 32 1811 1511 67 33
Average of the two No Phosphate plots........................ 165 150 66 35


___






Bulletin 158, Fertilizing the Irish Potato Crop


No Phosphate Pebble Phosphate No Phosphate
Grades .... 1 [ 2 3 4 1 1 2 3 1 4 1 1 2 1 3 4
138 152 53 24 319 224 74 35 170 173 74 28
119 154 66 32 173 166 69 29 78 113 59 34
Pounds 235 183 72 34 275 173 62 38 208 165 68 40
223 170 67 29 301 185 58 23 2021 148 60 30
158 150 79 42 266 178 56 22 1571 139 55 37
Total ........1 873 809 337 161 13341 926 319 147 815 738 316 169
Average ..] 1751 162 67 32 267 185 64( 29 163 148| 63 34
Average of the two No Phosphate plots........................ 169 155 651 33



TABLE 6.-YIELD IN POUNDS AND BY GRADES OF PHOSPHATE AND
ADJACENT No PHOSPHATE TENTH-ACRE PLOTS, 1920


No Phosphate Acid Phosphate
Grades .... 1 2 1 3 I 4 1 1 2 3 1 4
226 180 147 42 414 272 90 48
155 186 62 32 482 225 74 31
Pounds 251 230 91 42 425 233 85 45
200 237 113 64 464 320 113 48
237 157 56 42 562 173 42 12
Total .......(1069 990 4691 222 2347 11223 404I 184
Average .. 214 198 94 44 469 245 81 37
Average of the two No Phosphate plots......................


No Phosphate
11 2 31 4
253 276 118 52
211 231 108 41
263 154 67 36
266 271 132 59
392 142 35 9
1385 1074 4601 197
277 215 921 39
2451 206 931 42


No Phosphate Soft Phosphate No Phosphate
Grades .... 1 I 2 [ 3 4 1 2 3 4 1 3 4
192 206 87 39 395 2451 86 39 155 1861 62 32
200 229 114 60 386 257 81 44 251 230 91 42
Pounds 254 250 108 42 339 221 80 39 200 237 113 64
274 225 95 34 309 169 58 23 237 157 56 42
296 215 83 -29 217 232 106 51 201 214 110 56
Total ........11216 1125 487 204 1646 1124 411 196 104411024 432 236
Average -. 243 225 97 41 329 2251 82 39 209 205 86 47
Average of the two No Phosphate plots....................... 2261 215 92 44


No Phosphate Pebble Phosphate No Phosphate
Grades .... 1 2 3 4 1 1 2 1 3 4 1 2 3 1 4
63 2541 125 61 476 2391 75 39 254 250 1081 42
168 178 75 40 384 233 79 33 274 225 951 34
Pounds 253 276 118 52 548 283 102 47 296 215 83 29
211 231 108 41 370 278 108 39 275 198 73 36
263 154 67 36 435 245 82 34 426 208 63 23.
Total ........ 958 1093 I 493 230 2213 1278 4461 192 1525 11096 422 164
Average .. 192 219 99 46 443 .256 89 38 305 219 84 33
Average of the two No Phosphate plots...................... 249 219 92 40


I






Florida Agricultural Experiment Station


TABLE 7.-PHOSPHATE EXPERIMENT, 1918; YIELDS IN BARRELS AN ACRE

Grade Acid Pebble Soft No
.Phosphate Phosphate Phosphate Phosphate
1 13.9 8.7 6.3 3.8
2 5.0 4.5 3.8 2.6
3 2.2 2.5 2.4 1.6
4 1.2 1.9 1.8 1.5
Total .................. 1 22.3 17.6 14.3 9.5

TABLE 8.-PHOSPHATE -EXPERIMENT, 1919; YIELD IN BARRELS AN ACRE

Grade Acid Pebble Soft No
Phosphate Phosphate Phosphate Phosphate
1 21.4 16.3 15.5 9.9
2 10.0 11.2 10.9 9.1
3 3.2 3.8 3.8 4.0
4 1.4 1.8 2.0 2.1
Total ................. 36.0 33.1 | 32.2 25.1

TABLE 9.-PHOSPHATE EXPERIMENT, 1920; YIELD IN BARRELS AN ACRE

Grade Acid Pebble Soft No
I* Phosphate Phosphate Phosphate Phosphate
1 1 28.4 26.8 20.0 14.6
2 14.8 15.5 13.6 12.9
3 4.9 5.4 5.0 5.6
4 2.2 2.3 2.4 2.5
Total ..................---- ----- 50.3 | 50.0 [ 41.0 35.6

It will be noted that the yields in 1918 were very low on all
of the plots. This was probably due to the newness of the land.
In 1919 and 1920 the yields of all of the plots were much better
and those from the acid phosphate plots approached the average
yield of the fields not included in the experiment. Both pebble
phosphate and soft phosphate have shown striking increases in
yield as compared to those obtained where no phosphate was
used. In 1920 the total yield where pebble phosphate was used
was nearly equal to that of the acid phosphate plots; but the
amount of No. 1 grade potatoes was slightly less where the for-
mer was used.
While the initial cost of the pebble phosphate was about the
same as the acid phosphate the total cost was somewhat greater
for the pebble phosphate because it was applied separately from
the rest of the fertilizer.
GROWTH OF THE PLANTS
The growth from the tubers in 1918 on the plots receiving
fertilizer mixtures without phosphate and in those receiving






Bulletin 158, Fertilizing the Irish Potato Crop


mixtures with the raw phosphates, was somewhat irregular, giv-
ing a poor stand of plants. Late in the season plants here and
there were just breaking thru the.soil. It was also noticed
that after the plants in these plots became independent of the
tubers, growth was checked. After a period of several weeks,
the plants in the raw phosphate plots increased rapidly in size,
but by the end of the season had not become quite as large as
those in the acid phosphate plots.
In the plots which received no phosphate the plants made
slow growth thru the entire season. At the end of the growing
season they averaged fully 50 percent smaller in size than those
in the acid phosphate plots. The character of growth was also
different. The leaves were somewhat undersized, and the inter-
nodes of the stems were longer. The plants had a rather stiff,
upright appearance. Early in the season their color was slightly
yellowish; later it became a deep green. The plants were slow
in maturing. At the end of the season the majority of plants were
still alive and making some growth, while the tops in the other
plots were all dead.
This condition of slow growth is apparently coupled with a
lack of available phosphoric acid and indicates the need of this
material in the vegetative growth of the plants, particularly in
the early stages.
In 1919 the differences in growth of the plants in the plots
receiving acid phosphate and those receiving the raw phosphates
and no phosphoric acid, were practically the same as in 1918. The
same slowness of growth in the plants receiving the raw phos-
phates and no phosphoric acid was noted, but this was not at all
so pronounced in the former as in 1918.
The sprouting of the tubers was not as slow this year as
in 1918. There was practically a perfect stand of plants. The
plants receiving acid phosphate were large, bushy, stocky and of
a normal green color. Many showed strong branches from the
lower nodes that formed strong stalks with well formed leaves
and leaf stalks. Those receiving raw phosphates were practically
of the same type but were not as large. There were fewer plants
that showed branching. The plants on the plots receiving no
phosphate were undersized, slender, spiky and of an abnormal
green color. The leaves were undersized, curled and upright,
giving a mouse-eared appearance. It is assumed that this type of
growth is indicative or characteristic of phosphoric acid hunger.
Also a slowness of maturity in the plants receiving no phosphate





Florida Agricultural Experiment Station


was again observed. The plants in these plots were still alive
and growing when all the plants in the other plots were prac-
tically dead.
In 1920 the plants receiving acid phosphate made a bushy
growth that was normal in all respects. The plants receiving
pebble phosphate were not quite so good, while those receiving
soft phosphate were distinctly less bushy and somewhat slender
in growth. The plants receiving no phosphoric acid were much
undersized but did not show the slender, spiky growth as in 1919.
It is assumed that the more favorable soil moisture condition,
prevalent during 1920, allowed enough phosphate in the soil to
become available to avoid the starvation phenomena as shown in
1919.
On May 25, 1920, the plants in the acid phosphate plots
were all dead. While those in the no phosphate plots were still
alive and growing. The plants in the plots receiving the raw
phosphates were somewhat intermediate. Groups of plants here
and there on these plots, particularly the pebble phosphate plots,
were dead. This indicates that soluble phosphoric acid is con-
ducive to early plant maturity.
INFLUENCE OF FERTILIZERS ON SUCCEEDING CROPS
After the potatoes were harvested in 1918 the mounds were
leveled and the beds planted to cowpeas by broadcasting. No
fertilizer was applied as it was assumed that there was a suf-
ficient amount left in the soil from that used on the potatoes to
make this crop.
The vines made a luxuriant growth on all the plots that had
received phosphate, regardless of the source. Those on the plots
that had received no phosphate grew very much as the potatoes
did on these plots. When the vines became independent of the
seed, the growth became slow and continued so thruout the
season. At the end of the season the vines were only from 50 to
60 percent as high as those on the phosphate plots.
Figure 1 shows the dividing line between two plots. The
one in the foreground was given no phosphate, whereas the one
in the background received acid phosphate. The difference in
height is indicated by the distance between the man's hands.
The same differences in color and maturity that were noticed
in the potatoes were also present in the cowpeas. The vines
were slightly yellow early in the season, but from normal to deep
green later. When the vines were all dead on the phosphate plots,
many were still alive and growing on the plots that had received
no phosphate.






Bulletin 158, Fertilizing the Irish Potato Crop 15

Unfortunately, it was not possible to obtain a record of the
yield of seed on the different plots. After the crop had matured
the vines were plowed under to improve the soil.
After the potatoes were harvested in 1919 the land was
planted to corn. Owing to excessive rains the crop was
a failure. A crop of grass and weeds developed on the land.
This was plowed under to add humus. In 1920 the land was al-
lowed to grow up to weeds and grass, following the harvesting of
the potatoes.
THE POTASH EXPERIMENT
The purpose of this experiment was to study the results to
be obtained from the application of fertilizers containing various
percentages of potash for Irish potatoes planted on virgin land,
in comparison with those obtained where no potash fertilizers
were used. The experiment was carried out on virgin land that
had never received any fertilizer.
This experiment occupied the east half of the field mentioned.
Seven beds were included in the experiment. Beginning on
the south, all the plots on the odd beds were given a fertilizer
mixture containing about 5 percent of ammonia, 8 percent of
available phosphoric acid and no potash. The plots on the even
beds were given fertilizer mixtures containing the same amounts
of ammonia and phosphoric acid and 1 percent, 3 percent, and 5
percent respectively of potash. The plots were so arranged that
each particular mixture was used at regular intervals in the field
five times (see Fig. 2). Thus each plot receiving a fertilizer
mixture containing potash was flanked on either side by plots re-
ceiving mixtures with no potash.
TABLE 10.-ANALYSIS OF FERTILIZER ON 1 PERCENT POTASH PLOT

AMMONIA POTA A PCID PHOS. ACID
AMMO N IA P OA SH D.. p S. -


S S. < M < 03 '< S
200 Sulphate of
Amm onia .. 25.24% 2.52% ................................................................
500 High Grade
Tankage .... 10.84 2.71 ..... .......... 2.45% .61% 4.80% 1.20%
75 Nebraska
Potash .................. ....... 8.0 1.05% ............ .......... ............ ..........
860 Acid
Phosphate ............ .......... ............ .......... 17.57 7.52 18.20 7.82
365 Sand Filler ............ .......... ........ .... .......... ......................
20001 1 ............ 5.23 ............ 11.05 1............ 18.13 |............ 19.02







16 Florida Agricultural Experiment Station
TABLE 11.-ANALYSIS OF FERTILIZER ON 3 PERCENT POTASH PLOTS

AMMONIA POTASH Av. POS. TOTAL
ACID P1HOS. ACID






200 Sulphate of
Ammonia .. 25.24% 2.52% ....... ............-......................
500 High Grade
Tankage .... 10.84 2.71 .......... ......... 2.45% .61% 4.80% 1.20%
225 Nebraska
Potash ...................... 28.00% 3.15% ....... ................
860 Acid
Phosphate ........... .................. .......... 17.57 7.52 18.20 7.82
215 Sand F miller ........... ...................... .......... ............ ..........
20001 ............ 15.23 1............ 3.15 ............ 8.13' I............ 9.02
TABLE 12.-ANALYSIS OF FERTILIZER ON 5 PERCENT POTASH PLOTS

AMMONIA POTASH A PHOS. TOTA
ACID PHos. ACID


ao
~ N
aa
au


.bo
S:

S
U)


bD M
N N

S a


bo btD bC


a S
nJ d


200 Sulphate of
Ammonia .. 25.24% 2.52% ............. ..........................................
500 High Grade
Tankage .... 10.84 2.71 ..................... 2.45% .61% 4.80% 1.20%
375 Nebraska
Potash ...... ........... ......28.00% 5.25% ...................... ... .. ............
860 Acid
Phosphate ................... ...... .......... 17.57 7.52 18.20 7.82
651 Sand Filler ............ .......... ............ .......... ............ ........ ............
20001 1 ............ |5.23 |............ |15.25 |............ |8.13 ............ 19.02
TABLE 13.-ANALYSIS OF FERTILIZER ON PLOTS WHERE NO POTASH
WAS USED

AMMONIA POTASH A PHOS. TTA
ACID PHOS. ACID


Mfl bac b M ba
.B .B ."
N h N~
a a a a
S D S ~
.C ) U


Sulphate of
Ammonia .. 25.24% 2.52% ............ ..........
High Grade
Tankage .... 10.84 2.71 .......... ..........
Acid
Phosphate ............ ............ ..........
Sand Filler ........... .......... I.... ..........


9 ~a S "


S .......... ..... .... ..


2.45% .61% 4.80% 1.20%

17.57 7.52 18.20 7.82
............ .......... ---- --- ...- ....


2............ 15.23 1............ I.......... I............ 18.13 I............ 9.02


gS
n Cd U


20001






Bulletin 158, Fertilizing the Irish Potato Crop


Tables 10, 11, 12 and 13 show the analyses of the fertilizer
mixtures used.

TABLE 14.-YIELD IN POUNDS AND BY GRADES OF POTASH AND
ADJACENT NO POTASH TENTH-ACRE PLOTS, 1918
No Potash 1% Potash No Potash
Grades .... 1 1 2 1 3 |4 1 2 1 3 4 1 2 | 3 4
891 461 27 19 2091 731 301 11 511 351 18 14
115 80 39 26 204 761 38 23 113 58 35 21
Pounds 64 33 17 13 276 911 32 18 155 74 30 16
124 70 30 14 1991 831 34 11 81 531 28 17
861 621 36 24 128 791 341 24 117 581 38 26
Total ....... 478 I 291 149 96 10161 402 168 87 517 278 149 94
Average .. 961 58 30 19 2031 80 34 17 1031 56 30 19
Average of the two No Potash plots.......................... 99 57 30 19

No Potash 3% Potash No Potash
Grades ....1 2 [ 3 | 4 1 I 2 3 4 1 2 3 1 4
S43 46 21 117 367 98 34 14 63 52 28 19
51 35 18 14 293 91 37 18 48 37 20 13
Pounds 113 58 35 21 282 72 32 18 138 66 36 19
155 74 30 16 195 104! 35 19 74 45 27 23
1 811 53 28 17 182 87 38 20 210 85 33 17
Total ........ 443 266 132 85 13191 4521 1761 89 533 285 144 91
Average .. 89 53 26 17 2641 901 351 18 107 571 29 18
Average of the two No Potash plots............................. 98 55 28 18

No Potash 5% Potash No Potash
Grades ....I 1 | 2 1 3 | 4 1 | 2 | 3 I 4 1 2 I 3 4
104| 52 24 15 4071 941 25 10 64 33 17 1 13
106) 67! 32 21 3841 96 29 12 124 701 301 14
Pounds 631 52 28 19 339 95 41 19 861 621 261 24
481 37 20 13 168 54 46 21 2001 841 401 19
1381 66 36 19 120 67 35 20 204 881 441 20
Total ........ 459 274 1401 87 1418 406 176 82 678 337 167 90
Average .. 92 551 281 17 284 81 35 16 136 67 33 18
Average of the two No Potash plots........... ........... 114 61 31 18

TABLE 15.-YIELD IN POUNDS AND BY GRADES OF POTASH AND
ADJACENT NO POTASH TENTH-ACRE PLOTS, 1919
No Potash 1% Potash No Potash
Grades .... 1 1 2 | 3 4 1 2 1 3 1 4 1 | 2 1 3 4
I 1801 164 61 26 443 185 52 27 1791 151 55 22
400 172 63 64 4771 168 49 27 353 157 46 25
Pounds 206 145 50 21 197 146 46 16 110 123 51 26
287 1601 53 26 464 172 44 40 237 155 44 18
168 1461 481 24 328 271 50 28 178 154 56 23
Total ....... 1241 7871 275 161 1909 942 1 241 138 1057 7401 252 114
Average .. 248 157 55 3211382 1881 48 28 211 148 50 23
Average of the two No Potash Plots.............................. 230 152 53 28






Florida Agricultural Experiment Station


No Potash 3% Potash No Potash
Grades .... 1 2 3 4 1 2 3 4 1 2 4 1 3 | 4
150 169 62 28 498 125 36 18 175 159 57 31
179 151 55 22 283 149 50 22 191 152 52 24
Pounds 353 157 46 25 560 185 49 20 366 164 48 24
110 123 51 26 439 179 48 23 148 138 59 23
237 155 44 18 539 146 381 20 279 132 33 18
Total -..-.. 11029 755 258 119 2319 784 221 103 1159 745 249 120
Average .. 206 151 52 24 464 157 44 21 232 149 50 24
Average of the two No Potash plots ..................... 219 150 51 24
No Potash 5% Potash No Potash
Grades .... 1 2 1 3 | 4 1 1 2 T 3 | 4 1 2 3 4
135 114 46 21 382 150 40 16 206 145 501 21
295 201 65 31 642 144 41 19 287 160 53 26
Pounds 175 159 57 31 486 146 38 18 168 140 48 24
191 152 52 24 359 158 45 23 183 130 28 20
366 164 48 24 622 164 42 35 447 153 39 17


Total ........1162 790 268 131 2491 762 206 I111 291 728 218
Average .. 232 158 54 26 498 152 41 22 258 146 44
Average of the two No Potash plots...............- .......... 245 152 49


TABLE 16.-YIELD IN POUNDS AND BY GRADES OF POTASH AND
ADJACENT NO POTASH TENTH-ACRE PLOTS, 1920
No Potash 1% Potash No Potash
Grades .... 1 | 2 3 4 1 1 2 I 3 1 4 1 I 2 3 | 4
456 259 81 33 595 182 53 12 277 198 60 17
193 189 70 29 589 186 50 16 322 170 41 16
Pounds 346 186 49 16 458 147 29 15 334 138 40 10
289 167 69 21 496 142 37 14 303 194 51 22
396 130 46 18 638 190 44 32 444 132 36 10
Total ........ 1680 931 315 | 117 2776 1 847 213 89 1680 I 832 228 75
Average .. 336 186 63 23 p555 169 43 18 3361 166 46 15
Average of the two No Potash plots.............................. 336 1 176 55 19


No Potash 3% Potash
Grades .... 1 2 31 4 1 2 | 3 I 4
243 2691 1111 44 535 2231 80 40
423 162 45 15 680 187 47 13
Pounds 180 193 75 30 708 185 51 24
298 194 58 18 470 106 36 36
307 183 44 13 654 146 36 28
Total ........ 1451 1001 333 120 13047 847 250 141
Average .. 2901 200 67 24 609 169 50 28
Average of the two No Potash plots.....................


No Potash
1 21 31 4
193 189 70 29
346 186 49 16
289 167 69 21
396 .130 46 18
328 188 49 13


1552 860 283 97
310 172 57 19
300 186 62 24


No Potash 5% Potash No Potash
Grades .... I 1 2 3 4 1 2 13 4 1 1 2 | 3 4
370 209 66 23 672 200 60 24 180 19 75 30
500 208 64 20 722 168 50 20 298 194 58 18
Pounds 277 198 60 17 612 150 43 18 307 183 44 13
322 170 41 16 644 103 32 15 321 166 39 14
334 138 40 10 652 129 35 16 337 209 53 20
Total ....... 18031 923 271 86 33021 7501 2201 93 1443 945 269 95
Average .. 361 185 54 17 660[ 150 44 19 289 189 54 19
Average of the two No Potash plots.............................. 325 187 54 I 18






Bulletin 158, Fertilizing the Irish Potato Crop


RESULTS
Tables 14, 15 and 16 show the yield of the tenth-acre
plots receiving potash and the adjacent no potash plots for the
three years. Tables 17, 18 and 19 show the acre yields figured in
barrels, 165 pounds to the barrel.
TABLE 17.-POTASH EXPERIMENT, 1918; YIELDS IN BARRELS AN ACRE
Grade 5% Potash 1 3% Potash 1% Potash No Potash
1 17.2 16.0 12.3 6.3
2 4.9 5.5 4.8 3.5
3 2.1 2.1 2.0 1.8
4 1.0 1.1 1.0 1.1
Total .............. 25.2 24.7 20.1 I 12.7

TABLE 18.-POTASH EXPERIMENT, 1919; YIELDS IN BARRELS AN ACRE
Grade | 5% Potash 3% Potash 1% Potash No Potash
1 30.2 28.1 23.1 14.0
2 9.2 9.5 11.4 9.1
3 2.5 2.7 2.9 3.1
4 1.3 1.3 1.7 1.5
Totals ................ 1 43.2 41.6 39.1 27 7

TABLE 19.-POTASH EXPERIMENT, 1920; YIELDS IN BARRELS AN ACRE
Grade 5% Potash 3% Potash 1% Potash No Potash
1 40.0 36.9 33.6 20.2
2 9.1 10.3 10.3 11.3
3 2.7 3.0 2.6 3.5
4 1.2 1.7 1.1 1.2
Totals ............. 53.0 | 51.9 47.6 36.2

In 1918 the yield of the whole field was low, probably because
the land was new. The yields have been increasing yearly as the
land has been improved by the addition of humus and probably
by the accumulation of fertilizer residues. The differences be-
tween the application of various, amounts of potash have been
very uniform. The largest increase each year was with the 1
percent potash, while the 5 percent has given an increase over
the 3 percent which only a little more than covered the cost of
the additional 2 percent. The increase in yield in every case was
largely of first grade potatoes which makes the value of the in-
crease greater.
INFLUENCE UPON GROWTH OF TOPS
In 1918 the plants receiving no potash produced practically
as good top growth as those receiving potash. The character of
the growth was bushy, with well developed foliage of good
color.





Florida Agricultural Experiment Station


SYMPTOMS OF POTASH STARVATION
In the season of 1919 an entirely different situation occurred.
The plants receiving no potash fertilizer made a very poor
growth and developed certain appearances evidently character-
istic of potash starvation in plants.
During the first half of the season the plants in the no
potash plots made a normal growth and apparently were just
as vigorous and thrifty as those receiving potash. Early in
April, 1919, it was noticed that the plants on the beds where no
potash was applied were beginning to show a deeper green color
than those on the other beds, and that they were not growing
quite as fast. As the season progressed this appearance be-
came more intensified until the beds without potash showed as
dark green bands across the field. The plants became stunted
and were lacking in business. At the end of the season they
averaged fully 25 percent smaller in size than those receiving
potash.
After the crop was 40 days old plants here and there
began to develop an inward curling of the margins of the leaves
with more or less crinkling of the tissue between the larger
veins. The surfaces of the leaves showed a waxy sheen as if they
had been polished with parafin. In later stages of growth there
was a bronzing of the surfaces of the leaves and a dying of the
tissue in spots along the margins and toward the tips. As the
season progressed, the condition became more widespread until
it was general on all the beds without potash. It was noticed,
however, that in spots here and there the trouble was not so
pronounced, or it was entirely absent. This was probably due
to variations in the soil and to the fact that these areas contained
sufficient potash to supply the needs for the top growth.
The fact that the crop in 1918 made a good top growth but
failed to make a good crop of tubers, and that the symptoms of
potash hunger did not develop in 1919 until the plants had almost
attained full size and had begun to set tubers, indicates that the
virgin land contained enough potash for the top growth in 1918.
It also indicates that the plants draw most heavily upon the
supply of potash in the soil during their late growth when the
tubers are being made, and that only small amounts of potash
are needed during the early growth of the crop.
In 1920 the plants in the plots receiving no potash were
somewhat undersized and showed a distinctly darker green color
than did those receiving potash. Thus the field had the same





Bulletin 158, Fertilizing the Irish Potato Crop


banded appearance that it did in 1919. But the plants showed
none of the acute symptoms of potash hunger as they did in
1919. It is assumed that either the better soil moisture condi-
tion in 1920 made some of the residual potash available for the
plants; or that the soda from the top dressing of nitrate of soda
acted to some extent as a substitute for the potash.
Very little difference in growth could be seen in the plants
receiving various amounts of potash. The chief difference
seemed to be in the tuber production.
On May 25 the plants in the no potash plots were all dead,
while those on the plots receiving potash were just beginning to
die. Apparently the lack of balance with potash allowed the
phosphoric acid effect to predominate, so that the plants in these
plots reached an earlier maturity.
SUCCEEDING CROP
After the crop was harvested in 1918 the mounds were
leveled and the field planted to cowpeas. The vines made as good
growth where no potash was applied as where applied. It was
not possible to get a record of the yield. After the plants died
they were plowed under to improve the soil. In 1919 corn was
planted but it was a failure because of excessive rains. No suc-
ceeding crop was planted in 1920. The field was allowed to grow
a volunteer crop of grass and weeds.
GREENHOUSE EXPERIMENTS
Early in the season of 1919 experiments were begun in the
greenhouse at the Experiment Station, Gainesville. Fertilizers
from the lot used at Hastings were used here. (See tables 10,
11, 12 and 13.) The soil used was a sandy loam from a field that
had been cropped repeatedly with velvet beans and other crops,
but it had never been given any fertilizer. In these experiments
the potato plants in every plot where potash was not applied,
developed the same symptoms as did those in the field at Hast-
ings during that year. The symptoms appeared at about the
same stage of growth but were not pronounced. Every plant
showed evidence of potash hunger.
These experiments confirm the results obtained in the field
in 1919. It is probable that the stronger development of the
symptoms was caused by the soil used. Since it had been re-
peatedly cropped without the addition of fertilizer, there was not
sufficient available potash for a normal development of the
plants.





Florida Agricultural Experiment Station


EXTENSION OF EXPERIMENTS
Ten beds of approximately one acre each were included in.
the potato experimental field in 1919 and 1920. (See page 5.)
During 1918 only the first seven beds on the south were used
(Fig. 2). The remaining three beds formed a part of an adjacent
field planted to potatoes and were given the same amount and
about the same kind of fertilizer mixture, containing acid phos-
phate, as was used in the phosphate experiment. It analyzed
5 percent ammonia, 8 percent available phosphoric acid, and 21/2
percent potash.
In 1919 the three beds were plotted and given the same
fertilizer treatment as the plots in the phosphate and the potash
experiments. The arrangement and treatment of the plots is
shown in figure 1. From the arrangement of these it is seen
that there is only one bed, where no phosphate and no potash
was used in 1919, that is exactly comparable with the plots re-
ceiving potash or phosphate during that year.

EXTENSION OF PHOSPHATE EXPERIMENT
In 1918 all plots on the three beds in the experiment received
the fertilizer mixture containing acid phosphate. In 1919 all
plots on the middle one of the three beds received the mixture
containing no phosphate (Fig. 2). Thus the sequence of treat-
ment for these plots are acid phosphate in 1918 and no phosphate
in 1919 and 1920. By comparing the yields from these plots with
those in the phosphate experiment proper that received no phos-
phate in 1918 and in 1919, an indication can be obtained of the
influence of the residual phosphoric acid in the soil from the
preceding season upon the succeeding crop.
The plots on the remaining two beds were given fertilizer
mixtures containing acid phosphate, pebble phosphate and soft
phosphate respectively. The treatments were so alternated that
each of the mixtures were used on three or four different plots on
the beds (Fig. 2). Thus there is the following different sequences
of treatment on the three beds in the experiment:
Acid Phosphate, 1918.........--.......Acid Phosphate, 1919 and 1920;
Acid Phosphate, 1918................Pebble Phosphate, 1919 and 1920;
Acid Phosphate, 1918..........--....--Soft Phosphate, 1919 and 1920;
Acid Phosphate, 1918......................No Phosphate, 1919 and 1920.






Bulletin 158, Fertilizing the Irish Potato Crop


TABLE 20.-YIELD IN POUNDS AND BY GRADES OF PHOSPHATE AND
ADJACENT NO PHOSPHATE TEN-ACRE PLOTS
(Acid Phosphate 1918) (Acid Phosphate 1918)
Acid Phosphate 1919 No Phosphate 1919
Grades .............. 1 2 3 4 1 2 3 4
297 137 40 14 256 165 46 22
Pounds ............ 317 138 40 20 202 143 49 23
393 166 58 28 236 170 64 34
Total .................. 1,007 441 138 I 62 694 478 I 159 79
Average ............ 336 147 46 .21 231 159 53 26

(Acid Phosphate 1918) (Acid Phosphate 1918)
Soft Phosphate 1919 No Phosphate 1919
Grades .............. 1 2 I 3 4 1 I 2 3 I 4
178 126 44 16 256 165 46 22
Pounds .............. 304 126 38 17 142 147 57 20
173 140 52 25 202 143 49 23
S196 151 47 23 292 154 41 20
Total ............ 851 543 181 81 892 609 193 85
Average ............ 213 136 45 20 223 152 481 21

(Acid Phosphate 1918) (Acid Phosphate 1918)
S Pebble Phosphate 1919 No Phesphate 1919
Grades ..............1 1 2 3 4 1 2 3 4
229 166 59 28 142 147 57 20
Pounds ........... 182 158 60 32 236 170 64 34
305 147 45 26 292 154 41 20
Total ............... 716 471 164 86 670 471 162 74
Average ............ 239 157 55 29 223 157 54 25
Average Yield of No Phosphate Plots .............. 226 156 52 24

TABLE 21.-YIELD IN POUNDS AND BY GRADES OF PHOSPHATE AND
ADJACENT NO PHOSPHATE PLOTS, 1920
Acid Phosphate 1918 Acid Phosphate 1918
Acid Phosphate 1919 No Phosphate 1919
Acid Phosphate 1920 No Phosphate 1920
Grades ..............I 1 2 3 4 1 2 3 4
379 197 52 21 260 170 49 22
Pounds................ 411 186 61 22 373 145 37 14
566 102 40 14 421 153 31 13
Total ............... 1,356 485 153 57 1,054 468 117 49
Average ............ 452 162 51 19 351 156 39 16

Acid Phosphate 1918 Acid Phosphate 1918
Soft Phosphate 1919 No Phosphate 1919
Soft Phosphate 1920 No Phosphate 1920
Grades .............. 1 2 1 3 4 1 2 3 4
395 186 45 29 373 145 37 14
Pounds .......... 469 103 13 28 421 153 31 13
324 156 48 16 378 179 47 19
371 106 24 2 443 99 25 11
Total ............ 1,559 551 130 75 1,615 576 140 57
Average ............ 390 138 32 19 404 144 35 14





Florida Agricultural Experiment Station


Acid Phosphate 1918 Acid Phosphate 1918
Pebble Phosphate 1919 No Phosphate 1919
_Pebble Phosphate 1920 ..No Phosphate 1920
Grades .......... 1 2 3 4 | 1 ] 3 4
359 195 64 30 378 179 47 19
Pounds................ 635 155 31 53 443 99 25 11
S251 137 43 _19 260 170 49 22
Total .......... 1,245 487 138 102 1,081 448 121 52
Average ......... 415 162 46 34 360 149 40 17

TABLE 22.-YIELDS IN BARRELS AN ACRE

C Acid Phosphate 1918
Grade-------
SAcid Phos. Pebble Phos./ Soft Phos. No Phos. o
S 1919 1920 11919 11920 1919 I 1920 1919 1920 Z
1 ............ 24.7 20.4 27.4 14.5 25.2 13.0 23.6 13.7 22.7 14.6
2 ............ 5.4 9.0 9.8 9.5 9.8 8.2 8.4 9.5 8.0 12.9
3 ............ 1.7 2.8 3.1 3.3 2.8 2.6 1.9 3.1 2.3 5.6
4 ..........-.8 1.3 1.2 1.8 2.1 1.2 1.2 1.4 .9 2.5
Total ...... 32.6 1 33.5 I 41.5 1 29.1 1 39.9 f 25.0 35.1 27.7 I 33.9 35.6

RESULTS
Tables 20 and 21 show the yields in pounds and by grades of
the phosphate and adjacent no phosphate tenth-acre plots on the
three beds. Table 22 shows the average yields in barrels an acre
of the three beds in 1918; those of the different phosphate plots
in 1919 and 1920; and the 1920 yield of the plots in phosphate
experiment proper which had received no phosphate at any time.
Comparing the 1920 yield of first grade potatoes obtained
where acid phosphate was used in 1918 and no phosphate in 1919
and 1920 with that where no phosphate was used at all, a dif-
ference of eight barrels is seen. This increase is apparently due
to the residual phosphoric acid from the 1918 application. Where
acid phosphate was used during all three years the increase
amounts to nearly 13 barrels.
Soft phosphate substituted for acid phosphate during the
second and third years of the experiment failed to keep up the
yield of the first grade potatoes. The yield obtained here was
little better than that where no phosphate was applied during
the second and third years. This is probably due to the lack of
soluble phosphoric acid in this material. Pebble phosphate gave
-somewhat better results.
The growth of the plants during 1919 and 1920 on the plots
given raw phosphates during the second and third years was not
as good as that where acid phosphate was used both years, but it
was much better than that on the plots receiving no phosphate






Bulletin 158, Fertilizing the Irish Potato Crop


in 1919 and 1920. The growth on the plots receiving acid phos-
phate in 1918 and no phosphate in 1919 and 1920, was markedly
better than that on the plots that received no phosphate during
the'three years, and was more comparable with that on the plots
receiving the raw phosphates in 1919 and 1920. While there was
a reduction in growth in the plants on the plots receiving acid
phosphate in 1918 but no phosphates in 1919 and 1920, practi-
cally none of the starvation phenomena seen in the plants that re-
ceived no phosphate during the three years were observed here.
EXTENSION OF POTASH EXPERIMENT
The three beds adjacent to the potash experiment on the
north were included in the extension of potash experiment in
1919 (Fig. 2). In 1918 these plots received a fertilizer analyzing
about 5 percent ammonia, 8 percent available phosphoric acid
and 21/2 percent potash, which was the same as that given the
acid phosphate plots in the phosphate experiment. (Table
3, page 7.) While this fertilizer contained the same amount of
ammonia that was contained in the fertilizers applied to the
potash experiment, it was derived from more sources. Also the
percentage of potash in it was different from that in any formula
used in the potash experiment, but was nearest the 3 percent
potash formula. (Table 9.)
In 1919 the beds were plotted and all the plots on the middle
bed were given the no potash fertilizer mixture. The plots on
the other beds received fertilizers containing 1 percent, 3 percent
and 5 percent respectively of potash (Fig. 1).
TABLE 23.-YIELD IN POUNDS AND BY GRADES OF POTASH AND
ADJACENT No POTASH TENTH-ACRE PLOTS, 1919
(21% Potash 1918) (2z% Potash 1918)
S 1% Potash 1919 No Potash 1919
Grades .............. I 1 2 3 4 1 | 2 3 4
157 80 47 81 289 133 44 20
Pounds -............ 318 138 39 21 292 162 48 24
408 180 39 32 316 189 62 33
Total ..-....... 883 398 125 134 897 484 154 77
Average ............ 294 133 42 45 299 161 51 26

(2/2% Potash 1918) (2% Potash 1918)
3% Potash 1919 No Potash 1919
Grades .............. 1 2 | 3 [ 4 1 | 2, 3 4


587 144 43
Pounds .............. 437 162 45
325 127 38
539 194 50
Total .......... 1,888 627 176
Average ...:......: 472 157 I 44-


36 221 145 47
26 389 179 52
17 289 133 44
27 292 162 48
106 1,191 I 619 I 191
27 298 155- 48


i






Florida Agricultural Experiment Station


(2%2% Potash 1918) (2%/2z Potash 1918)
S _56% Potash 1919 I No Potash 1919
Grades ............ I 2 3| 4 1 2 3 4
655 168 46 24 316 189 62 33
Pounds ........... 588 161 50 26 221 145 47 29
434 148 46 26 389 179 52 29
Total ................. 1,677 477 142 76 926 513 161 91
Average ........... 559 159 47 25 309 171 54 30
Average Yield of No Potash Plots.................. 302 162 51 27

TABLE 24.-YIELD IN POUNDS AND BY GRADES OF POTASH AND
ADJACENT NO POTASH TENTH-ACRE PLOTS, 1920
(2%% Potash 1918) (2%'% Potash 1918)
1% Potash 1919 No Potash 1919
1% Potash 1920 No Potash 1920
Grades ..............I 1 2 3 4 1 2 3 4
146 58 15 6 243 136 41 16
Pounds .............. 743 175 43 18 513 203 51 25
693 183 66 45 402 209 57 22
Total ............... 1,582 416 124 69 1,158 548 149 63
Average ............ 527 139 41 23 386 183 49 21

(2/%o Potash 1918) (212% Potash 1918)
3% Potash 1919 No Potash 1919
3% Potash 1920 No Potash 1920
Grades .............. 1 2 3 4 1 2 1 3 4
530 146 34 25 313 122 39 18
Pounds .............. 824 330 70 32 ,366 272 74 26
481 100 28 25 243 136 41 16
713 233 57 44 513 203 51 25
Total .................. 2,548 809 189 126 1,435 733 205 85
Average ............ 537 202 47 31 359 183 51 21

(21/2% Potash 1918) (21z% Potash 1918)
5% Potash 1919 No Potash 1919
5% Potash 1920 No Potash 1920
Grades .............. 1 2 3 4 1 2 1 3 4
681 214 60 20 402 209 57 22
Pounds .......... 620 142 37 32 313 122 39 18
906 356 50 46 366 272 74 26
Total ................. 2,207 712 147 98 1,081 603 170 66
Average ............ 736 237 49 33 360 201 57 22

TABLE 25.--YIELDS IN BARRELS AN ACRE

Ug 21/27o Potash 1918 Eg
Grade -S
2 5% Potash I 3% Potash 1% Potash No Potash P0
1919 I1920 11919 11920 11919 11920 1919 11920 zg'
1 ............ 24.7 33.9 44.5 28.6 38.6 17.8 31.9 18.3 22.5 20.2
2 ............ 5.4 9.6 14.4 9.5 12.2 8.1 8.4 9.8 9.0 11.3
3 ......... 1.7 2.8 3.0 2.6 2.8 2.5 2.5 3.1 3.2 3.5
4 .... .8 1.5 1.9 1.6 1.9 2.7 1.4 1.6 1.3 1.2
Total ....| 32.6 1 47.8 63.8 42.3 55.5 31.11 44.2 I 32.8 I 36.0 I 36.2






Bulletin 158, Fertilizing the Irish Potato Crop


Table 23 and 24 show the 1919 and 1920 yields in pounds on
tenth-acre plots; and by grades of the plots that received 21/2
percent potash in 1918, and 1 percent, 3 percent and 5 percent re-
spectively in 1919 and 1920. Table 25 shows (1) the average
yields of the three beds in 1918; (2) the average yields of the
plots in the extension experiment as shown in tables 23 and 24;
(3) the average yields of the plots in the potash experiment that
received no potash; all calculated to barrels an acre.
INFLUENCE OF RESIDUAL POTASH ON 1919 AND 1920 CROPS
The results of this experiment show the influence of residual
potash from the 1918 application upon the crop of the succeeding
years, 1919 and 1920. The fertilizer applied in 1918 contained 21/2
percent of potash. The application was uniform over all the
beds.
In 1920 those plots, receiving 21/2 percent potash in 1918
and no potash in 1919 and 1920, gave a yield of first grade po-
tatoes which was 2.3 barrels an acre greater than the plots in the
adjacent potash experiment that received no potash during the
three years. The plots receiving 1 percent potash in 1919 and
1920 gave an increase of 11.7 barrels, while those receiving 3
percent and 5 percent potash gave increases of 18.4 and 24.3
barrels respectively.
The plants in this- experiment made practically a uniform
growth. None of the symptoms of potash hunger seen in the
potash experiment were noticed on the plots that received no
potash in 1919.

RESUME
From the results obtained thus far in these experiments a
fertilizer analyzing four to five percent ammonia, eight percent
available phosphoric acid and three to five percent potash would
be a balanced and economical fertilizer.
The experiments do not give any conclusion concerning the
best amount of fertilizer to be used on an acre, nor what sources
or combination of sources of ammonia and potash is best. While
the sources of ammonia used give good results, it is possible that
other sources added to the combination might give better results.
For example, no source of immediately available ammonia was
used in the experiments. A better growth and yield as a whole
might have been obtained by using nitrate of soda as one of the
sources of ammonia.





Florida Agricultural Experiment Station


The yield of potatoes in the experiment as a whole has been
low. This is only partly explained by the newness of the land.
While this is true, the variations in the yields caused by the dif-
ferent fertilizer treatments have been pronounced, so that the
factor of low yield probably has not been an interference.
The experiments prove that both phosphoric acid and potash
are limiting factors for growth and crop production in this
region, and must be supplied in the form of fertilizers in order
to produce the most profitable crop.
CONCLUSIONS
The results show further that:
1. Soluble phosphoric acid was necessary in the early
stages of growth to produce vigorous plants.
2. Raw rock phosphates failed to produce maximum top
growth.
3. Pebble phosphates in 1920 gave a yield that was nearly
as great as from acid phosphate.
4. Soft phosphate has not proven as good as the pebble
phosphate.
5. In absence of sufficient potash tubers did not reach full
size, and in extreme scarcity the normal growth of the tops was
also interfered with and certain appearances characteristic of
potash starvation developed.




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