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AGRICULTURAL EXPERIMENT STATION

A. B. CONNER, DIRECTOR
COLLEGE STATION, BRAZOS COUNTY, TEXAS

BULLETINNNQQ. 524 MARCH, 1936

DIVISION OF HORTICULTURE

FERTILIZER EXPERIMENTS WITH
YELLOW BERMUDA ONIONS IN
THE WINTER GARDEN
REGION OF TEXAS

 

AGRICULTURAL AND MECHANICAL COLLEGE 0F TEXAS
T. O. WALTON, President

Phosphoric acid had the most effeqt 0n yields, nitrogen was the
next most effective, and potash had practically no efiect in four
years of fertilizer experiments with Yellow Bermuda onions on
Webb fine sandy loam soil at the \Vinter Garden Station. After
the first year, potash sometimes decreases yields rather than in-
creasing them. The use of 600 to 900 pounds per acre of a 6-12-0
fertilizer or a fertilizer which furnishes the nutrients in equivalent
amounts and proportions is‘ in general suggested. An amount as
large as 1200 pounds, and a fertilizer containing potash, may
prove profitable on previously unfertilized land the first year, but
is not likely to be profitable thereafter. In the light of the findings
reported herein every situation requires individual consideration.

While ammonium sulphate applied alone is 11ot likely to prove
very profitable (and in fact may decrease yields on previously
unfertilized land), 20 per cent superpho-sphate used alone at the
rate of 360 pounds per acre will normally increase yields to a
profitable extent. The two materials combined to make an appli-
cation equivalent to 600 pounds of 6-12-0 fertilizer were usually
more efiective in increasing yields than the superphosphate by
itself.

The experiments indicate that the application of all the fertilizer
to the soil previous to the setting out of the onion plants is the
most desirable practice. Sodium nitrate or ammonium sulphate
applied as a side dressing is very likely to decrease yields instead
of increase them, except in the case 0f previously unfertilized
onions which may respond with slight increases in yield.

The value of several nitrogen carriers including cottonseed
meal is reported.

Normally onions receiving 600 to 900 pounds of a 6-12-0 or
similar fertilizer will be earlier and also have a higher percentage
of U. S. No. 1 bulbs than onions fertilized with other grades.

Whenever larger amounts of nitrogen than those recommended
are applied, the harvested onions are likely to decay quicker in
common storage than they will if less nitrogen has been applied.

The ill efiects due to the damage by thrips (ThVi/ZJS tabaci) can
be overcome to a great extent by proper fertilizer practices. A
severe attack of the pink root disease (Fusarium mam) appar-
ently cannot be combated profitably by applications as large as
1800 pounds per acre of 6-12-6 fertilizer, nor by ordinary fer-
tilizers having other formulas.

CONTENTS

Page

Introduction 1. _______________________________________________________ 1
Review of other work  ____________ 1 5
Methods employed   _ __ __ 6
Effects of pink root, thrips, and freezes ________________________________________________ 1 1O
Effect of nitrogen on yield of onions11 11
Varying the proportion of nitrogen in a complete fertilizer .......... _- 11
Nitrogen applied alone _  11
Sources of nitrogen 13
Effect of phosphoric acid on yield of onions __________________________________________ __ 15
Varying the proportion of phosphoric acid in a complete fertilizer 15
Phosphoric acid applied alone ________________________________________________________ _- 16
Effect of potash on yield of onions 1 1 17
Varying the proportion of potash in a complete fertilizer ............ 1 17
Fertilizers with potash omitted 1 17
Relative effect of the different nutrients in a complete fertilizer ........ -- 17
Rates of application of complete fertilizer- 1 18
Time and methods of application of fertilizer ...................................... 1 20
Time of application of complete fertilizer (6-12-6) ______________________ 1 2O
Side dressings _________ -. 21
Effect of fertilizer on other characteristics 1 22
Earliness 22
Grade 23
Keeping qualities 26
Discussion and recommendations  29
Acknowledgments  32
Summary 32
Literature cited _1 34

BULLETIN NO. 524 MARCH, 1936

‘ FERTILIZER EXPERIMENTS WITH YELLOW BERMUDA
ONIONS IN THE WINTER GARDEN REGION OF TEXAS

Leslie R. Hawthorn, Horticulturist, Substation N0. 19, Winter Haven

The culture of Bermuda onions is an important industry in Texas.
In 1932, the last year for which published car-lot shipments are available,
28,055 cars 0f onions were shipped in the United States, 8,342 of which
originated in Texas (13)*. This was a greater number than originated
in any other state. Practically all of these cars from Texas were
Bermuda onions. In 1926 Texas was credited with raising annually 80
per cent or more of the Bermuda onions in the United States (11).
Texas has not always shipped more onions than any other state, but for
a number of years the acreage and the car-lot shipments have been high.
A large proportion of the onions raised in Texas are grown under irriga-

tion on various sandy loam soils in the Winter Garden area of South-.

west Texas (4, 8).

Because the culture under such a system is rather intensive, the cost
of growing such a crop is considerably higher than it is with many other
vegetables. With such a system it becomes essential that the crop be
produced efficiently and economically; otherwise in a year of low prices
for the harvested product the losses are likely to be heavy.

The studies reported in this bulletin were carried out at the Winter
Garden Substation No. 19 for the purpose of determining as accurately
as possible the fertilizer needs of Bermuda onions. Since by far the
greater acreage of Bermuda onions is devoted to the Yellow Bermuda
variety (4, 11), this was the variety used throughout these experiments.
It was planned to find answers to such questions as these: What for-
mula should the fertilizer have? How much of it should be applied?
When and how should it be applied? Are side dressings profitable? If
so, what kind of side dressings? When should they be applied? Are
some fertilizer materials more desirable than others? Does it pay to use
fertilizer even in a year of low prices? These and other questions if
satisfactorily answered might well lead to a more efficient production of
onions at a lower cost per bushel.

REVIEW OF SOME PREVIOUS WORK

Investigations looking toward better fertilizer practices with onions
were carried out on a limited scale from 1904 to 1908 at the Beeville
Substation (14). Results of these experiments conducted on a Goliad
fine sandy loam indicated that neither nitrogen, phosphoric acid, nor
potash applied alone or in combination could be used profitably, as
yields from all these treatments were lower than those from the non-
fertilized plats. Barnyard manure at the rate of 20 tons per acre re-
sulted in yields higher than those produced on the non-fertilized plats,
but the increase in yield was not striking. Cottonseed meal applied alone

* This and similar numbers refer to references under “Literature Cited.”

6 BULLETIN NO. 524, TEXAS AGRICULTURAL EXPERIMENT STATION

produced the lowest yield of all treatments. None of these results can
be considered very reliable in the light of present experimental methods,
since only single plats of each treatment were used.

Fertilizer experiments from 1926 to V1930 on a sandy 10am soil in
Virginia indicated that of the three nutrients, nitrogen, phosphoric acid,
and potash, phosphoric acid was the most essential (12). “The fertilizers
from which phosphorus was omitted gave the lowest yields each year. . .”
Nitrogen also seemed necessary for good growth since yields were in-
creased, as the percentage of ammonia was increased from 0 to 6 per cent
in a formula in which the phosphoric acid and the potash were each held
constant at 8 per cent. Potash had but little effect on yield. In con-
trast to this, very decided increases in yield have been obtained in Michi-
gan and New York from increased amounts of potash (3, 6). The
experiments in those states, however, were on muck soils deficient in
potash. In recent studies in the Connecticut Valley of Massachusetts
where the N-P-K ratio was varied on a fine sandy loam, the “greatest re-
sponse was obtained from an increase of phosphorus, but significant
increases were obtained only when potassium was increased also” (1).
The most desirable application was 2500 pounds per acre of a 4-12-8
mixture‘. Raising the percentage of nitrogen from 4' to 6 failed to pro-
duce any significant increases in yield when all the fertilizer was applied
before sowing the seed (the crop was seeded directly in the field), but
when nitrogen was applied later as a side dressing, beneficial increases
in yield were obtained. Onions grown from dried sets, however, did not
respond to nitrogen side dressings.

In experiments conducted at the New Mexico Agricultural Experiment
Station with the new Early Grano onion, superphosphate alone at 220
pounds per acre resulted in the lowest yields in comparison with treat-
ments of ammonium sulphate alone, ammonium sulphate and super-
phosphate in combination, a complete fertilizer, barnyard manure, and
no fertilizer at all (10). The highest yields were from the plats receiving
the complete fertilizer. In a storage test connected with these same
experiments there was a slight tendency for the onions taken from the
heavier yielding plats to show a greater shrinkage in storage, although
evidently no significant differences Were established.

METHODS EMPLOYED

Formulas and Amounts Used: In order to obtain information of a
fundamental nature the first experiments to be carried out in the season
of 1931-32 were planned to determine the relative value of nitrogen,

phosphoric acid, and potash, and the ratio in which they should be

present in a fertilizer mixture.

For this study a 6-12-6 fertilizer made up from 20% sulphate of
ammonia, 20% superphosphate, and 48% or 50% muriate of potash
applied at a rate equivalent to 600 pounds per acre was used as the
basic treatment. This amount and kind of fertilizer is commonly applied
by commercial growers. In order to test the value of the individual

FERTILIZER EXPERIMENTS WITH YELLOW BERMUDA ONIONS 7

nutrients separately, the percentage of each was varied in a series of
treatments in which the percentages of ‘the two nutrients not being
tested were kept constant. (See table 2a). In this manner the effect of
each nutrient could be determined separately without any undue limita-
tions because of lack of the others. This system of testing also enabled
a number of formulas with different ratios to be studied. Various
amounts ranging from 0 to 1800 lbs. per acre of ‘the complete fertilizer
(6-12-6) were also tried. (Table 7a). These experiments were conducted
for four seasons ending in 1934-35. Each plat received the same treat-

ment every year.

In 1932 another series of treatments was laid out to supplement and
check still further some of the results obtained in the fundamental series
initiated in 1931. Ammonium sulphate was tried alone at rates of 180,
360, and 540 pounds per acre, which was equivalent to applying 600,
1200, and 1800 pounds of 6-0-0 fertilizer per acre. Similarly 20 per cent
superphosphate was tested alone at rates of 360, 720, and 1080 pounds
per acre, which was equivalent to applying 600, 1200, and 1800 pounds
of 0-12-0 fertilizer per acre. Both nutrients were then applied together
in amounts equivalent to 600, 1200, and 1800 pounds of 6-12-0. With
these were compared similar rates of 6-12-6. (Table 3).

Sources of nitrogen were also tried. In this test, nitrate of soda, sul-
phate of ammonia, cyanamid, and cottonseed meal were all applied at
rates to supply 36 pounds of nitrogen per acre. Each was combined with
superphosphate to give 72 pounds of phosphoric acid per acre, and with
muriate of potash to give 36 pounds of potash per acre. These applica-
tions were each equivalent to 600 pounds of 6-12-6 fertilizer per acre.

In addition the two materials having formulas of 11-48-0 and 16-20-0
were also tried at rates to give 36 pounds of nitrogen per acre. Since the
formulas of these materials were already fixed, no attempt was made to
create a 6-12-6 fertilizer out of them, and hence although they supplied
exactly the same amount of nitrogen as 600 pounds of 6-12-6 the amounts
of phosphoric acid were different. The 11-48-0 fertilizer gave 157.08
pounds of phosphoric acid per acre, and the 16-20-0 fertilizer supplied
65.45 pounds. All of the treatments testing the source of nitrogen are
listed in Table 4. These additional experiments, started in the fall of
1932, were conducted through three seasons ending in 1934-35.

In 1933-34 and 1934-35 an application of 510 pounds per acre of
cottonseed meal alone was tried. This was broadcast and harrowed in
a week before the onion plants were set out.

Side Dressings: During the seasons 1932-33 to 1934-35 various tests
were carried out to determine the value of side dressings, since some
growers depend entirely on side dressings of nitrate of soda, and others
who make an initial application of a complete fertilizer frequently sup-
plement this later with one or more side dressings of sodium nitrate.

Treatments were therefore devised to determine the value of side
dressings on onions receiving no fertilizer at time of planting, as well as
on onions fertilized at that time. In addition the attempt was also made

8 BULLETIN NO. 524, TEXAS AGRICULTURAL EXPERIMENT STATION

to discover if it is profitable to apply a total amount of complete fertilizer
as great as 1200 pounds all at one time, or if it is more desirable to split
it into an initial application and one or more later applications in the
formiof side dressings. Besides these side dressings of complete fer-
tilizer three other materials were used as side dressings: nitrate of soda,
ammonium sulphate, and ammonium phosphate (11-48-0). The amounts
of these materials were adjusted so that the quantity of nitrogen applied
by each was equivalent to the amount of that material contained in 100
pounds of ammonium sulphate. The ammonium sulphate, the ammonium
phosphate, and half of the sodium nitrate, were applied around the middle
of January each year, and the remaining half of the sodium nitrate was
applied about a month later. Some of the treatments were fertilized
before planting with 600 pounds of a 6-12-6 fertilizer; others were not.
The exact treatments are listed in Table 8. The side dressings were
scattered between the rows by hand and cultivated in, and the plats were
irrigated.

Size and Arrangement of Plats: The plats in the fundamental series,
started in 1931, consisted of eight rows fifty feet long and 14 inches
apart. The outer row on each side of the plat was used as a guard row
and Was_ not included in the recorded yield of the plat. Likewise an area
one foot wide across each end of the plat was not recorded. The area
on which data were based was a trifle larger than 1/130 of an acre. Each
plat was separated from those on either side of it by a three-foot raised
border. A similar border extended across the lower end of each plat.
These borders not only separated the fertilizer treatments but prevented
the movement of irrigation water from one plat to another. The various
tiers of plats were irrigated with water coming directly from the reservoir.
Drainage ditches were placed to catch any water which broke over or
through the lower border of a plat, so that none of it ever reached a
supply ditch. ‘

Because the land used for this experiment was terraced and of an
irregular shape, the plats could not be arranged in regular straight lines
and in large blocks but had to be grouped for the most part in small
blocks. The treatments were arranged in the order given in Tables 2a
and 7a and were replicated four times.

As it was found that a plat only 50 feet long with a border across
the lower end to stop the flow of water did not always “wet up” well,
without an opening in the lower end to allow the water to run through a
longer time, plats in all the experiments laid out after the first season
were made twice as long; that is, 98 feet. The recordable area remained
exactly the same, as the yields were based on three rows instead of six.

The plats used for the nitrogenous side dressings, as well as the treat-
ment calling for cottonseed meal alone, were the only ones laid out in
new locations each season.

The land used for all of these experiments was a Webb fine sandy loam.
It was cleared of native brush in 1930, and some of it had been planted
to snap beans and later to field corn before being measured off for the

FERTILIZER EXPERILIENTS WITH YELLOW BERMUDA ONIONS 9

onion experiments in the fall of 1931. In Table 1 chemical analyses of
the soils by the Division of Chemistry are given. These analyses give

Table 1. Analyse of the soils used

Fundamental series Supplementary series
Nutrient
Surface soil Subsoil Surface soil Subsoil
0—7in 7-19in 0- in 7—19in
Nitrogen . . . . . . . . . . . . . . . . . . . . . .. 0.33% 0.27% 0.031% 0.035%

Active phosphoric acid . . . . . . . . . . 21 ppm 9 ppm 28 ppm 9.5 ppm

Total phosphoric acid . . . . . . . . . . . 0.023% 0.022% 0.022% 0.023%

Active potash . . . . . . . . . . . . . . . . . . 200 ppm 185 ppm 200 ppm 223 ppm

Total potash . . . . . . . . . . . . . . . . . . . 0.54% 0.54% 0.60% 0.60%

ACld consumed . . . . . . . . . . . . . . . . . 3.0% 2.0% 2.0% 3.0%

pH . . . . . . . . . . . . . . . . . . . . . . . . . . .. 6.43 6.66 6.60 7.13

the composition before the application of any fertilizers or before any
crop of onions had been grown. They indicate an abundance of potash
but a low supply of nitrogen and phosphoric acid.

Culture: In all experiments in which the fertilizer was applied before
planting, the material was broadcast by hand. Following this the ridges
on which the onion plants were later set out were made. The shovels of
the cultivator in making the furrows and in throwing the earth into
ridges mixed the fertilizer rather thoroughly throughout the ridge. Broad-
casting the fertilizer preceded the setting out by only a. day or two. All
the planting, was done by hand, in the regular commercial way, help
especially adept at this operation being employed. Plants were spaced
about 3% inches apart and all spacing in the rows was equal, since the
same marking machine was used in all the experiments.

Slight variations in procedure occurred in some seasons, but in any
one season all treatments were handled alike. In 1933-34, sulphate of‘
potash was used instead of muriate of potash but tests with onions in
Massachusetts have failed to indicate that any significant differences in
yield is likely to result from these two sources of potash (1). In 1933-34
and 1934-35, the tops of the onions were not clipped back as is the usual
custom, and as they had been in the first two seasons.

Aside from the variations in method made necessary by the technique
of the experiment, and bry the treatments themselves, the cultural
methods followed throughout all the tests were similar to those generally
practiced in the Winter Garden area. "

Onion Storage: An attempt was made in 1931-32 and again in 1932-33
to see whether the various fertilizer treatments of the “fundamental”
series had any effect on the keeping quality of onions in common storage.
As each plat in this series was harvested, a random sample of 30 to 35
onions from the U. S. No. 1 grade was taken and set aside. In all there
were 72 samples, one from each plat. Within a few days or a week
these were regraded and reduced in each case to 25 good onions free
from decay. All samples, still in paper bags, were then placed in com-

10 BULLETIN NO. 524, TEXAS AGRICULTURAL EXPERIMENT STATION

mon storage. In 1931-32 they were stored on a shelf under the tile roof
of an open implement shed. In 1932-33 they were placed on the dry
concrete floor of a ventilated room in a hollow tile barn. The tops of
the bags were left open. Periodically they were examined (see dates in
Tables 10 and 11) and the decayed bulbs were counted and removed. In
October when there was an increasing tendency for the remaining bulbs
to begin sprouting, the test was concluded.

EFFECTS OF PINK ROOT, THRIPS, AND FREEZES

During the course of these fertilizer experiments, various factors be-
yond control affected the results of certain treatments. Since a knowl-
edge of these uncontrolled factors aids in a better understanding of the
results produced by the various fertilizers, consideration is given to
them here before the detailed discussion of the results is given.

Freezing injuries: In the season 1932-33, a severe freeze occurred in
early February. This has been fully described in connection with its
effect on 20 varieties of onions (7). A temperature as low as 18 degrees
F. and a strong continuous wind severely injured the tops of all onions.
Many onions were completely killed, and at harvest time a large propor-
tion were classed as splits and doubles (Table 9).» This increased the
proportion of culls, undoubtedly at the expense of the No. 1 onions.
Plats which received little or no fertilizer, or fertilizer lacking an essen-
tial nutrient, lost more plants than well-fertilized plats. On the other
hand well-fertilized plats, while losing very few plants, had a reduced
yield of U. S. No. 1 onions because of the large numbers of splits and
doubles.

In the 1934-35 season a similar freeze occurred in late January, when
the temperature dropped to 19 degrees FL For some reason, possibly
the lack of wind when the temperature was at its lowest, the onions were
not injured as severely as they were in 1932-33.

Pink root and thrips: In the third season (1933-34), pink root due
to Fusarium mam was noticeable here and there throughout the funda-
mental series. It did not, however, affect ryields to any measurable ex-
tent. In the following season (1934-35), pink root was very serious in
this series, affecting almost every plat. As can be seen in Tables 2a and
7a, yields were very much reduced that year and not one of the treat-
ments made profitable yields.

Thrips tabaci was very severe in both 1933-34 and 1934-35 but it is
believed-that the ill effects of thrips can be more easily overcome than
those of pink root. The main supplementary series had pink root to
some extent in 1934-35 and in general had lower yields that year (Tables
3 and 4). Outside of these two important series none of the other
experiments described herein, nor those as yet unreported, suffered from

pink root, chiefly because they have been rotated with other crops._

However, in spite of suffering iust as seriously from the thrips, all treat-
ments yielded very heavily in comparison with those of 1934-35 in the

FERTILIZER EXPERIMENTS WITH YELLOW BERMUDA ONIONS 11

fundamental series in which there was severe pink root infection. A
comparison of almost any of the tables with Tables 2a and 7a illustrates
this point.

EFFECT OF NITROGEN ON YIELD OF ONIONS

Varying the Proportion of Nitrogen in a. Complete Fertilizer

A study of the results obtained during four years from the treatments
in which the amount of nitrogen applied was varied while the phosphoric
acid and potash were kept constant, indicates that in general nitrogen is
beneficial when contained in fertilizers used in onion culture (Tables 2a
and 2b). Increasing the amount of nitrogen has not had as marked an
effect as increasing the phosphoric acid, nor has the effect been as sus-
tained throughout the four years. In 1931-32 the yield of U. S. No. 1
onions from the 9-12-6 fertilizer treatment was 156 per cent greater
than that from the 0-12-6 fertilizer, but three years later (in 1933-34)
it was only 16 per cent greater, the same as the 6-12-6 fertilizer, and
but one per cent more than the ‘yield produced by 3-12-6. In 1934-35,
marked increases in percentage similar to those obtained in 1931-32
were again obtained, but this can be attributed to the low yields through-
out, a condition which accentuates the percentage. For the four years
of the experiment the 9-12-6 fertilizer made an average yield of 179
bushels of U. S. No. 1 onions per acre as compared with a yield of 128
bushels of U. S. No. 1 onions for the 0-12-6 fertilizer (Table 2a). When
total yields are considered, the 9-12-6 fertilizer averaged 274 bushels
against 209 for the 0-12-6. '

While there was a noticeable tendency throughout the four years of’
observations for the yields to increase as the amount of nitrogen was
increased from O to 9 per cent in the formula, a careful analysis of the
figures obtained indicates that each added increment of nitrogen did not
produce in itself a significant increase in yield. In other words, while
the difierence in yield between the 0-12-6 and the 9-12-6 fertilizer treat-
ments was usually significant, the differences in yield between 0-12-6
and 3-12-6, or between 3-12-6 and 6-12-6, etc., were frequently not so,
although. the yields always tended to be higher with the greater amount
of nitrogen. The difierences became less as the seasons Went by until in
the third season (1933-34) the yields produced by the 3-12-6, 6-12-6,
and 9-12-6 fertilizer treatments were all practically the same. The re-
sults indicate that while some nitrogen is beneficial, a high proportion
of it in the fertilizer mixture is not profitable year after year.

Nitrogen Applied Alone

In the experiment just described each of the three nutrients had been
varied in quantity in the presence of constant amounts of the other two.
As increasing the nitrogen produced marked increases in yield, the pur-
pose of a supplementary test was to determine if a nitrogenous fertilizer
by itself has any value. Ammonium sulphate. was used as the carrier.

12 BULLETIN NO. 524, TEXAS AGRICULTURAL EXPERIMENT STATION

Table 2a. The eflfect of varying the ratios of nitrogen, phosphoric acid,
and potash on the bushels of onions per acre

U. S. No. 1 Total yield
Fertilizer used

1932* 1933 1934 1935 Aver. 1932 1933 1934 1935 Aver.

N0 fertilizer . . . . . . . . 59 186 119 6 93 153 242 203 S0 162
Nitrogen series:

0-1 — . . . . . . . . . . . . . 66 258 182 7 128 170 353 266 48 209

3-12-6 . . . . . .' . . . . . . . 116 302 209 14 160 244 386 301 68 250

6—12—6 . . . . . . . . .  . . 142 280 212 15 162 251 389 299 69 252

9-12-6 . . . . . . . . . . . . . 169 318 211 18 179 286 436 300 73 274
Phosphoric acid series:

6-0-6 . . . . . . . . . . . . . . 40 156 98 4 75 128 202 190 36 139

90 251 172 ' 13 132 200 315 258 71 211
169 261 192 21 161 253 384 284 78 250
198 294 201 16 177 299 450 288 74 278

132 284 236 19 168 255 438 339 75 277
161 304 210 14 172 276 376 301 60 253
137 291 195 13 159 247 387 281 68 246
164 267 234 22 172 308 374 335 85 276

 

* This and other years given are the years in which harvest occurred.

Table 2b. Percentages of increase o'r decrease in yield of onions due to
varying the ratios of nitrogen, phosphoric acid, and potash in the formula

U. S. No. 1 Total yield
Fertilizer used

1932* t 1933 1934 1935 Aver. 1932 1933 1934 1935 Aver.

Nitrogen series:

 

0-12 —6, check . . . . . . . -— --- -—~ — — —- — -- -- -
3-—12—6 . . . . . . . . . . . . . 76 17 15 100 25 44 9 l3 42 20
6—12—6. . .. . . . . . . . .. 115 9 16 114 27 48 10 l2 44 21
9-12-6 . . . . . . . . . . . . . 156 28 16 157 40 68 24 13 52 31
Phosphoric acid series:
6~0—6, check — -— -- —— -— — -— —- -— —-
6-6-6 . . . . . . . . . . . . . . 125 61 76 225 76 S6 56 36 97 52
6—12—6 . . . . . . . . . . . . . 323 67 96 425 115 98 90 49 117 80
6-18-6 . . . . . . . . . . . . . 39S 88 105 300 156 134 123 52 106 100
Potash series:
6 - 12-0, check . . . . . . . —-- — —— —- — —- -- --- — '-
6—12—3. . . . . . . . . . . . . 22 7 —11 —26 2 8 —14 —-11 —20 -9
6—12—6 . . . . . . . . . . . . . 4 2 -17 —32 ~—5 —3 —12 -l7 —9 -11
6-12-9‘ . . . . . . . . . . . . . 24 —6 -1 16 2 21 -15 —:1 13 0

* This and other years given are the years in which harvest occurred.

This material is sometimes used in just this way by commercial growers.

The plats receiving 540 pounds of ammonium sulphate (equivalent to’

1800 pounds of 6-0-0) made an average yield equivalent to 90 bushels
of U. S. No. 1 onions per acre for the three years of the experiment as
compared with a yield of 124 bushels of U. S. N0. 1 onions for the 180
pounds of ammonium sulphate equivalent to 600 pounds of 6-0-0 (Table
3)‘. The average total yield of onions resulting from the application of
540 pounds of ammonium sulphate was 152 bushels per acre, as com-
pared with an average total yield of 205 bushels from thei180 pounds
of ammonium sulphate. In each of the three years, the lowest amount
of ammonium sulphate gave as high a yield as any of the ammonium
sulphate applications, no significantly higher yields resulting from either

FERTILIZER EXPERLNIENTS WITH YELLOW BERMUDA ONIONS 13

of the other treatments. In the first year of this test (1932-33) all
applications of ammonium sulphate resulted in lower yields than were
obtained from the no-fertilizer treatment. In 1933-34 and 1934-35 sig-
nificantly higher yields resulted from the application of the lowest
amount of ammonium sulphate, viz. 180 pounds per acre. Evidently
ammonium sulphate used alone is not only less effective, but in large
applications is even harmful, reducing yields of onions instead of in-
creasing them. This result is much in contrast with that obtained when
ammonium sulphate was used as an ingredient of the 3-12-6, 6-12-6,
and 9-12-6 fertilizers.

Sources of Nitrogen

The results from the treatments in this test have varied somewhat
from year to year. This indicates that as soil and climatic conditions
vary from year to year the response of the crop may also vary. The
fertilizers themselves may influence soil conditions from one year to the
next, because they often leave residues.

Nitrate of Soda: In the first season (1932-33) the 6-12-6 fertilizer
containing nitrate of soda resulted in a yield of 282 bushels of U. S.
No. 1 onions per acre (Table 4). It was the highest yield in this par-
ticular test that year (there were 146 bushels of U. S. No. 1 onions from
the unfertilized treatment). In the following season the nitrate of soda
treatment failed to produce as well in comparison with the other nitro-
gen carriers. While it was exceeded in yield by most of them, the sodium
nitrate treatment was not significantly lower. In the third season it

p resulted in next to the highest yield of U. S. No. 1 onions. In general it

seems to be a fairly satisfactory carrier of nitrogen. When used by itself
its results may not be so good. (See results reported under “Side Dress-
ingsf’)

‘Sulphate of Ammonia: The mixture containing ammonium sulphate,
which was standard in all these tests, resulted in the third highest yield
(255 bushels of U. S. No. 1 onions) in the first season. The following
season the U. S. No. 1 yield from this treatment was the highest, al-
though it exceeded some others by an insignificant margin (Table 4).
In the third year the yield was lower than those from most of the treat-
ments. Sulphate of ammonia has in general given satisfactory results.
Theoretically it should in the long run be more beneficial in alkaline
soils than sodium nitrate, as its residue is acid, that of nitrate of soda
being alkaline. Like sodium nitrate it may not be so beneficial when
used alone. (See earlier discussion under “Nitrogen Applied Alone,” as
well as the report of “Side Dressings” later.)

Oyanamid: In two out of three seasons the use of this material in
the 6-12-6 mixture resulted in the lowest yields of U. S. No. 1 onions,
with the exception of the no-fertilizer treatment (Table 4). In the other
season (1933-34) it placed fourth with a yield of 194 bushels, as com-
pared with 207 for ammonium sulphate (highest), and 93 for the un-
fertilized treatment (lowest).

14 BULLETIN NO. 524, TEXAS AGRICULTURAL EXPERIMENT STATION

Table 3. Effect of various applications of nitrogen and phosphoric acid, alone
and in combination, as well as with DOfaSh, on the yield of onions (bu. per acre)

U. S. No. 1 Total yields
Fertilizer used
1933 1934 1935 Aver. 1933 1934 1935 Aver.
No fertilizer (check) . . . . . . . . . . . . . . 146 93 37 92 208 172 106 162
Nitrogen alone:
180 lbs. of ammonium sulphate. . . . . 138 175 60 124 172 308 136 205
360 lbs. of ammonium sulphate. . . . . 139 148 63 117 195 231 134 187
540 lbs. of ammonium sulphate. . . . . 83 143 43 90 115 227 113 1S2
Phosphoric acid alone:
360 lbs. of 20% Superphosphate . . . . 211 194 64 156 279 306 131 239
720 lbs. of 20% Superphosphate . . . . 191 199 76 155 298 320 148 255
1080 lbs. of 20% Superphcsphate . . . . 237 208 75 173 321 310 143 2S8
Nitrogen and phosphoric acid in
combination:
600 lbs. of 6-12-0 . . . . . . . . . . . . . . . . . 211 207 112 177 294 . 333 184 270

600 lbs. of 6-12-6 . . . . . . . . . . . . . . . . . 231 187 103 174 310 289 178 259

1200 lbs. of 6-12-0 . . . . . . . . . . . . . . . . . 207 189 10S 167 327 301 176 268

1200 lbs. 0f 6-12-6 . . . . . . . . . . . . . . . . . 223 214 91 176 335 316 166 272

1800 lbs. of 6-12-0 . . . . . . . . . . . . . . . . . 149 168 88 135 2S7 254 164 225

1800 lbs. of 6-12-6 . . . . . . . . . . . . . . . . . 213 170 79 154 342 277 135 251

11-48-0 Fertilizer: The yields obtained from treatments receiving the
11-48-0 fertilizer (ammonium phosphate) have in comparison with the
yields from most other treatments been increasingly satisfactory each
year. In the second season the yield of‘ 206 bushels of U. S. N0. 1 onions
from this treatment was for all practical purposes the same as the highest
yield (207 bushels) from the ammonium sulphate treatment (Table 4).
In the third season the 11-48-0 treatment resulted in the highest yield
(86 bushels), although this was not significantly greater than several
others. A probable explanation of the success of this fertilizer lies in
its high phosphoric acid content.

16-20-0 Fertilizer: This material did not‘ prove as satisfactory the
first season, resulting in a yield of only 209 bushels of U. S. No. 1 onions,
as compared with 282 bushels (highest) from the sodium nitrate treat-
ment. In the following two seasons it resulted in yields which were only
very slightly below the highest yield. For all practical purposes they
were about the same.

Cottonseed Meal: Although this material used in a 6-12-6 fertilizer
resulted in the lowest yield (unfertilized plats excepted) in the second
season, its effect on yield in the first and last seasons was far from un-
satisfactory, and even in the second season the yield was very far from
being a failure when compared with the unfertilized treatment (Table 4).
In Table 5 yields are given for the harvests of 1934 and 1935 for onions
receiving the cottonseed meal alone. This was in a separate series from
those just described above, and hence the records for the unfertilized
plats, as well as for those receiving the standard 600 pounds of 6-12-6
fertilizer, differ from those given in Table 4. When cottonseed meal is
applied alone (a fairly common practice in years when it is cheap),
yields are shown to be not very much greater than when no fertilizer at

FERTILIZER EXPERIMENTS WITH YELLOW BERMUDA ONIONS 15

Table4. The effect of the source of nitrogen on yield per acre. (All fertilizers
were applied to give 36 lbs. of nitrogen per acre)

Cost of U. S. No. 1 (bu.) Total yield (bu.)
Entire
Nitrogen carrier used Fertili-

zer* 1933 1934

Aver.

   

193s ‘Aver. 1933 l 1934 193s

 

No fertilizer- . . . . . . . . . . . . . . . . 0.00 146 93 37 92 208 172 106 162
Nitrate of soda in 6-12-6 . . . . . . 11.62 282 191 84 186 376 279 149 268
Sulphate of ammonia in 6-12-6. 11. 11 255 207 74 179 317 305 137 253
Cyanamid in 6-12-6 . . . . . . . . . . 9. 76 203 194 68 15S 277 277 133 229
Cottonseed meal in 6-12-6. . . . . 13. 18 266 181 80 176 329 267 148 248
11-48-0 327% lbs. per acre . . . . 11 .08 248 206 86 180 361 316 150 276
16-20-0 225 lbs. per acre . . . . . . 6.53 209 202 82 164 264 300 154 239

*Based on average selling prices as given in Texas Agr. Exp. Sta. Bul. 498, Commercial Fertilizers
in 1933-34, p. 9. '

Table 5. Effect of cottonseed meal in comparison with no fertilizer and 600
lbs. of 6-12-6 fertilizer on the bushels of onions per acre

U. S. No. 1 Total

Fertilizer used
1934 1935 Aver. 1934 1935 Aver.

No fertilizer . . . . . . . . . . . . . . . . . . . . . . . . . .. 90 l 46 6s 156 101 129
510 lbs. of cottonseed meal . . . . . . . . . . . . . . 112 49 81 177 132 155
600 lbs. 6-12-6 . . . . . . . . . . . . . . . . . . . . . . . . . 23s 10s 169 31s 181 25o

all is applied. Compared with those from the 600 pounds of 6-12-6
fertilizer, they are extremely 10W.

Cost of Various Nitrogen Sources: The most costly treatment does
not necessarily result in the greatest yield (Table 4). Some treatments,
too, may be more profitable in one year than they are in others. In
1932-33 the 16-20-0 fertilizer resulted in a return hardly as profitable
as those produced from most other treatments. In ‘the two following
seasons, however, this material, as has been pointed out, resulted in
yields practically equivalent to the highest ones. Figured at the average
prices reported for the State of Texas in 1933-34 (2) the 16-20-0 fer-
tilizer cost only $6.53 an acre, more than $4.50 less than the 11-48-O
fertilizer, as Well as the one in which sulphate of ammonia was used.
It cost almost $5.20 less than the fertilizer containing nitrate of soda.
Assuming the response obtained in these two seasons represents normal
yields, in those years the 225 pounds of 16-20-0 was the best investment
among the various possibilities offered by the treatments in the source
of nitrogen test. Because of the low ratio of phosphoric acid to nitrogen
in the 16-20-0 fertilizer, it probably would not be as desirable to apply
the first year on previously unfertilized land, for reasons which will be
discussed later.

EFFECT 10F PHOSPHORIC ACID ON THE YIELD OF ONIONS
Varying the Proportion of Phosphoric Acid in a Complete Fertilizer

Of the three nutrients—nitrogen, phosphoric acid, and potash_-phos_
phoric acid has consistently produced the most marked increase of yield
in all four years, and wherever it has been omitted from the fertilizer

16 BULLETIN NO. 524, TEXAS AGRICULTURAL EXPERIMENT STATION

the yields have always been the lowest of all treatments, no-fertilizer
includ-ed (Table 2a). These results resemble rather strikingly those
reported from Virginia in 1930 (12).

The 6-18-6 fertilizer resulted in an average yield of 177 bushels of
U. S. N0. 1 per acre for the four years of test, as compared with a yield
of 75 bushels of U. S. No. 1 onions from the 6-O-6 treatment (Table 2a).
Average total Iyields for the four years are in similar proportions, that
from the 6-18-6 fertilizer being 278 bushels and that from the 6-0-6
fertilizer 139 bushels. In 1931-32 the yield of U. S. No. 1’s from the
6-18-6 was 395 per cent higher than that from the 6-0-6, while in 1933-
34 it was down to 205 per cent (Table 2b). This was still a considerable
percentage of increase as compared with the nitrogen series. In 1934-35
all yields in this series were seriously reduced by the pink root disease
mentioned above, and percentages of increase were hence much accent-
uated. In that season the increased yield of U. S. No. 1’s from an appli-
cation of 6-18-6 fertilizer was 300 per cent greater than the yield from
the 6-0-6 mixture.

The increases in yield which can be attributed to each added increment
of phosphoric acid as the formula has been stepped up from 6-0-6 to
6-6-6, to 6-12-6, to 6-18-6, have been markedly moresignificant than
those in the nitrogen series. The greatest difference, with one exception,
has always been between the 6-0-6 and the 6-6-6 treatments. Adding a
relatively small amount of phosphoric acid to a soil which is apparently
very deficient in it produces striking results. As the years have passed,
the differences between the 6-12-6 and the 6-18-6 treatments have
lessened until in 1934-35 the plats receiving the 6-12-6 fertilizer yielded
heavier than those receiving the 6-18-6 mixture (Tables 2a and 2b).

Phosphoric Acid Applied Alone

Unlike the nitrogen carrier ammonium sulphate, the phosphoric acid
carrier superphosphate increased yields when used alone, in all the three
years. Yields did not increase with every increase of the fertilizer
material to the extent that they did when the ratios varied all the way
from 6-0-6 to 6-18-6 in the fundamental series. Thus 1080 pounds of
superphosphate (equivalent to 1800 pounds of 0-12-0) made an average
yield of 173 bushels of U. S. No. 1 onions per acre for the three years of
the test as compared with 156 bushels of U. S. No. 1 onions resulting
from 360 pounds of superphosphate, equivalent to 600 pounds of 0-12-0
per acre (Table 3). There was no significant difference in yield between
the applications of 360 pounds and 720 pounds per acre. Under com-
mercial conditions the additional yield obtained from the 1080 pounds
per acre would be rather expensive. A comparison of the no-fertilizer
treatment and the 360 pounds per acre application of superphosphate
indicates that superphosphate applied alone at this rate would be profit-
able. The average yield for three years from the no-fertilizer plats was
92 bushels of U. S. No. 1 onions, and that from the 360 pounds of super-
phosphate was 156 bushels of U. S. No. 1 onions.

FERTILIZER EXPERIMENTS WITH YELLOW BERMUDA ONIONS 17

EFFECT OF POTASH ON THE YIELD OF ONIONS
Varying the Proportion of Potash in a Complete Fertilizer

\ Applications of potash have sometimes increased onion yields, and
sometimes decreased them, and in general there has been very little
correlation between the result produced by one formula and that pro-
duced by another. Omitting potash has never resulted in as low yields
as have been obtained by omitting nitrogen and phosphoric acid separate-
ly, nor has the addition of potash ever resulted in as marked an increase
in yield as can be attributed to the addition of either nitrogen or phos-
phoric acid (Table 2a and 2b). In 1931-32 the highest yield of U. S.
No. 1 onions in the potash series came from the plats receiving the
6-12-9 fertilizer, and the lowest came from those receiving the 6-12-0.
However, plats receiving 6-12-3 that year had yields almost as great as
those receiving 6-12-9, while the 6-12-6 plats had yields almost as low
as those from the 6-12-3 plats. In 1932-33 in the same series, ‘the pot-
ash treatment with highest yield of U. S. No. 1 was 6-12-3, and the one
with lowest yield was 6-12-9. In 1933-34 the plats receiving no potash
had the highest yield, while the plats receiving 6-12-6 had the lowest.
The 6-12-9 plats had an even smaller yield than those receiving no pot-
ash at all. '

A statistical analysis of these results indicates they have very little
significance one way or another. This conclusion is supported further by
results obtained in the supplementary series first laid out in 1932. In
that series potash likewise increased the yield of both U. S. No. 1 onions
and ‘the total yield in the first year of both series, and has decreased it
in most cases in succeeding years (Table 3).

Fertilizers with Potash Omitted

In the first year of these fertilizer experiments the only application
omitting potash was the one in which ‘600 pounds of 6-12-0 fertilizer was
applied. The supplementary tests begun in 1932 included 1200 and 1800
pounds as well as 600 pounds of 6-12-0 fertilizer.

In the average of the three ‘years the application of 600 pounds of
6-12-0 fertilizer made just as high a yield of U. S. No. 1 onions as did
any other treatment including those containing potash (Table 3). This

yield of 177 bushels was considerably higher than the yield of 135-

bushels obtained from the 1800 pounds of 6-12-0 and slightly higher
than the yield of 167 bushels from the 1200 pounds of 6-12-0. It would
seem that while applications of nitrogen and phosphoric acid together
in such a formula as 6-12-0 are usually more profitable than applications
containing potash as well, such as 6-12-6, very large applications are not

_likely to be profitable.

RELATIVE EFFECT OF THE DIFFERENT NUTRIENTS

Under the discussion of phosphoric acid it has already been pointed
out that yields were reduced more by the omission of that nutrient than

18 BULLETIN NO. 524, TEXAS AGRICULTURAL EXPERIMENT STATION

by any other. However, additions of both nitrogen and phosphoric acid
increased yields. The comparative effectiveness of all the nutrients is
shown in a more condensed form in Table 6.

All unfertilized plats yielded considerably less than those receiving
600 pounds of a 6-12-6 fertilizer, All treatments lacking phosphoric

Table 6. Comparative effectiveness of the various nutrients

Yield of U. S. N0. 1 (bu.) Total yield (bu.)
Treatment Average Average
1st year 3rd year of 1st year 3rd year of

1931-32 1933-34 4 years 1931-32 1933-34 4 years

No fertilizer . . . . . . . . . . . . . . . 59 119 93 153 203 162

0-12-6 (600 lbs.) . . . . . . . . . . . 66 182 128 170 266 209

6- 0-6 (600 lbs.) . . . . . . . . . . . 40 98 75 128 190 139

6-12-0 (600 lbs.) . . . . . . . . . . . 132 236 168 255 339 277

6-12-6 (600 lbs.) . . . . . . . . . . . 149* 200* 161* 250* 288* 249*

*An average of the three sets of 6-12-6 plats.

acid resulted in yields less than those obtained without fertilizer, indi-
cating the serious deficiency of available phosphoric acid in the Webb
fine sandy loam as regards the need of the onions for this nutrient. This
result also indicates that the applications of nitrogen and potash without
phosphoric acid would be a very wasteful and unproductive practice.
It would add the expense of applying this unbalanced fertilizer, and yet
the yields might be less than if no fertilizer had been applied. Where
phosphoric acid was present, but no nitrogen included, all yields were
still below those obtained from the 6-12-6 fertilizer. This indicates that
while both nitrogen and phosphoric acid are effective separately, they
are more effective when applied together. Only in the first year was
potash at all effective in increasing yield. t

On the basis of the soil analyses given in Table 1 these results might
be expected. The low amounts of nitrogen and phosphoric acid shown
there explain the responses to these nutrients when they are added. The
lack of response to additions of potash is consistent with the large amount
of that nutrient‘shown in the analyses.

RATES OF APPLICATION OF COMPLETE FERTILIZER (6-12-6)

On the basis of a four-year average, 1800 pounds of 6-12-6 resulted in
a yield of 220 bushels of U. S. No. 1 as compared with 93 bushels of
U. S. No. 1 from the no-fertilizer plats (Table 7a). The difference in
yield between these two treatments has less significance when the results

of the individual years are studied separately. In 1931-32 there were‘

320 bushels of U. S. No. 1 onions per acre from the 1800. pounds of
6-12-6, as compared with only 59 bushels where no fertilizer was applied.
With every increase in the amount of fertilizer that year, there was a
corresponding increase in both U. S. No. 1 onions as well as in the total

FERTILIZER EXPERIMENTS WITH YELLOW; BERMUDA ONIONS l9

Table 7a. Effect of various amounts of complete fertilizer (6-12-6) on the
bushels of onions per acre

U. S. N0. 1 Total yield
Pounds of complete

fertilizer (6-12-6)
1932 1933 1934 1935 Aver. 1932 1933

1934 I 1935 Aver.

No fertilizer . . . . . . . . . . . . 59 186 119 6 93 153 242 203 SO 162

300 lbs . . . _ . . . . . . . . . . . . 100 343 149 17 152 190 417 232 73 228

600 lbs . . . . . . . . . . . . . . . . 140 357 205 16 180 240 464 281 76 265

900 lbs . . . . . . . . . . . . . . . . 219 281 230 2O 188 317 441 339 79 294

1200 lbs . . . . . . . . . . . . . . . . 288 295 21S 20 205 367 454 303 79 301

1800 lbs . . . . . . . . . . . . . . . . 320 297 246 16 220 381 524 340 72 329

Table 7b. Efiects of various amounts of complete fertilizer (6-12-6) on the
percentage increase or decrease in yield over or below the check

U. S. No. 1 Total yield
Pounds of complete

fertilizer (6-12-6)
1932 1933 1934 1935 Aver. 1932 1933 1934 1935 Aver.

None (check) . . . . . . . . . . . —- -—- —- —— — -—- — — —- -—
300 . . . . . . . . . . . . . . . . . . . 69 84 25 183 63 24 72 14 46 41

600 . . . . . . . . . . . . . . . . . . . 137 92 72 167 94 57 92 38 S2 64

900 . . . . . . . . . . . . . . . . . . . 271 51 93 233 102 107 82 67 58 81

1200 . . . . . . . . . . . . . . . . . . . 388 S9 81 233 120 140 88 49 58 86

1800 . . . . . . . . . . . . . . . . . . . 442 6O 107 167 137 149 117 67 44 103

None . . . . . . . . . . . . . . . . . . —58 -—48 ~42 —62 —48 -36 —48 —28 —34 -39

300 . . . . . . . . . . . . . . . . . . . —29 -4 -27 6 —16 —21 —10 —17 -4 -—14

600 (check) . . . . . . . . . . . . -— — —— -—- —- -—- -—- ——- — —

900 . . . . . . . . . . . . . . . . . . . 56 —21 12 25 4 32 —5 21 4‘ 11

1200 . . . . . . . . . . . . . . . . . . . 106 -—17 S 25 14 53 -2 8 4 14

1800 . . . . . . . . . . . . . . . . . . . 129 —17 20 0 22 59 13 21 -5 24

yield. The U. S. No. 1 yield that year from the 1800 pound plats averaged
442 per cent greater than that from the no-fertilizer treatment (Table
7b). These remarkable increases in yield with increased amounts of
complete fertilizer have never been obtained since. With the exception
of the plats receiving no phosphoric acid, the no-fertilizer treatment has
always had the lowest yield of U. S. No. 1 onions and the lowest total
yield, but since the first year, amounts higher than 900 pounds per acre
have not always produced higher yields. Sometimes yields have de-
clined with amounts of 6-12-6 fertilizer greater than 900 pounds.

If one is accustomed to using about 600 pounds of 6-12-6 or its
equivalent per acre, and hence wishes to consider that amount as the
check, then it will be found that with the exception of 1932-33 (year of
severe freeze) 900 pounds has always given a yield of U. S. No. 1 onions
at least 12 per cent higher than that from the 600 pounds of fertilizer.

Comparable treatments in the supplemental series begun in 1932 pro-
duced results which support those just discussed, in spite of the fact that
the freeze in February 1933 was a factor in the first ryear of that series
which had been absent in the first year of the fundamental series the year
before (Table 3). Quality as expressed in U. S. No. 1 onions was re-
duced by this freeze, and total yields were also slightly reduced through

20 BULLETIN NO. 524, TEXAS AGRICULTURAL EXPERIMENT STATION

loss in stands, and delay in maturity. Hence the increases in yields of
U. S. N0. 1 onions with every increase of complete fertilizer did not occur
in the first yearof the supplemental series as it did in the first year of
the fundamental series. However, total yields responded in a similar
way in both series. The decreasing effect of the larger amounts of fer-
tilizer as the years have gone by is also evident in both series.

TIME AND METHODS OF APPLICATION OF FERTILIZER
Time of Application of Complete Fertilizer (6-12-6)

In 1931-32 the 1200 pound rate of 6-12-6 produced a noticeably higher
yield than did 900 pounds per acre (Tables 2a and 2b). A question
a-rose. If this continued to be a profitable application, then should the
entire 1200 pounds of 6-12-6 be applied all at one time, and if not, when
should it be applied? As can be seen from the treatments listed in
Table 8, three were tried. The average yields for the three years indi-
cate that applying the entire amount to the soil just before the young
onion plants are set out is the best practice. An application of 1200
pounds of 6-12-6 fertilizer broadcasted previous to transplanting made

Table 8. Effect of time and method of application of complete fertilizer,
as well as side-dressings on the yield of onions (bu. per acre)
U. S. N0. l Total
Fertilizer used
1933 1934 1935 Aver. 1933 1934 1935 Aver.
Applications of complete fertilizer
(6-12-6): _

Initial application 1200 lbs . . . . . . . . . 278 223 107 203 397 347 183 309
Initial application 900 lbs. + s. d.

300 lbs . . . . . . . . . . . . . . . . . . . . . . . . . 287 223 95 202 425 332 159 305

- Initial application 600 lbs. + 2 s.
d. 300 lbs. each . . . . . . . . . . . . . . . . . 274 201 105 193 350 314 190 285
Nitrogenous side-dressings: 4

600 lbs. of 6-12-6 with no side-

dressings later . . . . . . . . . . . . . . . . . . ——- 235 103 169 —— 318 181 250
600 lbs. of 6-12-6 plus ammonium _

sulphatel side-dressing . . . . . . . . . . . -— 213 86 150 — 294 157 226
600 lbs. of 6-12-6 plus sodium

nitrate? side-dressing . . . . . . . . . . . . — 156 104 130 —- 226 178 202
No fertilizer . . . . . . . . . . . . . . . . . . . . . . — 9O 46 68 — 156 101 129
No fertilizer initially, but sodium

nitrate side-dressinglater? . . . . . . . . —— 103 48 76 ——— 174 121 148
No fertilizer initially but 11-48-03

side-dressing later . . . . . . . . . . . . . . . — 143 6S 104 —~ 217 138 177

1—-—At rate of 100 lbs. per acre. Applied in January.

2—In two equal side-dressings totaling 133 lbs. per acre (equivalent to 100 lbs. of ammonium sul-
phate). Applied in January and February.

3—At a rate of 181.8 lbs. per acre (to give same amount of N as 100 lbs. of ammonium sulphate).
Applied in January.

4—Yie1ds from these treatments should not be directly compared with the three above as they
were not in the same fields.

an average yield of 203 bushels of U. S. No. 1 onions or a total yield of
309 bushels, as compared with a yield of 193 bushels of U. S. No. 1 onions
or a total yield of 285 bushels for the treatment in which 600 pounds
of 6-12-6 fertilizer was broadcasted initially, and the remaining 600
pounds (making 1200 pounds of 6-12-6 in all) applied in two side dress-

FERTILIZER EXPERIMENTS WITH YELLOW BERMUDA ONIONS 21

ings~one in January, the other in February. On the average of three
years, the treatment in which 900 pounds was broadcasted initially and
the remaining 300 pounds put on as a side dressing in January, almost
equalled the high yielding treatment. Statistically the yields were not
significantly less.

Even had the yields from all treatments been alike, the conclusion that
the initial application of the entire amount is the best practice would
still be correct. Applying the fertilizer at that time is easier, and it
eliminates entirely the labor and time consumed in making side dressings
later.

Side Dressings

Side Dressings to previously fertilized plats: The plats receiving 600
pounds of 6-12-6 fertilizer made an average yield of 169 bushels per acre
of U. S. No. 1 onions and a total yield of 250 bushels for the two ‘years
that this experiment has been under way (Table 8). The no-fertilizer
treatment in this same series averaged 68 bushels of U. S. No. 1 onions
and a total of 129 bushels for the same period. In contrast with these
results, the plats receiving 600 pounds of 6-12-6 fertilizer, plus 100
pounds of ammonium sulphate as a side dressing in January, averaged
150 bushels of U. S. No. 1 onions per acre and 226 bushels total. The
treatment in which nitrate of soda was substituted for ammonium sul-
phate averaged 130 bushels of U. S. No. 1 onions and 202 bushels total.
In other words, the extra nitrogen either in the form of ammonium sul-
phate or as nitrate of soda decreased the yields normally resulting from
600 pounds of 6-12-6 fertilizer alone. For some reason the ammonium
sulphate gave higher yields the first year than did the sodium nitrate,
but the second year it gave lower yields than the sodium nitrate did in
either year. The plats receiving ammonium sulphate as a side dressing
yielded considerably less than did the plats where it had not been applied
at all. Nitrate of soda decreased -the yield only in the first year, but
although it did not do so the second year, it failed to increase ‘it, and
hence was an unprofitable application. The reversal in performance of
the ammonium sulphate and nitrate of soda side dressings in 1934-35
corresponded to the treatments in which these had been applied initially
as part of a complete fertilizer (Table 4). In 1933-34 the 6-12-6 fer-
tilizer containing ammonium sulphate yielded more than the 6-12-6
fertilizer containing nitrate of soda. In 1934-35 the reverse was true.

The results of the side dressing experiments described above would
indicate that applications of either sodium nitrate or ammonium sulphate
are likely to be unprofitable in the side dressing of onions which have
already received complete fertilizer.

Side Dressings Without Previous Fertilization: Sodium nitrate applied
to previously unfertilized plats at the same rate as in the side dressings
discussed above made an average yield of 76 bushels of U. S. No. 1 onions
and a total of 148 bushels per acre for the two years of this experiment.

22 BULLETIN NO. 524, TEXAS AGRICULTURAL EXPERIMENT STATION

This exceeded the no-fertilizer treatment by an average of 8 bushels of
U. S. N0. 1 onions.

Similar plats unfertilized initially, but receiving a side dressing in
January of 181.8 pounds of 11-48-0 per acre (containing the same amount
of nitrogen as 100 pounds of 20% ammonium sulphate) yielded ‘an
average of 104 bushels of U S. No. 1 onions per acre, and an
average total yield of 178 bushels. Apparently the phosphoric acid
contained in this fertilizer helped -the onions more than nitrogen applied
alone.

While nitrogenous side dressings on onions previously unfertilized are
usually at least slightly beneficial, the practice of side dressings in gen-
eral is not as effective in increasing yields as suitable fertilizer applied
before the onion plants are set out. Where a complete fertilizer has
been applied before planting, nitrogenous side dressings are likely to
reduce yields.

EFFECT OF FERTILIZER ON OTHER CHARACTERISTICS
Fertilizer and Earliness

Although onions require a certain length of day before they will bulb
up, and hence cannot be unduly hastened toward maturity, they will
respond somewhat to other factors, and when the length of day ceases
to be a limiting one, they may mature early or late according to these
various conditions. Normally in any given locality and with the same
variety this variation in time of maturity will not be greater than about
two weeks. As it is frequently to the growers’ advantage to harvest as
early as possible because prices sometimes fall from day to day, any
factor contributing to earliness is important.

All the plats in any one series of the Station’s experiments were always
harvested on the same day. The complexity and extensiveness of the

experiments, in addition to other considerations, made this procedure

a practical necessity, aside from the fact that by such harvesting no
treatment had the advantage of others in being able to grow for a
longer period.

From general observations it was obvious that the onions in certain
treatments were always ready to harvest before those in other treat-
ments. Onions receiving fertilizer mixtures which caused them to pro-
duce higher yields were usually ready to harvest before onions which
received less favorable fertilizer applications. In the case of certain
treatments, the onions could usually have been harvested a week to ten
days ahead of most other treatments. These early treatments were the
following: 600 pounds of 6-18-6 fertilizer; 900, 1200, and 1800 pounds
of 6-12-6 fertilizer; 1200 and 1800 pounds of 6-12-0; and 327.1, pounds
of 11-48-0 fertilizer.

Onions growing on plats receiving no fertilizer, or on plats receiving

mixtures which did not especially increase yields, tended to mature later.
Hence with such treatments yields were not only lighter but under prac-

FERTILIZER EXPERIMENTS WITH YELLOW BERMUDA ONIONS 23

tical commercial conditions the possibilities are that the market price
would often be lower by the time suclnonions were ready to harvest.

It would seem that the onion plant if given favorable conditions, such
as those created by an adequate amount of the suitable fertilizer applied
before the plant is set out, will grow vigorously throughout the winter
months. Then, when the days lengthen sufficiently, it at once begins to
bulb. The bulb is likely to become fairly large—hence increasing yield.
With the plant which is poorly fertilized the growth is much less vigor-
ous, the tops never become as large, and when the length of day favors
bulb formation the process gets under way slowly and usually slightly
later than in the case of the more vigorous plant. In all of the four
years of these experiments differences in color, size, and general ap-
pearance of the top growth due to the various treatments were notice-
able within a month of the time when the plants were set out, and these
differences became increasingly apparent as the weeks and months went
by. This striking visual evidence combined with the final results of
yield and date of maturity indicated the value of the early application
of the desirable fertilizer.

Grades as Afiected by Fertilizer

Yield in itself is not the only result in which a grower is interested.
The yield may be good and yet the quality of the product so poor that
the possibilities of selling it at a profit are very limited. The percentages
of the total crop that fall into the various grades gives an indication of
the quality of the crop. These grades are Jumbo, U. S. No. 1 (medium),
boilers, and culls. The first three grades are size groups, and all are
really U. S. No. 1, but as in the trade U. S. No. 1 commonly refers to
the medium grade which is rarely mentioned as such, it seemed desir-
able to use the terms in the sense in which they are regularly used.

In reporting the yields of the various tests in terms of U. S. No. 1 as
well as total, the quality of the crop has already been indicated to some
extent. In Table 9, however, the yields of all the grades harvested from
the fundamental series during four years are given, and hence it is pos-
sible to see what effect, if any, a particular fertilizer had on any given
grade.

It is evident that fertilizer is not the only factor having an efiect on
quality. In 1931-32 the percentage of U. S. No. 1 onions was rather
low in general, and the percentage of boilers rather high, as compared
with 1932-33 when the percentage of U. S. N0. 1 was fairly high, and
the percentage of boilers low. In 1931-32 the new land may have had
a retarding effect on the growth of the onions, or they may have been
harvested somewhat prematurely. The serious February freeze came in
the 1932-33 season, yet as indicated above, the percentages of U. S. No. 1
onions were greater that year. Culls which are largely splits and doubles
were in general present in larger numbers in 1932-33, presumably be-

cause of the freeze.

24 BULLETIN NO. 524, TEXAS AGRICULTURAL EXPERIMENT STATION '

As has been pointed out before, the pink root disease became a serious
factor in 1934-35. The growth of the onions was greatly retarded by it,
and large numbers of bulbs which did not make the U. S. No. 1 grade
on account of small size had to be classified as boilers. It is interesting to

Table 9. The efiect of fertilizer 0n the percentages of the total yield falling
- in the various grades (see next page)

1931-32 1932-33
Fertilizer used
' U. S. U. S.
Jumbo No. 1 Boilers Culls Jumbo No. 1 Boilers Culls
Nitrogen series:

- 2- . . . . . . . . . .. 0 38.9 38.4 22.7 0.6 73.1 15.3 '11.0
3-12-6 . . . . . . . . . . . O 47.5 36.4 16.1 1.3 78.2 4.1 16.3
6-12-6 . . . . . . . . . .. 0 56.3 26.4 17.3 2.6 72.0 3.3 22.1
9-12-6 . . . . . . . . . .. 0 59.3 25.7 15.0 1.8 72 9 3.2 22.0

Phosphoric acid

series:

6-0-6 . . . . . . . . . . . . 0 316 49.6 18.8 0 77.2 20.3 2.5
6-6-6 . . . . . . . . . . .. 0 45 0 37.8 17.2 1.6 79.7 7.6 11.1
6-12-6 . . . . . . . . . .. 0 66 9 23.8 9.3 4.7 68.0 4.2 23.2
6-18-6 . . . . . . . . . .. 0 66 0 21.9 12.1 2.2 65.3 2.2 30.2

Potash series:

-12- . . . . . . . . . .. 0 51 6 34.2 14.2 5.9 64.8 4.8 24.4
6-12-3 . . . . . . . . . . . 0 S8 3 27.0 14.7 2.4 80.9 5.9 10.9
6-12-6 . . . . . . . . . .. O 55 4 31 4 13.2 1.0 75.2 4.9 18.9
6-12-9 . . . . . . . . . .. O 53.1 27.7 19.2 1.1 71.4 3.5 24.1

Complete fertilizer
series:
No fertilizer . . . . .. ' 0 38.6 39.9 21.5 0 76.9 18.6 4.5
300 lbs of 6-12-6 0 52.7 31.1 16.2 1.7 82.3 5.8 1O 3
600 lbs of 6-12-6 0 58.2 29.6 12.2 0 76.4 3.7 19 4
900 lbs of 6-12-6 0 69.1 21.4 9.5 6.3 63.7 0.9 29 0
1200 lbs of 6-12-6 0 78.6 13.7 7.7 0.7 65.0 2.9 31.5
1800 lbs. of 6-12-6 0 84.0 9.4 6.6 3.1 56.7 3.4 36.8

note that the percentage of culls was in general no greater than normal
in 1934-35. The greatest tendency toward culls was evident in 1932-33,
the year of the severe freeze, rather than in 1934-35, a. year of severe
pink root infection. The low percentages of U. S. No. 1 onions in 1934-35
of course lowers the average percentage for the four seasons. This
aver-age should not be considered typical for onions grown year after
year on land free from pink root.

Although the effect of fertilizer on quality is nowhere extremely
striking, it is nevertheless evident. In an average of four years there
was a tendency toward a greater percentage of U. S. No. 1 onions from
the fertilizers containing a greater percentage of nitrogen. The U. S.
N0. 1 onions averaged 56.8 per cent for the four years from the 9-12-6
mixture and only 48.8 per cent from the 0-12-6 mixture (Table 9). The
intermediate treatments 3-12-6 and 6-12-6 had intermediate percentages

.of U. S. No. 1 onions of 54.0 and 55.2 respectively. This trend toward

more U. S. No. 1 onions with more nitrogen in the fertilizer was more
obvious in 1931-32 -and 1934-35 than in any other years. In 1931-32
the percentages of both boilers and culls tended to fall as the amount

FERTILIZER EXPERIMENTS WITH YELLOW BERMUDA ONIONS 25

of nitrogen was increased; in 1934-35 only the percentage of the boilers
fell, and then the fall was not welhcorrelated with the increase in
nitrogen.

In the first season, 1931-32, an increase of phosphoric acid from
6-0-6 up through 6-6-6 to 6-12-6 had a remarkable effect in increasing

Table 9. The effect 0f fertilizer on the percentages of the total yield falling
in the various grades-Continued

1933-34 1934-35 Average
U. S. U. S. U. S.

Jumbo No. 1 Boilers Culls Jumbo No. 1 Boilers Culls Jumbo No. 1 Boilers Culls
1.1 68 4 16.2 14.3 0 14.6 7078 14.6 0.4 48 8 35.2 15.6
0.3 69 5 16.6 13.6 0 20.6 52.9 26.5 0.4 54 0 27.5 18.1
0.3 714 14.5 13.8 0 21.7 60.9 17.4 0.7 55 2 26.3 17.8
0 70 3 17.7 12.0 0 24.7 61.6 13.7 0.5 56 8 27.0 15.7
0 51.6 34.7 13.7 0 11.1 75.0 13.9 0 42 9 44.9 12.2
0.8 66 8 23.3 9.3 0 18.3 69.0 12.7 0.5 52 4 34.2 12.9
0 67.6 22.5 9.9 0 26.9 57.7 15.4 1.2 57 4 27.0 14.4
0.3 69 8 15.3 14.6 0 21.6 62 2 16.2 0.6 55 7 25.4 18.3
0 69.6 15.6 18.6 0 25.4 57 3 17.3 1.5 52 9 28.0 17.6
0 3 69.8 15.0 14.9 0 23.3 61 7 15.0 0.7 58 1 27.4 13 8
0 4 69.4 16.0 14.2 0 19.1 69 1 11.8 0.4 54.8 30.3 14.5
0 69.9 14.0 16.1 0 25.9 57 6 16.5 0.3 _ 55.1 25.7 18.9
0 58 7 30.5 10.8 0 12.0 62.0 26.0 0 46.6 37.7 15.7
0 64 2 22.0 13.8 0 23.3 58.9 17 8 0.4 55.6 29.5 14.5
0 73 0 1617 10.3 0 21.0 63.2 15.8 0 57.3 28.3 14.4
0 67 8 13.3 18.9 0 25.3 53.2 21.5 1.6 56 5 22.2 19.7
0 3 71 0 11.9 16.8 0 25.3 59.5 15.2 0.2 60.0 22.0 17.8
0 72 4 8.8 18.8 0 22.2 50.0 27.8 0.8 58.8 17.9 22.5

the percentage of U. S. No. 1 onions. In the 6-0-6 treatment 31.6 per
cent of the onions were U. S. No. 1. The 6-18-6 mixture resulted in 66
per cent, practically the same as for the 6-12-6. Most of this gain in
percentage of U. S. No. 1 was lost in the boilers, which fell from 49.6
per cent in the 6-0-6 treatment to 23.8 per cent in the 6-12-6 treatment.
In 1932-33, the season of the severe freeze, the numbers of U. S. No. 1
onions in the phosphoric acid test fell off as the phosphoric acid was
increased. The better fertilized onions seemed unable to withstand the
low temperatures, probably because they» were more succulent. As the
percentage of the U. S. No. 1 grade fell off with increases of phosphoric
acid, the percentage of culls increased. The‘ 6-18-6 treatment had 30.2
per cent of its yield in culls, while from the 6-0-6 treatment only 2.5
were in that grade. The percentage of boilers also fell off with increases
of phosphoric acid. The average of the four years, even with the adverse
1932-33 season included, indicates that phosphoric acid has more effect
on quality in terms of percentage of U. S. No. 1 onions than either
nitrogen or potash. With the exception of 1932-33, the culls remained

26 BULLETIN NO. 524, TEXAS AGRICULTURAL EXPERIMENT STATION

fairly constant in all treatments, but the percentages of boilers tended
to decrease as the percentages of U. S. N0. 1 onions increased.

Of the three nutrients, potash had the least effect on quality. On the
average of four years the U. S. No. 1 onions ranged between 52.9 and
58.1 per cent with no correlation at all between the amount of potash
and the percentage obtained. The boilers and culls were likewise
apparently not influenced. '3

The amount of complete fertilizer had practically as much effect on
quality as phosphoric acid did. In 1931-32, only 38.6 per cent of the
onions from the no-fertilizer treatment were U. S. No. 1 grade, but 84
per cent of those from the 1800 pound an acre treatment belonged to
that grade. In that year as the amount of fertilizer was increased the
percentage of U. S. No. 1 onions increased, and the percentages of both
boilers and culls decreased.

In 1932-33 the freeze resulted in what amounted to almost a reversal
of the results obtained in 1931-32. In the heavily fertilized treatments
there were many culls (mostly splits and doubles), and a correspond-
ingly smaller amount of U. S. No. 1 onions. In the no-fertilizer plats
4.5 per cent of the onions were culls, but in the plats receiving 1800
pounds of 6-12-6 fertilizer 36.8 per cent were culls.

Never since the first year has the 1800 pound per acre treatment pro-
duced such a high percentage of U. S. No. 1 onions as it did in that year—-
84 per cent. It will be recalled that after the first“ year this treatment
did not increase yields as it had at first.

Apparently the most desirable fertilizer for a given situation will not
only increase the yield as a whole but cause a larger proportion of it to
fall in the U. S. No. 1 grade than otherwise would do so with a less
desirable fertilizer.

Fertilizer and Keeping Quality

It is not a common commercial practice to store Bermuda onions for
any length of time in the Winter Garden area. Even cold storage is
rarely, if ever, resorted to. The best market is usually at the time of
harvest, and the onions are disposed of at that time. In addition to this,
Bermuda onions have a reputation as poor keepers.

Although storage, at least planned storage, is not a common practice,
growers are occasionally forced to hold a portion of their onion crop
a week or two because of market or weather conditions. In other words,
while storage is not usual in Bermuda onion production, and hence the
factors which affect it are of less importance to the grower than those
factors which affect yield and quality, it is nevertheless a matter on
which any available information is pertinent.

In Tables 10 and 11 are given the dates on which the various samples
in storage were examined and the percentages of onions which had to

FERTILIZER EXPERIMENTS WITH YELLOW’ BERMUDA ONIONS 27

be discarded on those dates as unmarketable. The results of 1932 show
somewhat more definite trends than those of 1933. The proportion of
nitrogen in the fertilizer mixture, and the total amount of complete
fertilizer, seemed to have the most effect on the keeping quality of the
onions. Phosphoric acid and potash had little effect.

In 1932 the onions which had come from the plats receiving no
nitrogen (0-12-6) decayed the slowest, and by October 13, after 175
days, only 22 per cent had been removed as unmarketable, while the
samples coming from the 9-12-6 plats had lost 54 per cent (Table 10).

Table. 10 Percentages of onions placed in storage, no longer marketable, 1932

June June July August August Sept. Oct.
1 16 7 2 23 9 13
(41 (56 (77 (103 (124 (138 (175
days) days) days) days) days) days) days)
Nitrogen series:

-12-6 . . . . . . . . . . . . . . . . . . . 0 0 4 8 12 16 22
3-12-6 . . . . . . . . . . . . . . . . . . . O 0 8 12 24 24 36
6-12-6 . . . . . . . . . . . . . . . . . . . 8 1O 16 20 22 22 48
9-12-6 . . . . . . . . . . . . . . . . . . . O 2 2 22 32 44 S4

Phosphoric acid series:

- -6 . . . . . . . . . . . . . . . . . . . . 4 4 8 15 21 24 37
6-6-6 . . . . . . . . . . . . . . .. l‘. . . O 0 0 12 16 28 44
6-12-6 . . . . . . . . . . . . . . . . . . . 3 S 15 16 19 20 34
6-18-6 . . . . . . . . . . . . . . . . . . . 3 4 1O 18 32 38 48

Potash series:

-1 - . . . . . . . . . . . . . . . . . . . 1 4 11 17 29 23 41
6-12-3 . . . . . . . . . . . . . . . . . . . 0 1 7 17 21 21 32
6-12-6 . . . . . . . . . . . . . . . . . .. 4 4 12 17 25 37 51
6-12-9 . . . . . . . . . . . . . . . . . . . 4 4 7 12 25 33 45

Complex): fertilizer series
No fertilizer . . . . . . . . . . . . . . 4 8 13 20 27 29 45

300 pounds . . . . . . . . . . . . . . . 10 14 20 32 32 36 33

600 pounds . . . . . . . . . . . . . . . 0 2 12 30 36 48 S8

900 pounds . . . . . . . . . . . . . . . 0 2 10 28 36 40 64

1200 pounds . . . . . . . . . . . . . . . 4 6 16 26 42 44 60

1800 pounds . . . . . . . . . . . . . . . 12 20 40 52 68 76 96

The samples coming from the plats receiving the 6-12-6 fertilizer had
lost 48 per cent, and those from the 3-12-6 plats had lost 36 per cent.

In 1933 the trend was not as clear cut, although it was in the same
direction (Table 11). The samples taken from the O-12-6 plats decayed
on the whole the slowest, and at end of the storage period (October 23,
181 days) had the only 52 percent (the lowest) removed. For some
reason the samples from the 6-12-6 plats of the nitrogen series ended
with the highest percentage of loss—77 per cent, and those from the
9-12-6 plats were the next highest——68 per cent. In comparison with

samples from the 6-12-6 plats of other series, those of the nitrogen A

series lost a higher percentage and hence were somewhat out of line.

The highest percentage of decay (96 per cent) in 1932 occurred in
the samples taken from the plats receiving 1800 pounds of 6-12-6 per
acre (Table 10). While the no-fertilizer treatment did not have the
smallest amount of decay, it was considerably lower (45 per cent) than

28 BULLETIN NO. 524, TEXAS AGRICULTURAL EXPERIMENT STATION

the 1800 pound treatment. In general, decay was more rapid and
ended at a higher percentage as the amount of complete fertilizer
increased. This was even more noticeable in 1933, for in that yearthere
was anincrease in decay with every added increment of fertilizer when
the final score was taken on October 23 after 181 days of storage
(Table 11).

Table 11. Percentages of onions placed in storage, no longer marketable, 1933.

JuneJuneJuneJuIyJuIyAug. Aug. Sept. Sept. Oct. Oct.
~ 1 13 28 7 21 5 18 1 2O 3 23
(37 (49 (64 (72 (87 (102 (115 (129 (148 (161 (181
days) days) days) days) days) days) days) days) days) days) days)
Nitrogen series:
0-12-6 . . . . . . . . . . . . . . . . . . O 1 1 1 7 15 25 31 36 39 S2
3-12-6 . . . . . . . . . . . . . . . . .. 0 1 2 3 6 11 19 23 41 45 54
6-12-6. . . . . . . . . . . . . . . 4 4 9 11 15 22 36 44 62 62 77
9-12-6 . . . . . . . . . . . . . . . . . . 3 4 6 7 12 19 3O 34 55 59 68
Phosphoric acid series:
6-0-6 . . . . . . . . . . . . . . . . . . . 0 3 5 6 15 20 31 38 50 68 71
6-6-6 . . . . . . . . . . . . . . . . . . . 9 9 9 9 12 17 21 32 46 52 62
6-12-6 . . . . . . . . . . . . . . . . . . 0 1 3 3 8 18 23 28 4O 46 56
6-18-6 . . . . . . . . . . . . . . . . . . 5 6 8 9 18 26 35 41 56 63 72
Potash series:

-12-0 . . . . . . . . . . . . . . . . . . 7 8 8 8 12 22 36 43 54 59 72
6-12-3 . . . . . . . . . . . . . . . . . . 3 6 6 6 10 20 28 36 43 52 61
6-12-6 . . . . . . . . . . . . . . . . . . 2 3 5 7 15 23 28 34 48 59 67
6-12-9 . . . . . . . . . . . . . . . . .. 6 9 12 13 22 34 36 43 47 52 60

Complete fertilizer series
No fertilizer . . . . . . . . . . . . . 1 2 3 4 8 12 15 16 26 29 42

300 pounds . . . . . . . . . . . . . . 3 5 6 6 11 16 25 34 38 40 49

600 pounds . . . . . . . . . . . . . . 1 1 1 6 9 12 18 21 34 40 50

900 pounds . . . . . . . . . . . . . . 4 4 7 11 12 20 22 26 35 49 65

1200 pounds . . . . . . . . . . . . . . 3 3 4 6 13 24 29 37 47 56 68

1800 pounds . . . . . . . . . . . . . . 4 7 11 14 32 41 46 54 64 74 78

It is possible that nitrogen is the only nutrient involved. The greater
amount of decay in the samples coming from the plats receiving large
amounts of complete fertilizer may be due to the larger amount of
nitrogen present in such applications. If phosphoric acid and potash
have no effect on the keeping quality one way or the other, they may
not have any deterring influence on the effects of the large amounts of
nitrogen automatically present in large applications of complete
fertilizer. A

While the results of this storage test probably cannot be taken as
conclusive, they are at least indicative of trends. It is common knowl-
edge that nitrogen frequently causes succulent growth, and if the bulbs
grown with more nitrogen are more succulent, it would not be expected
that they would store as Well.

Phosphoric acid was the most beneficial nutrient in increasing yields
and in increasing the percentages of U. S. No. 1 onions. »It would seem
that the keeping qualities of the onions would not be reduced by larger
applications of this nutrient. This storage study indicates, however, that
it is probably a wise procedure to avoid storage when large amounts of
complete fertilizer have been used.

FERTILIZEItEXPERIlNIENTS WITH YELLOW BERMUDA ONIONS 29

DISCUSSION AND RECOMMENDATIONS

Most of the experiments described and discussed have rather clear cut
results. The question now is: How far can these results be applied to
practical commercial practice? Before any specific recommendations
suggested by these results, a few general recommend-ations need to be
considered.

First of all, there is no series of fertilizer practices adapted to all
growers, all soils, and all situations. Before any decision can be made
the soil and its previous handling must be known. With these facts
in mind, the results of the Station’s experiments can be studied and the
most promising practices decided upon. After this decision, the question
of cost still has to be considered. Some methods of handling the crop
are more costly than others. There is more to lose from an expensive
treatment than there is from a cheaper one in the event of a complete
crop loss. On the other hand with any venture there ‘is always a
possibility of complete loss because of a catastrophe of some kind.
Whatever the price received per bushel for the harvested onions, as
long as it is above the cost of harvesting the more of them there are per
acre the less the net loss, or the greater the profit.

Results reported in Table 8 can be used as an example to illustrate this
point. F0-r the two harvest years 1934 and 1935 the treatment in which
600 pounds of 6-12-6 fertilizer have been applied to the ground before
the onion sets have been set out made an average yield of 169 bushels
of U. S. No. 1 onions without any further fertilizer application. Growing
and harvesting costs amounted to about $104.20*. If 75 cents’; per
bushel were received for these onions, the net return would be about
$22.55 an acre. In contrast with this, the average yield for the same two
seasons from the treatment receiving no fertilizer initially, but instead
two side dressings with nitrate of soda later (a common commercial
practice), was 76 bushels of U. S. No. 1 onions. Growing and harvesting
costs amounted to about $70.30*. If 75 cents a bushel were received
for these onions, there would be no net profit at all, but a loss of $13.30
per acre. Had the price per bushel been $1.00, then there would have
been a net return in this last case of $5.70 an acre, but the net gain from
the 6-12-6 treatment would have risen at this price to $64.80 per acre.

Importance of Ratio. Another point to be considered when adapting
the results of these experiments is that the exact materials and
formulas used by the Station do not have tobe used to obtain success.
They were chosen because they were available, and because many

*Estimated costs common to both treatments: Seed $4,00, transplanting
$12.50, irrigation $18.00, cultivation $5.00, total $39.50; costs peculiar to
each treatment: fertilizer in 6-12-6 treatment $12.00, labor_0f applying i1:
$2.00, harvesting and bags for 169 bushels $50.70; fertilizer for side
dressing treatment $3.00, labor of 2 applications $5.00, harvesting and
bags for 76 bushels $22.80. ,

tAn arbitrary average price for U. S. N0. 1 onions. In the 1933-34 season
the price sank to 50c or lower; in 1931-32 it was up to $2.55 and higher;
in 1934-35 it was mostly above $1.50.

30 BULLETIN NO. 524, TEXAS AGRICULTURAL EXPERIMENT STATION

farmers were using them in some form or other. Taking the amounts,
formulas, and yields obtained in these experiments, it is possible to
figure out entirely new amounts and different formulas. The important
thing is to get the right balance of nutrients in the fertilizer used. This
is expressed by the ratio of the formula; for example, the formulas
6-12-6 and 10-20-10 have a ratio of 1-2-1; while 6-18-6 and 5-15-5
have a 1-3-1 ratio, and so on. Different situations and conditions may
require difierent ratios.

Fertilizer for New Land. Phosphoric acid seems to be the most
important nutrient, nitrogen probably next, and potash the least impor-
tant. On new land or on land which has onions for the first time, and
has never been fertilized, 900 to 1200 pounds per acre of 6-18-3 Would
probably produce good results. In this formula the ratio of nitrogen
to phosphoric acid is 1 to 3; this gives more phosphoric acid than the
6-12-6 formula. The small amount of potash as represented by the
figure “3” is included because in the first year on new land potash
increased yields slightly. Present in slightly greater or smaller amounts
potash would not be expected to affect yields greatly. Hence such
applications as 900 to 1200 pounds of 5-15-0, 5-15-5, or 300 to 350
pounds of 11-48-0 should all give satisfactory results. A 11-48-0
formula is closer to a 1-4-0 ratio than it is a 1-3-0, but nevertheless this
particular formula has given satisfactory results at this Station‘ (Table 4).

Fertilizer for Old Land. Where onions are being grown for the
second year on the same land any of the above applications should be
satisfactory, if no fertilizer Was used the first year. If fertilizer including
potash was used, then no more potash need be added for several years.
An application of 600 to 900 pounds of 6-18-0, 5-15-0, or any equivalent
amount of fertilizer with a 1-3-0 ratio, should give good results. Such
formulas should be cheaper, as they exclude potash.

Superphosphate alone often valuable. On new land, or on previously
fertilized land, it is better to add superphosphate alone rather than to
add no fertilizer at all. An application of 350 to 400 pounds per acre
of 20 per centpsuperphosphate is recommended. Superphosphate is one
of the cheapest of the nutrients, and also the most efiective. Amounts
larger than 400 pounds are hardly profitable. Where a higher grade
material (i. e., one with a larger percentage of phosphoric acid) is used,
the amount per acre should be reduced proportionately.

Where a green manure has been plowed under, the superphosphate
alone might often be expected to be all that is needed to make the
fertilization a complete and economical one.

Apply Fertilization Before Transplanting. The time of application of
any fertilizer seems very important. All the results at the Station
indicate that the earlier the onions can make use of the fertilizer the
more vigorous, healthy, and heavy yielders they will be. Fertilizer of
any kind should be put in the soil before the plants are set out. If as

FERTILIZER EXPERIMENTS WITH YELLOW BERMUDA ONIONS 31

much as 1200 pounds is going to be applied anyway, then it is better and
cheaper to put all of it at the beginning than to make several applica-
tions. Yields will be higher.

Side Dressings of Doubtful Value. Applying nitrogenous side dress-
ings in January and February to onions previously fertilized with a
complete fertilizer may reduce yields instead of increase them. Such side
dressings applied to onions which have as yet received no fertilizer may
increase yields to some extent. Such a late application of fertilizer
might better be a more balanced material such as 11-4 8-0, which happens
to be fairly soluble. However, more good can be done not only in
increasing yields but also in making plants more vigorous and better
able to stand up under attacks of thrips and pink root, by putting the
fertilizer in the ground early so the young transplanted seedlings can
use it then, rather than later.

Irrigation and Side Dressings. Irrigation is linked with fertilizer
practices. There may be some surprise that side dressings with nitrate
and ammonium sulphate reduced yields instead of increasing them at
the Station in 1933-34 and again in 1934-35. It is possible that this
would not always happen. However, in line with the results of the
irrigation experiments of previous years (5, 9) a minimum of irrigation
was practiced on these plats. Frequent irrigation will leach out
soluble salts such as nitrate. Hence, under such conditions, sodium
nitrate or ammonium sulphate side dressings may replace the lost
nitrogen. Where there is not too much irrigation, the additional nitrogen
may make the fertilizer balance unfavorable and hence affect the plants
and final yield adversely. Avoiding over-irrigation may not only save
water and labor expense, but reduce the necessity of nitrogen side
dressings also, and finally increase yields. While this suggestion is
without all the supporting facts at this time, it is nevertheless worthy
of careful thought in view of the results so far obtained.

Fertilizer on Heavier, Darker Soils. All. of the Station's experiments
were on a Webb fine sandy loam. On heavier soils the needs are
somewhat different. Judging by analyses and other information, potash
is still as little needed on those soils as it is on sands. In general, 200
to 300 pounds less of mixtures such as 6-12-6 and 5-15-5 can probably be
used on the heavier, darker soils than would be necessary on the sands
and sandy loams. Superphosphate alone should probably still be applied
at around 300 to 400 pounds per acre, as in all the soils phosphoric
acid is always becoming “tied up” and unavailable.

Changing Fertilizer Program May Be Desirable and Profitable. Since
the application of fertilizers one year may change the need of the soil
the following year, the fertilizer program should not be an invariable
one under practical commercial conditions. There are a number of
instances in these fertilizer tests of certain fertilizer mixtures failing
to produce year after year the high yields attributed to them in the first
season. Evidently suflicient residues are left in the soil so that in

32 BULLETIN NO. 524, TEXAS AGRICULTURAL EXPERIMENT STATION

another year another large application is no longer as effective as the
first. While such applications may be very profitable the first year on
new land (or on previously unfertilized land), economies can be effected
in succeeding years by applying smaller amounts, or fertilizers with
other formulas.

Proper Fertilizers Applied Early May Lead to Earlier Crop. The Well-
fertilized onion plant is very likely to bulb up as soon as the day becomes
long enough. This is a distinct advantage as the early prices are some-
times higher than the later ones. The poorly fertilized onion plant may
not bulb up promptly even after light conditions become favorable.

Amount of U. S. No. 1 Grade Increased by Proper Fertilizer. The all
important yield of U. S. No. 1 onions is, under normal conditions,
increased by the same fertilizers which increase yields. That is, not
only is the total yield increased, but the percentage of this total classify-
ing‘ as U. S. No. 1 is generally larger than it is with a less desirable
fertilizer. It is such tendencies as these that under practical conditions
help to make the correct fertilizer practice a profitable venture.

Combating Pink Root and Thrips. Land known to be infested with
pink root (Fusarium malli) should be avoided if possible when planting
onions. No matter how well such land is fertilized the crop is still likely
to be a failure from the commercial point of view. However, even with
a heavy infestation of the disease, yields are very likely to show the
same trends in differential fertilizer treatments as they would if there
were no disease.

If a crop of onions has received satisfactory application of fertilizer,
damage by thrips (Thrips tabaci) will usually be reduced to the point where
the chances of obtaining a profitable harvest are greatly increased.
In 1933-34 and again in 1934-35, two seasons in which thrips have been
a major problem of the onion grower, yields of U. S. No. 1 onions of
over 200 bushels to the acre have been obtained from various treatments
at the Station.

ACKNOWLEDGMENTS

The author is indebted to Dr. H. C. Thompson, Head of the Depart-
ment of Vegetable Crops at Cornell University, whose suggestions were
very helpful in the initial establishment of the fundamental series.
Thanks are also due to Dr. G. S. Fraps, Chief of the Division of
Chemistry, Texas Agricultural Experiment Station, in Whose Division the
soil analyses were made, and to Dr. E. B. Reynolds, Chief of the Division
of Agronomy, for aid in the statistical analysis of the data.

SUMRIARY

The results obtained in the fertilizer and cultural experiments with
Yellow Bermuda onions at the Winter Garden Substation over a period
of four years on Webb fine sandy loam lead to the following conclusions:

1. Phosphoric acid is the most needed nutrient, since increasing its

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FERTILIZER EXPERIMENTS WITH YELLOW BERMUDA ONIONS 33

amount through the successive formulas 6-0-6, 6-6-6, 6-12-6, 6-18-6,
increased yields to a greater extent than was recorded in the correspond-
ing similar series with nitrogen and potash. Withholding phosphoric acid
entirely (6-0-6) caused lower yields than any other treatment including
the no-fertilizer treatment. Like nitrogen, phosphoric acid can accumu-
late so that high applications of it after several years on the same land
are not as effective as at first. During the four years of these tests,
however, phosphoric acid was always more effective than nitrogen.

2. Nitrogen is a needed nutrient since increasing its amounts through
the successive formulas 0-12-6, 3-12-6, 6-12-6, 9-12-6 increased the
yields of U. S. No. 1 onions as well as the total yields obtained. How-
ever, this effect tended to decrease in successive years.

3. Potash is the least essential of the three chief nutrients. It
increased yields slightly the first year, but thereafter tended to decrease
them. Results were never as consistent with potash as they were with
either nitrogen or phosphoric acid.

4. On new land, increasing amounts of complete fertilizer (6-12-6)
from 0 to 1800 pounds per acre increased the yields of U. S. No. 1
onions as well as the total yield. Applications above 1200 pounds are
hardly profitable, however, even the first year. In succeeding years,
amounts above 900 pounds per acre are rarely profitable.

5. Ammonium sulphate applied alone in amounts greater than 180
pounds (equivalent to 600 pounds of 6-0-0) are hardly profitable. Even
this amount applied for the first time to new land may decrease yields
rather than increase them.

6. Twenty per cent superphosphate applied alone is more effective
than ammonium sulphate alone. Increasing the application from 360
to 1080 pounds per acre will usually increase yields, but amounts much
greater than 360 pounds are usually not profitable. Superphosphate
alone is a useful and. economical material.

7. Nitrogen and phosphoric acid in combination at a rate equivalent
to 600 pounds of 6-12-0 fertilizer are usually more effective in increasing
yields than either nutrient is by itself. At rates equivalent to 1200 and
1800 pounds of 6-12-O they are often less effective than superphosphate
alone.

8. Side dressings of any kind are not as efiicient, economical, or
efiective as fertilizer applied before transplanting.

9. The various nitrogen carriers may vary from year to year in
efiectiveness as judged by the yields obtained. Nitrate of soda, sulphate
of ammonia, and cottonseed meal have all given fairly favorable results
when combined with superphosphate and muriate of potash. Cyanamid
has rather consistently resulted in lower yields than other forms of
nitrogen in equivalent amounts.

34 BULLETIN NO. 524, TEXAS AGRICULTURAL EXPERIMENT STATION

10. Cottonseed meal applied alone at a rate of 510 pounds per acre
is not a satisfactory practice in terms of the yields produced at anything
like normal prices.

11. The 11-48-0 fertilizer applied at around 325 pounds per acre
can be expected to produce yields in the neighborhood of those produced
by 600 pounds of 6-12-6 fertilizer.

12. The 16-20-0 fertilizer applied at a rate as low as 225 pounds per
acre is not the best for new land or for land previously unfertilized. In
the second year of a fertilizer program applied at the same rate, it is
likely to produce yields in the neighborhood of those produced by 600
pounds of 6-12-6, and prove to be an efficient, economical fertilizer.

13. Other conditions being equal, onions receiving adequate amounts
of a Droperly balanced fertilizer will be in some seasons, as much as
a Week to 10 days earlier than unfertilized onions.

14. In terms of the percentage of the total yield that classifies as

U. S. No. 1 onions, the quality of the crop is affected mostly by

phosphoric acid, to a less extent by nitrogen, and least by potash.

15. Onions taken from land fertilized with materials high in nitrogen
are likely to decay quicker in storage than onions taken from land which
received fertilizer with a low nitrogen content.

16. Although correct fertilizer practices are likely to result in at
least fair yields in spite of thrips, it is difficult to obtain anything but
low yields whenever the soil harbors the pink root disease.

LITERATURE CITED

1. Beaumont, A. B., M. E. Snell, W. L. Doran, and A. L. Bourne. 1935.
Onions in the Connecticut Valley. Mass. Agr. Exp. Sta. Bul. 318.

2. Fraps, G. S., and S. E. Asbury. 1934. Commercial Fertilizers in
1933-34. Tex. Agr. Exp. Sta. Bul. 498.

3. Harmer, Paul M. 1927. The Management of Michigan Muck Soils
for the Production of Onions. Michigan Agr. Exp. Sta. Special Bul.
168.

4. Hawthorn, Leslie R. 1932. Bermuda Onion Culture in Texas.
Tex. Agr. Exp. Sta. Cir. 65. g

5. Hawthorn, Leslie R. 1933. Onion Irrigation. 46th Ann. Rep.
Tex. Agr. Exp. Sta., p. 244.

6. Knott, J. E. 1930. Growing Onions on the Muck Soils of New
York. Cornell Univ. Agr. Exp. Sta. Bul. 510.

7. Magruder, Roy, and Leslie R. Hawthorn. 1935. Freezing and Cold
Weather Damage to Immature Onions. U. S. Dept. of Agr. Cir. 355.

10.

11.

12.

13.

14.

FERTILIZER EXPERIMENTS WITH YELLOW BERMUDA ONIONS 35

Mortensen, E. 1932. The Winter Garden Region of Texas. Texas

Agr. Exp. Sta. Cir. 62_.

Mortensen, E., and L. R. Hawthorn. 1934.
Records in Irrigation Experiments with Truck Crops.
Hort. Sci., V01. 30, 466-469.

New Mexico Agricultural Experiment Station.
Report, pp. 56-57.

The Use of Evaporation
Amer. Soc.

1934. 45th Annual

The Marketing and Distribution of
U. S. Department of Agricul-

StevensIW. Mackenzie. 1926.
American-Grown Bermuda Onions.
ture, Dept. Bul. 1283.

Strong, W. 0., H. H. Zimmerley, and H. T. Cook.
Culture. Va. Truck Exp. Sta. Bul. 72.

United States Department of Agriculture, Bureau of Agricultural
Economics. 1934. Car-lot Shipments and Unloads of Fruits and
Vegetables for the Calendar Years 1931 and 1932. U. S. Dept. of
Agr. Statis. Bul. 46.

Waschka, S. A. 1908.
Exp. Sta. Bul. 115.

1930. Onion

Fertilizer Test with Onions. Texas Agr.