LIBRARY,
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CKEPUS .

TEXAS AGRICULTURAL EXPERIMENT STATION

A. B. CONNER, DIRECTOR,
College Station, Texas

BULLETIN NO. 596 JANUARY 1941

ONION FERTILIZER EXPERIMENTS AT
LAREDO, BIG WELLS, AND
EAGLE PASS, TEXAS

LESLIE R. HAWTHORN

Division of Horticulture

 

AGRICULTURAL AND MECHANICAL COLLEGE OF TEXAS
T. O. WALTON, President

A107-141-7M-L180

[Blank Page in Original Bulletin]

 

In experiments completed in 1935 at the Winter Garden station,
onions grown 0n Webb fine sandy loam gave a profitable response
to fertilizers containing nitrogen and phosphoric acid. Additions
of potash did not give definite increases in yields.

Later, in a similar series of experiments, onions on Laredo silt
loam near Laredo and Monteola clay near Big Wells responded
to fertilizer in general but not to the marked extent which they
had in previous experiments on Webb fine sandy loam near Winter
Haven. There was no consistent response to fertilizer in general
on Laredo very fine sandy loam near Eagle Pass.

As in the previous work, there was no marked response in yield
by the onions to potash.

Side dressings of nitrate of‘ soda tended to increase onion
yields at all three localities, but most markedly on Laredo very
fine sandy loam at Eagle Pass. On Monteola clay the increase
due to nitrate side dressings was practically negligible.

Fertilizers with 1-3-0 or 1-3-1 ratios were no more effective
than those with 1-2-0 or 1-2-1 ratios in increasing onion yields.

As before, potash had little or no efiect on the keeping quality
of the onions.

CONTENTS
Page
Introduction . . . . . . . . . . . . .’ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Review of Previous Work . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 5

Method of Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 6

Results in Terms of Yields . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 9

Results at Laredo . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 9

Results at Big Wells . . . . . . . . . . . . . . . . . . .§ . . . . . . . . . . . . . . . . . . . . . .. 11

Results at Eagle Pass . . . . . . . . .9 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 12

Discussion and Recommendations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 14

Results of Storage Tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 18

Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 19

Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 20

Literature Cited . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 20

ONION FERTILIZER EXPERIMENTS AT LAREDO,
BIG WELLS, AND EAGLE PASS, TEXAS

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

Upon the conclusion in 1936 of the detailed fertilizer experiments with
Yellow Bermuda onions at the Winter Garden Substation No. 19, it was
considered desirable to try some of the treatments on other types of soil
used for onion culture in southwest Texas. Consequently, tests were
conducted on Laredo silt loam near Laredo, on Monteola clay near Big
Wells, and on Laredo very fine sandy loam near Eagle Pass. Among the
important questions of the growers in these localities were: (1) Would
the findings, particularly those relating to potash on the sandy loams
at the Station’s farm near Winter Haven, still hold good on these other
soils? (2) Does presence or absence of potash in the fertilizer affect the
keeping qualities of onions? (3) Are side dressings with nitrate of soda
profitable?

Review of Previous Work

Previous studies having most bearing on the fertilizer problems involved
are those conducted at this Station several years ago and reported in
1936 (4). After four years of testing various amounts of potash in the
presence of constant amounts of nitrogen and phosphoric acid, and on
a soil which chemical analysis indicated as being well supplied with
potash, it was concluded: “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.” It might be added that
the results with nitrogen and phosphoric acid, especially the latter, were
for the most part very clear-cut, and left no question as to the effect
which these nutrients had on the productiveness of onions. The importance
of phosphoric acid in onion fertilizers has been established on various
soils in Virginia, Michigan, New York, and Massachusetts (1, 3, 5, 6, 8).
With the exception of some newly cleared woody muck soils in New York,
nitrogen has been shown to be usually more or less effective in increasing
onion yields in the four states listed above, as well as in New Mexico
(1, 2, 3, 5, 6, 8). In contrast to these fairly consistent results with phos-
phoric acid and nitrogen, potash has been responsible for some variable
results depending on the location and soil where the experiments were
conducted. In Virginia, potash had little effect on the yield of onions
according to a report in 1930 (8), and in 1935 only a slight increase in
yield due to potash was reported from New Mexico (2). Reports from
Michigan and New York on the contrary have credited decided increases
in yields of onions due to potash (3, 5, 6). Such diverse findings due

6 BULLETIN NO. 596, TEXAS AGRICULTURAL EXPERIMENT STATION

apparently to the different soil conditions under which the experiments
were conducted suggested different results might easily be possible in
southwest Texas if tests were conducted on different soils.

In the storage test conducted with the onions harvested from the
fertilizer tests at the Station, keeping quality was not affected by the
presence or absence of potash in the fertilizer (4).

Side dressings of nitrate of soda t0 previously fertilized onions failed
in tests at the Station to result in higher yields, and in fact one year
actually resulted in a decrease of yield (4). Somewhat erratic results
have been reported from Massachusetts as regards the effect of nitrate
of soda as a side dressing to previously fertilized onions started from
seed (1). In general, however, such a side dressing was beneficial. With
onions started from dry sets, however, such a practice was clearly not
beneficial.

Method of Procedure

Since it was desirable to keep the experiment as simple as possible,
the treatments were limited to six or seven at each location in any one
season. With the exception of the grower’s treatment—where this was
used——the treatments were the same at all locations, but were not the
same all three seasons. The experiments were started in the season of
1936-37, and completed in the season of 1938-39.

In the first season, 1936-37, the following six treatments were tried
at all three locations:

No fertilizer

600 pounds per acre of 6-12-6

600 pounds per acre of 6-12-6 plus a side dressing of nitrate of soda at the
rate of 133 pounds per acre. .

600 pounds per acre of 6-18-0

600 pounds per acre of 6-18-6

600 pounds per acre of 6-18-12

mm» Qpw

These treatments were similar to those previously conducted at Winter
Haven in order to see if the same general response would be obtained on
different soils.

In the seasons of 1937-38 and 1938-39, the 6-18-6 fertilizer treatment
was dropped and a 6-12-0 substituted. Also the nitrate of soda side dress-

ing was transferred from the 6-12-6 to the 6-18-12 treatment. They then .

became:

No fertilizer

600 pounds per acre of 6-
600 pounds per acre of 6
600 pounds per acre of 6-
600 pounds per acre of 6-18-12

Quhppw

rate of 133 pounds per acre.

600 pounds per acre of 6-18-12 plus a side dressing of nitrate of soda at the

These were designed to compare fertilizers both with and without§

potash, as well as those having 1-2-0 or 1-2-1 ratios with those having

 

ONION FERTILIZER EXPERIMENTS 7

 1-3-0 or 1-3-1 ratios, als_o unfertilized onions with those fertilized in
. various ways, and finally onions receiving side dressings of nitrate of
' soda with those not receiving such treatment.

In addition to these six standard treatments at each location, plats

;_ using the grower’s special mixture or a fertilizer with some other formula
 were planted at Laredo and Big Wells in some seasons.

In all three locations the plats were laid out in approximately the same

liway. Minor variations in cultural procedure of course had to be made
1 at each place to accommodate the methods of the cooperating growers.

The plats at all places were close to 1/20 acre in size, and in round

= figures were 9 to 12 feet wide by 200 or more feet long. At Laredo and

Eagle Pass where the border method of surface irrigation is practiced,

I each plat consisted of a single area surrounded by the raised border which
is confined the water during irrigation. The rows were planted fiat and
l were one foot apart. At Big Wells each plat consisted of seven rows each
g in the form of a low ridge. The rows were 16 inches apart there.

All the fertilizer treatments (except the nitrate side dressing) were
applied broadcast several days before the onion plants were set out. The
weighing, mixing and application of the fertilizer were all done by the

IStation which also supervised the harvesting, and collected the records
‘at the various harvests which occurred in April and May. Weeding,
I cultivating, irrigating and all other cultural operations were carried out

at the discretion of the individual cooperators, care being taken that all
plats were handled alike and at the same time.

At Big Wells the outside rows, as well as several feet at each end of

A the plats, were not included in harvest records. At Eagle Pass and Laredo

the entire plat was harvested. Aside from the possibility of a slightly
heavier yield on the outside rows there was practically no possibility of
interaction between the treatments. From the practical point of view,
this method of harvesting coincided very well with the grower’s methods,
since his entire onion acreage was planted in such plats.

At Laredo and Eagle Pass the yields were usually so large that it was
physically impossible under the circumstances to weigh all the onions as
had been done on the smaller plats in the tests conducted at the Station
itself. In some seasons such as the 1938 season at Eagle Pass, the yields
were low enough to permit the weighing of all the onions. Where the
onions were not all weighed, the measured bushels were counted and ten
sample bushels from each plat weighed.

In all three locations three samples totaling approximately a bushel
of clipped onions were taken from each plat for grading purposes in order
to determine the percentages of U. S. No. 1 jumbos, U. S. No. 1 mediums,
boilers and culls. Two samples were taken towards the ends of each plat,
while the third was taken approximately in the middle. The samples were

l taken so as to represent all the onions in the given area. The variety

8 BULLETIN NO. 596, TEXAS AGRICULTURAL EXPERIMENT STATION

Yellow Bermuda was used at all locations in all three seasons, except at
Big Wells in 1936-37 when Crystal White Wax was grown.

Storage Tests. In the summers of 1938 and 1939 simple storage tests
were conducted to compare the keeping quality of onions which had received
potash fertilizer, with those which had not. From each outlying location
a bushel of U. S. No. 1 onions taken from the plats receiving the 6-18-12
fertilizer, and another taken from the plats receiving 6-18-0 were placed
in common storage in a tile barn at the Experiment Station at Winter
Haven. Periodic examinations were made of these stored onions throughout
the summer and early fall. Losses in weight and in numbers of bulbs
from decay were determined.

Previous Handling 0f Soil. A knowledge of the manner in which the
soils on which these experiments were conducted is desirable for a better
understanding of the results obtained.

At Laredo the Laredo silt loam was newly cleared land in the first year
of test, and so the onion crop was the first grown upon it. The field was
a large one of well over 100 acres, and since it was planted entirely to
onions, the experimental planting represented only a small fraction of it.
With the exception of the test plats, the entire field received an application
each year of 400 to 450 pounds per acre of a fertilizer analyzing
approximately 13.5-34-0. Thus as the experimental planting was set in
a different location in this same field each year, the second and third
year’s plats were located in areas which had received rather heavy fertilizer
applications in the previous year or two.

At Big Wells the onions were grown on land which had been in cultivation
for a number of years. In the first and third years of these tests the
onions followed crops other than onions, but in the second season they
followed onions after an intervening period of summer fallow. In the
first two years the preceding crops had been fertilized fairly generously
with balanced fertilizers. In the third year the onion plats were placed
on land on which sorghum had been planted for the preceding four years,
and which had not had an onion crop, nor received fertilizer in a longer
period than that.

At Eagle Pass the onions were also grown each year on land which
had been under cultivation for a number of years. In general, rotation
had been practiced, and in each of the three seasons that these tests were
conducted, the soil had received good applications of a balanced commercial
fertilizer in the previous season. In the second year of the tests the
plats were located on an area in which onions had been planted the year
before.

Soil Analyses. As a further check and possible aid in the interpretation
of results, an analysis of the soil at each location was also made the first
year (Table 5). These analyses were made by the Division of Chemistry.

ONION FERTILIZER EXPERIMENTS 9

Interpretation 0f Results. In order to obtain a satisfactory basis for
determining whether the differences in yield between various treatments
was due t0 the fertilizer applied or instead to some chance effect common
in experiments of this type, most of the yield data were subjected to an
analysis of variance in accordance with the procedure outlined by
Snedecor (7). For each year there were three sets of data—one for each
locality, and since the tests extended over three years there were nine
such sets of data in all. Each of these sets was examined for significance
separately. Following this the three year record at any one locality was
taken as a unit and analyzed for significance. Actually the plats had not
been arranged in the best way for statistical analysis since for the sake
of simplicity in the cooperative work they had been systematically arranged
rather than truly randomized. Because of this, values of F below that
for Fisher’s 1% point as given by Snedecor (7), but above those for his
5% point were considered of questionable significance, and only those
above his 1% point considered truly significant. Values below the 5%
value were considered as indicating a definite lack of significance.

When comparing two treatments, the minimum difference necessary to
indicate a real or significant difference between them was calculated by
multiplying the standard error by the t value corresponding to Fisher’s
5 per cent point for the degrees of freedom involved.

Results in Terms of Yields
Results at Laredo

Yields as Affected by Fertilizer in General: The application of fertilizer
resulted in noticeably higher yields of onions in practically all instances,
than where no fertilizer was added at all (Table 1). In the average yield
of U. S. No. 1 onions for 1938 and 1939 the fertilizer treatment with
the lowest yield of onions was the 6-18-0 treatment resulting in a yield

Table 1. Effect of various fertilizer applications on the bushels of onions per acre on Laredo
silt loam at Laredo, Texas

U. S. N0. 1 (Jumbo & Medium Size) Total Yields
Fertilizer Ilsed* Ave. Ave.
1937 1938 1939 1938 and 1937 1938 1939 1938 and
‘ ’39 only _ ’39 only
None . . . . . . . . . . 496 347 476 412 618 430 588 509

6—12—O . . . . . . . . . . . . . . . . . 541 492 516 . . . . . . . . 630 630 630

6—12— . . . . . . . . . 549 526 523 524 682 619 641 630

6—12—6 +N** 603 . . . . . . . . . . . . . . . . . . . . . . . . 716 . . . . . . . . . . . . . . . . . . . . . . . .

6-1 . . . . . . . . . 467 526 470 498 611 601 625 613

6——18—6_ . . . . . . . . 481 . . . . . . . . . . . . . . . . . . . . . . . . 604 . . . . . . . . . . . . . . . . . . . . . . . .

6——18—12 . . . . . . . . 5F 559 487 523 660 630 628 629

6-18-12 +N**. . . . . . . . . . 586 493 540 . . . . . . . . 657 634 646

13%—34—O . . . . . . 549 636 501 568 671 748 625 686

*All fertilizers except 13%—34—0 and the side dressings applied at rate of 600 pounds per
acre. The l3,1/;—34—0 applied at approximately 450 pounds per acre.
**N was a nitrate of soda side dressing applied at the rate of 133 pounds per acre.

10 BULLETIN NO. 596, TEXAS AGRICULTURAL EXPERIMENT STATION

of 498 bushels per acre. This was 86 bushels per acre more than the
onions receiving no fertilizer. Onions receiving other fertilizer treatments
yielded as high as 568 bushels, or as much as 156 bushels more per acre
than onions receiving no fertilizer. Such a record would indicate that
the application of fertilizer is on the whole decidedly profitable on the
Laredo silt loam, even though it is a productive soil when left unfertilized.

Effect of Potash on Yield. A comparison of the yields attributed to
the fertilizers with the formulas 6-12-0 and 6-12-6, as well as 6-18-0 and
6-18-12 in Table 1, shows that in practically every instance the onions
receiving the 6 or 12 per cent of potash produced more U. S. No. 1 onions,
as Well as a higher total yield than those not receiving potash. The
average increases due to potash however were not great. The onions
receiving 600 pounds of 6-12-6 fertilizer yielded an average of 524 bushels
per acre of U. S. No. 1 onions for the years 1938 and 1939 as against
516 bushels from the onions receiving the same amount of 6-12-0. The
total yields from each of these two treatments were identical. Onions
fertilized with the 6-18-12 mixture produced on an average for the same
years, 523 bushels of U. S. No. 1 onions as against 498 bushels from the
onions receiving the 6-18-0 mixture. The average total yield from the
onions receiving the 6-18-12 fertilizer was 629 bushels per acre while
that from the 6-18-0 fertilizer treatment was 613 bushels, or only 16
bushels less. This difference from a statistical point of view is too small
to be significant. Thus although the presence of potash in the fertilizer
tended to increase yields, its effect was of no commercial importance.

Effect of Nitrogen Side Dressing on Yield. The addition of 133 pounds
per acre of nitrate of soda to onions which had already received the
complete fertilizer 6-12-6 or 6-18-12 resulted in increased yields in all
instances (Table 1). These increases although consistent were usually
small. For example, the onions receiving the 6-18-12 fertilizer plus the
side dressing of sodium nitrate in February yielded on the average in
the years 1938 and 1939, 540 bushels of U. S. No. 1 onions per acre or
only 17 bushels more than onions also fertilized with 6-18-12 but receiving
no side dressing. The difference in the total yields for these same
treatments was also only 1'7 bushels. Such a difference is too small to
have significance. Thus it appears that a side dressing of nitrate of soda
to onions on a Laredo silt loam which has already received as much as
600 pounds of 6-18-12 fertilizer is of questionable value. It will do no
harm, but it may not result in any increased yields.

Comparison of Ratios. If the yields of onions resulting from the
application of fertilizers with 1-2-0 and 1-3-0 ratios, that is, those having
the formulas 6-12-0 and 6-18-0, are studied it will be seen that in all
instances they were smaller whenever the latter fertilizer was applied
(Table 1). Differences were not usually very great however. A similar
but more marked trend was shown in 1937 between those receiving fertilizers
with 1-2-1 and 1-3-1 ratios, namely the 6-12-6 and 6-18-6 fertilizer

ONION FERTILIZER EXPERIMENTS 11

treatments. This difference of 68 bushels of U. S. N0. 1 onions per acre
although not a definite proof in itself, Was great enough, especially when
considered in the light of the following year’s results with the 1-2-0 and
1-3-0 ratios mentioned above, to indicate a trend in favor of the 1-2-0 or
the 1-2-1 ratio. Even if the differences are interpreted as having no
significance, it can be safely said that onions receiving fertilizers with
1-3-0 or 1-3-1 ratios did not outyield, even slightly, those onions receiving
fertilizers with 1-2-0 or 1-2-1 ratios.

The 13.5-34-0 Fertilizer Treatment. The grower at Laredo applied to
his general onion crop a broadcast treatment of 13.5-34-0 fertilizer at the
rate of about 450 pounds per acre ahead of planting time. This was made
up by mixing the 11-48-0 and 16-20-0 in equal proportions. Table 1
shows while on an average onions receiving this fertilizer outyielded
onions receiving other mixtures, it also shows that this was not the case
every year. In 1937 onions receiving 6-12-6 at the rate of 600 pounds
per acre produced just as many bushels of U. S. No. 1 onions as those
receiving 450 pounds of 13.5-34-0.

Results at Big Wells

Yields as Affected by Fertilizer in General. Onions receiving fertilizer
in any one of the treatments followed in these experiments at Big Wells
produced higher yields both of U. S. No. 1 bulbs and total yield, than
those onions receiving no fertilizer at all (Table 2). In the average yield
of U. S. No. 1 onions for 1938 and 1939 the fertilizer treatment with the
lowest yield of onions was the 6-18-12 treatment resulting in a yield of
237 bushels per acre, or 31 bushels more per acre than those left unfertilized.
The highest yielding fertilized onions produced 262 bushels of U. S. No. 1
onions per acre, or 56 bushels more per acre than the unfertilized ones.
While the trend was always towards higher yields whenever fertilizer
was used, the increases which could be attributed to fertilizer were not
always great, nor could they, on the basis of an analysis of their causes,
always be attributed to fertilizer.

Table 2. Effect of various fertilizer applications on the bushels of onions per acre on Monteola
clay at Big Wells, Texas

U. S. No. 1 (Jumbo & Medium Size) Total Yields

Fertilizer Used* Ave. Ave.
1937 1938 1939 1938 and 1937 1938 1939 1938 and
’39 only ’39 only

No fertilizer. . . . 146 315 97 206 200 414 218 316

6—12—O . . . . . . . . . . . . . . . . . 371 125 248 . . . . . . . . 458 250 354

6-12-6 . . . . . . . . . 181 367 115 241 226 475 248 362

6-12—6 +N**. .. 171 . . . . . . . . . . . . . . . . . . . . . . .. 212 . . . . . . . . . . . . . . . . . . . . . . ..

6-18-0 . . . . . . . . . 187 380 131 256 235 461 252 356

6-18-43 . . . . . . . . . 190 . . . . . . . . . . . . . . . . . . . . . . . . 232 . . . . . . . . . . . . . . . . . . . . . . . .

6—18—l2 . . . . . . . . 206 .334 140 237 249 445 260 352

6-18-12 +N**. . . . . . . . . . 374 150 262 . . . . . . . . 464 268 366

*All fertilizers except lhe si_de dressings applied at the rate of 600 pounds per acre.
**N was a nitrate of soda side dressing applied at the rate of 133 pounds per acre.

12 BULLETIN NO. 596, TEXAS AGRICULTURAL EXPERIMENT STATION

Effect 0f Potash 0n Yield. On the basis of the records summarized in
Table 2 there is a trend towards lower yields in most instances where
potash was applied, as compared with where it was not applied. For
example, the average yield of U. S. No. 1 onions for the years 1938 and
1939 in the plats receiving 600 pounds per acre of 6-18-O fertilizer was
256 bushels, while that from the plats receiving 6-18-12 fertilizer was
only 237 bushels.

Effect of Nitrogen Side Dressing 0n Yield. The application of a nitrate
of soda side dressing to onions which had already received a complete
fertilizer resulted in increased yields in most cases (Table 2). However,
yields were not strikingly greater on the average. If the average yields
for the years 1938 and 1939 are considered it is seen that onions which
received the 6-18-12 fertilizer produced 237 bushels per acre of U. S.
No. 1 onions as compared with 262 bushels per acre of N0. 1 onions from
the plats which received the 6-18-12 fertilizer plus 133 pounds of nitrate
of soda as a side dressing later. Total average yields for the same period
were also increased, but to a lesser extent. Although there seems to be
a trend towards increased yields due to the nitrate side-dressings, such
increases are not very significant; in many cases they were small, and
in a few the yields were lower where the side dressing was applied.

Comparison of Ratios. Although a study of the figures in Table 2
indicate that slightly greater yields were obtained from the onions fertilized
by the 6-18-6 and the 6-18-0 fertilizers (1-3-1 and 1-3-0 ratios), than
were obtained from onions fertilized by the 6-12-6 and 6-12-0 fertilizers
(1-2-1 and 1-2-0 ratios), the increases due to the greater application of
phosphoric acid were so slight in most instances that they are really
not significant. From the practical point of view the yields with fertilizers
with formulas 6-12-0 or 6-12-6 should be just about as satisfactory as
yields with the formulas 6-18-0 and 6-18-6, and less expensive.

Results at Eagle Pass

Yields as Affected by Fertilizer in General. On the Laredo very fine
sandy loam used in these experiments at Eagle Pass, none of the fertilizers
listed in Table 3 caused noticeable increases in the average yield of onions
as compared to Where no fertilizer at all was applied. A study of the
records for the individual replications from which the averages for each
have been obtained shows considerable inconsistency. Even in 1937 when
the average of the four replications gave an advantage in yield to all the
fertilized plats as compared to the unfertilized ones, some individual
replications in the fertilized treatments had smaller yields than the same
replication in the unfertilized treatment. Whether this was due to a
naturally high fertility of the soil or to the preceding program of soil
management, is difiicult to say. The possible explanations for these
results are discussed later.

ONION FERTILIZER EXPERIMENTS 13

Table 3. Effect of various fertilizer applications on the bushels of onions per acre on Laredo
very fine sandy loam at Eagle Pass, Texas

U. N0. 1 (Jumbo & Medium Size) Total Yields

Fertilizer Used* Ave. Ave.
1937 1938 1939 1938 and 1937 1938 1939 1938 and
’39 only ’39 only

No fertilizer. . . . 534 85 674 380 572 146 722 434

6-12-0 . . . . . . . . . . . . . . . . . 105 643 374 . . . . . . . . 160 702 431

6-12- . . . . . . . . . 659 75 536 306 677 132 580 357

6-12-6 +N**. 731 . . . . . . . . . . . . . . . . . . . . . . . . 760 . . . . . . . . . . . . . . . . . . . . . . . .

61-18-0 . . . . . . . . . 619 1'30 605 368 651 188 659 424

6-18-6 . . . . . . . . . 674 . . . . . . . . . . . . . . . . . . . . . . . . 697 . . . . . . . . . . . . . . . . . . . . . . . .

6-18-12 . . . . . . . . 664 104 571 338 689 164 623 394

6——18—l2 +N**. . . . . . . . . . 155 695 425 . . . . . . . . 212 750 481

*All fertilizer except the side dressings applied at the rate of 600 pounds per acre.
**N was a nitrate 0f soda side dressing applied at the rate of 133 pounds per acre.

Effect 0f Potash on Yield. A comparison of the yields of onions
influenced by fertilizers containing potash (those with formulas 6-12-6
and 6-18-12) with those lacking potash (those with formulas 6-12-0 and
6-18-0) shows that in nearly every case onions receiving potash produced
less than those not receiving it (Table 3). In other words potash in the
fertilizer seemed more often to depress onion yields rather than to
increase them. In the first year, 1937, however, stepping up the potash
from 0 to 6 per cent (compare 6-12-0 with 6-12-6, and 6-18-0 with 6-18-6
in Table 3) increased yields, but where it was stepped up to 12 per cent
(see 6-18-12), the yield was slightly lower than that of the 6-18-6
treatment, but still above that of the 6-18-0 treatment. However, fertilizer
in general was more effective in 1937 than in either 1938 or 1939 (see
above).

Effect of Nitrogen Side Dressing on Yield. Wherever a side dressing
of sodium nitrate was applied to onions which had already received either
the 6-12-6 or the 6-18-12 fertilizer initially, yields were noticeably increased
in all instances (Table 3). Of all the treatments at Eagle Pass the
nitrate of soda side dressing was not only the most marked in its efiect,
but the most consistent from replication to replication and year to year
in producing a large increase in yield, both of U. S. No. 1 onions and
of total yield. In 1937 onions receiving an initial application of 6-12-6
plus a side dressing of sodium nitrate in February produced 731 bushels
of U. S. No. 1 onions per acre as compared with only 659 bushels from
onions receiving the 6-12-6 fertilizer but no side dressing (Table 3).
Similarly the same table shows that an average of the U. S. No. 1 yield
for the two years 1938 and 1939 the onions fertilized initially with the
6-18-12 mixture and receiving the side dressing later produced 425 bushels,
while those receiving the 6-18-12 mixture and no side dressing only
produced 338 bushels. There was a similar average difference in the
total yield. The yields for these treatments in 1938 and 1939 separately
all show rather clear cut differences. Side dressings of sodium nitrate
were profitable at Eagle Pass.

14 BULLETIN NO. 596, TEXAS AGRICULTURAL EXPERIMENT STATION

Comparison of Ratios. From the results obtained it is impossible to
say whether fertilizers with 1-3-0 or 1-3-1 ratios, or fertilizers with
1-2-0 or 1-2-1 ratios were the most effective in increasing yields at
Eagle Pass. A study of Table 3 will show that the average yields
for each year varied, and behind these varied averages were replica-
tions with varied results. The average yields as computed on the
basis of the 1938 and 1939 seasons are very close together for the
6-12-0 and the 6-18-0 fertilizer treatments indicating still further that
one is probably just as effective as the other.

Discussion and Recommendations

Since the tests reported in this publication were primarily an extension
of some of the key treatments used in extensive onion fertilizer experiments
conducted on Webb fine sandy loam at Winter Haven, it seems desirable
to consider the results in the light of those previously reported (4).
Onions have also been grown at the Station on Crystal loamy fine sand
and have responded according to unpublished records in much the same
way as on Webb fine sandy loam. Table 4 gives in a condensed form the
general results found on the different soils. It is obvious that in some
instances the results were similar to those previously found at the Station,

Table 4. Response to fertilizers 0f Yellow Bermuda onions grown on various soil types

_ _ _ Fertilizers
Location Fertilizer Potash** Nitrate side with T1-3-0
Soil Type 0f in General* dressing*** or l-3-l ratios
Experiments _
Yield trend Yield trend Yield trend Yield trend
Webb fine sandy loam. Winter definitely up possibly possibly probably up
Haven down down
Crystal loamy fine sand VVIXHCI‘ definitely up possibly possibly probably up
Haven down down
Laredo very fine sandy Eagle Pass variable possibly probably up variable
loam down
Laredo silt loam . . . . . . Laredo up possibly up up possibly
down
lVlonteola clay... . . . . . Big Wells up down (1') possibly up possibly up

*C.omplete fertilizer mixtures, or nitrogen-phosphoric acid mixtures only.
**In presence of nitrogen and phosphoric acid.
***Following initial applications of complete fertilizer.
1In comparison to fertilizers with 1-2-0 or 1-2-1 ratios.

in others they were not. With the exception of the results especially
pertaining torpotash, those at the outlying locations rarely if ever showed
as great differences in yield between the various treatments as occurred
in the earlier experiments. With potash the results again lacked any
really clear-cut trends. These results should enable growers on a wider
range of soils to fertilize their onions with greater understanding.

ONION FERTILIZER EXPERIMENTS 15

Soil Analyses. A study of soil analyses also throws some light on
the problem of fertilizers. In Table 5 is given the analyses of the soils
used in various tests at Winter Haven as well as those in the outlying
experiments. On the basis of the figures in this table one would expect
all the soils in the outlying tests to be more fertile than those at Winter
Haven, for the analysis of each of them shows more nitrogen, more
phosphoric acid, and more potash. The Laredo silt loam ran particularly
high in phosphoric acid, and all three soils at the outlying locations ran
extremely high in potash. A word of caution as regards the interpretation
of the data in Table 5 is perhaps necessary here. Because of the high
lime content of these latter soils as indicated by high percentage of acid
consumed one cannot always be sure of readings obtained with active
phosphoric acid and active potash. Where the acid consumed is over 90,
it may have interfered with the determination. These nutrients were
however present more abundantly at Laredo, Big Wells, and Eagle Pass
than they were at Winter Haven. This fact has some bearing on the
following discussion.

Table 5. Analyses of top seven inches of soil in the localities of onion tests*

Winter Haven Eagle Pass Laredo Big Wells
Nutrient and pIl Crystal Webb Laredo Laredo Monteola
loamy fine fine sandy very fine silt loam clay
sand loam sandy loam
I
Nitrogen . . . . . . . . . . . . . . . . . . . . . .. 0.033%' 0.031% 0.079% 0.071% 0.128%
Active phosphoric a(vid**. . .. . . . . . 21 ppm 28 ppm 68 ppm 447 ppm 180 ppm
Total phosphoric acid . . . . . . . . . . . 0.023% 0.022% 0.123% 0.091% 0.107%

Active p0tash** . . . . . . . . . . . . . . . . 200 ppm 220 ppm 415 ppm 382 ppm 476 ppm

To_tal potash . . . . . . . . . . . . . . . . . .. 0.54 % .60 % 2.25 % 2.22 % 1.10 %

Acid consumed . . . . . . . . . . . . . . . .. 3.0% 2.0% 100.0% 83.3% 91.6%

pH . . . . . . . . . . . . . . . . . . . . . . . . . . .. 6.43 6.60 8.30 8.28 8.23

*The analyses in this table were made from the soil taken from the actual fields where the
tests were conducted. It should not be assumed that the analysis would always be the same
for the type given. although it would probably approximate it.

**Givcx1 in parts per million—ppm.

Yields as Affected by Fertilizer in General. Only on Laredo very fine
sandy loam was the use of fertilizer in general found to be of doubtful
value (see Table 4). The response to fertilizer on the Laredo silt loam
and the Monteola clay, while probably profitable in terms of yield return,
was not nearly as marked as it had been on Webb fine sandy loam, as
reported earlier (4). The results on Laredo silt loam and Monteola clay
are to be more or less expected, as observations by agriculturists in
general indicate that these soils are naturally more fertile than Webb
fine sandy loam. The response shown by Laredo very fine sandy loam is
somewhat unexpected, and not quite in line with the experiences claimed
by growers who operate on this soil. In other words, a more definite
response to fertilizer would normally be expected, on such a soil type.
The lack of response of all the soils in the outlying locations as compared
to that at Winter Haven is not surprising in the light of the analyses
given in Table 5.

16 BULLETIN NO. 596, TEXAS AGRICULTURAL EXPERIMENT STATION

Effect 0f Potash on Yield. Nowhere was the response to potash sig-
nificant. Such a result is not unexpected when one considers Table 5.
On Laredo silt loam there was a tendency for the yields to be higher
when potash was present in the fertilizer, but this trend was in no sense
clear cut (see Table 4). On the other soils the trend if any, was down,
just as it had been on the Webb fine sandy loam. While, of course, it is
impossible to know the exact fertilizer requirements of every piece of
land in the Winter Garden area, the results thus far obtained suggest
rather clearly that potash is not a limiting factor in onion production in
this section. Soil analyses also seem to justify this conclusion. Whether
a grower applies potash or not, the yields of onions which he obtains
are not going to be strikingly lower or higher in either case. Since it
is a fact that soils can and do become depleted of various nutrients
including potash it might be a desirable practice for a grower to include
some potash in his fertilizer every five or six years. Better still would
be trial applications of potash-containing fertilizer in a number of strips
or plats across fields which had not received any potash in a number
of years. If these areas showed a marked and consistent response to
this treatment potash could probably be applied to such a field before
the planting of another cash crop, especially onions. Such a trial treatment
would probably be desirable at more frequent intervals on Laredo silt
loam than it would on the other soil types mentioned in Table 4. On the
other hand the yields of onions obtained on Laredo silt loam were always
high, even from the unfertilized plats (see Table 1), emphasizing once
again that even though potash seemed to increase yields there more than
at any other place, it could not be the limiting factor that phosphoric
acid proved to be on Webb fine sandy loam (4).

The Value of Nitrate Side Dressings. In all the outlying experiments
reported upon here, there was a tendency for higher onion yields Where
nitrate side dressings were applied. On Laredo very fine sandy loam it
was clear-cut, yields being very materially higher; on Laredo silt loam
the increase in yield While usually noticeable was not always great enough
nor consistent enough to assure that it would always be profitable under
commercial conditions; on Monteola clay, the increase while more often
there than not, was usually so small that one would not be warranted in
saying that it would ever be profitable.

In view of the decided response of onions to the nitrate side dressings
on Laredo very fine sandy loam, combined with the lack of response on
this same soil to fertilizers in general as well as the variable results
obtained in the treatments involving the fertilizers of varying ratio,
it is possible that much heavier applications of nitrogen-carrying fertilizers
should be made initially to onions grown on this soil type.

Comparison of Ratios. In none of the outlying experiments were ferti-
lizers with 1-3-0 or 1-3-1 ratios as effective as they were at the Station on
Webb fine sandy loam. On Laredo silt loam there was a very slight

ONION FERTILIZER EXPERIMENTS 17

tendency for the onions to produce less when they received a fertilizer
with a 1-3-0 0r a 1-3-1 ratio than where they received one with a 1-2-0
0r a 1-2-1 ratio. On the Monteola clay the results were the opposite.
On neither of these soils however were the differences really significant
when examined statistically.

At Eagle Pass on the Laredo very fine sandy loam the results varied
so much, it was impossible to find any trend whatsoever. In view of the
rather striking response to nitrate side dressings on this soil, it is possible
as already pointed out that this soil needs nitrogen to such an extent,
that without it, the onions are unable to respond normally to applications
of other materials.

It is of course realized that the data are insuflicient to give complete
support to some of the tentative conclusions discussed above, as for
example the need for nitrogen on the Laredo very fine sandy loam. It
was not feasible to plan these experiments on such an extensive scale
that every question was answered. Where such circumstantial evidence
exists however, a grower can conduct a simple test of his own to obtain
further corroboration. Even when results of the most comprehensive of
tests are available, growers should often conduct simple tests on their
own land to determine the treatment best suited to their particular
situation. The results of fertilizer experiment only suggest the most
possible and desirable treatments, but such treatments may not necessarily
be best under all circumstances.

Recommendations. From the results obtained in these experiments and
in line with the discussion above the following recommendations can be
made. Although the application of a complete fertilizer to an onion crop
on Laredo silt loam and Monteola clay (both representative of some of
the darker colored heavier soils in the Winter Garden-Laredo area) is
not as profitable as similar applications on the sandy loams, it is never-
theless profitable and the practice can well be followed by onion growers.

Since potash is apparently no more needed on these heavier soils than
it is on the sandy loams, mixtures such as 6-12-0, 6-18-0, 5-15-0, 11-48-0,
and 16-20-0 can all be applied profitably, the first three at a rate of
around 600 pounds per acre, the last two correspondingly less. Some
growers mix 11-48-0 and 16-20-0 sack for sack (a 50:50 mixture), thus
obtaining a fertilizer with a formula 135-34-0. In view of the fact that
fertilizers having 1-2-0 and 1-2-1 ratios caused the onions to produce
about as well as those receiving fertilizers with 1-3-0 and 1-3-1 ratios,
the 1235-34-0 mixture works out better than 11-48-0. Fertilizers lacking
potash, and having a ratio approximating 1-2-0 should be cheaper than
fertilizers with 1-3-0 or 1-4-0 ratios.

Sodium nitrate side dressings can still not be recommended as very
profitable, except apparently on Laredo very fine sandy loam.

 
  
   
     
 
   
  
 

18 BULLETIN NO. 596, TEXAS AGRICULTURAL EXPERIMENT STATION

Results of Storage Tests 

The storage tests were primarily to determine the effect of potash
keeping quality. Those lots which had higher percentages 0f the origi
bulbs still marketable at the periodic inspections were considered _
having the better storage quality. Results in general indicated ‘f’
potash did not increase keeping quality, although results varied somew 
with location and season. a

The onions grown on the Laredo silt loam at Laredo showed a tenden
in 1938 to keep better where they had received no potash during thi
growth period (Table 6). In 1939 they showed the opposite tendency
about the same extent (Table 7).

Table 6. Percentages of onions placed in storage, still marketable at diflerent dates in l9 A

Number of
Location bulbs
where grown originally May June July August Sept.
and fertilizer placed in 23 18 28 23 \ 24
received storage

Laredo: (18 (44 (84 (110 (142
days) days) days) days) days)

6—18—0............ 122 98.4 94.3 82.8 73.8 63.1
6—18—l2........... 110 97.3 89.1 78.2 66.4 54.5
Eagle Pass: (18 (44 (84 (110 (142
days) days) days) days) days)

6—18—0 . . . . . . . . . . .. 283 97.4 83.5 65.5 55.6 49.5
6-18-12 . . . . . . . . . .. 240 92.0 77.1 66.9 55.9 49.2
Big Wells: (26 (66 (92 (124
days) days) days) days)

6—18—0............ 194 —* 99.6 95.8 84.8 79.5
6—18—12........... 118 —* 100.0 97.5 89.2 81.2

*St0rage only started on this date.

Table 7. Percentages of onions placed in storage, still marketable at dilferent dates in l A

Number of
Location bulbs
where grown originally June July August Sept. Oct.
and fertilizer placed in 7 3 16 6 4
received storage

Laredo: . (32 (58 (102 (123 (151
. days) days) days) days) days)
6—18—0............ 146 93.2 91.1 78.8 75.3 69.9
6-18-12 . . . . . . . . . .. 153 94.8 92.2 88.3 85.9 83.0
Eagle Pass: (34 (78 (99 (127
days) days) days) days)

6—-l8—O............ 175 —* 92.6 77.1 73.1 73.4
6—l8—12........... 215 -* 94.9 78.6 67.4 60.9
Big Wells: (32 (58 (102 (123 (151
days) days) days) days) Clays)

6-18-0 . . . . . . . . . .. 244 99.6 96.7 82.4 73.0 66.8
6—18—12........... 260 98.1 95.0 79.6 70.4 57.7

*Storage only started May 30.

ONION FERTILIZER EXPERIMENTS 19

With the onions grown on the Laredo very fine sandy loam at Eagle
Pass, it seemed to make little difference in either 1938 or 1939 whether
they had received potash or not. In both seasons, both treatments
fluctuated back and forth so far as having the greater percentage of
marketable onions still remaining at the successive inspections (Tables
6 and 7). At no time was there ever any great difference between the
two lots.

On the Monteola clay at Big Wells, the onions again showed little

' difference in keeping quality on the basis as to whether they had received

potash or not. At each inspection in both 1938 and 1939, there was always
about the same percentage of marketable onions still remaining irrespective
of whether they had received potash or not (Tables 6 and 7 ). The results
secured in these experiments, suggest that potash fertilizer is no more
a factor in the keeping quality of onions grown on the various soils of
the Winter Garden Region of Texas than it was when first reported in
1936 in connection with the fertilizer experiments on Webb fine sandy
loam (4).

Acknowledgments

The Station, and particularly the author, wants to express appreciation
to the American Cyanamid Company, as well as to N. H. Clark of Laredo,
to E. W. Ritchie of Eagle Pass, and to C. W. Barker and Paul Levering
of Big Wells, without whose helpful cooperation the experiments reported
upon here would have been impossible. The American Cyanamid Company
made funds available for the purchase of materials and the additional
labor connected with the collection of data. The four growers aided in
supplying the land, the onion plants, the irrigation water, and all the
ordinary labor required in the growing of an onion crop.

20 BULLETIN NO. 596, TEXAS AGRICULTURAL EXPERIMENT STATION
Summary

The results obtained in the outlying fertilizer experiments conducted
with Yellow Bermuda onions in the Winter Garden-Laredo area over a
period of three years lead to the following conclusions:

1. The response by the onions to fertilizer in general on the Laredo
silt loam (Laredo) and the Monteola clay (Big Wells) was not nearly
as marked as it had been in previous experiments on Webb fine sandy loam.

2. There was no consistent response to fertilizer in general on Laredo p

very fine sandy loam. This may be due to a deficiency in available nitrogen,
or an unsatisfactory nutrient balance caused by a lack of nitrogen.

3. In none of the outlying locations was the response to potash
significant. This finding agreed with the previous one on Webb fine sandy
10am.

4. In all the outlying locations there was a tendency towards higher
onion yields whenever nitrate of soda had been added to previously
fertilized onions. This tendency was the most clear-cut on Laredo very
fine sandy loam, was somewhat less on Laredo silt loam, and so small on
Monteola clay that it lacked significance.

5. In none of the outlying experiments were fertilizers with 1-3-0 or
1-3-1 ratios noticeably more effective than fertilizers with 1-2-0 and
1-2-1 ratios in increasing onion yields. On Laredo silt loam there was
a very slight tendency for the onions to be less productive with a fertilizer
having a 1-3-0 or a 1-3-1 ratio than with one having a 1-2-0 or 1-2-1
ratio. On Monteola clay the results were the opposite. '

6. With onions grown on any of the soils on which the fertilizer tests
herein reported were conducted, the presence or absence of potash in the
fertilizer used, seems to make little difference in their keeping quality.

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. Fite, A. B. 1935. Onion Fertilizer Experiments. N. M. Agr. Exp. Sta. Bul. 233

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. 1936. Fertilizer Experiments with Yellow Bermuda Onions in the
Winter Garden Region of Texas. Texas Agr. Exp. Sta. Bul. 524

5. Knott, J. E. 1936. Fertilizing Onions on Muck Soils. Cornell Univ. Agr. Exp. Sta.
Bul. 650

6. Knott, J. E. 1934. Growing Onions on the Muck Soils of New York. Cornell Univ.
Agr. Exp. Sta. Bul. 510 (Revised)

7. Snedecor, G. W. 1934. Calculation and Interpretation of Analysis of Variance and
Covariance. Ames, Iowa

8. Strong, W. O., H. H. Zimmerly, and H. T. Cook. 1930. Onion Culture. Va. Truck
Exp. Sta. Bul. 72