THE EFFECT OF POTASH FERTILIZER
ON THE COLOR OF' BOILED
POTATOES WITH SOME REFERENCE
TO YIELD

Thesis for the Degree of M. S.
MICHIGAN STATE COLLEGE

Leroy R. Miller
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THE EFFECT OF POTASH FERTILIZER ON THE COLOR
OF BOILED POTATOES WITH SOME REFERENCE TO YIELD.

THE EFFECT OF POTASH FERTILIZER ON THE COLOR OF
BOILED POTATOES WITH SOME REFERENCE TO YIELD.

by

Leroy Ross Miller

A THESIS

Submitted to the Graduate School of Michigan
State College of Agriculture and Applied
Science in partial fulfilment of the
requirements for the degree of

MASTER.OF SCIENCE
Department of Farm Crops

1940

ACKNOWLEDGEMENTS

The writer wishes to express his appreciation
to Professor H. C. Moore and Mr. E. J. Wheeler for
valuable suggestions and criticisms during the course
of the experiment and also to Dr. W; D. Eaten and
members of the Farm Crops and Soils Departments of
Michigan State College, whose aid was invaluable through—
out the.course of the investigation.

1-2374591;

1.
3.
3.

6.

TABLE OF CONTENTS

Introduction

Review

of Literature

Plan of Experiment

A.
B.
C.

G.
Results
A.

B.

Summary

Literat

Location and Size of Plats
Treatments Used
Stand Observations made During the Growing Season
Method of Harvesting
Method of Cooking
Method of Determining Culinary Quality
Method of Statistical Analysis
and Discussion

Analytical Comparison of Results Between Treatments
and Color of Boiled Potatoes.

Analytical Comparison of Results Between Treatments
and'Yield per Acre.

ure Cited.

INTRODUCTION

Quality in potatoes is difficult to define as no
standard is available which is accepted by all consumers.
For example, in France where deep-fat frying is a common
method of cooking, consumers prefer a non-mealy potato which
will not disintegrate but remain firm when cooked. In the
United States, potatoes are most commonly boiled and the
American consumer prefers potatoes which are mealy and is
insistent that they remain white after being cooked. Many
lots of potatoes in Michigan and other states turn gray or
dark as soon as they are boiled and displease the consumer
to the extent that some growers and shippers have found it
difficult to hold their markets.

For many years experimenters have studied factors
that may affect the cohesion, texture and flavor of cooked
potatoes, but only recently have they given much attention
to factors that cause potatoes to cook dark. Their results
indicate that variety, maturity, type of soil, storage temp-
erature, and mechanical injury may be some of the factors
affecting the color of boiled potatoes.

Three investigators in Wisconsin and one in Scotland
reported that potash applied to the soil as a fertilizer re-
duced darkening while one in New York state obtained negative
results. Since the results of four widely separated experi-

ments were in close accord, and since the amounts of potash

applied on Michigan potato fields vary greatly, it was
decided to investigate the influence of varying amounts of
potash on the color of boiled potatoes. Also to observe
their effects on the yield per acre and on the market grade

of potatoes grown under different soil conditions.

Review of Literature

Ashby (1), working in England, states that
physical properties of the soil cause the greatest influence
on quality, especially temperature and water supply. Loamy
soils gave uniform warmth and water supply, therefore produc-
ed the best quality.

Bewell (2) states that good culinary quality is
associated with a dry matter content of 30 per cent, and
poor quality is associated with a dry matter content of
15 per cent.

Butler, Morrison and Boll (3) found that mealiness
was modified by the water content, potatoes high in water
being less mealy than those relatively low in water. The
percentage of starch in the tuber was not an indicator of
mealiness, and the presence of sugar tended to produce an
undesirable taste.

Carolus (4) found that, "The potato crop is a gross
feeder and has a large total nitrogen, phosphorus, potassium,
magnesium and calcium requirement." The maximum nutrient re-
quirement of the potato plant usually occurs about 50 to 80
days after planting.

Cobb (5) states that chemical and cooking tests
show that good culinary quality of potatoes is closely
related to high dry matter, high starch and low nitrogen
contents of the tuber._

Dietz (8) found that potash is needed to produce

high yields of potatoes.

Findlay (7),working in Scotland, showed that:

l.

Hantke (8)
concludes that:

1.

A light type of soil produced better
quality potatoes than a heavier type

of soil such as clay or peat.

The use of a poorly balanced fertilizer

or excessive amounts of nitrogen result-
ed in poor quality.

Early planting in wet or dry seasons
usually gave extremely dry potatoes, while
late plantings gave wet, soapy potatoes.

from his work at University of Wisconsin,

"The blackening is caused by the reaction
of certain free amino acids in the potato
and oxygen."

"The condition is physiological and not

.pathological.'

When the rainfall or soil moisture is
sufficient throughout the season, the
application of potash to the soil is
associated with a decrease in the darken-
ing of tubers when cooked.

The addition of some rare elements such as
boron, COpper, zinc and manganese to the
soil may have some effect on the darkening
of the potatoes.

Hardenburg (9), in New York State, concludes that good

quality is a result of many factors. Two of the most import-

ant are:

1.

Cultural methods: proper rotations and
better seed.

5

2. Harvesting and grading methods: Harvest—
ing potatoes when immature usually results
in poor quality as the tender skin will
slough off. The potatoes will bruise very
easily. Thorough grading as to size,
shape and appearance is very important
from the consumers standpoint.

Neil and Whittemore (10) found that potatoes were
more mealy when fertilized with a high quantity of potash
than when fertilized with a low quantity of potash in the
form of muriate or sulphate; the value of these two forms
seems to be equal in producing a mealy potato. No correlat-
ion was noted.between mealiness and starch content.

Odland (11) found that the amount of phosphorus does
not influence the potato yields as much as variations in
nitrogen or potash.

Smith (12) found that the darkening of cooked potatoes
is not associated with the amount of potash used in the ferti-
lizer.

Stevenson and Whitman (13) state that the inherent
differences of some varieties have a tendency to prevent
blackening of the tubers.

Sweetman (l4) concludes from factors affecting the
cooking qualities of potatoes that:

l. The consumer prefers potatoes Which are
uniform in size, have a bright skin,
and.possess good cooking quality.

2. The conflicting evidence as to what
causes good cooking quality in potatoes

is probably due to the standards by
which quality is determined and evaluated.

Tottingham, Nagy, and Ross (15) conclude from
their work on culinary quality of potatoes that:

1. ”The blackening of cooked potatoes does
not appear to be associated with trans-
missible pathological conditions.”

2. Analysis in the raw state of tubers which
blacken upon cooking shows high content
of free amino acids. This association
applies particularly to tyrosine.

3. ”Samples of potatoes containing large pro-
portions of blackening tubers contained
an average of less than 1.8 per cent
K20 in the dry matter, whereas the aver—

age content was above this level in the
normal tubers.”

Location and Size of Plats

The experimental work herein reported was conducted
at each of three locations: Potato Experiment Station,

Lake City, Michigan State College Agricultural Experiment
station, East Lansing, and in cooperation with Mr. Percy King,
Waterford, Michigan.

The experimental area at Lake City was laid out on
Ottawa sandy loam: the area at the College and the King plate
was on Hillsdale loam.

Previous to planting time a cover crop of rye, at
the Lake City and College Stations, and an alfalfa sod, at the
King farm, was plowed.under. At the time of planting, repre-
sentative soil samples were taken from each area and tested
by the Spurway Simplex Method for available potash. They
showed comparatively medium potash at the Lake City station

and the King farm, and low potash at the College station.

The size of the plats varied with the location.
At Lake City, they were 40 feet long x 12 feet (4 rows) wide
and at the other two places they were 40 feet long x 9 feet
(3 rows) wide.

All plats were randomized and replicated six times
at Lake City, four times at East Lansing, and three times at
King's. Lack of space prevented a uniform number of six

replications in all trials.
Treatments Used

The treatments and rates of application which made

up the experiment were as follows:

Treatment No. Treatment Rate of Application

1 4 - 16 - O 400 lbs. per acre

2 4 - 16 - 4 fl 0 u n

3 4-16-8 " " u w
4 I'4 - 16 - 8 " " " "

5 *4 - l6 - 8 800 " " "

6 4 - 16 ~16 400 ” " fl

7 4 - 16 -24 fl " " "

8 4 - 16 -32 " " " "

9 Check No treatment

*Commercially mixed fertilizers, all others hand—mixed.

The hand-mixed fertilizers were made up of sulphate

of ammonia, 20% superphosphate, and muriate of potash.

The Russet Rural, which is grown extensively by
Michigan farmers, was used in the experiment. This seed
was certified and was relatively free of virus diseases.
The seed was cut into uniform pieces and spaced approximately
13 inches apart in the rows which were 36 inches apart.

The fertilizer for each plat was applied evenly in
the rows and thoroughly mixed with the soil. The potatoes
were planted at Lake City on May 18, at East Lansing on

June 7, and at King's on June 16.
Stand Observations Made During the Growing Season

Table (1) presents the average per cent of stand
of each treatment for each individual location. It is seen
that treatments 7 and 8 seriously reduced the stand.

Table (1)
location.

The average per cent stand per treatment at each

Treatment No. Treatment Location

Lake City East Lansing King's

l 4 - l6 - 0 100.0 88.2 93.2
2 4 - l6 - 4 100.0 85.8 95.3
3 4 - l6 - 8 lO0.0 78.0 95.4
4 *4v- l6 - 8 100.0 94.3 98.2
5 '"4 - 16 - 8 100.0 100.0 97.5
6 4 - 16 -l6 97.0 77.2 90.8
7 4 — 16 -24 87.6 73.3 84.5
8 4 - 16 -32 89.7 56.2 69.6
9 Check 100.0 100.0 100.0

I"Commercially mixed fertilizer; T5 at 800 lbs. per acre.

Method of Harvesting

The dates of harvest were October 4, at Lake City,
October 8, at King's, and October 10, at East Lansing. A
40-foot row was harvested from the center row of each plat
except at Lake City, where the two center rows were harvested.
All yield data are presented on the basis of a single 40-foot
row. The potatoes from each plat were graded and weighed
separately. Only those potatoes which met the specifications
of a U. S. No. 1 grade were considered in this experiment.
From this grade a cooking sample of 10 to 15 tubers were
taken at random from each plat. After harvest, all samples
from each location were placed in storage at Lansing, where
they remained at a temperature of 40°F. until March 27, 1939,'

When they were taken from the storage room for cooking tests.

Method of Cooking

Four tubers of uniform size were selected from each
sample. The potatoes were washed free of dirt, peeled thinly,
and placed in an aluminum kettle and.boiled with just enough
water to cover the tubers. The kettle was provided with a
galvanized wire basket divided into four compartments, one for
each tuber, and was so built that the bottom of the container
did not reach the bottom of the kettle. The potatoes were
boiled until they could be pierced easily with a fork, then
removed from the water and placed on a table to cool. One-
half of each of the four tubers was riced and used as a
representative sample of the lot to be judged for taste. The

other half was judged for color. Ordinarily, samples were

10
left 10 to 15 minutes to cool before judging. Since color
was the most important factor in this experiment, it was
decided to lengthen the time of cooling to 30 minutes before
judging to determine more definitely the intensity of color

of each cooked sample.

Method of Determining Culinary Quality

The culinary quality Of the potatoes was determined
on the basis of color, texture, cohesion, mealiness and flavor.
The score card submitted by the Bureau of Home Economics,
United States Department of Agriculture was used. A study of
the results showed practically no variations in texture,
cohesion, mealiness and flavor of the potatoes grown under the
various treatments. Considerable variation was found in color
and it is only this Culinary quality factor which is hereafter
discussed in this report. The color score card used is given

in Table 2.

Table 2, Score card used by the Bureau of Home Economics,
United States Department of Agriculture, to designate color
of boiled potatoes.

 

COLOR WHITE \/ CREAM YELLOW GRAY max
INTENSITY 1:2 3:4 5:e\/ 7:8 9:10

 

 

Three members of the Farm Crops Department acted as
judges and indicated their score of color on individual cards

for each sample and for each judge.

11

The sample of boiled potatoes was scored on the
basis of its color and then on the intensity of the color
throughout the sample. The intensity factor indicated the
amount or degree of the color.

Several sample lots of cooked potatoes were scored
by the judges individually. Their scores were then compared
so that the standard of color would remain relatively constant
throughout the entire cooking test.

A White and cream were considered equally desirable
colors of boiled potatoes while yellow and gray were undesir-
able. To facilitate the analysis of the results a continuous
numerical classification was used as is shown in Table 3.
Intermediate intensities on the score card (Table 2) are given

whole numbers in the revised score (Table 3).

Table 3. Revised score card to allow for complete numerical
classification of color of boiled.potatoes.

WHITE AND CREAM

 

INTENSITY IO 9 8 7 6 5 _ 4 3 2 1
SCORE 40 38 36 34 32 30 28 26 24 22

 

YELLOW AND GRAY

 

INTENSITY 10 9 a 7 6 5 ’ 4 3 2 1
SCORE 20 18 16 14 12 10 8 s 4 2

 

The revised color scores as obtained.by Table 3,

were used in all subsequent tables. For example, the color

12

and intensity as checked.by the judge, Table 2, might have
intensity of 6, would give a revised score according to

Table 3 of 32.

Method of statistical Analysis
Since the experiment was completely randomized
in layout and each plat was represented in the cooking
test and in the yield determinations, the data obtained
on color scores and yield were analyzed by the variance
method to determine the significance of differences between
treatments for each location and for the three locations

taken together.
RESULTS AND DISCUSSION

Analytical Comparison of Results Between Treatments and Color
of Boiled Potatoes.

Table 4 gives the judge's score as to color of
boiled potatoes for each plat in the Lake City test and
Table 5 gives the treatment mean scores arranged in order of
score magnitude. From Table 5 it may be seen that the most
desirable color (high score value) was not uniformly due to
high amounts of potash nor were the color scores of the three
higher potash treatments (6, 7 and 8) all higher than, and
significantly different from, the three lower potash treat-
ments (2, 3 and 4). High potash in the fertilizer, seemingly,

was not the determining factor for high color score.

Table 4.

The judge's color scores of boiled potatoes from

13

the nine treatments and six replications grown at Lake City.

Replic.

(DUer-OJNH

03010;)me

Mean

CDUHPOJNH

5
S

25.0 29.3 35.5 34.3 32.8 33.8 35.3 34.5 32.7

17.2 24.5 34.0 33.2 30.3 31.0 34.5 33.7 30.2

10
34
14
12
26
34

21.7 28.0 34.5 32.2 26.5 27.0 34.3 29.5 22.5

36
34
36
35
32
34

Treatment

T4 T5 T6 1'7
Judge A

31 35 37 36
35 37 35 36
34 32 31 36
33 26 35 36
35 34 33 36
38 33 32 32

Judge B
32 35
35 36
32 33
33 10
32 33
35 35

Judge 0
34 34
36 36
34 34
15 6
36 14
38 35

34

8
32
36
32
35

14

Table 5. The treatment mean color scores of potatoes

grown at Lake City.

Treatment No.

7

HNCDU'IOiCDDP-(fl

Treatment

4 ~ 16
4 ~ 16
'4 ~ 16
4 ~ 16
4 ~ 16
*4 ~ 16
Check
4 ~ 16
4 ~ 16

~24
- 8
~ 8
~32
~16
- 8

~ 4
~ 0

Mean Score

34.7
34.7
33.2
32.5
30.6
29.9
28.4
27.3
21.3

s Commercially mixed fertilizer; T5 at 800 lbs. per acre.

The experimental error was 5.79 and all differences between

means greater than 3.8 are significant (5% point) and greater

than 5.9 are highly significant (1% point).

Table 6 gives the judge's score as to color for

each plat in the East Lansing test and Table 7 gives the

treatment mean scores arranged in order of score magnitude.

It is again seen that the most desirable color of boiled

potatoes was not strongly dependent upon the amount of

potash added in the fertilizer.

Table 6. The judge's color scores of boiled potatoes
from the nine treatments and four replications grown at

East Lansing.

Replic. Treatment

T1 T2 T3 T4 T5 T6 T7 T8 T9
Judge A

32 32 34 14 10 34 30 35 35

33 30 36 33 34 34 30 36 7

37 34 36 36 10 34 30 - 34 34
36 33 34 9 34 36 36 33 32

ammH

Mean 34.5 32.2 35.0 23.0 22.0 34.5 31.5 34.5 27.0

Judge B

32 29 32 26 11 15 33 35 32
34 10 33 12 36 14 32 36 6
34 33 33 33 31 34 35
33 23 33 8 34 34 34 36 34

IPOJNH
03
O)
|--'
0)

Mean 33.7 19.5 33.0 19.7 28.5 24.0 32.5 35.2 26.7

Judge C

8 36 32 14 23 34 16 32 34
14 14 35 12 35 36 31 34 5
34 8 36 34 10 34 16 26 28
35 14 34 8 35 34 34 30 34

#0303!“

Mean 22.7 18.0 34.2 19.9 17.0 34.5 24.2 30.5 25.2

16

Table 7. The treatment mean color scores of potatoes grown

at East Lansing.

Treatment No. Treatment Mean Score
3 4 ~ 16 ~ 8 34.1
8 4 ~ 16 ~32 33.4
6 4 ~ 16 ~16 31.0
1 4 ~ 16 ~ 0 30.3
7 4 ~ 16 ~24 29.4
9 Check 26.3
5 ''4 ~ 16 ~ 8 25.4
2 4 ~ 16 ~ 4 23.2
4 *4 ~ 16 ~ 8 19.9

l"Commercially mixed fertilizer;

The experimental error was 5.67

T5 at 800 lbs. per acre.

and all differences

between means greater than 4.6 are significant (5% point),

and greater than 6.2 are highly

significant (1% point).

Table 8 gives the judge's score as to color for

each plat in the King farm test

and Table 9 gives the

treatment mean scores arranged in order of score magnitude.

It may be seen that high color score again was not dependent

upon the varying amounts of potash added in the fertilizer.

17

Table 8. The judge's color scores of boiled potatoes from

nine treatments and three replications grown at the King

farm.
Replic. Treatment
T1 T2 T3 T4 T5 T6 T7 T8 T9
Judge A
l 24 27 28 28 36 35 32 30 32
2 34 35 30 34 36 36 34 34 26
3 35 36 32 34 32 38 34 38 34

Mean 31.0 32.7 30.0 32.0 34.7 36.3 33.3 34.0 30.7

Judge B
12 28 28 13 33 35 38 31 32
32 34 28 32 34 35 37 34 12
35 32 “ 31 34 34 36 34 35 18

Mean 26.3 31.3 29.0 26.3 33.7 35.3 36.3 33.3 20.7

CANE-4

Judge C
1 14 28 28 18 36 34 34 35 36
2 34 36 18 34 32 36 34 16 10
3 36 34 10 36 32 38 34 35 30

Mean 28.0 32.7 18.7 29.3 33.3 36.0 34.0 28.7 25.3

18
Table 9. The treatment mean scores of potatoes grown at

the King farm.

Treatment No. Treatment Mean Score
6 4 ~ 16 ~16 35.9
7 4 ~ 16 ~24 34.5
5 *4 ~ 16 ~ 8 33.9
2 4 ~ 16 ~ 4 32.2
8 4 ~ 16 ~32 32.0
4 *4 ~ 16 ~ 8 29.2
1 4 ~ 16 ~ 0 28.4
3 4 ~ 16 ~ 8 25.9
9 Check 25.6

*Commercially mixed fertilizer; T5 at 800 lbs. per acre.
The experimental error was 4.39 and all differences between
means greater than 4.2 are significant (5% point) and

greater than 5.7 are highly significant (1% point).

The results, then, from each location would lead
to the same conclusion that desirable color of boiled
potatoes (high color score value) was not dependent upon
the amount of potash added in the fertilizer whether it be
on the sandy loam at Lake City or the heavier loams at
East Lansing and the King farm.

Even though each location gave evidence that high
color score was not uniformly due to high potash content of
the fertilizer, it was deemed advisable to average all three
locations and compare the resulting treatment mean color

scores. Table 10 gives these values.

19
Table 10. The treatment mean color scores of potatoes when

all three locations were taken together.

Treatment No. Treatment Mean Score
7 4 ~ 16 ~24 32.9
8 4 ~ 16 ~32 32.6
6 4 ~ 16 ~16 32.5
3 4 ~ 16 ~ 8 31.6
5 *4 ~ 16 ~ 8 29.7
2 4 ~ 16 ~ 4 27.6
4 *4 ~ 16 ~ 8 27.4
9 Check 26.8
1 4 ~ 16 ~ 0 26.7

*Commercially mixed fertilizer; T5 at 800 lbs. per acre.
The experimental error was 3.43 and all differences between
means greater than 3.3 are significant (5% point) and greater

than 4.4 are highly significant (1% point).

It may be seen that when considering the three
locations together, the three treatments containing the higher
amounts of potash (6, 7 and 8) did produce the most desirable
color of boiled potatoes, although not significantly higher
than the lower potash treatment 3.

In studying the location mean color scores it was
found that the King farm had the highest mean score with 30.9,
Lake City followed closely with a mean of 30.3 and that
East Lansing had the significantly lower score of 28.1. (The
5% difference level was 2.1 and 1% difference level was 2.8).

20

That personal bias is a factor which must be
eliminated wherever possible is well brought out by the
judge mean color scores. Judge A gave an average score Of
31.9 which is significantly higher than 29.4 of judge B and
highly significantly different from 27.9 of judge C. (The
different levels of significance being the same as for

locations.)

Analytical Comparison of Results Between Treatments and Yield

per Acre.

Although the study of the relation of fertilizers
with varying amounts of potash to color score was the primary
object of this investigation, yet it was deemed advisable to
study the relation of these varying amounts of potash to
yield of U. S. No. 1 potatoes. As with the color scores the
plat results for each location and for all three locations
are given.

I Table II gives the yield in pounds per plat for
the Lake City test and Table 12 gives the treatment
averages both in pounds per plat and in bushels per acre.
It is seen that the amount of potash was not directly

associated with the yield of U. S. NO. 1 grade potatoes.

Table 11.

21

The pounds per plat of U. S. No. 1 potatoes grown

at Lake City.

Replic.

030135030)!“

Mean

Table 12 .

1'1 T2
31 27
21 35
18 37
30 31
38 31
59 39

Treatments

T5 T6 T7
29 23 9
29 34 20
37 33 22
39 38 39
48 38 42
46 4O 39

32.8 33.3 37.8 31.0 38.0 34.3 28.5 32.8 21.3

The mean yields in pounds per plat and the yields

in bushels per acre of potatoes grown at Lake City.

Treatment No.

\ItRI-‘(DNCDOICH

9

Treatment
*4 ~ 16 ~ 8
4 ~ 16 ~ 8
4 ~ 16 ~16
4 ~ 16 ~ 4
4 ~ 16 ~32
4 ~ 16 ~ 0
*4 ~ 16 ~ 8
4 - 16 ~24
Check

38.0
37.8
34.3
33.3
32.8
32.8
31.0
28.5
21.3

Mean yield in
pounds per plat

Bushels
per acre

233
230
209
204
200
200
190
174
131

*Commercially mixed fertilizer; T5 at 800 lbs. per acre.

The experimental error was 8.39 lbs. and all differences

between means greater than 9.8 lbs. per plat are significant

(5% point) and greater than 13.1 lbs. per plat are highly

significant (1% point).

22

The yields in pounds per plat for the East Lansing
test are given in Table 13 and the treatment averages both
in pounds per plat and in bushels per acre are given in Table
14. In this test the treatments containing 16 per cent or
less of potash had a tendency to produce larger yields of
U. S. No. 1 grade potatoes than did the treatments containing
over 16 per cent potash.
Table 13. The pounds per plat of U. S. No. 1 potatoes grown
at East Lansing.

Replic. Treatments
T1 T3 T3 T4 T5 T6 T7 T8 T9

14 29 12 43 40 41 23 8 24
49 40 60 49 54 43 18 21 32
39 51 54 59 34 31 15 2 42

7 34 21 21 59 51 35 16 32

UPGNH

Mean 27.2 38.5 36.7 43.0 46.7 41.5 22.7 11.7 32.5
Table 14. The mean yields in pounds per plat and the

yields in bushels per acre of potatoes grown at East Lansing.

Treatment No. Treatment Mean Yield in Bushels

Pounds Per Plat Per Acre
5 *4 - 16 ~ 8 46.7 283
4 *4 ~ 16 ~ 8 43.0 260
6 4 ~ 16 ~16 41.5 251
2 4 ~ 16 ~ 4 38.5 233
3 4 ~ 16 ~ 8 36.7 222
9 Check 32.5 197
l 4 ~ 16 ~ 0 27.2 165
7 4 ~ 16 ~24 22.7 138
8 4 ~ 16 ~32 11.7 71

*Commercially mixed fertilizer; T5 at 800 lbs. per acre.

The experimental error was 13.00 lbs. and all differences

between means greater than 13.4 lbs. per plat are significant

23
(5% point) and greater than 18.2 lbs. per plat are highly
significant (1% point).

The yields in pounds per plat for the King farm
are given in Table 15 and the treatment averages both in
pounds per plat and in bushels per acre are given in Table
16 as at East Lansing, the treatments containing 16 per
cent or less of potash had a tendency to produce larger
yields of U. S. No. 1 potatoes than did the treatments

containing over 16 per cent potash.

Table 15. The pounds per plat of U. S. 10. 1 potatoes

grown at the King farm.

Replic. Treatments
T1 T2 T3 T4 T5 T6 T7 T8 T9
1 18 27 33 23 29 22 16 14 27
2 25 33 26 24 30 27 23 l3 l7
3 18 27 31 28 30 32 14 9 12

Mean 20.3 29.0 30.0 25.0 29.7 27.0 17.7 12.0 18.7

Table 16. The mean yields in pounds per plat and the

yields in bushels per acre of potatoes grown at the

King farm.

Treatment No. Treatment

3 4 ~ 16
5 *4 ~ 16
2 4 ~ 16
6 4 ~ 16
4 *4 ~ 16
1 4 ~ 16
9 Check

7 4 ~ 16
8 4 ~ 16

*Commercially mixed fertilizer; T5 at 800 lbs. per acre.

The experimental error was 4.36 lbs. and all differences

~ 8
~ 8
~ 4
~16
~ 8
~ 0

~24

Mean Yields in
Pounds Per Plat

30.0
29.7
29.0
27.0
25.0
20.3
18.7
17.7
12.0

Bushels
Per Acre

181
179
175
163
151
123
113
107

73

24

between means greater than 7.5 lbs. per plat are significant

(5% point) and greater than 10.4 lbs. per plat are highly

significant (1% point).

25
Table 17. The mean yields in pounds per plat of potatoes

grown at all three locations.

Treatment No. Treatment Mean Yields in Bushels

Pounds Per Plat Per Acre
5 I"4 ~ 16 ~ 8 38.1 230
3 4 ~ 16 ~ 8 34.8 210
6 4 ~ 16 ~16 34.3 207
2 4 ~ 16 ~ 4 33.6 203
4 *4 ~ 16 ~ 8 33.0 200
1 4 ~ 16 ~ 0 26.8 162
9 Check 24.2 146
7 4 ~ 16 ~24 23.0 139
8 4 ~ 16 ~32 18.8 114

*Commercially mixed fertilizer; T5 at 800 lbs. per acre.
The experimental error was 5.48 and all differences greater
than 9.5 pounds per plat are significant (5% point) and
greater than 13.0 pounds per plat are highly significant
(1%Ipoint).

Table 17 shows the treatment mean yields in pounds
per plat and in bushels per acre when the three locations
are combined. It is seen in this table that treatments
containing over 16 per cent of potash produced significantly
less U. S. No. 1 potatoes than treatments containing 16 per
cent or less potash. The yield results from the Lake City
(Tables 11 and 12) were inconsistent when compared with those
from East Lansing (Table 13 and 14) and the King farm
(Table 15 and 16). It has been previously shown in Table 1

26
that treatments containing over 16 per cent potash had a
tendency to reduce the stand. The soil at Lake City was
a sandy 8011 compared to the heavy loam soil at East Lansing
and the King farm. It is possible that the mixture of soil
and fertilizer around the seed piece was more thorough in the
sandy soil than in the loam soil. The thoroughness of mixing
may be a possible explanation for the inconsistent results
between locations when yield of U. S. No. 1 potatoes is

considered.

SUMMARY

The foregoing experiment would indicate that of
the characters used in judging culinary quality of boiled
potatoes, namely color, texture, cohesion and flavor, color
was the only one affected sufficiently by different treat-
ments and location to warrant statistical analysis.

White or cream color of boiled potatoes (high color
score) was considered to be more desirable and indicate better
quality than yellow or gray color (low color score). From
the study of each individual location it may be concluded,
in most cases, that varying amounts of potash applied did not
give consistent results when the color of boiled potatoes
was considered. However, when the results of all three
locations were considered together, the treatments containing

16 per cent or more potash produced the best color of boiled

potatoes.

27

When considering the yield of U. S. No. 1
potatoes, treatments containing 16 per cent or less potash
produced the higher yields per acre. The treatments con.-
taining over 16 per cent potash seriously reduced the stand
of plants.

From the results obtained this one year (1938), no
definite recommendations can be made as to the particular
fertilizer analysis to use to promote white or cream color
in boiled potatoes. The results tend to show, however, that
high analysis fertilizers when used on heavy loam soils may
so reduce stands that yields of U. S. No. 1 grade potatoes

are appreciably reduced.

 

lo.

28
LITERATURE CITED

Ashby, S. F. A Contribution to the Study of Factors
Affecting the Quality and Composition of Potatoes.

Jour. Ag. Sci. (England) 1: 347 ~ 357, 1906.

Bewell, E. R. The Determination of the Cooking Quality
of Potatoes. Amer. Pot. Jour. 14: 235 ~ 242, 1937.
Butler, 0., Morrison, F. B., and Boll, F. E. Studies

of the Factors Affecting the Culinary Quality of Potatoes.
Jour. Amer. Soc. of Agron. 5: 1 ~ 33, 1913.

Carobus, R. L. Chemical Estimations of the Weekly
Nutrient Level of a Potato Crop. Amer. Pot. Jour. 14:
141 ~ 153, 1937.

Cobb, J. S. A Study of Culinary Quality in White Potatoes.
Amer. Pot. Jour. 12: 335 ~ 344, 1935.

Dietz, F. C. Fertilizer Experiment with Potatoes.

Amer. Pot. Jour. 5: 15 ~ 18, 1928.

Findlay, N. M. Quality in Potatoes. Scot. Jour. of Agr.
11: 339 ~ 344, 1928.

Hantke, A. W. Cooked Potatoes Blacken Because. ..........
Better Crops with Plant Food 22: 71, 1938.

Hardenburg, E. V. Improving Market Quality in Potatoes.
Amer. Pot. Jour. 7: 348 ~ 351, 1930.

Neil, Bernice and Whittemore, Margaret. Relation Between
Mealiness in Potatoes and the Amount of Potash in the

Fertilizer. Amer. Pot. Jour. 7: 275 ~ 283, 1930.

11.

12.

13.

14.

15.

29
Odland, T. E. The Relative Response of Potatoes to
Different Fertilizer Elements. Amer. Pot. Jour. 10:
27 ~ 31. 1933.
Smith, Ora. Some Factors Affecting Culinary Quality
of Potatoes. Amer. Pot. Jour. 14: 222, 1937.
Stevenson, F. J., and Whitman, E. F. Cooking Quality
of Certain Potato Varieties as Influenced by
Environment. Amer. Pot. Jour. 12: 41 ~ 47, 1935.
Sweetman, M. D. Factors Affecting the Cooking Qualities
of Potatoes. Maine Agr. Exp. Sta. Bul. 383, 1936.
Tottingham, W. E., Nagy, Rudolph, and Ross, Frank A.
The Problem of Blackening in Cooked Potatoes.
Amer. Pot. Jour. 13: 297 ~ 309, 1936.

 

 

 

   

 

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