70
Effects of Planting Density and Nitrogen Rate
on the Performance of New Potato Varieties and Advanced Selections
K.A. Rykbost and J. Maxwell'
INTRODUCTION
Seed certification listings for western states with significant
potato seed acreages included 52 named varieties and nearly half that
number of advanced numbered selections in 1989. While Russet Burbank
accounts for over 75 percent of the northwest potato acreage, growers
are increasingly looking to new varieties for various marketing opportunities. Most of the varieties and selections will not achieve their
optimum performance at management practices designed for Russet Burbank.
The development of variety-specific cultural management practices prior
to large scale commercial production will reduce the risks of poor performance and enhance the opportunity for successful commercialization of
new cultivars.
A program was initiated at KES in 1987 to evaluate the response of
new varieties or advanced selections to plant population densities and
nitrogen rates. These are two of the most important aspects of cultural
management practices that affect yields, tuber size distribution and
physiological disorders. In 1989 eight named varieties and two advanced
selections were included in these studies.
NEW VARIETIES OF INTEREST IN THE REGION
HiLite Russet
This variety is a patented variety marketed by Northwest Potato
Sales, Inc. It is a mid-season, blocky, medium-russet with good fresh
market quality and some potential for frozen fry processing. HiLite has
produced relatively high yields in commercial fields in several areas,
including the Klamath Basin. It produces a much higher percentage of
No. l's than Russet Burbank. HiLite is very susceptible to early blight
and white mold. Skinning and bruising problems have been encountered
under high nitrogen fertilization rates.
1/ Superintendent/Associate Professor, Biological Sciences Research
Technician, respectively, Klamath Experiment Station.
Acknowledgment:
Partial funding by the Oregon Potato Commission and the Cooperative
State Research Service is gratefully acknowledged.
71
Russet Norkotah
This early-maturing, long russet has largely replaced Norgold
Russet as the early fresh market russet in the northwest. It has
exceptionally attractive appearance and produces a high percentage of
No. l's. Norkotah is very susceptible to early blight, verticillium
wilt, white mold and black dot. The performance of Norkotah has been
very erratic. In the absence of disease problems, yields and pack-out
are high. Very poor yields have occurred under heavy disease pressure.
Buyers in the fresh market chain have a strong preference for Norkotah
due to its appearance. It will not process satisfactorily.
Krantz
This oblong, russetted variety is slightly later in maturity than
Norgold Russet. It produces a small but erect plant type, which probably accounts for much better resistance to foliar fungal diseases than
Russet Norkotah. In local production Krantz has been much more consistent in yielding ability than Norkotah. Tuber appearance is not outstanding. Growth cracks are common in large tubers and in heavy soil
types. Krantz has not been widely accepted but several growers in the
Klamath Basin remain interested in this variety.
Sierra
This long, heavily-russetted variety is rapidly gaining interest in
the Klamath Basin and Kern County, California. Its maturity is slightly
earlier than Russet Burbank Tuber set occurs late but bulking progresses rapidly. Sierra has a short dormancy and should be marketed by
early winter. Yields have been similar to Russet Burbank yields, but
with a higher percentage of No. l's. Sierra is much less prone to
physiological disorders than Russet Burbank. Low dry matter content
precludes the use of Sierra for processing. Supplies of high quality
seed are very limited.
Shepody
Shepody has become the variety of choice for early processing in the
Columbia Basin and the Treasure Valley area of Oregon and Western Idaho.
This long, white variety has medium maturity and excellent processing
quality. With superior culinary quality Shepody is gaining usage in the
restaurant trade in the east. It is not attractive when washed. Shepody
is very susceptible to common and powdery scab and moderately susceptible to pink rot. This is the first variety to impact the traditional
place of Russet Burbank in the french fry industry. It accounts for
nearly 50 percent of french fry production in Maine and Eastern Canada
Atlantic
Atlantic has round, buff colored, slightly-netted tubers and produces high yields with high dry matter and low sugar content. It is the
second leading chipping variety in North America and its utilization is
increasing in the northwest. Internal tuber necrosis restricts its
adaptability in sandy soils in the Atlantic coastal region. The problem
has not been noted in the Klamath Basin.
72
A74212 1 (Century Russet)
This seedling will probably be released in 1990. The name Century
Russet has been proposed. A74212-1 is a blocky to long, light russet
with very high yield potential and late maturity. Its yields have been
outstanding in trials over many locations and in commercial plantings in
Oregon, Wisconsin, Colorado and Texas. A light net may be inadequate in
organic soils. Tuber damage susceptibility in harvest and handling has
led to some storage rot and seed decay problems. A74212-1 is not suitable for processing.
-
Frontier Russet
This new release has been evaluated under the seedling number
A74114-4. It is an early-to medium-maturity, long russet with good
quality for fresh market and processing use. It is one of few new
russets with a long dormancy, and is reportedly equivalent to Russet
Burbank in storability. It produces a high percentage of US no. l's and
is much less susceptible to physiological disorders than Russet Burbank.
A7411 2
This long, russetted selection has excellent processing quality and
moderate resistance to dark ends when grown under stress. On mineral
soils in the Klamath Basin it may be too long and thin for fresh market
acceptance. Tuber type has been good on organic soils. Total yields
are high with fewer off-types than Russet Burbank. The decision to name
and release or discard will probably be made in 1990 based on processing
evaluations.
-
Gemchip
Gemchip was tested under the selection number BR7093-24 and released
in 1989. It is a round, white chipping variety, with very high yields
and low sugar content. Gemchip's dry matter content is lower than
Atlantic's but higher than Norchip's. It offers local growers another
opportunity as a chipping variety for contracts out of the field.
PROCEDURES
Plant population and nitrogen fertilizer responses of 10 varieties
or advanced selections were evaluated in two separate experiments.
Split-plot designs with four replications were employed. Standard
management practices were followed for weed control, disease and pest
management and irrigation.
The variety by seed spacing experiment was planted on May 26. Mainplot treatments were seed spacings of 6.8, 8.7 and 12.0 inches in 32inch rows. Individual plots were two rows, 30 feet long. Fertilization
included 600 lbs/A of 16-16-16 banded at planting and 50 lbs N/A sprayed
on and incorporated with a rolling cultivator on June 5. Vines were
desiccated with 1.5 pints/A of diquat on September 12 and potatoes were
harvested on October 5. Field weights were determined on all tubers
from both rows. Approximately 120 lbs/plot were stored and graded in
early November.
73
The variety by nitrogen rate experiment was planted on May 26. Mainplot treatments were N rates of 130, 160 or 190 lbs N/A, achieved by
supplementing 800 lbs/A of 16-16-16 at planting with 0, 30 or 60 lbs N/A
applied on June 6. Plots were four rows, 30 feet long with Russet
Burbank spaced at 12 inches in the two outside rows and test varieties
uniformly spaced at 8.7 inches in the center rows. Plant emergence data
was obtained in both experiments on June 21 and June 28. Vines were
desiccated as above and tubers were harvested on October 4. Total plot
weight from the center two rows was determined in the field. Approximately 120 lbs/plot were stored and graded in early November.
RESULTS AND DISCUSSION
Variety Response to Seed Spacing:
In general, plant emergence was quite uniform and final stands were
in excess of 90 percent (Table 1). Crop vigor was excellent and foliar
fungal diseases were notably absent in all selections. Metribuzin
injury was observed in Shepody. Yields were relatively high for most
varieties. The effects of seed spacing were more pronounced in tuber
size distribution than in total yield or total yield of US No. l's.
HiLite Russet was included in trial for the first time in 1989. It
was slower to emerge than most entries but achieved high plant stands.
Plants were quite small and compact compared with other varieties. In
total yield of US No. l's, HiLite was lower than all entries except
Shepody (Table 1). Seed spacing had little effect on yield levels but
tuber size increased with lower plant density. HiLite produced a very
smooth crop with no hollow heart, very few off-types and intermediate
specific gravity. Considering yield and size distribution, the 8.7-inch
spacing was optimum for this variety.
Russet Norkotah exhibited early emergence and good vigor throughout
the season. Yields were high with a high percentage of US No. l's.
Seed spacing had no effect on total yield of US No. l's; however, at
the 12-inch seed spacing tuber size was excessive on a significant percentage of tubers. Averaged over three years, a spacing of 8.7 inches
has been optimum for Russet Norkotah. A significant amount of hollow
heart was detected in large tubers. Specific gravity is consistently
low in this variety.
Although emergence was slow, Krantz achieved better stands than in
previous trials. Plant vigor was also better than in other years.
Yields exceeded those of Russet Norkotah in 1989 for the first time at
KES. Seed spacing response was much less pronounced than in 1987
trials. Excessive tuber size was observed at the 12-inch spacing. In
three years of evaluation a spacing of 6.8 inches has been optimum for
this variety. Krantz exhibits very little hollow heart but growth
cracks are common in very large tubers. Specific gravity was intermediate for Krantz.
74
Sierra was included in this experiment for the second time. It
produced optimum yield and tuber size distribution at 8.7-inch seed
spacing in both 1988 and 1989. In both years yields dropped substantially as spacing increased from 8.7 to 12 inches. Hollow heart is
seldom observed in Sierra. Specific gravity is consistently very low.
Shepody yields were reduced by metribuzin injury. This variety
achieves a low tuber set and is prone to excessive tuber size. In three
years of evaluation, the intermediate planting density has been optimum
for fresh market or processing crops. Large tubers are undesirable for
seed crops due to poor eye distribution. For seed production, early
vine killing would be required to achieve satisfactory tuber size, even
at the highest planting density evaluated. Shepody achieves intermediate specific gravity and has had little hollow heart, even in very
large tubers.
In both 1988 and 1989 Atlantic achieved optimum yields at a seed
spacing of 8.7 inches. At lower planting density tuber size is excessive for chip production. In this experiment hollow heart incidence was
high in large tubers. Atlantic exhibited high specific gravity in both
years.
Poor stands have been observed in A74212-1 in most trials with this
selection. In 1989 stands were quite good and the optimum seed spacing
was 8.7 inches; however, in view of a high susceptibility to tuber
damage at harvest, particularly in large tubers, and a history of poor
stands in research plots and commercial fields, a high planting density
is appropriate for A74212-1.
Frontier Russet was included in this trial for the first time in
1989. It demonstrated high percentage of US No. l's, an intermediate
specific gravity and a low incidence of hollow heart. Tuber size was
excessive at the lower planting densities. For fresh market and processing usage the 8.7-inch spacing was optimum. For seed production the
combination of poor eye distribution and a tendency for large tubers
would favor the high population density.
A7411-2 was included in this experiment in both 1988 and 1989. It
achieved a high total yield in both years but had a relatively high
yield of US No. 2's and culls. Long, thin tubers are less desirable for
fresh market usage than other russet types in this trial. For processing use the 12-inch spacing was optimum in 1988 while 8.7-inch spacing
was optimum in 1989. A7411-2 had almost no hollow heart in either year.
Specific gravity was acceptable for processing.
Gemchip was included in this trial for the first time in 1989. It
achieved a significantly higher yield than all other entries with a high
percentage of US No. l's. Specific gravity was intermediate, significantly lower than Atlantic. Hollow heart incidence was less than for
Atlantic, but higher than that observed in other selections. Gemchip
produced the highest yield of US No. l's at the 6.8-inch seed spacing.
75
Variety Response to Nitrogen:
The same seed sources and similar cultural practices and timing of
planting and harvesting were followed in both experiments. However, a
portion of this experiment was influenced by adverse soil conditions.
Plant vigor and yields were poor in the fourth replication and in a few
plots in the third replication. Statistical analyses were performed
using data from either three or four replications. On the basis of this
comparison, data only includes three replications. Yields of US No. l's
were approximately 40 cwt/A lower for most entries in this experiment
and variability was greater than in the seed spacing study (Table 2).
The relative performance of varieties was similar in both trials.
N rates had less effect on tuber size distribution than seed spacing (Table 2). Effects on yields varied considerably among varieties
but the interaction of varieties and N rates was not statistically significant. N rates did not influence the incidence of hollow heart,
except in Russet Norkotah where more hollow heart occurred at the lower
N rates. As in the seed spacing study Atlantic, Gemchip and Norkotah
exhibited the most hollow heart.
Specific gravity was consistent with results obtained in the seed
spacing experiment. Increasing N rate resulted in a slight reduction in
specific gravity in Shepody and Frontier Russet but not in other varieties. Sierra and Norkotah were lowest and Atlantic highest in specific
gravity in both trials.
HiLite Russet achieved the highest yield at the 130 lbs N/A rate.
Norkotah and A74212-1 also produced the highest yields at low N rates.
This contrasts with 1988 results when both varieties achieved their
best yields at the 190 lbs N/A. In 1988 Norkotah was influenced by
early dying which was controlled to some extent by higher nitrogen
levels. In 1989 early dying was not a problem in this experiment. It
appears that nitrogen management for Norkotah will be complicated by the
extent of disease pressure.
The use of low N rates on A74212-1 should help to overcome difficulty in achieving vine and tuber maturity and reduce the risk of tuber
damage at harvest. This variety has demonstrated high yields of marketable tubers at all N rates evaluated. A small sacrifice in yield in
some years at low N rates would probably be more than offset by reduced
handling damage and subsequent storage loss.
In 1988 Krantz produced approximately 300 cwt/A of US No l's at all
three N rates. In this trial Krantz had better stands and much higher
yields. Tuber size was excessive at the highest N rate. Optimum yield
and size was observed at the 160 lbs N/A rate.
Sierra achieved maximum yield of US NO l's at 130 lbs N/A in 1988.
In this trial N rate did not affect yield or size distribution. Therefore, the low rate appears to be optimum for Sierra.
76
Shepody has consistently shown optimum performance at an intermediate N rate. This is similar to results of extensive evaluations in
Eastern Canada. As in 1988, Atlantic also achieved maximum yield at 160
lbs N/A.
Frontier Russet and Gemchip produced the highest yield of US No.
l's at 190 lbs N/A. However, tuber size was excessive at this rate in
Gemchip. Both varieties will be evaluated again in 1990. Preliminary
research in Idaho suggests that both varieties require less nitrogen
than Russet Burbank.
The A7411-2 selection achieved maximum yield at 130 lbs N/A in 1988
and 160 lbs N/A in 1989. Total yields were similar for this selection
in both years; however, type was much better in 1989 and US No. 1
yields were about 30 percent higher than in 1988.
SUMMARY AND CONCLUSIONS
Response to seed spacing and N fertilization rates varied between
entries, and in some cases between years for a given entry. Most of
these varieties set fewer tubers per stem than Russet Burbank and
develop excessive size when planted at a density appropriate for Russet
Burbank. Most of them are also earlier maturing and require less
nitrogen, even though yields may exceed Russet Burbank yields. In the
report which follows Russet Burbank experienced increasing yield at N
rates up to 240 lbs N/A under 1989 growing conditions. Only Krantz,
Frontier and Gemchip had maximum yields of US No. l's at the 190 lbs N/A
rate, and tuber size was excessive for Krantz and Gemchip at this rate.
Three years of observations on Shepody have confirmed results from
the east. Shepody requires an intermediate planting density and N rate
for fresh market or processing crops. For seed production a high planting density is required to achieve acceptable tuber size.
Russet Norkotah requires an intermediate plant density. Nitrogen
requirement appears to be highly influenced by disease pressure. Under
low disease pressure low N rates are appropriate. In the presence of
fungal diseases elevated nitrogen rates may delay disease onset and
increase yields significantly.
A74212-1 has a potential for very large tubers which are easily
damaged in harvest. It has experienced stand problems in most commer-
cial fields and research plots. A high planting density is required to
overcome these limitations. With high resistance to early dying A742121 is difficult to kill. Low N rates will enhance plant and skin maturity, help to avoid excessive tuber size, and still support high yields
in this selection.
These experiments will be continued in 1990. Shepody, A74212-1 and
Russet Norkotah will be replaced by Cal-Ore, the early clone of A74212-1
and C008014-2, a selection with promise for the Columbia Basin.
77
Table 1. Effect of seed spacing on performance of ten potato varieties, Klamath
Experiment Station, 1989.
Variety
Seed
spacing
inches
4-6
QZ
Yield No. l'$
6-10 in )10'oz Total
cwt/A
Ws
Yield
No 2's
Total
Stand
Specific
Gravity
HiLite
6.8
8.7
12.0
186
151
118
173
172
158
68
93
117
427
416
393
93
79
50
8
20
28
531
528
481
91
95
98
1.074
1.074
1.074
R.Norkotah
6.8
8.7
12.0
140
137
113
181
174
168
143
155
184
464
466
465
60
51
38
27
22
14
581
564
546
93
98
95
1.070
1.070
1.069
Krantz
6.8
8.7
12.0
174
118
116
222
187
178
109
164
222
505
469
516
61
48
33
15
18
20
602
554
590
85
87
88
1.078
1.076
1.078
Sierra
6.8
8.7
12.0
190
182
149
136
189
135
95
83
102
421
454
386
95
75
68
43
26
45
586
596
542
87
86
85
1.069
1.069
1.066
Shepody
6.8
8.7
12.0
90
95
65
140
117
95
171
191
148
401
403
308
33
33
20
65
37
47
534
526
434
88
92
93
1.080
1.075
1.078
Atlantic
6.8
8.7
12.0
151
138
111
164
177
148
131
126
164
446
441
423
53
46
38
39
33
52
565
561
549
88
90
87
1.092
1.088
1.089
A74212-1
6.8
8.7
12.0
174
166
163
189
187
169
100
120
189
463
473
521
103
97
53
31
15
17
618
605
610
87
86
92
1.078
1.075
1.077
Frontier R.
6.8
8.7
12.0
155
151
104
190
166
156
84
157
178
429
474
438
64
60
37
8
10
8
518
560
494
94
96
97
1.078
1.079
1.079
A7411-2
6.8
8.7
12.0
156
154
110
190
170
140
104
136
158
450
460
408
68
62
51
50
51
52
591
595
564
92
98
95
1.081
1.081
1.081
Gemchip
6.8
8.7
12.0
192
201
142
238
210
178
146
122
181
576
533
501
71
79
39
16
21
29
687
668
624
88
91
91
1.081
1.081
1.080
95
95
87
86
91
88
88
96
95
90
1.074
1.070
1.077
1.068
1.078
1.090
1.077
1.079
1.081
1.081
Variety Main Effect: (Average of three spacings)
HiLite
R.Norkotah
Krantz
Sierra
Shepody
Atlantic
A74212-1
Frontier R.
A7411-2
Gemchip
CV(%)
LSD(.05)
152
130
136
174
83
133
168
137
140
178
168
174
196
153
117
163
182
171
167
209
93
161
165
93
170
140
136
140
133
150
412
465
497
420
371
437
486
447
439
537
74
50
47
79
29
46
84
54
60
63
19
21
18
38
50
41
21
9
51
22
513
564
582
575
498
558
611
524
583
660
16
19
16
23
25
28
10
37
24
12
48
11
9
41
0.400
0.002
Seed Spacing Main Effect: (average of ten varieties)
6.8"
8.7"
12.0"
CV(%)
LSD(.05)
161
149
119
182
175
153
115
135
164
458
459
436
70
63
43
30
25
31
581
576
543
19
15
15
14
21
16
7
18
38
13
27
4
7
22
89
92
92
1.078
1.077
1.077
0.240
NS
78
Table 2. Effect of nitrogen rate on performance of ten potato varieties, Klamath
Experiment Station, 1989.
Yield No. l's
6-10 oz >10 oz
N-Rate
lbs/A
4-6 oz
130
160
190
155
126
111
151
170
125
79
386
68
364
88
87
76
313
R.Norkotah
130
160
190
135
95
85
169
141
140
164
142
143
Krantz
130
160
190
103
103
119
160
197
168
Sierra
130
160
190
108
140
129
Shepody
130
160
190
Atlantic
Variety
Total
cwt/A
B's
No 2's
Yield
Total
Stand
Specific
Gravity
74
16
6
10
502
473
409
95
93
95
1.074
1.072
1.074
468
378
369
44
32
52
23
16
18
560
443
465
93
94
94
1.070
1.069
1.069
126
169
204
389
470
490
48
47
36
31
22
32
493
557
571
82
83
83
1.077
1.077
1.076
159
159
132
90
69
87
356
368
348
67
93
71
45
35
36
499
530
499
86
85
83
1.067
1.068
1.067
56
52
67
100
98
115
139
185
165
295
335
348
33
25
30
58
74
63
446
513
500
88
91
89
1.080
1.076
1.076
130
160
190
93
80
82
133
163
143
135
166
138
361
410
363
48
51
514
88
49
50
34
46
540
489
90
89
1.089
1.088
1.090
130
160
190
139
161
141
200
170
150
175
154
195
514
484
486
59
72
72
10
11
19
607
596
612
87
88
82
1.076
1.071
1.074
Frontier R. 130
160
190
91
99
142
150
165
147
133
140
142
374
404
431
49
57
56
30
9
10
479
480
514
93
94
97
1.082
1.077
1.078
A7411-2
130
160
190
97
121
115
177
179
173
153
165
152
427
464
440
45
55
52
54
49
41
566
600
576
95
93
95
1.083
1.081
1.081
Gemchip
130
160
190
155
130
162
185
205
209
148
130
162
489
465
533
67
72
53
37
41
45
642
632
672
89
92
90
1.079
1.080
1.081
83
43
11
19
461
489
94
94
1.073
1.069
1.077
1.067
1.077
1.089
1.074
1.079
1.082
1.080
HiLite
A74212-1
Variety Main Effect: (average of three N-Rates)
131
105
108
126
58
85
147
111
111
149
149
150
175
150
104
146
173
154
176
200
74
150
166
82
163
146
175
138
157
147
354
405
450
357
326
378
495
403
444
496
44
28
540
83
77
29
49
68
54
51
64
39
65
44
13
16
48
41
509
486
514
605
491
581
649
85
89
89
86
95
94
90
CV(l)
LSD (.05)
26
27
21
31
24
32
14
53
32
17
51
16
13
64
N-Rate Main Effect :
(average of 10 varieties)
36
30
32
531
536
531
HiLite
R.Norkotah
Krantz
Sierra
Shepody
Atlantic
A74212-1
Frontier R.
A7411-2
Gemchip
130 lbs/A
160 lbs/A
190 lbs/A
CV(%)
LSD(.05)
0.200
0.003
113
111
115
158
165
150
134
139
146
406
414
412
55
59
55
13
NS
30
NS
32
NS
19
NS
18
60
18
0.500
NS
NS
NS
NS
90
90
90
1.076
1.077
1.077