Potato Cultivar Response to Plant Population
K.A. Rykbost and J. Maxwell'
Introduction
Russet Burbank has declined to less
than one-third of total potato production
acreage in the Klamath Basin. Russet Norkotah
currently is the variety of choice for fresh
market and seed crops. High susceptibility to
potato virus Y infection and annual occurrences
of early senescence of some Russet Norkotah
fields result in low yields, and keeps interest in
alternative varieties at a high level. A number
of potential new fresh market varieties are
progressing through the regional variety
development program. Since 1988, a
systematic effort has been pursued at the KES
to evaluate the response of potential new
cultivars to a range of plant populations. Seed
spacing is a very important factor determining
tuber size distribution. Cultivars have a
relatively wide range in stem and tuber
numbers per plant. Cultivars that produce high
tuber numbers, such as Russet Burbank, require
low populations to produce adequate tuber size.
Others such as Century Russet and Shepody
produce few tubers and tend to achieve
excessive size unless populations are much
higher than the ideal population for Russet
Burbank. In 1996, response to plant
populations was evaluated for Russet Burbank
and Russet Norkotah standards, and three
advanced russet selections. A085165-1, an
Oregon fresh market selection, was included for
the third year. Dual purpose Idaho selections
A84118-3 and A8495-1 were included for the
first and second year, respectively. Both of
these selections have produced very attractive
tubers in previous KES trials.
Procedures
Seed of all selections was hand cut to
1.5 to 2 ounces/seedpiece, treated with Tops 5.0
fungicide, and suberized for two weeks prior to
planting. The experiment was conducted as a
split-plot with seed spacings of 6.8, 8.7, or 12.0
inches in 32-inch rows as main plots, the five
selections as split-plots, with four replications.
Individual plots were two rows, 30 feet long.
Potatoes were planted with a two-row, assistedfeed planter on May 24. Cultural practices
were the same as described for variety trials on
page 41. Vines were desiccated with 1
pint/acre Diquat applied on September 12.
Potatoes were harvested with a one-row,
digger-bagger on October 1. Field weights
were determined for all tubers from both rows.
Approximately 100-pound samples from each
plot were stored and graded to USDA standards
in late October. Specific gravity was
determined by the weight-in-air, weight-inwater method on a 10-pound sample of 6- to
10-ounce No.1 tubers. Ten large tubers from
each plot were cut longitudinally and inspected
for internal defects.
Superintendent/Professor and Biological Sciences Research Technician III, respectively,
Klamath Experiment Station, Klamath Falls, OR.
Acknowledgments: Partial funding from the Oregon Potato Commission and CREES is gratefully
recognized.
Klamath Experiment Station
61
Results and Discussion
Emergence data were recorded on June
24, 31 days after planting. All selections had
achieved at least 90 percent emergence. Final
stands exceeded 95 percent in all treatments.
Crop development was affected by heat stress
in July and August. A high incidence of hollow
heart was observed in A085165-1 (43 percent)
and Russet Norkotah (20 percent). However,
most of the tubers inspected for internal defects
were over one pound in weight.
Yield, grade, and tuber size distribution
data are presented in Table 1. Russet Norkotah
produced significantly higher No.1 yield than
Russet Burbank, A8495-1, and A84118-3.
A085165-1 has consistently produced
significantly higher yields than both Russet
Burbank and Russet Norkotah in variety trials.
Over 11 KES trial years, total No.1 yield
averaged 50 percent more for A085165-1 than
for both standard varieties. The similar yields
for A085165-1 and Russet Norkotah in this
trial are, therefore, surprising. Lower yields for
A8495-1 and A84118-3 are consistent with
previous experience with these selections.
A significant interaction was observed
between selection and seed spacing for total
No.1 and total yield. Russet Burbank, Russet
Norkotah, and A8495-1 produced their highest
yields at the lowest plant population. In each
case, the increased yield was attributable to
larger tuber size with more No.ls over 10
ounces, and fewer Bs. Yields declined for
A085165-1 and A84118-3 when seed spacing
increased from 8.7 to 12 inches. Neither
selection produced higher yields of large tubers
or lower yields of Bs at the lowest population.
The response to seed spacing over three years
for A085165-1, Russet Burbank, and Russet
Norkotah is shown in Table 2. Effects of seed
spacing on Russet Burbank and Russet
62
Norkotah were the same, when averaged over
three years, as results observed in 1996. Both
varieties produce higher yields and larger tuber
size at 12-inch seed spacing. However, Russet
Norkotah produces excessive tuber size and a
relatively high incidence of hollow heart in
large tubers at 12-inch spacing. The
intermediate population has been adopted as
standard management for Russet Norkotah in
commercial crops. A085165-1 typically
produces larger tuber size than Russet Norkotah
and usually has a higher incidence of hollow
heart in very large tubers. Results from three
years of evaluation indicate a seed spacing of 7
to 8 inches will be required to avoid excessive
tuber size in this selection.
In 1995, A8495-1 produced 365, 382,
and 377 cwt/acre of No.ls at 6.8, 8.7, and 12
inches, respectively. Averaged over two years,
there is little difference in yield between the
seed spacings. This selection has not produced
excessively large tubers at the low plant
population and is not as susceptible to hollow
heart as Russet Norkotah. This selection is
being considered for release by Idaho. It is
probably the most attractive russet in the
regional variety development program. In spite
of somewhat lower yields, it appears to be a
good candidate for fresh market use in the
Klamath Basin. It will be evaluated for one
more year in this trial.
A84118-3 is also a very attractive russet
from the Idaho program. It completed three
years of evaluation in the western regional
variety trial in 1996. Due to lower yield than
many other advanced clones, this selection will
not be pursued for release from the Idaho
program. No further evaluations will be
conducted at KES.
Klamath Experiment Station
Table 1.
Effect of seed spacing on yield, grade, and tuber size distribution of five varieties/
grown at Klamath Falls, OR, 1996.
Variety/
Selection
Seed
Spacing
Yield U.S. No. is
4-6 oz. 6-10 oz. >10 oz.
inches
R. Burbank
6.8
8.7
Total
Yield
No.2s
Bs
cwt/A
163
134
53
12.0
130
126
152
179
60
101
405
86
53
6.8
8.7
12.0
117
102
89
149
136
144
99
160
190
365
398
423
64
51
40
A085165-1
6.8
8.7
12.0
98
71
62
132
120
106
147
211
199
377
401
366
A8495-1
6.8
8.7
12.0
93
101
81
145
133
133
58
89
123
296
322
6.8
8.7
12.0
125
122
106
101
118
98
139
R. Norkotah
A84118-3
Total
350
341
94
13
12
26
10 466
8
9
15
5 442
8 465
10 488
48
27
23
14
20
18
14 452
6 453
5 411
12
10
337
69
58
28
13
4 381
5 395
9 386
39
66
32
264
306
235
91
80
82
9
8
4
5 369
8 402
4 324
71
150
186
90
45
365
395
381
318
268
78
52
33
51
84
17
103
77
92
118
155
143
119
137
106
14 473
7 465
8 439
6 387
6 365
16
14
18
20
33
30
9
27
25
13
57
6
6.8
119
132
79
330
73
11
7 422
8.7
12.0
105
93
132
132
117
129
354
353
60
45
12
15
8 433
9 422
11
9
19
NS
42
35
18
NS
6
3
37
NS
116 14
NS NS
13 451
18 502
Variety Main Effect:
R. Burbank
R. Norkotah
A085165-1
A8495-1
A84118-3
CV (%)
LSD (0.05)
11
17
12
7
72
5
8
25
Spacing Effect:
CV (%)
LSD (0.05)
Klamath Experiment Station
63
Table 2.
Three-year summary of effects of seed spacing on yield, grade, and tuber size distribution of
Russet Burbank, Russet Norkotah, and A085165-1 grown at Klamath Falls, OR, in 1994-1996.
Variety/
selection
Seed
spacing
Yield U.S. No. is
4-6 oz. 6-10 oz. >10 oz.
R. Norkotah
A085165-1
6 4
Bs
Culls
Total
cwt/A
inches
R. Burbank
Total
Yield
No 2s
6.8
8.7
12.0
138
114
117
124
127
150
45
69
91
308
309
356
120
90
62
28
41
38
14
31
19
470
470
475
Mean
123
134
68
324
91
36
21
472
6.8
8.7
12.0
104
92
71
158
145
152
122
169
213
384
406
436
67
43
32
11
12
14
7
9
10
469
469
491
Mean
89
152
168
409
47
12
9
476
6.8
8.7
12.0
93
82
66
162
157
130
201
235
270
456
474
466
52
36
27
13
17
21
10
9
14
530
536
527
Mean
80
150
235
465
38
17
11
531
Klamath Experiment Station