40
Potato Cultivar Response to Seed Spacing and Nitrogen Fertilizer Rates
K. A. Rykbost and J. Maxwell s
INTRODUCTION
New potato varieties continue to erode the dominance of Russet Burbank in the
Pacific Northwest. A late spring and cool weather through much of the 1993 growing
season resulted in low yields, small size, and a high incidence of hollow heart and
brown center in Russet Burbanks grown in high elevation areas in Idaho and
Oregon. This experience and the economic consequences will further encourage
potato growers to seek varieties less susceptible to weather-related physiological
disorders and capable of producing a higher percent of marketable tubers.
Most new varieties and advanced selections require different cultural
management practices than Russet Burbank to produce optimum yields, size, and
quality. Effects of plant population and nitrogen fertilizer rates on the performance
of new varieties and advanced selections have been evaluated as an integral part of
the KES variety development program for several years. In 1993, these studies
included Russet Burbank, Russet Norkotah, Goldrush, Snowden, and five promising
advanced selections from the Oregon variety development program.
PROCEDURES
Nine varieties or advanced selections were evaluated in two separate
experiments. Split-plot experimental designs were used with four replications.
Standard practices were followed for disease and pest management, and irrigation
(see page 26). Weed control with Eptam was supplemented with 0.4 lb ai/A
metribuzin applied aerially on July 7. Potatoes were planted with a two-row,
assisted-feed planter in 32-inch rows on June 8. Vines were desiccated with diquat
applied at 1.0 pint/A with a ground sprayer on September 18.
In the seed spacing experiment, main plots were spacings of 6.8, 8.7, or 12
inches. Individual plots were two rows, 30 feet long. Fertilizer included 700 lb/A of
15-15-15 banded at planting, and 60 lb N/A applied as solution 32 and incorporated
with a rolling cultivator on June 14. Potatoes were harvested with a one-row diggerbagger on October 7. Field weights were determined for all tubers from both rows.
Approximately 120-pound samples from each plot were stored and graded to USDA
standards in early November. Specific gravity was determined by the weight-in-air,
weight-in-water method on 10-pound samples of 6- to 10-ounce No.1 tubers.
1
/ Superintendent/Professor and Biological Sciences Research Technician,
respectively, Klamath Experiment Station, Klamath Falls, OR.
Acknowledgment: Studies were funded in part by the Oregon Potato Commission
and the CSRS.
41
In the nitrogen fertilizer rate experiment, main plots were nitrogen rates of 130,
160, or 190 lb N/A. Fertilizer was banded at planting at 870 lb/A of 15-15-15.
Solution 32 was sprayed on with a ground sprayer at 0, 30, or 60 lb N/A and
incorporated with a rolling cultivator on June 14. Individual plots were four rows, 30
feet long, with Russet Burbank planted in the two outside rows at 12-inch seed
spacing. Varieties or advanced selections were spaced at 8.7 inches in the center
rows. All seed for both experiments was hand cut to 1.5 to 2.0 ounces/seedpiece,
treated with Tops 2.5 fungicide, and suberized for two weeks prior to planting.
Potatoes were harvested on October 8. Harvest and grading procedures were the
same as described for the seed spacing experiment. Internal tuber quality was
evaluated by cutting 10 large tubers from each plot (usually over 10-ounce tubers).
RESULTS AND DISCUSSION
Response to seed spacing
Plant emergence was recorded on July 5 and July 21, 27 and 43 days after
planting. A74212-1E, Goldrush, and ND02904-7 ranged from 80 to 88 percent
emergence, and all other selections were at 90 percent or more on July 5. All
selections exceeded 95 percent emergence on July 21. Plant stands were not a factor
in performance of any of the varieties or selections. Russet Norkotah was the only
variety that started senescence prior to vine desiccation. Canopy development was
delayed about three weeks due to late planting and cool weather in June and July.
Yields and tuber size of late maturing selections were clearly affected by the late
planting date and cool season. Russet Burbank total No.1 yields in this study in 1991
and 1992, averaged 378 cwt/A. The 1993 average of 280 cwt/A (Table 1) represents
a decline in No.1 yield of 26 percent. A74212-1E produced about 75 percent of the
No.1 yield achieved in the 1991 study. In contrast, the early maturing Russet
Norkotah produced an average No.1 yield nearly equal to the average for the two
previous years. Goldrush yields were also similar in 1991 and 1993. C0083008-1 and
A082611-7 were both included in the 1992 experiment. Total No.1 yields were only
slightly lower in 199 3 for C0083008-1, but were 100 cwt/A lower in 1993 for the
later maturing A082611-7. Yields of tubers over 10 ounces were much lower in
Russet Burbank, A74212-1E, and A082611-7 in 1993 than in previous years.
,
Significant differences were found between varieties for all yield parameters and
specific gravity (Table 1). C0083008-1, A74212-1E, and NDO2904-7 produced the
highest No.1 yields. Russet Burbank yield of No.ls was significantly lower than all
other varieties. C0083008-1 and ND02904-7 had high yields of count carton size
while Russet Burbank produced very few tubers over 10 ounces. Russet Norkotah,
Goldrush, and A082611-7 were intermediate in yields and had similar yields and
tuber size distribution. The two chipping varieties, Snowden and ND01496-1, were
similar in yields, tuber size, and specific gravity. Both selections produced high tuber
numbers and small size, with higher yields under 4 ounces than all selections except
Russet Burbank. Yields of No.2s and culls were low except for Goldrush, which
produced quite a few misshapen tubers.
42
Specific gravity followed expected trends. Snowden and ND01496-1 had
significantly higher specific gravity than all other selections. Russet Burbank,
C0083008-1, and A082611-7 were similar and intermediate in specific gravity.
Russet Norkotah, Goldrush, and ND02904-7 had lower specific gravity than
A74212-1E. As in past years, specific gravity was not affected by seed spacing.
The interaction between seed spacing and variety was only statistically significant
for small and intermediate No.1 tubers. Increased seed spacing resulted in much
lower yields of 4- to 6-ounce tubers in A74212-1E and A082611-7, but only minor
differences in the other selections. Russet Burbank produced higher yields of 6- to
10-ounce tubers as seed spacing increased. The yield of 6- to 10-ounce tubers
decreased when seed spacing increased in C0083008-1. Other selections showed
little effect of seed spacing on yield of this size fraction. Other effects of seed
spacing on yields produced similar responses in all varieties. General trends were
increased tuber size, but little effect on total No.ls, No.ls, culls, or total yield.
While seed spacing effects on total No.1 yields were not statistically significant,
the effects on economic returns are much more pronounced. Current fresh market
prices for russet varieties are over $20/cwt for count cartons and Nods over 10
ounces. No.ls under 8 ounces return about $6/cwt. Tubers under 4 ounces (Bs) are
valued at about $1.50/cwt. Based on these values, the optimum seed spacing was 12
inches for all russet varieties in this trial except Russet Norkotah. Norkotah
produced optimum returns at the 8.7-inch spacing, as in five previous years. Both
chipping varieties also achieved optimum production at the 12-inch spacing.
Response to seed spacing in A74212-1E was much different than in 1991, and in
the late maturing variant of this selection in several prior years of evaluation.
A74212-1 typically produces high yields of large tubers. In all previous trials,
excessive size has occurred at 12-inch spacing. In most cases, the total No.1 yield has
declined as spacing was increased beyond 6.7 inches. In 1993, tuber size was not
excessive at the 12-inch spacing and yield benefits were observed for each increase
in seed spacing. Russet Burbank also achieved greater benefits from the lowest plant
population than in either 1991 or 1992. Clearly, late maturing varieties require
adjustments in plant population when circumstances result in late planting in shortseason areas.
Russet Burbank had the highest incidence of internal defects, with about 5
percent hollow heart and 10 percent brown center. Other selections exhibited less
than 5 percent defects. Seed spacing did not affect the incidence of internal defects.
Response to nitrogen rate
Plant populations were similar to those observed in the seed spacing experiment,
with final stands exceeding 95 percent in all varieties. Canopy vigor was affected by
nitrogen rate. Most varieties were showing signs of senescence at the low nitrogen
rate by mid September. At the high rate, all varieties except Russet Norkotah
remained vigorous until vines were desiccated.
43
Average yields for all varieties or selections except Snowden and ND01496-1
were slightly lower than yields observed in the seed spacing experiment (Table 2).
The relative ranking of varieties was similar in both experiments except A74212-1E
had higher No.1 yields than C0083008-1 in the nitrogen rate study. Russet Burbank
No.1 yields were significantly less than yields of all other varieties.
Varietal response to nitrogen rate was varied. Several individual varieties
responded differently than in previous years. Higher nitrogen rates improved yield in
Russet Norkotah and A082611-7. In 1991 and 1992, Norkotah yields were highest at
130 lb N/A. The yield response in A082611-7 was the same in 1992 and 1993. The
130 lb N/A rate was optimum for Russet Burbank. In both 1991 and 1992, Russet
Burbank required 160 lb N/A for optimum yield. A74212-1E produced optimum
yields at 130 lb N/A in 1992 and 160 lb N/A in 1993. C0083008-1 achieved
maximum yield at 190 lb N/A in both 1992 and 1993. Increased nitrogen rates did
not improve yields in Goldrush, ND02904-7, or ND01496-1. The response for
Goldrush was the same in 1992. These varietal response differences were noted as
significant interactions for 6- to-10 ounce, total No.1, and under 4-ounce yield
components. Averaged over varieties, nitrogen responses were small for all yield
components, and non-significant for most.
Specific gravity declined slightly as nitrogen rate increased. This response has
been observed in each year of this study. Few internal defects were observed in any
of the selections, and nitrogen rate did not affect their incidence.
SUMMARY
A significant portion of the 1993 Klamath County potato crop was planted after
June 1. The Russet Burbank portion of this acreage produced low yields and small
size in most cases. The need for an earlier maturing variety in short-season areas is
evident. Russet Norkotah produced much higher returns than late planted Russet
Burbank under these conditions. However, variety changes are usually not an option
in late spring due to seed availability. Results of these studies suggest changes in
crop management will improve crop performance when late planting becomes
necessary. Specifically, lower nitrogen rates and lower plant populations will increase
yields, tuber size, and economic returns in Russet Burbank. Similar results were
observed in a four-year evaluation of Russet Burbank response to planting date,
nitrogen rate, and seed spacing conducted in New Brunswick, Canada in the early
1980's. Early maturing varieties may not respond in the same way.
As reported in the previous section, several advanced Oregon selections appear
to offer much improved performance compared with standard varieties. Yields and
tuber size distribution were excellent in both trials for A74212-1E, C0083008-1, and
ND02904-7. ND01496-1 produced higher yields than Snowden, with equal specific
gravity.
44
Table 1. Effect of seed spacing on performance of nine potato selections, Klamath Experiment
Station, Oregon 1993.
Variety/
Selection
Seed Yield U.S. No. is
Spacing 4-6 oz 6-10 oz > 10 oz Total inches
Bs
Yield Specific
No. 2s Culls Total Gravity
cwt/A
R. Burbank
6.8
8.7
12.0
169
149
149
88
105
134
8
13
24
265
267
307
123
113
84
10
9
I
23
28
16
421
417
408
1.084
1.084
1.083
R. Norkotah
6.8
8.7
12.0
129
135
105
192
179
151
60
83
95
381
397
351
78
56
42
2
19
7
11
10
21
472
482
431
1.075
1.076
1.072
A74212-1E
6.8
8.7
12.0
215
171
139
187
194
195
43
101
153
445
466
487
101
77
46
5
16
8
13
26
22
564
585
563
1.077
1.078
1.073
Goldrush
6.8
8.7
12.0
147
141
107
137
160
154
45
64
90
329
365
351
72
59
52
24
24
20
36
26
29
461
474
452
1.072
1.073
1.074
Snowden
6.8
8.7
12.0
182
156
176
99
123
129
25
45
51
306
324
357
127
101
106
1
0
0
16
14
11
450
439
474
1.091
1.090
1.090
CO083008-1
6.8
8.7
12.0
80
85
67
216
188
128
196
205
275
492
478
470
34
39
17
3
11
5
24
17
25
553
545
517
1.084
1.081
1.081
A082611-7
6.8
8.7
12.0
178
150
115
196
177
171
33
55
93
407
382
379
103
64
49
0
5
7
12
16
16
522
467
451
1.081
1.080
1.083
NDO 2904-7
6.8
8.7
12.0
121
126
92
186
196
172
140
121
170
447
443
434
52
55
36
4
8
9
11
10
17
514
516
496
1.072
1.073
1.072
NDO 1496-1
6.8
8.7
12.0
158
175
156
134
128
149
46
51
67
338
354
372
115
104
70
0
0
2
16
9
11
469
467
455
1.089
1.090
1.090
Variety Main Effect (average of three spacings)
R. Burbank
R. Norkotah
A74242-1E
Goldrush
Snowden
C0083008-1
A082611-7
NDO 2904-7
NDO 1496-1
CV (%)
LSD (0.05)
156
123
175
132
171
77
148
113
163
109
174
192
151
117
177
181
185
137
15
79
99
66
41
225
60
144
55
280
376
466
348
329
480
389
441
354
107
58
75
61
112
30
72
48
96
7
9
10
22
0
7
4
7
1
22
14
20
31
13
22
15
12
12
415
462
570
462
454
538
480
508
464
1.083
1.070
1.076
1.073
1.090
1.082
1.082
1.072
1.090
16
18
17
22
35
25
12
36
23
13
99
6
55
8
9
36
1
0.004
Seed Spacing Main Effect (average of nine selections)
6.8
8.7
12.0
CV (%)
LSD (0.05)
153
143
123
160
161
154
66
82
113
379
386
390
89
74
56
6
10
7
18
17
19
492
488
472
1.080
1.081
1.078
23
18
23
NS
46
23
17
NS
27
11
112
NS
37
NS
12
NS
NS
1
45
Table 2. Effect of nitrogen fertilizer rate on performance of nine potato selections, Klamath
Experiment Station, Oregon 1993.
Variety/
Selection
Nitrogen Yield U.S. No. is
Yield Specific
Rate
4-6 oz 6-10 oz > 10 oz Total Bs No. 2s Culls Total Gravity
lbs N/A cwt/A
R. Burbank
130
160
190
180
164
143
62
74
62
3
8
12
245 119
246 109
217
95
7
12
10
28
26
44
399
393
366
1.083
1.079
1.077
R. Norkotah
130
160
190
105
122
106
130
132
189
83
78
87
318
333
382
44
58
50
16
19
14
23
21
7
401
431
453
1.070
1.072
1.071
A74212-1E
130
160
190
196
163
157
148
220
162
72
90
99
416
473
418
69
68
72
9
5
8
13
14
15
507
560
513
1.077
1.072
1.072
Goldrush
130
160
190
132
126
129
144
137
130
59
50
63
335
313
322
53
64
60
16
23
18
29
21
34
433
421
433
1.074
1.071
1.071
Snowden
130
160
190
214
198
184
118
114
79
33
30
22
78
365
343
84
285 120
1
2
2
8
14
13
452
443
415
1.088
1.087
1.087
C0083008-1 130
160
190
82
93
85
135
155
180
209
132
168
426
380
433
28
38
40
9
11
1
13
34
10
476
463
484
1.082
1.081
1.079
130
160
190
142
143
127
155
177
173
68
55
92
365
375
392
63
62
44
10
12
13
7
12
21
446
462
470
1.079
1.080
1.076
2904-7 130
160
190
112
94
79
164
129
125
144
156
172
420
379
376
43
35
34
4
9
17
18
12
22
485
435
449
1.069
1.070
1.065
NDO 1496-1 130
160
190
208
209
200
124
112
110
24
28
31
356
349
341
74
84
67
2
0
0
6
8
9
438
441
417
1.090
1.088
1.088
10
16
7
19
2
7
12
10
1
33
17
14
28
12
19
13
17
8
386
429
527
429
437
474
459
456
432
1.080
1.071
1.073
1.072
1.087
1.081
1.079
1.068
1.088
A082611-7
NDO
Variety Main Effect (average of three nitrogen fertilizer rates)
R. Burbank
R. Norkotah
A74212-1E
Goldrush
Snowden
C0083008-1
A082611-7
NDO 2904-7
NDO 1496-1
CV (%)
LSD (0.05)
162
111
172
129
199
87
137
95
206
66
150
177
137
104
157
168
139
115
8
83
87
58
28
170
72
157
28
17
20
20
22
33
21
236 107
344
51
436
70
323
59
331
94
36
413
377
56
392
38
349
75
11
33
25
11
87
7
61
9
9
33
1
0.003
361
354
352
64
67
65
8
10
9
16
18
19
449
450
444
1.079
1.078
1.076
29 109
10
NS NS NS
44
NS
10
NS
1
0.003
N-Rate Main Effect (average of nine selections)
130
160
190
CV (%)
LSD (0.05)
153
146
134
131
139
134
77
70
83
21
17
9
8
16
7