Russet Burbank Response to Seedpiece Size
K.A. Rykbostl, J. Maxwell', and K Locket
Introduction
9
Procedures
Numerous studies have demonstrated the importance of seedpiece size
to potato performance in production areas across North America. Observations of commercial cut seed lots in the Klamath Basin over several years
have shown a lack of uniformity in seed size and a trend for use of smaller
than desirable seed. The Russet Burbank variety has plentiful eyes and
seedpieces without eyes (blind seed) are uncommon. Most newer varieties
have fewer eyes which are less well distributed. It is commonly recommended that larger seedpieces should be used for Russet Norkotah,
Shepody, Century Russet, and other varieties with fewer eyes. This study was
established to survey local commercial seed cutting practices and conduct a
controlled experiment to determine the effects of a range of seedpiece sizes
on Russet Burbank performance under Klamath Basin conditions.
Approximately 40-pound samples of cut seed were obtained from seven
commercial potato growers during the 1994 planting season. Each lot was
sorted to seedpiece sizes of <1.0 oz.; 1.0 to 1.5 oz.; 1.5 to 2.0 oz.; 2.0 to
2.5 oz.; and >2.5 oz. Weight and number of seedpieces in each size fraction
were recorded.
A Russet Burbank seed lot was sorted by tuber size to obtain 48
mother tubers weighing approximately 3, 5, 7, 9, and 11 ounces. Tubers
were hand cut into four equal sections to provide 192 seedpieces weighing 3/
4, 1-1/4, 1-3/4, 2-1/4, and 2-3/4 ounces. Cut seed was treated with Tops
2.5 - MZ and suberized for two weeks prior to planting. Potatoes were
planted in randomized complete block design single-row, 32-hill plots with six
replications on May 12. Seed was spaced at 12 inches in 32-inch rows.
/ Superintendent/Professor and Biological Sciences Research Technician III, respectively, Klamath
Experiment Station, Klamath Falls, OR.
2/ Klamath County Cooperative Extension Agent, Klamath Falls, OR.
1
Acknowledgment: Partial financial support for this study provided by the CSRS and the Oregon Potato
Commission is gratefully recognized.
Klamath Experiment Station 87
Russet Burbank Response to Seedpiece Size
Border rows on each side of test rows were planted with 1.5- to 2.0ounce seedpieces cut from the same Russet Burbank seed lot. Cultural
practices are described on pages 38 and 39. Vines were desiccated with
Diquat applied at 1.0 pint/acre on September 15. Potatoes were harvested
with a one-row digger-bagger on September 26. All tubers from each plot
were stored and graded in late October.
Emergence data were recorded on June 3, June 10, and June 16.
Stem numbers were counted on 10 consecutive plants in the center of each
plot on June 30. An economic interpretation of results was based on the
following assumptions:
1. Seed costs, including cutting and treating - $12/cwt.
2. 17,424 seedpieces/acre based on 10-inch seed spacing in
36-inch rows.
3. Crop values: Bs and culls - $1.00/cwt; No.2s - $3.00/cwt;
4- to 8-ounce No.ls - $4.00/cwt; 8- to 12-ounce No.ls $10.00/cwt; >12-ounce No.1 s - $8.00/cwt.
4. Yield of commercial seed lots would be proportional to ratio of
seed sizes and experimental yields for comparable seed sizes.
5. Seed costs for commercial seed lots based on average weight of
seedpieces in each size fraction.
Results and
Discussion
Slightly earlier emergence was observed in plants with larger seedpieces
(Table 1). Final stands were unaffected by seed size. Plant size during the
first four weeks after emergence was directly correlated with seedpiece size.
Stem numbers increased as seedpiece size increased. All of these characteristics were consistent with reports of other studies.
Yields and tuber size distribution were significantly affected by
seedpiece size (Table 2). The greatest yield increase occurred between 3/4and 1-1/4-ounce seed. The maximum tuber yield ofNo.ls over 8 ounces
was observed for 1-3/4-ounce seed. Larger seedpieces produced higher
yields of small tubers. Using crop values assumed for the various yield
components, the highest gross crop value occurred at the 1-3/4-ounce
seedpiece size.
88 Klamath Experiment Station
Russet Burbank Response to Seedpiece Size
if
Crop value estimates are based on approximate 1994-1995 fresh
market prices for product at the packing shed less some ofthe costs for
processing. However, the average return of about $6.00/cwt estimated using
these prices is nearly 50 percent above average returns received by local
growers on 1994 crops. The $6.00/cwt returns to growers would be a
reasonable long term average for fresh market crops.
Data from the grower seed lot survey shows a very wide range in
seedpiece size distribution (Table 3). Sample numbers 1 and 2 represent
seed lots with excessive numbers of small seedpieces. Excessively large
seedpieces were observed in sample number 3. Sample numbers 6 and 7
were clearly the best in size distribution. Seed costs were calculated for each
seed lot assuming one seedpiece for each hill at 10-inch spacing. In fact, very
small seed often drops as doubles or triples. This would result in higher seed
costs than reported for lots with a high ratio of seedpieces under 1.0 ounces.
Samples evaluated included four machine cut lots (sample numbers 1, 2, 4,
and 6), and three hand cut lots. Better seed size distribution occurred in hand
cut lots, except in the case of sample number 3.
Gross crop returns for grower seed lots were estimated based on the
percent of each seedpiece size fraction, the yields observed for that size
fraction in the experiment, and values assigned for yield components (Table
3). The estimates show a range of over $300/acre in gross crop value.
When seed costs are subtracted, the estimated returns are about $200/acre
higher for seed lots 5, 6, and 7 than for sample number 1.
The results observed in this experiment are quite consistent with research reported elsewhere for the Russet Burbank variety. Quite different
results would be expected for varieties with low numbers and poor distribution of eyes. Adverse soil conditions during the early part ofthe growing
season would also change the results as small seedpieces would be less able
to withstand environmental stress. Additional research in this area and more
extensive surveys of grower seed cutting practices is planned. Seed management is clearly an important aspect of crop management. The preliminary
findings ofthis research suggest there is a need for improvement in commercial seed cutting practices.
Klamath Experiment Station 89
Russet Burbank Response to Seedpiece Size
Table 1.
Effect of seedpiece size on emergence and stem numbers in Russet Burbank potato plants at
Klamath Falls, OR, 1994.
Seed
size
June 3
Emergence
June 10
oz
Table 2.
June 16
Stems/Plant
June 30
%
3/4
1-1/4
1-3/4
2-1/4
2-3/4
44
55
56
66
69
92
96
94
97
98
97
100
100
99
100
1.63
2.00
2.38
2.65
2.73
Mean
58
95
99
2.28
Effect of seedpiece size on yield, grade, and value of Russet Burbank potatoes at Klamath
Falls, OR, 1994.
Seed
size
Yield U.S. No. is
4-8 oz 8-12 oz >12 oz Total
oz
Bs
Yield
No. 2s Culls
Total
cwt/A
$IA
3/4
1-1/4
1-3/4
2-1/4
2-3/4
145
204
199
233
293
108
138
154
108
109
65
77
90
68
50
318
419
442
408
452
31
43
55
61
79
25
36
49
52
40
18
5
5
11
6
391
503
551
531
577
Mean
CV (%)
LSD (0.05)
215
15
38
123
28
42
70
40
33
408
13
63
54
31
20
40
47
23
9
121
NS
510
13
80
90 Manual: Experiment Station
Crop
value
2300
3010
3260
2780
2870
Russet Burbank Response to Seedpiece Size
Seedpiece size distribution, estimated seed costs, and estimated economic returns for seven
commercial seed lots evaluated at Klamath Falls, OR, 1994.
Table 3.
Net
Sample Seedpiece size Seed Gross
number > 1 oz 1-1.5 oz 1.5-2 oz 2-2.5 oz > 2.5 oz cost s return return3
% (number basis)
1
2
3
4
5
6
7
46.0
29.5
1.9
16.5
13.8
9.0
5.9
28.8
20.5
6.9
29.7
24.0
36.9
14.1
17.2
20.2
15.9
26.1
37.6
29.1
47.9
8.0
15.9
33.7
19.5
18.5
18.3
20.5
0
13.9
41.6
8.2
6.1
6.7
11.6
148
195
303
196
207
212
231
VA
2708
2796
2901
2902
2954
2968
3025
2560
2601
2598
2706
2747
2756
2794
1/ Based on seed price of $12/cwt and 10-inch spacing in 36-inch row.
2/
Based on yields, grade, and values from the replicated experiment with controlled seedpiece size.
3/
Gross return less seed costs.
Klamath Experiment Station 91