97
Effects of Hail Damage on Potato Crops
in the Klamath Basin
K.A. Rykbost', J. Maxwell', D. Beck', H. Bush'
INTRODUCTION
On the afternoon of August 8, 1989 a severe hail and wind storm
traversed a path from the Lower Klamath Wildlife Refuge, northeasterly,
through the town of Merrill and into the Poe Valley. Winds in excess of
100 mph and up to 5 inches of hail devastated crops in the direct path
of the storm. Following aerial reconnaissance, it was estimated that
total crop loss occurred on 3,000 acres of alfalfa, 2,000 acres of grain
and 600 acres of potato crops. Lesser damage occurred to crops in
fringe areas.
Numerous studies have been done simulating hail damage to potato
crops. However, it is impossible to create, artificially, the tissue
damage, stem punctures and water-logging that occur naturally in a storm
of this magnitude. The storm provided a unique opportunity to evaluate
the extent of damage and strategies for salvaging crops that received
less than total damage. Objectives were to: 1) visually estimate the
degree of stem and leaf damage; 2) quantify plant dry matter content as
an objective measurement of destruction of the above ground portion of
plants; 3) determine crop yield, size and quality soon after the storm
and at the time of final harvest to assess the extent and nature of crop
development subsequent to damage; and 5) assess grower options for
management of crops with less than total damage.
1/ Superintendent/Associate Professor and Biological Sciences Research
Technician, respectively, Klamath Experiment Station.
2/ Associate Professor, Klamath County Cooperative Extension Service
3/ Klamath County Executive Director, ASCS
Acknowledgments: Partial funding by the Oregon Potato Commission,
assistance by Basin Fertilizer personnel, and the cooperation of growers
Dean and John Wells, Dick Carleton, Gary Orem and Lynn and Randall Pope
made this study possible.
98
PROCEDURES
Approximately one week after the storm several fields, representing
a range of damage and three varieties, were selected for evaluation.
Fields selected for evaluation included the varieties Russet Burbank,
Russet Norkotah and Krantz. By August 8 the early maturing Norkotah and
Krantz had passed the peak of vegetative growth and were well into the
tuber bulking phase of growth. Russet Burbank was nearly at maximum
vegetative growth but early in the tuber development stage.
Individual fields represented a range of soil types, planting dates,
cultural practices and storm severity. Three of the fields with uniformly severe damage were sampled in one representative section only.
The field of Krantz represented two quite different situations. On one
end the soil was very sandy, plants were small and well into senescence
by August 8, and were severely shredded by hail and wind. The other end
of the field was finer textured soil, with more vigorous plants and less
severe damage This portion of the field received an aerial application
of a complete analysis fertilizer and an additional irrigation after the
storm.
One field of Russet Burbank included a gradation from very sandy
soil with smaller plants to a fine textured soil with larger plants.
Hail damage ranged from moderate to intermediate. Half of the field
received an aerial application of a complete analysis fertilizer.
Irrigation was resumed one week after the storm and continued until
frost killed the vines in mid-September. Four locations were selected
in this field to cover the range of damage and differential fertilization. An undamaged Russet Burbank control site was established in a
field at KES.
Initial evaluations were completed from 6 to 10 days after the
storm. Final yield measurements were obtained from 22 to 63 days after
the storm, depending on grower harvest timing. Plot areas were chosen
on a uniform basis in relation to field boundaries and irrigation
laterals. Plot edges were a minimum of 80 feet into the fields. The
samples were taken in the fourth row out from irrigation pipes. At each
site, four 25-foot sample areas were established equidistant from the end
of the field and at least eight rows apart, depending on lateral spacing.
Visual estimates of damage to stems and leaves were recorded on a
percentage basis. The number of plants in each plot area was determined.
Plant tops were cut three inches from the soil surface and total fresh
weight of tops was determined in the field. Approximately one-pound
samples were oven-dried for 96 hours to determine plant dry matter
content. Tubers were hand-dug after vine removal and graded to USDA
standards within two days.
Final harvest data were obtained from the same rows, starting five
feet beyond the initial plot area. Tubers were hand-dug and graded
within several days. In one field, tubers were dug with a windrower and
picked by hand.
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Sites A, B, C, D and E experienced 95 to 100 percent stem damage
Many stems were nearly severed in one or more places and most had hail
impact scars at one- to two-inch intervals along their entire length.
The majority of leaves were detached and most of the rest were perforated. At the time of initial sampling many of the stems were drying out
rapidly. These sites had received two to four inches of hail. Irrigation was stopped completely on sites A, B and D. Site C received one
additional irrigation and an aerial application of a complete analysis
fertilizer. Site E was irrigated three times after the storm damage
At KES, a second harvest sample was hand dug from the same rows on
September 1. To provide a much larger sample size and a measure of
potential yields for undamaged Krantz and Norkotah, final harvest data
was derived from two different experiments at KES.
RESULTS AND DISCUSSION
Dry weight per plant was very low on the Russet Norkotah and Krantz
varieties, due in part to natural senescence of these early varieties
(Table 1). Larger plants initially and slightly less hail damage
accounted for the higher dry weight of Krantz at Site C. Russet Burbank
plants at Sites D and E exhibited approximately 50 percent loss of dry
matter compared with the control site.
Russet Norkotah, at Site A, had the highest yield at the initial
sampling (Table 2). It is earlier maturing than either Krantz or Russet
Burbank. One-third of the crop was in the marketable size range of 6 to
10 ounces. There was no further increase in total yield during the 16
days to final harvest. The only noteworthy change at this site was the
decline in specific gravity and a slight increase in tuber size. This
suggests that tubers may have accumulated more water but probably lost
dry matter through respiration.
At Site B, Krantz had a total yield of US No. l's approximately
double yields observed in Russet Burbank fields. There was no further
increase in total yields and no change in specific gravity. However, a
slight increase in tuber size occurred between sampling dates.
Initially higher yields, larger size and higher specific gravity of
Krantz at Site C was due to better plant vigor in the finer textured soil
at this end of the field. This site also remained static in total yield
and experienced a slight increase in size. Fertilization and irrigation
did not increase yields or size.
At Site D Russet Burbank was similar to the control field in yield,
size and specific gravity at the initial sampling date. No change was
observed in yield of US No. l's. The increase in yield of B-size tubers
may have been due to sampling variability. Many of these smalls are lost
in conventional harvest.
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A small yield increase occurred at Site E. However, a significant
pythium rot problem developed in this field. Samples from the final
harvest exhibited approximately 10 percent rot at the time of harvest.
After storage for a week the percentage of visible rot increased. The
crop would not have been suitable for storage. Irrigation after the
storm clearly aggravated a disease problem in this field.
In the moderately damaged Russet Burbank field (Sites F through I),
plant dry matter contents of 71, 67, 71 and 95 percent of an undamaged
control corresponded to final US No. 1 yields of 83, 73, 79 and 103
percent of the control respectively. Visual estimates of stem and leaf
damage were not as well correlated with crop yield. Aerial fertilization
following damage did not appear to be beneficial in the least damaged
portion of this field.
Crop development at Sites F through I was impressive considering the
extent of plant damage experienced. The greatest percentage increase in
yields occurred in the unfertilized portion of the field, Sites F and G.
Tuber growth was quite normal for Russet Burbank. There was a lower
percentage of second growth, growth cracks and hollow heart than is often
observed in typical crops that have not experienced storm damage.
Russet Burbank crops were similar in yield and size to the undamaged
control at KES at most sites in mid-August. If final yields are compared
with yields of Russet Burbank in the N, P, K and S rate experiment (Table
2), fields with serious damage experienced a 75 percent reduction in
yield of US No. l's. The moderately damaged field ranged from 73 to 103
percent of the control in yield of No. l's. Norkotah yield in Site A was
57 percent of the average Norkotah yield in the seed spacing experiment.
Final yield of No. l's in Krantz at Sites B and C were 38 and 51 percent,
respectively, of the average Krantz yield in the seed spacing experiment.
SUMMARY AND CONCLUSIONS
Over a limited range of damage severity the data suggest that a 50
percent reduction of canopy dry matter one week after the storm was
sufficient to arrest crop development. At this level of damage a determination of tuber yield and grade at any time after the storm would
provide a satisfactory estimate of the crop for purposes of settling
insurance or disaster relief claims. Fertilization or irrigation of
crops damaged to this extent is unlikely to be beneficial.
Management of crops after damage is a major concern for both yield
and quality. It was expected that crop stress might lead to second
growth, growth cracks, hollow heart or other physiological disorders in
Russet Burbank. Failure to observe these effects at any of the sites
may be due to the timing of the damage. Russet Burbank was not in the
rapid bulking phase of development on August 8. Desiccation of vines to
prevent physiological disorders might be more appropriate than attempting
to nurture the crop to achieve higher yields when damage coincides with
the rapid bulking period.
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Table 1. Canopy characteristics of hail damaged potato crops, Merrill,
Oregon, August 1989.
Sample
date
#Plants
/acre
Plant damage
Stems
Leaves
X
Plant weight
Fresh
Dry
lbs/plant
Location
Variety
Site A
R.Norkotah
8/14
17,000
100
95
0.35
0.03
Site B
Krantz
8/14
17,100
100
100
0.22
0.02
Site C
Krantz
8/14
17,900
85
65
0.85
0.06
Site D
R.Burbank
8/14
12,500
100
95
0.94
0.10
Site E
R.Burbank
8/15
10,700
95
75
0.93
0.10
Site F
R.Burbank
8/18
12,900
90
55
1.68
0.15
Site G
R.Burbank
8/18
13,100
90
45
1.55
0.14
Site H
R.Burbank
8/18
13,500
80
40
1.63
0.15
Site I
R.Burbank
8/18
13,600
45
25
1.88
0.20
Control
R.Burbank
8/15
15,000
0
0
2.62
0.21
Table 2.
N
c)
,-.4
Tuber yield and grade of hail damaged potato crops, Merrill, Oregon, 1989.
Sample
date
4-6oz
Yield US No. l's
Total
>10oz
6-10oz
S.D.'
cwt/a-
B's
Yield
Total
2's & Culls
S.D.'
Specific
Gravity
Location
Variety
Site A
R.Norkotah
8/14
8/30
130
122
118
107
0
34
248
263
19.1
18.7
86
89
28
19
378
371
29.1
16.3
1.070
1.063
Site B
Krantz
8/14
8/30
106
113
76
54
0
20
183
187
30.3
14.8
99
83
10
18
293
288
22.2
16.2
1.068
1.067
Site C
Krantz
8/14
8/30
105
107
126
110
0
36
231
253
18.8
34.6
72
66
21
14
325
333
10.8
43.1
1.074
1.075
Site D
R.Burbank
8/14
8/30
84
83
14
14
0
0
98
97
5.1
38.7
129
169
23
24
250
290
22.5
33.0
1.075
1.074
Site E
R.Burbank
8/15
9/8
41
47
13
38
0
8
54
93
12.0
18.6
55
56
30
30
139
179
25.8
19.6
1.073
1.080
Site F
R.Burbank
8/18
10/10
53
154
28
126
0
37
81
317
8.6
29.1
113
57
6
29
199
403
29.1
56.6
1.067
1.082
Site G
R.Burbank
8/18
10/10
59
120
33
110
1
47
93
277
41.2
63.8
106
59
16
64
215
400
34.2
69.7
1.068
1.083
Site H
R.Burbank
8/18
10/10
76
135
42
116
14
50
132
301
28.3
49.7
112
65
10
24
254
390
25.1
46.8
1.068
1.078
Site I
R.Burbank
8/18
10/10
108
156
68
154
4
81
180
391
40.0
69.5
112
50
9
52
302
493
43.8
55.4
1.069
1.077
Control
R.Burbank
8/15
9/1
10/10
83
97
146
25
94
156
0
41
77
108
232
379
45.6
61.3
148
101
80
12
16
86
268
349
545
41.4
44.3
1.072
1.082
1.083
Control
R.Norkotah 10/5
130
174
161
465
50
49
564
--
1.070
Control
Krantz
10/5
136
196
165
497
47
38
582
--
1.077
1/ Standard Deviation - total yield of US No. l's
2/ Standard Deviation - total yield