March 2010
Simulated Hail Damage in Cotton
G. Wang, R. Asiimwe, P. Andrade, and M. Sheedy
University of Arizona Maricopa Ag Center, Maricopa, AZ
Summary
Response of cotton plant to fruiting branch loss due to hail damage is important
information for insurance adjustment and agronomic management. Current data
used by National Crop Insurance Services (NCIS) were developed from field
experiments in southern states, where growing conditions are different
compared to Arizona and California. We simulated fruiting branch loss due to
hail damage by removing 0%, 25%, 50%, 75%, and 100% of fruiting branches
manually at three growth stages when cotton plants had 8, 12, and 16 fruiting
branches (R8, R12, and R16). Cotton plants responded to fruiting branch loss by
increasing growth and boll setting in new fruiting branches. Yield reduction was
related to percentage of fruiting branch removal but not to growth stage at
which removal occurred (R8 to R16) in this study. If the apical growing point is
undamaged and only fruiting branch loss occurs during hail storm from R8 to
R16 stage, growers could recover 80% to 100% of their cotton yield, depending
on the level of branch loss, under growing conditions in Arizona. However,
management practices might need to be adjusted after hail damage to increase
cotton boll setting on new branches.
Introduction
Hail damage occurs each year in many areas where cotton is grown, and accurate estimations of crop yield loss are
important for taking management actions and adjusting hail insurance claims. Insurance adjusters use a step-by-step
procedure from National Crop Insurance Services (NCIS) to assess the effects of hail damage on cotton. The
assessment includes estimations of cotton yield reductions by stand loss (plant totally or partially destroyed and
apical growing point was damaged), by fruiting branch damage, and by boll and lock loss at different growth stages
(NCIS, 1997). Current data on the yield loss estimation was developed from field experiments in southern states
(NCIS, 1997). The information is not applicable to southwestern states such as Arizona and California, in which
cotton is grown in a much longer growing season.
In this study, we estimated cotton yield loss by different levels of fruiting branch removal at three growth stages in
Arizona. Seed cotton weight from different sections of cotton fruiting branches was also measured by plant mapping
to investigate cotton plant regrowth after hail damage.
Materials and Methods
The experiment was conducted at University of Arizona Maricopa Agricultural Center at Maricopa, AZ. The cotton
variety ‘Deltapine 164 B2RF’ was planted in dry soil and irrigated on April 4, 2008. Bed width was 40 inches, inrow spacing was 3.8 inches, and planting depth was 0.5 inches. The management of cotton (irrigation, fertilization,
and pest management) followed grower production practices at the research station. Cotton fruiting branch removal
was conducted when cotton plants had 8 fruiting branches (R8, first flower stage) on June 20, 2008, 12 fruiting
branches (R12) on July 7, 2008, and 16 fruiting branches (R16) on July 21, 2008. At each growth stage, five
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different treatments including 0, 25, 50, 75, or 100% of fruiting branches removal were applied (Table 1). Hail
damage was simulated by cutting fruiting branches that were longer than 1 inch from the top of cotton plants using
pruners. The experiment was a split-plot design within a randomized complete block design with four replications.
The main plots were growth stages and the split plots were damage levels.
The final irrigation was applied on September 2, 2008 and defoliants were applied on September 30, 2008. Five
plants from each plot were sampled randomly for mapping analysis on November 3, 2008. Each of five plants was
separated into three parts: lower main stem section, mid-section, and top main stem section. The lower main stem
section included all vegetative branches (node 1-5). The mid-section included nodes on which the treatments were
applied, which included node 6-13, 6-17, and 6-21 for R8, R12, and R16 treatments, respectively. The top mainstem section included the new nodes that cotton plant produced after the fruiting branch removal treatment. Boll
number and seed cotton weight from each section were recorded. The two middle rows were harvested on
November 10, 2008 by a two-row cotton picker and seed cotton was weighed for yield. After harvest, plant numbers
in a three-meter row were counted in each plot to establish plant density.
Table 1. The number of fruiting branches and the specific nodes removed for different damage levels at each growth
stage. The removal started from the top branch with a length longer than 1 inch.
Removal treatment
R8
R12
R16
0
0 (no removal)
0 (no removal)
0 (no removal)
25%
2 (node 12-13)
3 (node 15-17)
4 (node 18-21)
50%
4 (node 10-13)
6 (node 12-17)
8 (node 14-21)
75%
6 (node 8-13)
9 (node 9-17)
12 (node 10-21)
100%
8 (node 6-13)
12 (node 6-17)
16 (node 6-21)
Results and Discussion
The overall average of cotton plant density was 11.4 plant/m for this study. The growth stage at which fruiting
branches were removed had no significant effect on cotton yield (p=0.32), while percentage removal of fruiting
branches affected cotton yield significantly. The interaction of growth stage and fruiting branch removal was not
significant (p=0.72). Compared to the control, the effect of removing 25% of fruiting braches on the higher node
(node 12-13 for R8, 15-17 for R12, and 18-21 for R16) on cotton yield was not significant at all three growth stages
(Table 2). Removal of all fruiting branches (100%) caused 17.0%, 18.5%, and 20.1% yield loss for R8, R12, and
R16 stages, respectively. These results indicate that cotton plants can compensate for fruiting branch loss to a
significant degree under long growing season conditions.
Table 2. Cotton yield (lbs/A) affected by different fruiting branches removed at each growth stage
Removal treatment
R8
R12
0
5041.7 a *
5238.6 a
25%
4840.0 ab
5022.5 ab
50%
4523.1 bc
4844.8 b
75%
4355.1 cd
4700.8 b
100%
4182.2 d
4268.6 c
Average
4588.4
4815.1
* In the same column, values followed by different letters are significantly different at p=0.05.
R16
5118.5 a
5017.7 a
4883.2 a
4475.1 b
4091.0 c
4717.1
When cotton fruiting branches were cut at R8 (first flower stage), the relationship between cotton yield and
percentage of fruiting branch removal is shown in Figure 1. For removal at stage R8, it can be seen that for
removing every 10% of fruiting branches, approximately 88 lbs (1.7%) of yield was reduced. Removing every 10
percent of fruiting branches at the R12 and R16 growth stages caused 91 (1.7%) and 104 lbs (2.0%) seed cotton
yield loss, respectively.
At stage R8, removing fruiting branches did not affect the production of vegetative branches and top branches
(Table 3). The difference in total seed cotton weight was caused by boll number and weight difference in the midsection branches, indicating that cotton plants did not respond to fruiting branch removal by changing growth in
other parts of the plant significantly.
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When fruiting branches were removed at the stage R12, cotton boll numbers and weights on the top branches were
affected significantly. The treatments with 50%, 75%, and 100% fruiting branch removal significantly increased
open boll numbers and boll weights and reduced unopened boll numbers compared to the control and the 25%
removal. Removing 3 small branches near apical point of the plants (25% removal) did not affect boll number or
boll weights compared to the control. The boll numbers on each node of the top branches were increased as a result
of fruiting branch removal.
At stage R16, the treatment with 25% fruiting branch removal did not affect cotton growth except for boll numbers
per node on top branches. The treatments with 50%, 75%, and 100% fruiting branch removal at the R16 stage had a
similar effect on the cotton top branch growth as the same treatments at the R12 stage, except that the difference
between all treatments were more significant at the R16 stage. Compared to the control, cotton weights in the midsection branches from five plants in the 100% removal treatment was reduced from 219.0 g to 7.1 g. At the same
time, boll number and boll weight of the top section in the 100% removal treatment were two times larger than the
control treatment. As a result, the reduction in the total boll weight was only 89.2g. This indicates some degree of
compensation among cotton plants in response to fruiting branch removal from the mid-section branches.
References
NCIS, 1997. Cotton loss instructions. National Crop Insurance Services, Inc.
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Yield (lbs/A)
6000
5000
Yield = -8.8 * FBR + 5029.8
4000
2
R = 0.99
3000
0
20
40
60
80
100
80
100
80
100
Fruiting branch removal (%)
Yield (lbs/A)
6000
5000
Yield = -9.1 * FBR + 5269.6
4000
R2 = 0.96
3000
0
20
40
60
Fruiting branch removal (%)
Yield (lbs/A)
6000
5000
Yield = -10.4 * FBR + 5237.4
4000
2
R = 0.92
3000
0
20
40
60
Fruiting branch removal (%)
Fig 1. Relationship of fruiting branch removal (FBR) and cotton yield at different growth stage (From top: stage R8,
stage R12, and stage R16).
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Table 3. Plant mapping results before cotton harvest *
Lower main stem section
Mid-section fruiting
Fruiting
with vegetative branches
branches
branch
Stage
removal
Open boll Seed cotton
Open boll
Seed cotton
(%)
#
weight (g)
#
weight (g)
0
6.8 a
22.5 a
29.3 a
128.2 a
25
5.5 a
17.2 a
25.8 a
103.4 a
R8
50
8.5 a
27.3 a
14.3 b
58.6 b
75
4.5 a
17.7 a
4.5 c
18.6 c
100
6.5 a
23.9 a
1.5 c
4.1 c
Top main stem section with branches grown after
treatment
Open
Unopened Seed cotton
Boll/node
boll #
boll #
weight (g)
ratio
52.2 a
16.1 a
198.0 a
0.69 a
51.3 a
14.0 a
185.8 a
0.79 a
49.4 a
13.0 a
183.9 a
0.66 a
52.8 a
10.8 a
206.3 a
0.70 a
47.8 a
14.3 a
182.8 a
0.65 a
Total seed
cotton weight
from five
plants (g)
348.8 a
306.4 ab
269.7 bc
242.6 cd
210.8 d
R12
0
25
50
75
100
5.8 a
10.3 a
5.8 a
5.3 a
5.3 a
19.3 a
37.7 a
19.7 a
16.6 a
21.6 a
44.8 a
39.6 a
28.3 b
6.5 c
2.5 c
175.3 a
162.7 a
118.7 b
26.6 c
8.1 c
22.5 b
30.5 b
54.3 a
53.3 a
63.0 a
20.3 ab
24.2 a
14.0 bc
13.8 bc
8.5 c
87.0 b
102.3 b
193.2 a
212.1 a
244.2 a
0.45 b
0.63 b
0.94 ab
1.40 a
1.12 ab
281.7 ab
302.7 ab
331.7 a
255.3 b
273.9 ab
R16
0
25
50
75
100
6.5 ab
4.3 ab
5.6 ab
10.1 a
3.1 b
18.3 ab
14.9 ab
19.4 ab
32.5 a
10.8 b
58.0 a
48.0 a
34.3 b
15.8 c
2.0 d
219.0 a
198.1 a
139.7 b
55.9 c
7.1 d
16.3 c
24.5 c
37.5 b
41.8 ab
49.0 a
16.8 a
12.5 ab
14.3 ab
15.0 ab
6.5 b
56.7 c
90.7 c
137.2 b
148.6 ab
187.0 a
0.39 d
0.68 c
0.89 bc
0.99 ab
1.25 a
294.1 ab
303.7 a
296.3 ab
236.9 bc
204.9 c
* Boll number and boll weight are the total of five plants. The data followed by the different letters in the same column of each growth stage category indicate
significant difference at p=0.05.
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