Soybean Yield
Loss Due To Hail Damage |
| Hail can cause huge yield losses to
soybean fields. But as a grower it is in your best interest to be able to evaluate
your field after a hail storm and decide if the field indeed needs to be replanted.
Every little bit counts in terms of your bottom line and unnecessarily replanting soybean
fields is a waste of time and money. This information is intended for a guideline
only. Whenever in doubt it is always best to consult an Agronomist or Hail Adjuster
before replanting. |
First of all, remember that it is best to evaluate hail damage 7-10 days after the
damage occurred. This is hard to do when you want to get back into the field and
replant as soon as possible. This will allow you to see any regrowth that is
occurring.
 |
To be able to inspect soybean plants
properly it is important to know the parts of a soybean plant. Starting at
the bottom of the plant are the Lateral roots, these
intercept nutrients and take up water.
The stem or Hypocotyl translocates water and nutrients to the
rest of the plant.
The Cotyledons hold stored nutrients for the plant in its early
stages.
Above the Cotyledons are the Axillary buds and the Unifoliate
leaves. The plant will grow new branches from the Axillary buds.
The Growing point is where the main stem of the plant grows and
produces new tissue.
Finally, the Trifoliate leaves intercept sunlight for
photosynthesis which produces energy for the plant. |
When checking the plants for damage it is important to carefully inspect each
plant to see what kind of damage was inflicted by the hail. A plant cut off below
the cotyledons will not recover. Both cotyledons can be knocked off of the plant if
the growing point remains intact. Use the table below to help you decide which
plants will live and which ones will not.
| Condition |
Will
the plant survive? |
| Plant cut off below the cotyledons |
No |
| Plant missing one cotyledon |
Yes |
| Plant missing both cotyledons but growing point intact |
Yes |
| Plant cut off above unifoliolate leaves |
Yes |
| Plant with no remaining leaf tissue and shows no regrowth |
No |
| Plant lightly bruised on the stem |
Yes |
| Plant severely bruised and folds over |
No |
| After 7-10 days plant shows regrowth form axillary bud |
Yes |
Using these guidelines its time to head to the field. Bring a tape measure
along and measure out 10' of row. Start by checking each plant and count the ones
that are going to survive. You can lose up to half of the stand without losing much
yield. If you are in 30" rows and have a surviving stand of 5 plants per foot
you may not want to replant.
One other thing to remember is that you need to take into account the amount of
leaf area that was damaged. Plants that are damaged before flowering are not
significantly effected by loss of leaf area. If the plants are flowering
and some leaf area is damaged or missing you need to take that into account when figuring
yield loss.
| Percent held loss of indeterminate soybean varieties as affected by degree
of defoliation. |
| Growth Defoliation (% leaf area
destroyed) |
| Stage |
10 |
20 |
30 |
40 |
50 |
60 |
70 |
80 |
90 |
100 |
| R1-2 |
0 |
2 |
3 |
5 |
6 |
7 |
9 |
12 |
16 |
23 |
| R3 |
2 |
3 |
4 |
6 |
8 |
11 |
14 |
18 |
24 |
33 |
| R4 |
3 |
5 |
7 |
9 |
12 |
16 |
22 |
30 |
39 |
56 |
| R5 |
4 |
7 |
10 |
13 |
17 |
23 |
31 |
43 |
58 |
75 |
| R6 |
1 |
6 |
9 |
11 |
14 |
18 |
23 |
31 |
41 |
53 |
| Data from University of Nebraska NebGuide G85-762 |
Soybeans usually flower around the first week in July so you probably won't use
this chart in deciding to replant but it gives you an idea of yield loss from hail later
in the season.
Use the Planting Rate Recommendation
Chart to figure your surviving population. Find the row spacing that you use and
go down to "Feet Of Row/Acre". Multiply your surviving stand
(plants/foot) by the Feet Of Row/Acre number.
Sample for 30" rows. 5 plants/foot X 17,428
feet of row/acre = 87,120 plants/acre
You have 87,120 plants/acre, how does that effect yield?
| Effect
Of Population Reduction On Yield |
| Plants/Acre |
Percent of optimum |
Percent yield produced |
| 157,000 |
100% |
100% |
| 118,000 |
75% |
98% |
| 78,000 |
50% |
90% |
| 39,000 |
25% |
75% |
| Data from Minnesota Extension Field Book |
Now its time to check the calendar. If it is June 4 and you only have 40,000
plants/acre, its time to replant. If it is June 9 or later, you might not want to
plant. Refer to the table below. Even though 40,000 plants/acre is a thin stand, you could
end up with 75% of normal yield. If you replant on June 9 you also might get 75% of
normal yield. However, you would also have extra costs involved.
| Planting Date Effect On Soybean Yield |
|
| Planting Date |
Yield (%) |
| May |
1 |
|
100 |
| |
5 |
|
98 |
| |
10 |
|
97 |
| |
15 |
|
96 |
| |
20 |
|
92 |
| |
25 |
|
89 |
| |
30 |
|
85 |
| June |
4 |
|
80 |
| |
9 |
|
75 |
| |
14 |
|
69 |
Latham Seed Company
131 180th Street
Alexander, Iowa 50420
1-800-798-3258
Fax:
(641) 692-3258