Replanting Options and Considerations

Replanting Options and Considerations

June 6, 2008

With hail and wind damage and saturated or flooded fields in central to eastern Nebraska, some growers are considering whether replanting is warranted and, if it is, what cropping options would be best for the delayed planting date. In some areas producers haven't even been able to finish their initial planting due to wet field conditions.

Before making any decisions regarding replanting, contact your crop insurance agent about your insurance coverage and options. If you do replant, discuss whether you want or need to insure the second crop. (Also be sure to check the requirements of your operating loan and any farm program you're participating in.)

After insurance, consider these other factors:

 

  1. herbicides already applied to the field and their replanting restrictions;
  2. availability of the seed and traits you want; and
  3. approximately when you expect to be able to reenter the field and the remaining light and heat units in the season.

Soybeans are photoperiod sensitive and after June 21, day length will shorten, which may influence maturity selection. In some instances, replanting a field to a forage may be a good option. Next week's CropWatch will feature more information on replanting to a forage.

Replanting Soybean

Table 1. Relative yield potential for numerous planting dates and plant populations. (Source: Iowa State University Crop Production Web site, Determining yield potential for a problematic stand.)
 
Planting Date
 
April 20-May 5
May 13-19
May 26-June 1
June 10-16
June 24-28
Final Stand*
Relative Yield Potential (%)
28,000-32,000
100
99
90
68
52

24,000

94

93

85

64

49

20,000

81

80

73

55

42

16,000

74

73

67

50

38

12,000

68

67

61

46

35

Much soybean stand loss can occur within a few days under flooded conditions and warmer temperatures. (For information on how long a crop can remain under water, see the May 20, 2005 CropWatch for Flooded Fields and Crusted Soils: Determining When Replanting is Your Best Option.) This loss will increase if silt covers the leaves or buries whole seedlings. If hail breaks off the plants below the cotyledons, plants will not survive; however, if the leaves are merely tattered, full recovery is likely; however, injured plants have an increased risk of delayed problems from pathogens.

If there are more than two surviving plants per foot of row with25-inch rows or four per foot with 30-inch rows, replanting is not likely to increase yields. Full season varieties can be replanted until June 15. After June 15, consider planting a variety that's a step down from the maturity group you usually plant. For example, if you normally plant a Maturity Group 3 variety, after June 15 you may want to drop to a 2.5 Maturity Group.

With delayed planting of soybean, consider planting at a higher density. This should increase podding and thus, increase yield.

Also assess seed availability. Contact your seed dealer as soon as possible and expect to be a little flexible about what you'll use if your preferred varieties aren't available. UNL Foundation Seed still has quality seed in all its offerings, according to its director, Jeff Noels.

If soybean is to be planted into a field of damaged corn, check with your seed dealer regarding recommended herbicides that would work well under this circumstance. If the corn was not glyphosate-resistant, glyphosate is an option. Also, consider the residual effect that herbicides applied for corn will have on soybean.

Replanting Corn

Corn from germination to the 6-leaf stage can survive four days of flooding if air temperatures are below the high 70s. Corn should recover well from hail damage if younger than the 6-leaf stage. If the surviving stand is more than 60% of the intended stand, it is better not to replant in early June. Plants have the capacity to compensate for reduced stand, primarily by producing larger ears. Table 1 from Iowa State University Crop Production Web site relates final stand and planting date to relative yield potential. A surviving stand of 16,000 planted before May 5 is expected to provide a higher yield than replanting at 30,000 seeds/acre on June 12.

Pioneer also has addressed maturity time of varieties in relation to late planting. For the central Corn Belt the adjusted gross income is as good with 105-day maturities as with 100-day maturities, assuming grain drying is an option.

To Evaluate Corn Stand for Yield Potential

Yield
Plants

60 bu

8,400
80 bu
11,200
100 bu
14,000
120 bu
16,800
140 bu
19,600
160 bu
22,400
To evaluate stand you'll need to know:

With a 30-inch row width, there are 17,424 feet of row per acre
With a 36-inch row width, there are 14,520 feet of row per acre
To estimate the number of plants per acre, first count the number of plants in 1/1000 of an acre, using the following gauge:

17 feet 5 inches for 30-inch rows
14 feet 6 inches for 36-inch rows

And then multiple the number of plants by 1,000.

For example if you count 14 plants in 1,000th of an acre that would represent 14,000 plants per acre. Since it takes 140 0.50 lb ears to make a bushel (ear corn weighs 70 lbs/bu) 14,000 plants will equal 100 bushels of corn. See table, at right, for additional yields.

Table 2. Herbicides that can control existing corn standa
Herbicide Rate
Glyphosateb 11-22oz/ac (corn 6-20")
Assure IIa 5-8 oz/ac
Fusiladea 6 oz/ac
Fusiona 4-6 oz/ac
Poast Plusa 1.5 pints/ac
Selecta 4-6 oz/ac (corn 4-12")
aRefer to the label for specific details
bRoundup PowerMax™ used as an example  other glyphosate products may suggest different rates
 
Table 3. Rotational interval to plant soybean after corn, based on herbicide used in corn.a (Source: ISU Integrated Crop Management News.)
Herbicide
Rotational Interval
Any product with atrazine
Next year (regardless of rate)
Radius
6 months
Balance Pro
6 months
Guardsman Max
Next year
G-Max Lite
Next year
Bullet
Next year
Bicep II Magnum
Next year
Bicep Lite II Magnum
Next year
SureStart
Next year
Lumex
Next year
Lexar
Next year
Surpass
Next year
TopNotch
Next year
Hornet
10.5 months
Degree
Next year
Harness
Next year
Harness Xtra
Next year
Keystone
Next year
Camix
Next year
Callisto
10 months
Banvel
30 days
Basis
15 days
Laudis
8 months
aThis represents a partial list of products that restrict rotational crop option. Refer to the specific herbicide label to determine if the product used has a replant rotational restriction. If replanting, avoid planting when the soil is still wet to minimize compaction problems.

Nebraska Research on Corn Planting Dates

Research studies conducted at the Panhandle and West Central Research and Extension centers found that yields dropped precipitously when replanting corn after June 15, even with a shorter maturity hybrid. Producers who feed their own corn could go to a 100-day corn and get good plant production. The research indicated that pound for pound it produced as well as longer-term maturities that produced higher test weight ears. In research at the West Central site, yields dropped 25-30% between June 16 and June 23, even with shorter maturities.

 

Table 4. Agronomic performance of short season corn hybrids planted mid to late June and harvested December 10, 1992 at North Platte, Nebraska.
Hybrid
Days*
Yield, bu/ac
% Moisture
% Broken
wt/bu
Date planted
6/16
6/23
6/16
6/23
6/16
6/23
6/16
6/23
1
85
100
71
12.9
15.7
2
12
54.0
50.0
2
87
130
104
13.6
16.5
0
0
55.5
53.0
3
94
119
91
15.4
18.0
5
6
54.0
52.0
4
99
133
92
16.1
24.3
2
0
48.7
44.5
5
100
155
120
19.7
27.5
8
0
46.5
46.5
6
105
134
101
18.1
22.4
5
7
50.0
46.5
*Comparative relative maturity days

Other Replant Considerations

The information and tables (at right) are from an article by Professor Mike Owen in the ISU Integrated Crop Management News.

Listed below are a few of the options that are available to control existing corn stands and the rotational intervals for replanting to soybean. Please note that these are only an overview and the specific label should be checked prior to any replant decision.

Charles Wortmann
Extension Nutrient Management Specialist, Lincoln
Robert Klein
Extension Dryland Crops Specialist
West Central REC, North Platte