Replant Considerations, Early Corn Development  05/17/17 8:18:59 AM

Mynard Plot Tour—The process will be much as it has been in the previous years.  We have the tours RAIN OR SHINE—If raining--we will gather in our seed building—If the sun is shining--at our plot on the West side of Mynard Nebraska—1 mile South of our plant—1/4 west on Mynard Road OR 1-1/4 mile West of HWY 75 on Mynard Road—South Side of the Road.   The tours will last no longer than 1.5 hours and address any current agronomic issues as well as allow the attendees to monitor developmental progress of Asgrow and Dekalb genetics throughout the growing season.  View the current genetic lineup as well as population trials, planting speed trials, fungicide and insecticide seed treatment comparisons, biological seed treatments, the affects of starter fertilizers and more!   
2017 WBI Summer Dates
Date                            Location                      Time                            Guest Speakers/Topic
Wednesday  May 31th Mynard Plot                9-10:30 a.m.                Tim Mundorf_Midwest Labs—Post-emergence
Fertility Observations
Post-emergence Weed Control Options, Planting Re-Cap
Tuesday June 13th       Mynard Plot                9-10:30 a.m.   
Tuesday June 27th       Mynard Plot                9-10:30 a.m.               
Tuesday July 11th        Mynard Plot                9-10:30 a.m.
Tuesday July 25th        Mynard Plot                9-10:30 a.m.
August 2nd-6th              Springfield                                                      Sarpy Co. Fair
Tuesday August 8th     Mynard Plot                9-10:30 a.m.
August 9th-12th            Cass Co. Fairgrounds                                      Cass Co. Fair
Tuesday August 22nd  Mynard Plot                9-10:30 a.m.                Corn Breeder/Corn Lineup
                                                                                                            Soybean Breeder/Soybean Lineup
Tuesday August 29th   Cass Co. Fairgrounds                                      Late Summer Clinic\
After last night (Tuesday 5/16) and with the forecast for additional rain, there are some chances of more fields needing to be considered for re-plant.  In previous discussions, we have talked about how much stand loss warrants a re-plant consideration given the calendar date. 
Now is the time when corn producers should be out in their fields assessing stands to determine if any replanting is necessary.  Replant decisions are never easy and are ultimately determined by which decision provides the greatest net income.  Each field will have its own set of circumstances that will influence the decision.  Remaining stand levels and likely replant dates will be the deciding factors.
Young corn plants (<V5 stage of development) can tolerate significant leaf loss or damage due to hail or insects and yet remain viable and produce new leaves. This is because the growing point remains below the soil surface until approximately the V5-V6 stage.  Flooded or unemerged areas in fields may cause stand losses too, because small corn plants are not tolerant of flooding and may succumb to flooding in one to three days. Warm, sunny days help accelerate these losses.
Attempts to "thicken" a stand by planting directly into an existing stand generally result in complications. Larger plants will compete strongly for space, water, and nutrients and complicate the establishment of replanted corn.  So it is always recommended when replanting, destroy the original stand.
Switching to an earlier maturity can be done at any time but loss of yield potential can occur if done prematurely. Hybrid and planting date studies show an advantage to switching to a hybrid that is roughly five days earlier in maturity if planting is delayed beyond May 25, and another five days earlier if delayed beyond June 1. Switching to soybeans generally will not be an economical choice unless planting is delayed beyond June 10.
First, check your stand by counting the number of live plants per linear foot of row based on various row widths
15” row – 34’10”, 20” row – 26’1”, 30” row – 17’5”, 36” row – 14’6”

Survival of flooded plants and lingering effects

Crop Condition Potential for survival and problems      

Small soybeans Not completely submerged Will survive a "long time" in standing water      
Small soybeans Completely submerged Will survive several days to a week if air temperature is below 90oF.      
Soybeans 1 inch of water on surface at V4 and R2 for 2, 4, 7, and 14 days. (Univ. of Arkansas). Variety differences evident (all were determinates); R2 flooding resulted in greater losses that at V4. Yields reduced between 0.8 and 1.9 bu/acre per day of flooding at V4 and from 1.5 to 2.3 bu/acre per day of flooding at R2.      
Small soybeans Saturated soils Seed and seedling diseases like Phytophthora and Pythium may become a problem      
Corn Germinating Genetic differences among inbreds (and we assume hybrids) exist for responses to flooding      
Corn prior to 6th leaf stage Underwater (6 inches of water on surface); air temperature less than 77oF. Will survive for four days. Longer flooding results in lower yields especially at lower N levels.      
Corn prior to 6th leaf stage Underwater (6 inches of water on surface); air temperature greater than 77oF. May not survive more than 24 hours      
Corn prior to 6th leaf stage Saturated, cold soils, flooding Seed rots, seedling blights, various other pathogens, crazy top      

Compiled from various sources by Roger Elmore, Tamra Jackson, Loren Giesler, and Lori Abendroth, UNL Extension specialists.       
What about the cost of this consideration?
Here is the current programs offered from Asgrow and DeKalb
Asgrow® Brand Seed
First planted seed treated with Acceleron Seed Applied  Solutions ELITE or STANDARD
100% off the Suggested Retail Price on Replant Units
First planted seed treated with Acceleron Seed Applied Solutions BASIC or a competitive base treatment
75% off the Suggested Retail Price on Replant Units
DEKALB Brand Seed
75% off the Suggested Retail Price on Replant Units
Once corn has emerged and is between the 2-4 leaf stage of development, it has now accumulated approximately 200 (GDD).  The seminal and nodal roots have finally developed and now that corn has emerged the nodal roots will continue to further develop with every additional node of plant (on average 7-10 nodes total).  The nodal root system is the major supplier of water and nutrients to the plant by V6 (6 leaf corn).   This is important since the developing plant uses the kernel until about V6 for much of its nutritional requirements.  Once the nodal roots develop, then the plant roots into fertility zones for additional nutrient needs.   The lack of nodal root development is part of the reason why the corn had pale green/yellow color the past few weeks—along with cold weather, slow growth, wet conditions, insect feeding, etc.  The corn will now grow quickly and unfurl one leaf about every 3 days or every additional 65 GDD’s. 
Growing Degree Days for Corn Growth Stages for a 108 day Hybrid
Stage                                       GDD (Growing Degree Days--base 50)          
Emergence                                                                  120
2 leaf-V2                                                                     200
V6—tassel initiation                                                   475
V10                                                                              740
V14                                                                              1000
VT (tassel emergence)                                                1150
Silking                                                                          1400
R4 (Kernel dough stage)                                             1925
R5 (Kernel dent stage)                                                2450
R6 (physiological maturity—black layer)                   2700
*courtesy of Hollinger (University of Nebraska)
Un-even emerging corn occurs every year and this year is no different..  As with many problems there is probably no single easy answer to this one. There are several factors that could cause uneven growth. For many fields, the problem could be attributed to more than one. The uneven growth can be attributed to a deficiency of one or more essential nutrients. Deficiencies of potassium, sulfur, and zinc have been noted in parts of some fields. Research trials and experience have taught us that there can be a wide range in relative levels of plant nutrients in soils. For example, an analysis of a composite soil sample may show that the potassium value is in the medium or high range. Yet, there may be areas having a low soil test for K in the field. These areas having the low test, without the adequate application of K, may be the cause for stunted corn and subsequent uneven growth. The same explanation can apply to zinc. The soil test values for zinc may vary more than soil test values for potassium.
Nutrient deficiencies, do not explain all stunted corn situations. Observations from the fields where stunted corn has been a problem include: 1) high fertility, 2) a nice loose seedbed at planting, 3) one pass with a field cultivator for secondary tillage, 4) no problems in recently manured fields, and 5) taller corn in wheel tracks associated with the secondary tillage operation.
So, why should corn be taller in parts of the field usually associated with some compaction (wheel tracks, for example)? A reasonable, but not proven, explanation combines our knowledge of root growth and nutrient uptake.
Plant nutrients are known to move to plant roots by the three processes of: 1) mass flow, 2) diffusion, and 3) root interception. Nitrogen as nitrate N (NO3-N) moves to roots by mass flow as water is absorbed from the soil by plant roots. Phosphorus as (H2PO4- or HPO4=) and K+ reach the root by diffusion and root interception. In the diffusion process, the nutrient moves from an area of higher concentration (the soil particle) to an area of lower concentration (the root). Root interception is the process whereby the root comes in contact with the nutrient as it grows. Therefore, N can move over longer distance compared to P and K.
Loose soils, at planting result in having pore space (the open area between soil particles) with a high percentage of air and less water.  There was less air space under wheel tracks or where some other form of compaction existed. As roots grew into the pore spaces in these more compacted areas, there was more space occupied by water. Thus it was easier for young roots and young corn plants to get needed nutrients. As a result, plants in slightly compacted areas are showing up with better earlier growth.
Corn Plant Development: V3 to V12 stages
(Vn (vegetative stages) based on visible leaf collars)
  • 3 visible leaf collars
  • Occurs in the range of 300-375 GDU’s
  • All leaves and ear shoots that the plant will produce are being initiated (forming), plus the tassel.
  • Photosynthesis is now the energy source, replacing the seed as the food source
  • Growing point is below the soil surface, injury occurring to the leaves (i.e. hail, frost, insect feeding) will have minimal, if any, effect on final yield
  • Growth of the seminal root system is virtually complete as the nodal root system begins to function as the primary supplier of water and nutrients
  • Foliar feeding insects such as black or dingy cutworm should be monitored
  • Growing point is at, or near, the soil surface
  • Stalk elongation begins, and is entering a period of rapid growth
  • Yield components are being set in terms of the potential number of kernel rows
  • Tillers may begin forming
  • The leaves, shoots, and tassel have all been initiated and are located in the growing point
  • Injury to the leaves and/or stalk beginning to have greater impact on reducing yield potential, and if severe enough could result in plant death
  • Latest growth stage for some post-emergent herbicides to be applied, including for example, those with ALS mode of action.
  • Continue monitoring for cutworm injury
  • Period of rapid growth as new “V” stage is occurring about every 3 days
  • All leaves have been formed but most are still hidden in the whorl
  • Plant begins to lose lower leaves
  • Ear shoots visible behind leaf sheaths
  • Unrestricted root growth should measure about 18” deep x 15” wide, should have side-dress applications completed by now to avoid root pruning
  • Moisture and nutrient demands increasing rapidly
  • Fields should be scouted for 1st generation European corn borer, IF not planted to Corn Borer Resistant Hybrids.
  • Determination of the number of kernels per row is in progress and will continue through about V17. (Remember, the number of kernels rows was established by V6)
  • Rapid stalk growth is occurring through internode elongation
  • New “V” stages occur every 2-3 days
  • Nodal root system expanding quickly
  • Cumulative nutrient uptake by this stage has reached 30%, 20%, and 30% of the total N, P, and K, respectively which the plant will ultimately use.
  • Water use may reach about 0.20” per day
  • Lack of nutrients, moisture stress, or crop injury due to weather events, insect or mechanical damage can seriously reduce the potential number of kernels
Monitoring for root feeding insects such as corn rootworm should be in progress
John W. McNamara
Wiles Bros. Inc.
606 Wiles Road
Plattsmouth NE. 68048
(402) 298-8550--Office
(402) 499-3870--Cell
(402) 298-7174--Fax
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