Cold Soil Water and Germination  04/16/18 4:37:56 PM

Winter Annual Growth Update—As seen above, Winter annual weed pressure continues to develop and begin the process of stem elongation (bolting).  If burndown/pre-emergence herbicides applications have yet to be made on these types of situations, you may question whether or not the addition of a 2,4-D/Banvel combination is worth your investment.   The further along Henbit, Sheperd’s purse, and Marestail get in vegetative/reproductive growth, the harder they are to control with any herbicide treatment and tillage may be the best option for control.   The level of control, even with these applications being already applied, is likely being influenced extended cold temperatures.    
 LET”S REVIEW--Here is the on-going story on corn planting dates and maturities we are using in this area. Most 108-115 relative maturity hybrids will soon be entering the (Optimal Calendar Window) to be planted and maximize yield potential.  Remember, it generally takes about 125 growing degree units (GDU’S) for corn to emerge from the soil.  GDU’S are calculated from the soil temperature, not the air.  Here is where we are currently at according to the High Plains Regional Climate Center at Nebraska City.

Date Max Temperature Min Temperature Growing Degree Days (Base 50) Since 2018-04-01
Accumulation Missing Days
2018-04-10 37 25 0 0 1
2018-04-11 64 25 0 0 1
2018-04-12 74 39 7 7 1
2018-04-13 75 41 8 15 1
2018-04-14 87 38 13 28 1
2018-04-15 38 23 0 28 1
2018-04-16 31 22 0 28 1
Currently we have 28 GDU’s since April 1st.  No surprise given the current and past weeks soil temperatures—See below
Growing Degree Days for Corn Growth Stages for a 110 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
Early planted corn planted in cold soil conditions have inherent risks from a number of things……This early in the season, we talk about Water Imbibitional Chilling a lot.  (Cold soil water absorption into the corn kernel) and the importance of getting the kernel’s metabolic processes off to a good start with a warmer soil water temperature.  Cold water absorption into the kernel can, not always, cause some detrimental metabolic and structural affects to the developing seedling.    When the soil is this cold, it is doubtful that any large amounts of soil water can be absorbed into the kernel to start these processes and if it is occurring it is being done at a very slow pace.    It is believed that water absorption does not actively start until the soil temperature is consistently above 40-45.  The quick answer to this topic is—wait until the soil is warm enough to plant—consistently above 45 degrees.   BUT WAIT—For whatever reason, planting is delayed past my optimal planting date and the soil temperature is still cold---which is the bigger risk to my yield potential?  There are no definite answers to these questions because no-one can accurately predict the weather conditions for the next 2 weeks which is prime corn planting time.   Yes, there can be less than desirable effects on germination of corn planted early.  We have no replicated studies/data to back up this statement, but our experience shows that corn planted earlier in your “optimal corn calendar planting window” usually is some of your better yielding corn, regardless of if it was affected by absorbing cold soil water and/or the maturity of the hybrid.  Corn hybrids today do vary in their ability to germinate and uniformly emerge in these environments.  They all have improved even from 5 years ago, their ability to handle colder, wetter soils.  Early planted corn normally gets through the plant’s high soil moisture demands of the season prior to the hottest and driest time of the year.   
When you begin to plant your first fields, to minimize any “yo-yo” soil temperature swings, plant the corn deeper—2.5-3” deep to minimize the wild temperature affects until the soil decides to warm up for good.   

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