News Story

Answer Plot reminder tomorrow in Truman, Rainfall amounts and Growth Stages by GDU

Just a reminder of the Answer Plot tomorrow June 6th in Truman. Registration starts at 9:30AM with the Answer Plot at 10:00AM. Truman Answer Plot is 3 Miles North of Truman on MN Highway 15


This should be an interesting Answer Plot session in that the Corn color started the week  in a “Ghostbusters Yellow Green Slime” to a more acceptable shade of Green, and put on a leaf or two of growth. (Ghostbusters reference courtesy of Chad Wiersma Agronomist in Owatonna).


We did have spotty showers in the area with varying rainfall amounts from 0-2.2”. There were stronger winds and hail in the Albert Lea area that stripped some leaves on plants. Hail was also reported in the Otisco area, and I also believe in the Blue Earth and Guckeen area.




Albert Lea

.5 and Wind


1.1" and Hail







New Richland


Clarks Grove


West Concord


Blue Earth






St. Clair









I have been receiving some questions regarding the amount of Growing Degree Units (GDU’s) by growth stage and anticipated GDU/day. The table below gives an estimate as to how many GDU’s it will take to get from Germination to V6:


Plant / Leaf Stage

Growth Stage



10 to 20

Radicle Root Emergence

30 to 40

Coleoptile Emergence Seed

50 to 60

Seminal Root Emergence

60 to 70

Coleoptile Emergence Soil


100 to 150

First collar on emerged leaf


150 to 190

Collar on second Leaf


190 to 220

Collar on third leaf


280 to 310

Collar on fourth leaf


370 to 400

Collar on fifth leaf


450 to 470

Collar on Sixth leaf


530 to 550


To put on a new leaf from Emergence to V6 it takes approximately 85-90 GDU’s. The normal GDU accumulation per day in late May to early June is about 14.75 GDU/day. Another way to look at this is during late May or early June we will normally put a leaf on every 5-6 days.


90 GDU's/Leaf   ÷   14.75 GDU's/Day =   6.10 Days/Leaf


We will soon be approaching V5-V6 growth stage, once a corn plant reaches the V5-V6 growth stage:


  • the growing point is out of the ground
  • the plant is determining the number rows around the cob it will have
  •  the nodal root system has become the major root system in the plant
  •  tillers or sucker plants are starting to form
  •  the plant is starting its above ground growth spurt, and with good growing conditions the plant may double its height in a 10-14 day timeframe.

To use a parental analogy, your corn plant has entered its teenage years.


At the V5-V6 growth stage the growing point is about 1-1½” above the ground. Plants that break off at or near the ground at this stage due to hail, sandblasting, mechanical damage (cultivator blight) or other means, will die.


While the growing point is coming out of the ground, the number of rows around the cob is being determined. The row count around the cob will always be an even number with 14 to 18 rows around the cob being common in our area. If the plant is lacking water or nutrients due to a deficiency, disease or lack of weed control, at this stage the cob will drop rows. If a plant is at 18 rows around and drops to 16, you have lost 13% of your potential yield for that ear.


200 bu/acre  *   13%   =   26 bu/acre yield reduction



At the V5-V6 growth stage the nodal root system is now the major root system of the plant, with roots being 3-4” or more across and 6-10” deep. If your plants were a lighter shade of green prior to V5-V6 they should start to green up once you root system finds the nutrients in the soil around the plant. If you are planning on sidedressing Nitrogen or putting on other nutrients now is a critical time to get it done. Root growth from now until Tassel emergence will be dramatic.