We started the week on the rainy and windy side and were able to string together a few days of highs in the mid to upper 60°F into the mid 70°F’s. These warmer temperatures coupled with some drying winds allowed Farmers to work fields and also to start planting corn midweek.
Soil temperatures have fluctuated from 38°F- 80°F at the 2” depth and 41°F- 70°F at the 4” depth, with soil temperatures at the 8” depth ranging 43°F -60°F.
| Depth | Soil Temperature | Average |
| 2″ | 38°F-80°F | 59°F |
| 4″ | 41°F-70°F | 56°F |
| 8″ | 43°F-60°F | 52°F |
Soil temperatures in the 20” are in the 40°F’s to 50°F and at the 40” depth are in the upper 30°F’s to low 40°F ‘s range. With that being said I have heard from several drainage contractors who are encountering spotty frost in the 4’-5’ depth. (Soil temperature information is both from Central Valley data as well as data from U of M SROC in Waseca.)
Corn plant development is from germination (10-20 Growing Degree Units or GDU’s) for seed planted later in the week, to radical root emergence (30-40 GDU’s) for corn that was planted on Wednesday or before.
| Planting Date | GDU’S | Plant Stage |
| 15-Apr | 44 | Radicle Root Emergence |
We picked up 44 GDU’s from April 15th to April 18th which is 30 GDU’s more than the 30 year average of 14 GDU’s during this time frame. We accumulated 11 GDU’s per day during this time frame which is 7.25 GDU’s more than the 30 year average of 3.75 GDU’s per day.
| Dates | 30 Year GDU Average/Day | 2015 GDU/Day | Difference/Day |
| April 15-18 | 3.75 | 11 | 7.25 |
The seed pictured below and on the left is a seed that has germinated and has the radicle root just emerging from the seed, which is currently the furthest we are along in the corn plant development. With the seed pictured below and on the right from the 2014 growing season showing the Coleoptile starting its journey towards the soil with the radicle root extending down and the seminal roots extending out.
The radicle always emerges first from the tip of the embryo and will orient itself so it is growing down regardless of where the embryo of the seed is pointed. The ability of the plant to sense gravity is called Gravitropism. The coleoptile (shoot or spike) will be next to emerge from the embryo and the effects of Gravitropism will make it grow towards the soil surface.
For the process of Germination to start the seed must first take in or “Imbibe” 30% of its weight in water. After the plant has taken in the water, the radicle root will start to emerge, radicle root emergence normally takes place at 30-40 GDU’s, and as stated previously the radicle is the first to emerge from the embryo (seed). Following the radicle emergence the coleoptile or shoot will emerge from the embryo. It normally takes 50-60 GDU’s for the coleoptile to emerge.
Starting between 60-70 GDU’s, the seminal roots will start to emerge from the seed and almost immediately start taking in water and nutrients for the plant to continue to grow. The seminal root system and the radicle will anchor the plant and act as the main root system for the plant until VE (shoot or spike emergence) and will continue to grow until V3 (three collared corn) when the nodal root system will be the dominate anchor and root feeding portion of the plant.
The time it takes from the time the seed is planted and absorbs 30% of its weight in water (germination) to VE (shoot or spike emergence) is 5 days to 3 weeks. (The longest time I have seen a planted seed wait to germinate is 6 ½ weeks. It was plowed alfalfa ground that was planted mid-May and didn’t come up until July 4.) From germination to emergence it will take 90-150 GDU’s, with the difference being that some hybrids emerge faster than others.
| Plant / Leaf Stage | Growth Stage | GDU’s |
| Germination | 10 to 20 | |
| Radicle Root Emergence | 30 to 40 | |
| Coleoptile Emergence Seed | 50 to 60 | |
| Seminal Root Emergence | 60 to 70 | |
| Coleoptile Emergence Soil | VE | 100 to 150 |
Planting Progress-Corn planting progress is 15-20% complete with some farmers having everything planted and others waiting for some warmer temperatures. We did have some peas and alfalfa getting planted during the week with some small grain being seeded the week previous.
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