PROFITABLE TASKS TO DO THE FIRST FEW HOURS OR DAY OF PLANTING
Corn has been planted in a few areas across the Corn Belt, so this message may be on the late side for those who have started. With that being said, if you haven’t started planting yet or even if you have a few acres in the ground, take some time to step out of the tractor cab, get behind the planter and start checking how good of a job that planter is doing. You only get so many chances in a farming career to put a crop in the ground, so we need to do it correctly. What you get right or, in some cases wrong, in the spring with the planter, will either increase or decrease yield.
- Depth: Is the depth where you want it to be? Is it at a consistent depth from seed to seed as well as row to row? Most corn planting recommendations are 1.5 to 2 inches in depth. I prefer to be closer to the 2-inch depth, and this is after the soil has been compressed over the row with a foot or hand print which lessens the air above and around the seed. This mimics what the seed depth would be after a rain or a few days of a breeze and the soil settling.
- Seed Spacing: Today’s monitors do an outstanding job of measuring and recording spacing. However, the phrase “Trust but Verify” or ground truthing should be done to make sure the monitor is accurately measuring seed placement. Remove soil on two to four feet of row and measuring the distance between seeds to see if it is at the distance you want.
- Seed Shutoffs: If you are utilizing a GPS monitor that has shut offs, check to see how close they are engaging as you come off or approach the headlands/end rows. Properly calibrated seed shutoffs reduce overplanting in the headland as well as engaging them at the proper distance in the field so you don’t have a gap coming into or off the headland. Properly calibrated seed shutoffs may help reduce seed cost from overplanting, but may also increase yield due to proper seed spacing. Properly calibrated seed shutoffs may also decrease some of the spirited discussions at local gathering places.
- Seed Placement: Is the seed placed in the bottom of the seed furrow, in a consistent manner? If it is not, it may not be accessing nutrients or crop protection products such as fungicide or insecticide as efficiently and not receiving their full intended benefit.
- Soil Firming: Is the soil firmed around the seed? Closing wheel type and down pressure can make a big difference. Soil firmed around the seed will provide more consistent water imbibition and subsequent germination and emergence.
- Check every row on the planter -- not every setting is the same on each row unit all the time.
- Now check your settings and depth in a different part of the field or soil type and adjust those settings to maximize planter performance in varying soil types.
By taking time in the first few hours or first day of planter activity in the field, to tweak and fine-tune your planter to perform at its optimum, provides you the best chance for success for your crop.
CORN GERMINATION AND EMERGENCE
In the last week to 10 days, some areas have had favorable weather that has allowed farmers to plant corn. A corn seed has a few processes that it needs to accomplish prior to soil emergence. One of the processes is germination which takes place when a seed takes in or imbibes roughly 30 percent of its weight in water. During this process, the seed will swell slightly. In most instances, germination or seed swelling takes roughly 10 to 20 Growing Degree Units (GDU’s). (This is shown below on the left.)
Once germination has initiated, the radicle root will start to emerge. It normally takes 30 to 40 GDU’s for the radicle root to emerge. (This is shown in the photo above and on the right). The radical always emerges from the tip of the embryo and will orient itself due to gravity 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 or Geotropism.
The next process to take place is for the coleoptile to emerge from the seed (as shown below and on the left). It normally takes 50 to 60 GDU’s for the coleoptile to emerge from the seed. Starting between 60 to 70 GDU’s, the seminal root system 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/spike coleoptile emergence) and will continue to grow until V3 (three collared corn).
It normally takes 100 to 150 GDU’s for the coleoptile to emerge (VE) from the soil surface, (as shown above and on the right) with weather conditions and genetic makeup being factors affecting this process. At VE, the coleoptile will cease to elongate and the foliage that follows will be the embryonic leaves.
Plant / Leaf 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
COLD TEMPERATURES AND POSSIBLE FROST DAMAGE
Warmer than usual spring temperatures and drier field conditions resulted in more early planted fields this year. Most of the early planted crops are either emerged or starting to emerge, just in time for a cold snap. The weather prediction for this week shows several days where nighttime temperatures drop below freezing across a wide geography. This cold snap could place these early planted crops at risk for frost injury.
Most corn and soybean plants can withstand air temperatures down to 28°F for a few hours before damage occurs. In most instances, it is repeated exposure to low temperatures that will kill a plant rather than just one exposure for a few hours. Warmer soil temperatures at the surface can help protect the plant by transferring heat from the soil to the air. Soil temperatures around our area have been cooling off over the past week. Below is a map from the National Weather Service (https://www.weather.gov/ncrfc/LMI_SoilTemperatureDepthMaps) showing recent soil temperature readings for the combined 2- and 4-inch depths. This is a very good resource to keep an eye on what soil temperature trends are doing in your area.
Certain areas are more likely to see frost damage than others. These areas include:
- Low-lying areas which allow the cold, dense air to settle.
- Fields with residue cover or field edges. The residue slows the springtime warm up and reduces the amount of heat that can be transferred from the soil to the air.
- Dry soil, usually tilled, tends to have more air space around soil particles which allows temperatures to fluctuate more rapidly.
- Sandy (course textured) and peat soils have more air space which allows cooler temperatures to penetrate deeper in the soil.
The impact of the freezing temperatures will vary depending on several factors including the crop and growth stage of the crop.
The growing point of the corn plant remains below ground until the V5 to V6 growth stage. Frost before the V5-V6 growth stage would have to hit ¾ of an inch deep to reach the growing point. Symptoms of frost damage on corn are discolored and water-soaked leaves which dry and turn brown. It is best to wait 3 to 5 days after the freezing event to assess the stand so new growth has time to appear. If new growth is not appearing after 5 days, dig up the plant and split the stem to examine the growing point. A healthy growing point will be firm and white or yellow in color. If the growing point is damaged it will be water-soaked or brown or dark yellow in color.
In soybeans, the growing point is above ground once the plant is emerged from the soil. Soybeans at the cotyledon stage are more tolerant to freezing temperatures than older soybeans or even corn leaves because of the thick tissue that makes up the cotyledons. Frost injury symptoms will appear as water-soaked lesions on the cotyledons, leaves or hypocotyl (below the cotyledons and above the ground) that will turn brown. When assessing frost damage in soybeans it is best to wait about 5 days for new growth to appear. Check for new growth at the main growing point or the axillary buds at the base of the cotyledons.
Cold temperatures can affect both established and new seedings of alfalfa. As most alfalfa producers may have previously experienced, frost can nip some leaves on an established stand. When temperatures are below 26°F for a few hours, stems may be affected. If this occurs, the established plants will have regrowth coming from the crown buds at the base of the plant. To better assess the damage, wait 3 to 5 days to determine the amount of wilted or blackened leaves and the amount of regrowth.
New seeding alfalfa, much like an established stand can handle cooler temperatures of about 26°F. However, four hours or more at these temperatures can kill these seedlings. The cold tolerance in new seedlings declines rapidly when the plant reaches the second trifoliate leaf stage (two fully developed trifoliate leaves). Once these seedlings develop a more robust crown and root system, they will again be more cold/frost tolerant. Similar to assessing an establish stand, it is best to wait 3 to 5 days to evaluate the seedling stand.