What once looked like an early, dry spring in the Upper Midwest has now quickly become a possible late, wet spring. For those still holding 2016 grain, the benefit might be better prices. I have heard from a couple of marketing advisors that any type of weather scare should cause a rally in the markets. However, a wet spring does not always help maximize bushel production. Remember the old adage, “Plant in the dust, your bins will bust….Plant in the mud, your crop’s a dud.” Soil conditions at planting are extremely critical for maximizing yield, and soil temperature is one variable to watch closely. Once the yield potential of a kernel of corn has been reduced, it can never be regained. Let’s look at why soil temperatures are so important.
Corn is a warm season crop. Optimum soil temperatures for germination and emergence are roughly 85o F. It is not practical to wait until then to start planting corn. In regards to soil temperature, two conditions should be true before planting corn.
The first condition is the soil temperature is at a minimum of 50o F. When soil temperatures are above 50o F, germination and emergence will be significantly more uniform across the field. If the soil temperature is below 50o F, the seed may not germinate. Germination and emergence will be significantly slower and uneven at lower temperatures which could lead to yield loss.
The second condition that should be true before planting corn is that soil temperatures should be expected to continue to rise above 50o F. As soon as the seed is planted it begins to imbibe water, and the kernel will naturally expand. It takes approximately 24 to 36 hours after planting for the seed to imbibe 30% of its weight in water which will initiate germination. During this timeframe, the cell tissues and membranes of the kernel need to remain elastic in order to remain intact. However, if the soil temperature drops below 50o F within 36 hours after planting, chilling injury can occur. Chilling injury takes place when the cell membranes lose their elasticity, become brittle and rupture as the kernel swells. It can have several negative consequences, all leading to yield loss.
- The kernel could fail to germinate.
- Germination could initiate, however, the radicle root or coleoptile could stop growing after germination.
- As the kernel swells and cell membranes rupture, the cell contents could ooze from the kernel.The cell contents can provide nourishment for a host of pathogens in the soil and the cracked seed coat could allow an entry point for those pathogens.
- The coleoptile could continue to grow, however the mesocotyl could become damaged or deformed and the corn plant will corkscrew and leaf out underground.
Last year I looked at a plot that had uneven emergence across several hybrids. As I dug seeds, I found some had corkscrewed and leafed out underground. I found others where the radicle root was healthy, but the coleoptile only emerged ¼ of an inch from the kernel and stopped. This plot was planted on April 26th. On the morning of April 27th, a cold front moved through that brought almost an inch of rain. The rest of the field surrounding the plot had been planted on April 25th, only one day before the plot was planted. The corn planted within 36 hours of the cold rain experienced chilling injury while the rest of the field did not. On average, the plot had an emerged stand that was 4,000 plants per acre less than the emerged stand in the surrounding field.
There are conflicting sources on how low soil temperatures need to be for chilling injury to occur. We do know that seed is at risk when soil temperatures are anywhere between 40o F and 50o F. The colder the temperatures are, the greater the seed is at risk. Since it takes 24 to 36 hours for the seed to imbibe water, planting is not recommended 24 to 36 hours ahead of forecasted cold and wet weather conditions. If you experience a cold rain within 24 hours after planting, your seed will take a “cold drink” of water and your chances of experiencing chilling injury increase. In addition to cold soil temperatures, we also know that large swings in daily temperatures can cause chilling injury. Daily temperature swings greater than 25o F will also put your seed at higher risk of injury.
Weighing your options
Everyone’s operation is unique. Should you press forward and plant or should you wait? What if the soil temperature is above 50o F now, but the weather forecast is cold and wet? I have seen 30 bushel yield reductions caused by chilling injury. However, based on your operation, there may be reasons to plant. As much as you might not believe this, the forecast is not always right. The weather might not get as cold and/or wet as predicted. If you have thousands of acres to plant and you need several weeks to get it all done, it might be worth the risk. Nobody ever raised 250 bushel corn by leaving it in the bag. There will always be an optimal planting window for your region based on the calendar and the maturity of corn you are planting. Planting within that window will optimize corn yields. Late planting can reduce yields as well.
With the spring weather we have been experiencing the past few years, we seem to be having shorter and shorter windows necessary to accomplish planting in a timely manner. As we continue to push planting dates further ahead, we must also realize how colder soil temperatures can lead to chilling injury and negatively impact yield. Once you know the risks associated with planting into cold soils, you can make decisions based on what you think is best for your operation. Happy Planting in 2017!
References and additional information
Note: The information in this issue is based upon field observations and third party information. Since variations in local conditions may affect the information and suggestions contained in this issue, LG Seeds disclaims legal responsibility therefore. Always read and follow label instructions.
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Download a copy of this Technical Bulletin: Tech_328 - Avoiding Chilling Injury