The Midwest has experienced some stretches of below-normal temperatures, with cold, rainy conditions this spring. Research shows that the opportune time to plant corn is somewhere between the last two weeks of April and the first few days of May. However, Mother Nature isn’t necessarily on that same schedule. Fields that have been recently planted or those that will be planted in the next couple days may be subject to seedling injury.
SIGNS OF INJURY
Corn that has been recently planted in the Midwest has experienced less-than-ideal overall conditions, especially when it comes to temperature. In many locations, the weather pattern of cold rain and low temperatures has potential to promote a problem for young seedlings called “Imbibitional Chilling Injury.” Some basic visual symptoms may be corkscrewing of the young germinating plant or leafing out below ground level. Consider digging up a few seedlings and checking them for signs of corkscrewing, leafing out underground or damping off.
WHY WOULD SEEDLINGS REACT LIKE THIS?
A possible issue that cause less than optimum stands and poor emergence is chilling injury to the mesocotyl or coleoptile plant tissue caused by sub-lethal cold temperatures (less than 50 degrees) during the period very soon after planting when seeds begin to imbibe water. The seed will not begin to germinate until the soil temp approaches 50 degrees, however, the seed will allow water to enter regardless of temperature. This chilling injury basically equates to cells rupturing which results in the corkscrewing of the mesocotyl. This delays the emergence of the coleoptile prior to the usual emergence of leaves from the coleoptile.
In addition to slowing the germination process, cold temperatures, snow and cold rains may cause irreparable harm to the delicate structures of an emerging corn seedling. When dry corn seed absorbs cold water, Imbibitional Chilling Injury is not uncommon. Such injury in corn seeds ruptures cell membranes and results in aborted radicles, proliferation of seminal roots, delayed seedling growth and potential for diseases pathogens to attack the young seedling. When temperatures remain at or below 50 degrees Fahrenheit after planting or fall below 50 degrees within 24-48 after planting, damage to germinating seed can be particularly severe as they imbibe water. This should be considered as there is risk associated with the temperature and moisture roller coaster we have experienced so far this planting season.
If you have any questions, contact your local Hoegemeyer agronomist or District Sales Manager.
Every year, when the calendar gets close to June, the question of whether to back off on relative maturity or not arises at least somewhere in the Hoegemeyer footprint. Some areas this spring have been continually hit with significant rain events that have not allowed corn planting to progress. No matter what date you planted your corn, it still takes about 125 growing degree units (GDU’s) for corn to emerge. In addition, research has shown that full season corn hybrids can also adapt to GDU’s needed for growth and maturity when planted later. For example, a corn hybrid will adjust to late planting by reducing the GDU’s necessary to reach black layer by about 6 units per day. An example would be a hybrid planted on May 20th that would require about 150 fewer GDU’s than the same hybrid planted on April 25th. Although the time required for a late planted hybrid to go from silk to black layer is increased, the time period from planting to flowering (tassel) is actually significantly reduced. Although later corn planting dates are not beneficial overall in terms of yield response, later planting dates will help accelerate emergence out of the ground and the plant will benefit from more measurable GDU’s per day after emergence compared to significantly earlier dates.
There is a point when backing up in maturity does make sense, especially as one moves north. In general, the best chance to approach optimum yield vs. planting date is still achieved by sticking with the normal adapted corn maturity for that area until the last week of May. After that, reducing maturity by about 5 days is justified as we approach June 1st. As we enter the 2nd week of June, reducing maturity by another 5 days is justified. Beyond the 2nd week of June, planting corn is usually not advised. Note that these estimates vary some depending on the individual situation and geography. If we were able to predict a cooler than normal grain filling period (August and early September), then one might error on the side of caution and plant an earlier hybrid the closer we get to June.
Questions regarding corn replant? Several factors come into play but as the calendar moves into the 1st week of June, more times than not, the best choice is to leave your remaining stand. Table 2 from Iowa State University gives estimated yield potential for corn at different final plant populations and planting dates.
Heavy, persistent rains have also delayed soybean planting for several areas of the Hoegemeyer footprint. Take a look at this article from UNL extension in regards to delayed soybean planting decisions and practices. http://cropwatch.unl.edu/delayed-planting-in-soybeans This article uses June 15 as a potential date to consider a 1/2 maturity group reduction (example would be reducing from a 3.5 RM to a 3.0 RM). However, we feel June 20 is a more relevant date for locations south of Interstate 80. As one moves north of Highway 20 in Nebraska and Iowa, June 1st can be used as a potential date for a ½ maturity group reduction (example would be reducing from a 2.5 RM to a 2.0 RM). Past situations would show that fuller season soybeans give the best chance for yield, especially as we move south, for several reasons:
1. Late planted full-season soybeans south of I-80 are not at the same risk of a fall freeze as those planted further north.
2. For the most part, short season soybeans do not move south well. Soybeans are triggered to go into reproductive mode based off daylight. They are more sensitive to photoperiod than corn. There is typically more heat as you move south, but also longer nights. Soybeans that are very early in maturity, that are planted late into a southern zone will potentially be very short and will not produce much for pods or canopy.
3. Fuller season soybeans still have the best potential to capitalize on late season rains come September and early October.
If you have specific questions about your farm, please don’t hesitate to contact someone on our Agronomy team. We are here to ensure the long-term success on your farm!
Hopefully by now most of us are done planting corn and all that is left to work on between rains are the lingering soybean fields. I know in a few areas farmers have been challenged by the cool wet spring and there are some bald patches in fields that will need to replanted, or even planted the first time. While you understandably may be saying to yourself -“I can’t wait for the 2016 planting season to finally be over!”- there is one more important step to take before we park the planter in the shed for the year. The planting process post-mortem.
To be ready for next year, most of us take the time to clean and inspect the planter for damage or to fix wear and tear, but how many of us take the time to think about the process of planting and to record ideas for improvement? This is basically what a post-mortem involves, thinking about any problems you may have run into, how to avoid them and even make improvements in the future. The key to process improvement is becoming disciplined at collecting information. In some cases, with complex processes flowcharting can even be warranted, but at a minimum having a system that works for you to record information and ideas, and taking the time to do so is key.
A good place to start is with your goals, but also asking general diagnostic type questions. For example, did I achieve the desired planting populations, if not why? Are there areas of the fields that I need to pay special attention to as the season progresses or manage differently next year? If I had it to do all over again, would I have started planting in a different field, or if I am contemplating adding to my operation, how would this fit into my planting plans? In theory, the idea of process improvement may seem elementary, but the follow through and execution is where most of us falter. As we all know, each year brings a new set of challenges, so it’s hard to make improvements based on only one year of information. Doing this right requires a long-term commitment to process improvement. A planting post-mortem is like anything else in that you will get out of it what you put into it.
Nitrogen management in corn continues to evolve – with new ways to apply Nitrogen during the season, and new ways to measure it. Our understanding of the corn plant’s appetite for Nitrogen is evolving as well.
DuPont researchers have written an article recently on Nitrogen Uptake in Corn. It’s a lengthy read but interesting. If you don’t have time to read it, here are some of the main points:
Researchers are finding that modern corn hybrids are taking up nitrogen later into the season than older hybrids – to the tune of 29-40% more Nitrogen taken up after pollination when compared to older hybrids
Around 1/3 of a corn crop’s nitrogen may be taken up after pollination in modern corn production
Lower to average yielding environments still take up the vast majority of Nitrogen prior to pollination (as we’ve previously assumed)
High yield environments in particular may continue to take up significant amounts of nitrogen from the soil for several weeks after pollination
I don’t know about you, but spring planting season is probably the part of the job I enjoy the most. As we move from winter into spring and it starts to green up, getting out in the field again is always a great feeling. So far, the spring of 2016 has brought above average temperatures and the majority of March has felt more like April aside from a few snow events. With these warm temperatures, producers may be thinking about getting the planters rolling a bit early. Here are a few considerations and watch outs for spring planting.
Soil Temperature @ 50 Degrees: A good rule of thumb for when to start planting corn is when soils reach an average soil temperature of 50 ͦ or above every morning at 7:00 A.M. for a week. When soils are cooler than 50 ͦ typically emergence will be delayed for a few weeks. The longer the seed sits in cold soils the more potential there is for exposure to pathogens, reducing the chance of germination.
Imbibitional chilling: Imbibitional chilling occurs when seed is planted, begins to germinate and then the soil temperature drops below 50⁰. This will typically happen if seeds are planted into soil above 50 ͦ and then we catch a cold rain, freezing rain or a snow storm that brings to soils temperature down. Imbibitional chilling causes cells to rupture leading to corkscrewing of the mesocotyl. This can either delay emergence or possibly inhibit emergence if the coleoptile can’t get through the soil surface. Other symptoms of imbibitional chilling include aborted radicles, proliferation of seminal roots, delayed seedling growth and potential for diseases pathogens to attack the young seedling.
Sidewall compaction: Planting into fields that are too wet will typically cause sidewall compaction. Even waiting an additional 24 to 48 hours can reduce the potential for sidewall compaction. Remember we only get one chance to plant most fields so waiting for soils to dry out can make a big difference in a fields yield potential.
Planting season only comes once a year and there is nothing more important for setting ourselves up for maximum yields than getting a good even stand on all of our acres. Waiting until soils are fit to plant, waiting to start planting until soil temperatures are sufficient, and delaying planting if the forecast calls for cool wet weather are all good tips to avoid early season problems in our fields.
For more information about considerations for early planted corn, check out our agronomy article here. If you have any questions feel free to contact your local Hoegemeyer DSM or Agronomist.