For many, this spring has not allowed planting to progress as planned and already there have been some comments about when to switch corn maturity. As of May 1st, there is still plenty of time to get corn planted without having to worry about switching corn maturity. No matter what date you planted your corn, it still takes about 125 Heat Units or GDU’s for corn to emerge plus research has shown that corn can also adapt GDU needs for growth and maturity if corn is planted after May 1st.
For example, in an average year, a full season corn that normally needs 2800 GDU’s to reach black layer will adapt by requiring about 6.8 fewer GDU’s per day for every day planted after May 1st. Factoring the numbers, if a full season 2800 GDU corn was planted on May 15th, it would need about 95 fewer GDU’s to reach black layer (14 x 6.8) because the overall warmer conditions after May 1st will help accelerate emergence time out of the ground plus the first days after emergence will probably have more measureable GDU’s per day after emergence as compared to earlier planting which were more likely cooler days.
There is still a point though that a corn maturity switch might be considered but in general, experts say that date for the Western Corn Belt is between the 20th to 27th of May. Attached is “Switchybrids”, a 2011 article Tom Hoegemeyer wrote about making corn maturity switch decisions. I hope this article is helpful for those that may be wondering about switching corn maturities.
By Dr. Tom Hoegemeyer – from 2011
You have to love farming in the Great Plains—or it will drive you crazy. We have gone from having a mix of wet areas in a relatively dry region, to being cold and soaked. And the forecast is for another wet week or more before we will have a chance to get into the field. We have had several inquiries concerning planting dates for specific hybrids, and when will they need to consider switching hybrids and maturities.
The issue is how many heat units do we have to work with, and how is yield affected by later planting. First, the total heat unit accumulation from a presumed planting date to the average date of first freeze in the fall is fairly well known for each locality. If you look at these heat unit tables (on the web or from your university extension group) there, typically, is about 350 heat units accumulated between April 15 and May 15—that is not a lot of growth potential between those planting dates. Compare the tables of heat unit accumulation from spring dates to first freeze, and the heat unit requirements of your favorite “full season” hybrids in the 2011 Seed Guide. It is clear that at nearly every location there is likely to be enough heat units to mature our favorite hybrids if they are planted by May 20th. When it is cold, cloudy and wet (like the predictions) we accumulate few heat units. If the daily low is 40 degrees, and the high is 60, we average the two temps, and subtract 50, giving zero heat units for such a day—meaning corn isn’t going to grow anyway. We are likely to lose fewer than 150 heat units if planting is delayed for the next two weeks. And for each two days later emergence we might see (assuming a two week delay in planting), we will likely delay flowering only one day.
Second, how much is yield affected by a delay in flowering? For optimum yields, one wants to fill grain during longer days—that is as soon after July 4th as possible. However, actual yields are GREATLY impacted by heat (and moisture) stress in the period of a week before until 10 days after silking. Better or worse weather a few days earlier or later makes much more yield difference than precise planting date—and that’s mostly random in mid-July. However, if flowering is delayed until late July, the odds of hotter, drier weather increase. Especially in irrigated corn, the “optimum” planting date implies lower yields if planted BEFORE or AFTER the optimum date. And, historically those optimums lie between April 20 and May 5 for most of us.
Then, there is the issue of hybrid yield potential, by maturity. Longer season hybrids, in general, always have higher yield potential than earlier ones. They have greater leaf area—just a bigger factory to produce grain—and greater ear size and/or number of kernels—more room to pack starch and protein. Switching to earlier hybrids, even if they have high yield potential, almost always results in putting a “lid” on yield potential. As long as we have enough time (heat units) available to mature the fuller season hybrid, we are almost always better off NOT to switch to earlier hybrids with less yield potential. Hybrids of the same “heat unit maturity” will also vary in relative flowering dates, sometimes by several days. They can also vary in drydown rate (and staygreen, which affects drying rate).
So, taken together, what does this mean? In general, I can’t recommend switching hybrids from your “normal” full season choices until, AT LEAST, May 20th. While that will be later than the optimum planting date—you will sacrifice some yield, switching to earlier (and probably lower yield potential) hybrids isn’t likely to make you money. With some, relatively, earlier-flowering hybrids, that date is probably May 25th or after. One person asked me, “What about drydown problems, like we saw in 2009?” Those problems were largely the result of a cool July and cold August, REALLY RARE OCCURANCES! Even with some drying issues, full season hybrids consistently gave the highest yields and net profits.
, Don "Moe" Moeller
, Dr. Tom
Don "Moe" Moeller, Management, Planting, Planting Date, Switching Corn Maturity, Switchybirds
About this time every year in basketball “March Madness” occurs and if a team wins or loses, this is how the sports world figures out who the best team in the nation is. After a loss, the losing coach when interviewed is asked about the loss and the teams plans to improve. The answer that is given most often is that we just need to the work harder and remember the “basic fundamentals” of the game. Many things associated with the game may change but to be a winner, applying the “basic fundamentals” and adhering to the “basic fundamentals” during a game is what will make that team a winner.
So how does the game of basketball relate to planting crops? Over the past few years many changes have occurred in the game of planting too. One of the more recent changes that occurred is the technology associated with planting. Technology has improved planting in many ways such as RTK may be driving the equipment and the guy that used to drive is now going along for a ride. The satellites associated with technology also help with row direction, straightness and width efficiency. Companies like Trimble Manufacturing offer GPS, lasers, optics and positioning hardware to help save seed, correctly apply fertilizer and chemicals, and many other available options if you have the need and the resources to add them on. Almost everything can be adjusted or manipulated in some way on the go with the goal of saving time, saving money plus increasing overall efficiency.
Modern technology is great, it works and it’s here to stay plus many more technological options will be made available as the years go by. But, just like the game of basketball, crop planting has some “basic fundamentals” that you need to “apply” and “adhere to” in order to be the winner. Your “three point shot” in the field is only completed with good seed to soil contact. Just like a three point shot in basketball, getting good seed to soil contact takes practice and patience in order to get the planter set/adjusted right according to soil and field conditions. Your “two point shot” in the paint is proper seed depth. Improper depth can cause problems all year long from standability, harvestability and yield potential. Your “lay-up” is planter speed. In basketball, if you push that lay-up too hard or fast, chances are it might bounce out. The same goes for planter speed; going too fast might cause seed to jump at different depths or take away from proper spacing. Your “free throws” are the added things that you can do as you plant. Examples might include proper seed treatments as we plant crops earlier or in questionable seed beds, proper placement of fertilizer or starter in relation to the seed drop itself are just a couple of the free throw possibilities. Expect a “technical foul” if you push things along too fast and try to plant in poor soil conditions. And lastly, you will “foul out” if you (1) don’t understand the hybrid/varietyyou are planting, (2) don’t scout your fields, (3) have weed pressure, (4) don’t improve on poor soil fertility, (5) have a hard pan, or (6) don’t plant at the optimum planting dates.
Author Dr. Tom
Author Dr. Tom
Another planting season has rolled around, and by the time you read this some of the crop will already be in the ground. The last two planting seasons have been generally wet, too wet in some areas. While we got reasonably normal snow cover over the winter, last fall was generally drier than normal. So far, most of the central plains has also been dry, and the showers we’ve gotten have been light. As a result, our subsoil moisture going into spring is lower than we’ve seen for a few years, and the surface moisture situation is variable, and will depend upon local showers. The forecast is also for some periods of below normal temperatures during April and May. The combination may give us some considerably different planting conditions, perhaps cooler and drier, than we have seen for a while.
During the last few, relatively wet springs, especially in areas with clayey or silty soil types, some fields got planted on the shallow side. This combined with saturated soils in June resulted in shallow rooting. For the primary and secondary root systems to develop optimally, corn needs to be planted, at least, 1 ¾ inches deep. And deeper is better than shallower. If it also happens to be cool, it can be tempting to cheat on depth, attempting to plant in the warmer soil nearer the surface. However, this usually results in the secondary root system developing too near the soil surface.
If it continues to be drier than normal, avoiding tillage is absolutely the right move. Adjusting planting depth to a consistent 1 ¾ to 2 ¼ inches will pay dividends in larger root mass and deeper root placement, resulting in more efficient water and nutrient recovery. And, if our soils are a little drier, they tend to warm more during sunny days, as there is less water to heat.
This year we have teamed up with the Mike Peterson of Orthman Mfg., looking at the effects of hybrids, strip tillage versus no tillage, and fertilizer placement on corn rooting, plant development, and performance. Mike (who was an agronomy student when I was at UN-L, so he is still young!) is a soil scientist who spent most of his career with the USDA in Colorado and Idaho. He has been digging soil pits for decades, and has spent the last few years studying corn roots in Great Plains soils. We are looking forward to working with Mike and Orthman, and will keep you posted about what we are learning to help improve corn growing technology.
Author Dr. Tom
Thanks to everyone who turned out for our Homecoming Field Day last Thursday! We had a great crowd, and I think everyone really enjoyed Elwynn Taylor’s climate/weather talk, as well as Curt Tomasevicz’s tale of becoming a bobsledder and winning the gold medal. While it was a hot, humid day the air conditioners for both the warehouse and the big tent worked well, and it felt reasonably comfortable.
On my way to Hooper early Thursday, August 12th , I noticed that one of our seed fields was showing some yellow/gold leaves. I suspect that we will begin harvesting the seed crop in 10 days or so. Look at the cottonwood/birch/aspen (they are all closely related) trees in your neighborhood—they are beginning to show some light green to yellow leaves, a sure sign that fall is approaching. On my way home, I watched corn fields carefully. You expect the dryland fields to show yellowing/drying spots where there is compaction or light soils. But even irrigated corn fields are beginning to show lighter green color, and ears are beginning to lean away from the stalk, all indications of approaching maturity.
The USDA came out with their crop forcast, another binbuster. My feeling is that they may be a little high. I see lots of fields that look a bit uneven, more so than last year. There is some great corn, but in some spots we lost nitrogen with all the rain. Some fields have less even stands than last year—we just had some cold, wet weather this spring—and some areas of fields are late developing, and the heat likely affected them the last few weeks. By my calculations we are about as far ahead of normal heat unit accumulation this year as we were behind last year. We compacted the grain filling period by a week or so due to hot days and nights. The relatively high night temperatures tend to drive a little more respiration, so a little more of the sugar manufactured by the leaves during the day is used up at night. (The highest yield areas of the world have warm to hot, bright sunny days and 50 to 55 degree nights.) I think there will be some huge numbers on yield monitors, but also some lower yielding areas and fields compared to last year.
One of the perennial questions is when do I stop irrigating my corn? (I’d keep on watering beans until the leaves turn color!) You and your agronomist have been watching your fields, but I’d still suggest an old rule of thumb: you want two or three inches of water in the active root zone when the milk line is half way down the kernel. “Black layer” is an artifact, and grain filling stops days before the conductive cells at the cob/kernel juncture turn brownish, and several more before the “black layer” forms.
I hope that the milder weather that showed up this weekend holds!
Until next time,