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Tuesday, July 22, 2008 10:15 PM CDT
Corn crop races to beat the clock
By DENNIS BOWMAN
It is a standard plot device in action movies: the “bomb” has been activated and the clock is ticking down. Many area farmers with late planted corn have a similar feeling. Mother Nature has a bomb directed at their crop. This bomb, better known as fall frost is getting closer every day. Mother Nature doesn’t let us see the clock, so we don’t know precisely how much time we have, but the ticking seems to keep getting louder.
The development of corn is primarily driven by heat. With adequate water and sunlight heat is the main variable that impacts the rate of development. Corn likes temperatures between 50 and 86 degrees. This is one of the reasons the Midwest is a great place to grow corn. Our spring, summer and fall have lots of days that fall into this range. Additionally we look at the time period between the last spring freeze and the first fall frost. That is commonly referred to as the growing season. That is our window of opportunity to grow plants.
To keep track of this temperature impact on corn agronomists and climatologists use a calculation called Modified Growing Degree Days (MGDD) to keep track of how much useable heat the corn crop has been exposed to. A full season corn hybrid needs about 2800 MGDD to reach maturity. At this point the crop has pushed everything it can into the kernels and it is just a matter of drying down to a harvestable moisture level. Anything short of chopping the plant down won’t affect yield at this point.
Is there enough heat to get this late planted corn to maturity before the first fall frost? The later you planted the greatest risk. This week I put some numbers into an Accumulated and Predicted Growing Degree Calculator developed by the Midwest Regional Climate Center. (The actual reported numbers were calculated on July 15.) If you planted on time, May 1, your corn has been exposed to 1325 MGDD so far. May and June were cooler than normal and we are about 60 MGDD behind normal. With average temperatures for the rest of the season and average frost date, Oct. 16, the calculator predicted a total of 3111 MGDD for that period — May 1st to Oct. 16. Therefore a hybrid that needed 2800 MGDD would make it just fine. For the May 1 planting date with below normal temps and an early frost it predicted 2819 MGDD, just enough.
Things start looking a lot riskier when you look at planting in June, which many farmers were forced to do this year. With a June 1 planting date, the normal temperature and average frost calculation generated 2774 MGDD. This was just a little short of the 2800 MGDD needed by some full season hybrids. Some combination of above normal temperatures and later than average frost is needed for this hybrid to reach harvest without a weather related yield loss. A slightly shorter season hybrid (110-day) would put you in the safe zone here. What about worst case, below normal temperatures and early frost (Oct. 2)? That run generated 2497 MGDD. In order to reach full maturity you would need a much shorter season hybrid, 101 day hybrids need about 2450 MGDD.
Unfortunately, many farmers with repeated flooding were forced to plant in later June. I ran the calculator with a June 15 planting date and results are a little scary. The calculation with normal temperatures and average frost generated 2407 MGDD. A 100-day hybrid might just make it. A run with much above normal temperatures and a late frost generated 2683 MGDD.
This crop has faced many challenges and one of the biggest is just the calendar.
Coles County 4-H fair events
4-H members will be putting the finishing touches on their project exhibits in the next few days. Judging of General Projects gets underway Saturday morning at 9 a.m. on the fairgrounds and those exhibits will be on display through Thursday evening at the 4-H Extension Center. The building is open daily from 1 to 8 p.m. so stop by to see the conservation, photography, visual arts, gardening, woodworking and child care projects.
4-H livestock will start moving into the barns Saturday evening and be ready for shows throughout the week. Rabbits and poultry are scheduled Sunday afternoon with the larger species of livestock showing on Monday and Tuesday. The livestock shows conclude with the horse show on Friday morning.
The Coles County Extension Foundation is again conducting its annual raffle with the drawing for winners at the conclusion of the 4-H Livestock Auction on July 31. Grand prize this year is a 2009 Yamaha Scooter, which could help the lucky winner with high fuel costs. Other prizes include gift certificates for My Store, Festival Sausage, and Roc’s Blackfront Restaurant. Tickets are available from Extension Foundation board members and at the Extension office. Call Mark Cox at 254-4311 or Ed McKinney at 345-3208 if interested in purchasing a ticket. Profits from the raffle are used to support U of I Extension programming and to maintain the 4-H Extension Center on the fairgrounds.
Dennis Bowman is an Extension educator, crop systems, for University of Illinois Extension.
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