August 4, 2008
CORN GROWING DEGREES STILL LAGGING FAR BEHIND NORMAL
As we approach August and the prospects of shorting days and fewer growing degree days per day, it is now prudent to take of stock of where we are at with regards to corn development. It is obvious as you travel around the state, that corn development is far behind where it was last year. In fact, corn is just now beginning to tassel which compares with most fields tasseling in mid-July last year. A quick look at map of corn growing degree days (GDDs) on NDAWN shows that depending on the location in the state, GDDs are currently running about 100 to 150 behind the long term average when a May 1st planting date is assumed. In this article GDDs from Jamestown and Oakes will be used to illustrate the impact of the cool weather this year on corn development and the risks of insufficient GDDs on the corn crop this fall. As of yesterday (July 27th) Jamestown and Oakes were 211 and 112 GDDs behind the long term average, respectively (see Table 1). Generally, yield is not impacted by slow corn development. In fact, the lack of extremely hot days this summer has probably been beneficial to the crop as far as yield is concern. The problem with cool weather and slow corn development is that the crop may not reach physiological maturity before the first killing frost, but perhaps more importantly the grain will be so wet at harvest it will be difficult to handle and expensive to dry.
Hopefully this data has helped you visualize and quantify the delay in corn development this year. Though the data does not suggest that we will see large yield losses due to crop immaturity this year (assuming a relatively normal first frost date and that recommended hybrid maturities were grown), they do indicate that corn will probably need substantial drying after harvest before it can be safely stored. Obviously, warmer than average weather will hasten corn development and reduce the impact of our cool spring. Since we are dealing with "average" weather data, large deviations from the normal can be expected. A prolonged warm and dry fall, like we had in 2007 would be beneficial in reducing the need for drying time. On the other hand, cooler than average temperatures, during the remainder of the season, could exacerbate an already difficult situation.
