If Mother Nature finally smiles upon us, the last of the 2008 Corn Illustrated plots may finally be in the ground by now. If not, decision time will be fast approaching on how to proceed. Planting full-season corn after June 10 gets tricky in central Indiana where the plots are located. The population study went in May 5 and is up, although there were differences in hybrid emergence, as noted last week. Three more plots were on hold yet late last week.

Dave Nanda, consultant for Corn Illustrated plots and president of Bird hybrids, LLC, Tiffin, Ohio, tries to put a positive spin on the unfortunate delays. "It's terrible for farmers who waited this long to plant, but from a researcher's standpoint, this could be another one of those years that helps set the parameters of what's possible," he says. When weather conditions are extreme, researchers get to see how products and concepts react under the best or worst of conditions. Sometimes you learn more as a researcher when testing at the extremes than when it's a normal year."

Only problem is last year was also extreme- very dry with record-setting heat, especially late in the season. Even Nanda might be wondering when that so-called normal year is going to come along to set the norm for how products and concepts should react in a more typical environment.

In '07 Nanda and the CI crew discovered that without irrigation, yields on ground underlain with gravel, even planted timely, can be cut in half or more. Top yields in a nitrogen plot, with rates form zero to 150 pounds per acre, with three hybrids at 32,000 and 41,000 plants per acre, yields topped at 245 bushels per acre, despite 40 days of 90 degrees F or higher temperatures.

This year looks to test the theory of how much yield potential is lost by delayed planting. Agronomists Jim Herbek and others at the University of Kentucky, on the southern edge of the Corn Belt, in more recent studies claim that in their state the yield drops begins during the first week of May. The Purdue University Corn & Soybean Field Guide, prepared by the Purdue Crop Diagnostic Training Center, also supports yields starting to slip in early May. Earlier research indicated that the magic date historically was closer to May 10 to May 15.

Based on the most recent data, 20% yield reductions could be possible. That means instead of shooting for 300 bushels per acre, Nanda and company could hope for 240 bushels per acre at best. Ironically, that's the number they hit a year ago, planted on time but stricken with extreme heat and drought. The plot was irrigated, but Nanda is convinced there is no replacement for natural rainfall at the right time. And there is certainly no way to totally account for extra heat pumped into the equation. The only saving grace a year ago, certainly not guaranteed this year, was that heat started around August 1, with July, the critical pollination period a year ago, actually running slightly below normal on temperatures.