Degree Days are a critical driver of crop development

Iowa State University raises some good points about the delayed crop development that we’ve experienced this season. The 2009 season, in some areas, is mirroring the 2008 growing season. Many crops experienced several stress factors including wet, cool growing conditions, hail and strong winds.

Last season top corn hybrids throughout the industry experienced stalk lodging, so we’ll want to keep that in mind as harvest approaches. Continue to monitor your fields and note areas where there are hybrids with stalks that have been bruised by bad weather or where there are weaker stalks due to the growing conditions. Plan to harvest those areas first for a more successful harvest season.

Rich Pope of the Department of Plant Pathology and Elwynn Taylor from the Department of Agronomy at Iowa State University released this article recently that could be of help to farmers in evaluating performance this harvest season.

2009 Season in Degree Days through Late August

Degree days are a critical driver of crop development, and 2009 certainly illustrates that point. Wet soils and cool early season temperatures delayed some plantings and also delayed the development of crops that were planted on time. The early vegetative stages were slowed by cooler-than-normal temperatures, then July arrived with a remarkably un-summerlike chill that lasted the whole month.

Crop stages remained stagnant for three weeks, with corn silking and soybean pod set both delayed by ten days to two weeks in most areas. Because the weather is one major variable that we cannot change, but only observe and take action based on those observations, comparing 2009 with previous years is at least interesting, if not instructive for harvest-season planning.

The graph below illustrates the march of departures from long-term average degree day accumulations for 2009 and selected other years. The graph depicts the three most recent seasons; includes 1992, 2003 and 2004- three years that have compared with 2009, and 1994- a year that generated remarkably good yields.

Growing Degree Days in highlighted years