July 2004 Archives

Dale R. Hicks, Department of Agronomy and Plant Genetics, University of Minnesota

Plant height varies drastically in many cornfields in Minnesota. This has been the case for the past six weeks and is especially noticeable in fields where corn follows corn even though corn following soybean is also extremely variable in height. In some fields the plants are taller in the tractor tracks and tassels are coming out from those plants but not yet visible from other plants. This makes an interesting picture in many cornfields.

Dale R. Hicks
Department of Agronomy and Plant Genetics,University of Minnesota

Temperature affects crop growth and development. Accumulation of heat during the growing season can be used as a predictor of plant developmental progress. Growing Degree Days (GDD's) is a calculation to express the heat accumulation. GDD's are calculated using the maximum and minimum daily air temperature to determine the average daily temperature. From the average temperature, the base of 50° is subtracted to arrive at the daily GDD's. There are temperature limits used when calculating GDD's because little or no growth occurs when the temperature is greater than 86°F or less than 50°F. So when the maximum temperature is above 86°, then 86 is used as the maximum temperature and when the minimum temperature is below 50°, then 50 is used as the minimum temperature for the day. Daily GDD's are summed for the season beginning May 1.

Dale R. Hicks, University of Minnesota

This growing season is rapidly moving along and it continues to be cold and wet. For most areas of the state the growing degree days (GDD's) are lagging by more than 100 and as high as 300 GDD's in some areas as of July 11. As a result, corn is shorter than it normally is at this calendar date and growth stage. Corn is ten inches shorter than the last 5-year average and 14 inches shorter than it was at this time last year. Will corn height catch up? And will short corn have good yields?