Each year a corn planting date trial is established at the Northwestern Illinois Agricultural Research and Demonstration Center. Planting date studies can provide us with valuable information. For example, in a given year, with its unique weather conditions, we can find out which planting date resulted in the highest grain yields. Additionally, planting date trials over many years can help agronomists to fine-tune regional planting date recommendations.

2013 planting date trial. In 2013, the latest planted corn (June 4) was also the highest yielding corn (Figure). Corn planted on April 4 yielded on average 17 to 20 bushels less than corn planted two months later. June is typically outside of the 'ideal' and 'typical' planting date range for corn in Western Illinois. However, in 2013 the cool soil temperatures in April (51 degree average) and frequent and heavy rainfalls in April (7.2 inches total) and May (10.6 inches total) proved less favorable to corn yields than a shorter growing season.

Condition of corn planted April 9, 2014. In 2014, the first corn in the planting date trial was seeded on April 9. Cool air and soil temperatures delayed emergence, with plants spiking 22 days after planting. A photo of 28 day corn shows that the plants are at the V1 growth stage (1st leaf collar visible) 28 days after planting.

Plants also show injury symptoms across the width of each of the first leaves to emerge (Figure). This superficial injury is likely due to unfavorable conditions right at the soil surface to which the emerging leaves were exposed (ex. cold, wind, sand blasting).

For more information. For more information about corn planting date trials in the Northern half of Illinois over the past 7 years, visit a recent Bulletin article written by University of Illinois Extension Agronomist Emerson Nafziger.