The above photo depicts a corn planting date study being conducted by Pioneer at the Chatham Demonstration farm.The corn to your furthest left was planted May 9 ( its was at 6 true leaves on June 17) , the next 4 rows of corn were planted on May 19, ( this corn was at 4 true leaves on June 17, the adjacent 4 rows were planted May 26 ( this corn had 3 True Leaves on June 17) and the smallest corn to your right was planted on June 3.It had 2 true leaves on June 17 . All plantings are of the same hybrid - Pioneer brand 35F44.
It takes roughly 75 Ontario corn heat units for the corn plant to produce a new leaf. By evaluating true leaf formation you can estimate that the May 9th corn must have received close to 300 more heat units than the June 3rd corn given that on June 17 it had 4 more true leaves .Long term planting date studies would lead one to believe that the May 9th corn will outyield the June 3 corn by somewhere between 20-25bu/acre and run 2-3 points wetter at harvest.We'll see how yields and moisture compare this fall. TO VIEW THE ABOVE PLANTING DATE STUDY IN CLOSER DETAIL JUST DOUBLE CLICK ON THE ABOVE PHOTO AND MANEUVRE AROUND BY ADJUSTING YOUR SCROLL BARS.