When did your Dad plant corn, or tell you that it was time to plant corn? While that date may be plowed across our mental field, corn planting dates have to be adjusted about every year. Yes, early planting may lead to higher yields, but will not guarantee them. Essentially, the planting date is only one factor that influences yields, so if you are fretting about missing the target, there are still other targets to fire at.
If you are losing sleep about not being finished (or started) planting corn, get a grip, adjust your outlook on life, and remember that your Dad also told you that you can’t do anything about the weather. But with the wet spring that has washed out the April planting schedule, let’s see what the other factors are that may determine your yield. Purdue corn production specialist Bob Nielsen has a collection of “yield influencing factors” (YIF.)
Just so you would not have to do it, Nielsen analyzed the USDA’s Crop Progress reports for the past 20 years and found “there is NOT a strong relationship between planting date and absolute yield on a statewide basis for Indiana.” Sure he was looking at Indiana, but the same can be said for other states. And he adds that departures from annual trend yields are not strongly related to corn planting progress. Do you feel a little better now?
Nielsen says planting date is only one of those YIF’s, but is willing to address the issue of why he and all of his Cornbelt colleagues preach the importance of timely planting, yet only 12% of the variability in yields can be attributed to planting date. While many farmers look at the May calendar and start deducting yield, Nielsen says the yield “potential” does decline after May 1, however, he says the yield potential declines because of a number of other factors, including, “a shorter growing season, insect & disease pressure, and moisture stress during pollination.”
Nielsen says all of the yield influencing factors work together to determine a maximum possible yield. It the combination is a 200 bushel yield, then the planting delay might reduce it to 190 bushels. However, if the combination is a 160 bushel yield, then the planting delay would reduce it to 150 bushels. That’s why he says early planted corn one year may yield 190 bushels and the next year the same planting schedule may yield 150 bushels.
The Purdue agronomist wants you to think back to the 1997 crop that was planted early, but yielded 8% below the trend line. And he says think back to the 2009 crop that was planted late, but yielded 8% above the trend line. Nielsen says the difference is the other yield influencing factors, not the planting date.
If you don’t believe him, and are “mudding in” the corn crop, he says that is probably an unwise decision. You have the equipment to catch up when the weather and soil become favorable for planting. And based on the 2010 crop, 50% of the corn was planted over a period of 21 days, and a state can get 45% to 50% of its corn planted in a given week if there are good working conditions.
The planting date for corn is important, but not as important as a collection of factors that influence yield. Other factors include disease and insect pressure, moisture stress during pollination, and the length of the growing season. Corn can be planted early but yield below the trend line and corn can be planted late and yield above the trend line. And proper soil conditions at planting can be a significant factor, so don’t plant before the soil is ready.