Month-Long Window for 95% Yield Potential
Despite the trend of farmers planting earlier and earlier, research results recently released by Iowa State University Extension agronomists show that farmers have nearly a month-long window to plant their crops and still realize 95 percent of the crop’s yield potential. The optimal start dates to begin planting corn, according to this study, range from April 11 in southern Iowa to April 15 in northwest Iowa.
ISU agronomists conducted research on seven sites for three years – 2006, 2007 and 2008 – for a total of 21 site-years. Based on yield data obtained, recommendations have been developed to achieve maximum yield possible in relation to planting date for each of three regions across the state. Each region had a different window of time that optimized the yield, on average. A summary of these windows, as published in Integrated Crop News, follows:
Northeast region (red):
This region has the narrowest planting window due to the need to maximize the length of the available growing season. Grain yields begin to drop off more significantly here than the rest of the state if plantings are too late. We recommend planting between April 12 and May 2 (95-100 percent yield window) or between April 12 and 30 (98-100 percent yield window). The dataset is limited for plantings before April 12 in this region, hindering our ability to make recommendations prior to this date.
Northwest and central region (yellow):
This region has a flatter yield response to planting date than the other regions. In other words, planting date does not appear as important of a management practice here as in other parts of the state. We recommend planting between April 15 and May 18 (95-100 percent yield window) or between April 15 and May 9 (98-100 percent yield window). Again, information for this dataset is limited for plantings before April 15 in this region, diminishing our ability to make recommendations prior to this date.
Southern region (blue):
The yield response in this part of the state is presumably related more closely to rainfall patterns and soil moisture than the length of the growing season since this typically is not a limitation as it is in the northern part of the state. We recommend planting between April 11 and May 13 (95-100 percent yield window) or between April 17 and May 8 (98-100 percent yield window).
An expanded article, with more detail specifically on the methods behind this project and the development of recommendations can be found on the ISU Corn Production website.