Planting Date Effects on Corn Grain and Forage Yield
Corn planters will soon be rolling throughout Wisconsin and the Midwest Corn Belt. The annual struggle between field conditions being “just right” and not too wet versus delaying planting to another day will start to weigh on farmer’s minds. In addition, planting delays in the northern tier of U.S. states have greater impact on yield due to a shorter growing season and the added dimension (“double-whammy”) of drying costs at harvest that can occur during cool, wet growing seasons.
Figure 1 shows the impact of planting date on relative grain yield at Arlington. If all corn could be planted on one date, ideally it would be on May 1 or slightly earlier to decrease drying costs. Planting delays to June 1 will lower yields about 30%. However, in some growing seasons, 100% of the maximum grain yield can be achieved planting into late May. Grain yield decreases 0.5 bu/A per day on May 15 and accelerates to 2.5 bu/A per day on June 1.
Seeding Depth Affects Corn Plant Emergence Uniformity and Grain Yield
Rarely do we see a paper published on corn seeding depth and the subsequent impact on grain yield. Precision technologies have allowed for capabilities of variable rate seeding, multi-hybrid planting on the go, and the ability to vary planting depth in real time in response to real-time soil moisture data. In a paper published by Nemergut et al. (2021), corn seed was planted at 1-, 2-, and 3-inch depths on two soil types in Ohio over three growing season (2017 to 2019). Shallow planting resulted in less uniform more extended emergence periods than 2- and 3-inch planting depths. If a plant emerged within 3 days of the first emerged neighboring plants, then there was no effect on plant grain yield. Any plant that emerged more than 3 days after the first emerged plant had a 5% decrease in kernel weight per day. Grain yield per plant increased as planting depth increased. Grain yield per acre was significantly increased by planting depth with seed planted at 2- and 3-inches yielding 8 or 10% more than the 1-inch seeding depth on one of the two soils. Other researchers have also shown improving emergence uniformity can positively increase yield, and that optimum planting depth may vary by field.
Further Reading
Nemergut KT, Thomison PR, Carter PR, Lindsey AJ. Planting depth affects corn emergence, growth and development, and yield. Agronomy Journal. 2021;113:3351–3360.  https://doi.org/10.1002/agj2.2070