Single-Plant Grain Yield in Corn (Zea mays L.) Based on Emergence Date, Seed Size, Sowing Depth, and Plant to Plant Distance

The lack of seedling emergence uniformity in corn (Zea mays L.) is concerning for producers in the Midwestern U.S. These producers believe that just a few hours delay in emergence can increase interplant competition and decrease single-plant yield, thus reducing overall crop yield. It is speculated that lack of uniformity in seedling emergence occurs due to a variation in seed size within a commercial bag of seed, and variation in seed depth placement at sowing throughout the field. Due to these concerns, producers evaluate size seed variation within the bag before sowing. To date, research has investigated sowing dates, growing degree days, or varying sowing depths to simulate a delay in seedling emergence. These studies are important for understanding the effects of delayed emergence on overall yield, but they fail to examine the effect of inter-plant competition on single-plant yield. The objective of this study was to understand the effect of seed size and sowing depth on emergence and subsequent single-plant yield in a bare soil and a perennial groundcover (PGC) cropping system. Commercially sized seed and seed sized further in the laboratory to obtain a narrower seed size distribution were sown in Kentucky bluegrass and bare soil systems and at two sowing depths of 3.18 and 6.35 cm. The two-year experiment was planted in a split-plot design with four replications. Individual plants were flagged at emergence, and harvested individually. Seed placement was crucial to uniform emergence in both cropping systems, while seed size did not affect emergence in either system. The PGC cropping system delayed seed corn emergence and reduced grain yield as much as 50%. Single-plant yield decreased with delayed corn emergence in both cropping systems. Yield decrease as a function of emergence date followed either a quadratic or linear trend in each growing season, likely related to post emergence environmental factors. This information is important for producers and seed companies to understand the effect of seed size and sowing depth on yield and emergence. This study demonstrates that uniform sowing depth is more important than seed size distribution.