Seed Size, Planting Depth, and a Perennial Groundcover System Effect on Corn Emergence and Grain Yield

The intensive corn (<i>Zea mays</i> L.) and soybean (<i>Glycine max</i> (L.) Merr.) production practices currently used in the Midwestern U.S. concern producers and stakeholders. The negative impact of these two-crop rotations on the environment affects water quality and soil erosion and increases flooding risks. Due to these concerns, cover crops and, specifically, perennial groundcover (PGC) cropping systems have gained greater interest. These perennial species have growing patterns compatible with corn and soybean, and can help rebuild the ecosystem while maintaining good cash crop yields. In addition, producers also are interested in the possible effect of seed size and planting depth on uneven emergence in corn. The successful adoption of PGC systems ultimately depends on the successful corn seedling emergence and consistent yield. The objective of the study was to understand the effects of seed characteristics and placement on emergence, grain yield, and grain quality in corn planted using a Kentucky bluegrass (<i>Poa pratensis</i> L.) (KBG)-PGC and a bare-soil cropping system and to determine grain quality attributes and grain moisture dry-down in a PGC field when compared to a conventional cropping system. Commercially-sized seed and seed sized in the laboratory to represent a narrower seed size distribution were planted in KBG-PGC and bare soil systems at two planting depths (3.18 and 6.35 cm). The two-year experiments were planted in a split-plot RCB design with four replications. Individual plants were flagged at emergence, and ears from each plant were harvested individually. Separating the seed lot into different size distributions did not affect seed germination under ideal (standard germination and speed of germination tests) or stressful (cold test) conditions. Seed size distribution also did not influence emergence rate and yield in a conventional tillage (bare soils) or KBG-PGC system. These results indicate that seed sizing specifications and seed size cutoffs currently used by seed companies are suitable for uniform emergence and maximum grain yield in both cropping systems. Seed placement was crucial to uniform emergence in both cropping systems, while seed size distribution did not play a role in emergence for either system. The PGC cropping system delayed seed corn emergence and reduced grain yields as much as 50%. This information is important for those producers considering adopting a PGC system because it demonstrates that uniform planting depth is more important than seed size distribution.