This article was written by Emma Peel, a summer research assistant with OMAFA assisting with corn research and extension projects during the summer of 2025. Emma is an agriculture student at the University of Guelph
Background
Provided we are always planting into moisture, there can be various acceptable depths to plant corn depending on your soil type. A range between 1.5-2 inches is recommend by most seed companies, with the suggestion that you plant your corn deeper as the planting season proceeds. However, what is the ideal seed depth for corn to ensure optimal and uniform emergence? A question asked by growers for years as our climate continues to change.
Shallow Planting
While shallow planting may seem appealing, allowing corn to emerge earlier and potentially extending the growing season for higher yields, it comes with significant risks. Although early emergence can be a benefit, numerous problems can arise from planting corn too shallow.
Pioneer and other seed companies recommend a planting depth of 1.5 to 2 inches, warning against going any shallower. Shallow planting can impair the seed’s ability to access water and nutrients, resulting in poor root development. (Pioneer, 2019). This can leave plants vulnerable to summer drought stress, and in severe cases, lead to rootless corn syndrome which can be seen in (Fig. 1).
Rootless corn syndrome occurs when plants fail to develop a proper root system. Symptoms typically appear between the three-to-eight leaf stage and include lodging and a lack of nodal roots (too shallow and underdeveloped). The few roots that do emerge are often stubby and poorly anchored in the soil. To prevent this, it is essential to plant seed into moist soil at the recommended depth (Iowa State University, 2023).
Shallow or inconsistent planting depths can also lead to uneven emergence, non-uniform mesocotyl lengths, and an increased risk of lodging.
Another important consideration when planting shallow is the margin of error on the corn planter. Even if it’s set to your preferred depth, planters are not perfect, some seeds may be placed slightly shallower or deeper than intended. Given the risks associated with shallow planting, it’s important to regularly check and verify the actual planting depth throughout the season.
Pioneer emphasizes that in late-season planting, especially during a dry June, deeper planting is even more crucial. Soils tend to be drier and moisture is deeper in the profile later in the season, reducing the amount of moisture available to the seed. This makes it more difficult for plants to achieve uniform emergence and develop strong root systems. Poor root systems increase susceptibility to wind damage, potentially leading to significant lodging and yield loss (Pioneer, 2019).
Uneven emergence also results in “runt” plants that are unable to compete with their larger, earlier emerging neighbouring plants. Consistent seeding depth is critical for achieving uniform emergence. When emergence is delayed, smaller plants face increased competition, reducing their individual yield potential. The effect of late emerging plants can be seen in (Fig. 2). The later emerging plants are suffering significant yield losses from the already emerged plants. Even just a three-day delay can cause up to a 90% loss in yield for those late emerging plants (Koch Agronomic Solutions, 2018). In other research, yield can be reduced by 5% when half the stand emerges seven days late and by 12% when half the population suffers from a two-week delay (Brown, 2017). These delays compromise overall crop uniformity and yield potential creating serious losses for the grower
Deep Planting
So, what’s the solution? Is deeper planting the better option? According to trials conducted by Maizex Seeds, planting at a depth of at least 2 inches is recommended to ensure good seed-to-moisture contact and promote uniform emergence. Their research also suggests that planting as deep as 3 inches later in the season, when soils are warmer, can lead to more uniform stands, improved root development, and ultimately higher yield potential (Stewart, 2023) (Table. 1).
Clarke McGrath of Iowa State University adds a note of caution: while planting too deep, especially in cool, wet soils, can lead to stand loss, reduced vigour, and uneven emergence, shallow planting tends to cause more persistent, season-long problems. These include weaker root systems, poor drought tolerance, and uneven crop development (McGrath, 2016).
What is the significance of choosing an ideal planting depth based on your planting conditions?
Growers must carefully consider their soil conditions, time of planting, and forecasted weather when determining the ideal planting depth for corn. For example, in drier, sandy soils or during later planting dates, planting deeper can help ensure uniform emergence and create a good seedbed for optimal seed-to-soil contact.
Other important considerations include ensuring that your equipment is properly and uniformly serviced. When replacing planter openers for example, if all openers are not changed at the same time, there can be differences in diameters which can lead to differences in depth unit-to-unit. Components like openers and row cleaners directly impact how deep corn may be planted into the soil. If these parts are not properly aligned, they can introduce variability across the planter, resulting in inconsistent seeding depths and uneven emergence.
This issue can be especially problematic in parts of the field with knolls or stony areas. When the planter encounters these tougher soil conditions, it can disrupt ground contact, seed placement and spacing. It’s important to regularly check seed depths both after maintenance and while in the field, especially when working through different soil types.
Conversely, during early-season planting, in heavier soils, or with cooler more wet conditions, planting slightly shallower may be appropriate, as excessive depth could hinder emergence and reduce stand uniformity.
Ultimately, planting depth should be tailored to field-specific conditions and may vary from farm to farm. However, it is widely recommended that growers aim for a depth no shallower than 1.75 inches and no deeper than 3 inches to achieve optimal emergence, root development, and seed-to-soil contact.
References
Anonymous. (2023, December 22). Rootless corn syndrome. Integrated Crop Management. https://crops.extension.iastate.edu/encyclopedia/rootless-corn-syndrome
Brown, C. (2017). Agronomy Guide for Field Crops Publication 811. Ontario Ministry of Agriculture, Food and Agribusiness.
Koch Agronomic Solutions. (2018, January 18). Unlocking yield potential with uniform emergence. Plant Nutrient Solutions Leader – Koch Agronomic Services. https://kochagronomicservices.com/knowledge-center/unlocking-yield-potential-with-uniform-emergence
McGrath, C. A. C. (2016, April 16) Corn planting depth. Integrated Crop Management. https://crops.extension.iastate.edu/post/corn-planting-depth#:~:text=Planting.
Pioneer. (2019, April 25). Corn planting depth and spacing. Pioneer® Seeds. https://www.pioneer.com/us/agronomy/planting_depth_and_spacing_cropfocus.html
Stewart, N. (2023, March 17). Planting corn in Western Canada. Maizex Seeds Inc. https://maizex.com/planting-corn-in-western-canada/
Stewart, N. (2023, November 13). Avoiding the big 6 planting mistakes. Maizex Seeds Inc. https://maizex.com/avoiding-the-big-6-planting-mistakes/
Jeschke, M. (2025, April 2025). Rootless corn syndrome. Pioneer® Seeds. https://www.pioneer.com/us/agronomy/rootless-corn-syndrome.html#:~:text=Shallow%20Planting%20%E2%80%93%20Planting%20too%20shallow,less%20than%201%C2%BD%20inches%20deep.