By Matt Hutcheson, CCA, Product Manager, Seed Consultants, Inc.
Planting is one of the most critical management practices of the year because it sets the stage for the entire growing season. There are several key aspects of planting, one of which is planting depth. Invariably, every year Seed Consultants’ agronomists come across problems that are caused by variable and improper planting depth. Planting depth is critical because it impacts germination, seedling development, crop root development, emergence, and ultimately crop yields.
For corn, seed needs to be planted no shallower than 1.5 inches below the soil surface. Typically, the suggested range is 1.5 to 2 inches, however, some studies and growers have demostrated success at depths up to 3 inches. It is important to make sure that corn is planted into adequate soil moisture for germination. In addition, corn needs to be at least 1.5 inches deep for the proper early development the root system. After germination, as the coleoptile nears the soil surface, it senses light and signals the plant to stop elongation of the mesocotyl as well as signaling development of the root system. Corn that is planted shallower than 1.5 inches does not give the plant enough room between the seed and the soil surface to properly signal for and develop its root system. A shallow nodal root system can lead to decreased water and nutrient uptake as well as increased root lodging and standability problems later in the growing season.
Soybean seed should be planted at a depth of 1 to 1.5 inches. As with corn, it is critical to plant the soybean seed at the proper depth into adequate soil moisture to insure germination and emergence. Soybeans must take up 50% of their weight in water to germinate, therefore, ensuring they are planted at enough depth to imbibe moisture is the key to uniform emergence. Planting soybean seed too shallow can result in inconsistent soil moisture at the seeding depth and uneven emergence. Some studies have shown that planting at 1.5 to 2 inches provides more even emergence, however, soybeans should not be planted deeper than 2 inches.
Planting depth should be set properly and checked regularly throughout the planting season. Planting depth will vary throughout the season based on changing conditions and equipment will need to be adjusted periodically. Field conditions such as soil moisture, soil type, compaction, and tillage vs. no-till will impact planting depth settings. Moving from one field to the next can require an adjustment of gauge wheels. Planter weight and downpressure will also impact planting depth. Keep in mind that the changing weight of the planter (full vs. empty) as well as distribution of weight (center fill vs. row boxes) will also play a role in the downpressure and seed placement.
Planting depth is something that is easy to set at the beginning of the season and overlook as time goes on. Each year agronomists visit fields with standability problems and yield loss that could have been avoided if more attention was given to planting depth in the spring. The crop begins the season with its highest yield potential, it only makes sense to take the time to plant it at the correct depth so that it has the best change to achieve that potential.