Planting seeds at the optimal depth is a critical piece to the growing process. Since a variety of factors work together to determine the best depth for each planting year, it is necessary to evaluate your situation before each planting season.

The top factors you will need to consider include:

•    Soil moisture
•    Soil texture
•    Soil temperature
•    Tillage
•    Weather

Soil Moisture

Serving as one of the most important considerations in your seed depth dilemma, soil moisture is a key component in germination. Adequate levels of water help create a successful germination in your fields. To indicate the level of importance soil moisture plays into germination, Mahdi Al-Kaisi from Iowa State University shares in his article, Soil and Management Factors Influence Seeding Depth , when a corn seed absorbs 30 percent of its weight in water the germination process will start. Additionally, soybeans will absorb half of their weight in water before they will germinate.

Ideally, the soil moisture in your fields should be near field capacity during planting season. To test for field capacity, Al-Kaisi recommends taking a handful of soil from the proposed seeding depth and squeezing it. If your soil is near field capacity it will leave a trace of moisture in your hand.

Soil Texture

The texture of your soil will influence its ability to retain soil moisture, and this will also play into the depth at which you should plant seeds. Fine-textured soils have a greater tendency to move water towards the soil surface; whereas, coarse-textured soils tend to do the opposite.

Al-Kaisi shares that seeding depth can be shallower in fine-textured soils than in sandy soils depending on soil moisture. He also adds that generally when planting below field capacity, it is advisable to plant deeper.

Soil Temperature

Soil temperature goes hand-in-hand with planting date because the two factors affect each other. An early planting date, when temperatures are below 50⁰F, will not allow seeds to germinate.

On the other hand, if you are planting late, it may be easier for you to plant a little deeper due to warmer temperatures in the soil which will allow for germination. According to Corn Seeding Depth: Back to the Basics , an Iowa State University publication, North Dakota researchers found that as soil temperatures increase above 50⁰F, the impact of seeding depth on rate and timing of emergence is also reduced.

Tillage

Since conventional tillage is known to alter the soil surface condition which results in faster soil evaporation and moisture loss, it can cause problems especially in years of drought. This may make it necessary to plant deeper than in years of adequate moisture.

Tillage also destroys the soil structure and reduces water movement making it harder for moisture to move throughout soils Al-Kaisi adds. No-till operations allow the soil structure to remain intact and this allows moisture to move evenly to the soil surface. This makes it easier to plant shallower or in years of drought, not as deep.

Weather

Even though the weather can change from hot to cold or dry to rainy in just a matter of minutes, weather surrounding the planting date should also play a part in determining your optimal seed depth. Bob Nielsen from Purdue University added in the AgWeb.com article, Watch Corn Seedling Depth in Dry Soil , the risks and benefits of deep seed placement are influenced by the soil moisture uniformity and temperature at the seed depth and the 6-10 day rainfall and temperature forecasts.

Rainfall can help promote faster germination because it will add additional moisture to the soil, so weather forecasts should be considered in seed depth as well.

“Many agronomists agree that a seeding depth of 1.5 to 2 inches is a fairly all-purpose range that works well in most situations,” says Nielsen.

To determine the appropriate seed depth for this year, you will need to consider all of these factors. The optimal seed depth will set your planting season off on the right foot, and will encourage seed germination.