Factors Affecting Soil Temperatures

A large percentage of the 2024 corn and soybean crop is still in the bag waiting to be put into the ground. In some instances, the issue is having too much moisture and not being able to get in the field. In others, the issue is that the soils are too cold to plant, with no sign of warming up in the next few days.

Potential factors that can have an influence on soil temperature are:

Air temperature: Fluctuating air temperatures can and do influence soil temperatures.
Sunlight: The radiant energy of the sun warms the soil as well as other objects even on cold days. To reinforce this concept, I always think of snow melting off a roof on sunny days in the winter.
Daylight hours: This goes hand-in-hand with sunlight. However, as we increase or decrease the amount of potential sunlight during the day, this can and does impact soil temperatures. In much of the Corn Belt at this time of year, we are increasing potential daylight hours by 2 to 3 minutes per day. In 10 days, the cumulative effect results in approaching 30 more minutes of daylight. As we look at 20 days, that moves closer to 60 minutes.
Crop Residue: Having a heavy residue or a cover crop on the soil surface due to production systems and/or trying to reduce erosion can shade the soil and reduce soil temperatures. In my experience. heavy residue has the potential to reduce soil temperature 5 to 10°F or more.
Soil Moisture: As we decrease soil moisture and more air enters the soil, the air in the soil is influenced more by air temperatures as well as sunlight. Conversely, as we increase soil moistures, the amount of energy it takes to warm up increases. However, a moist soil tends to stay more constant in temperature.
Soil Type or Texture: Lighter textured soils, such as sand, dry faster and are influenced by air temperature and sunlight more rapidly. Soil temperatures in lighter soil types fluctuate quicker than heavy clay type soils which are slower to change or give up its temperature.
Soil Compaction: A compacted soil creates a layer that does not allow moisture or air to penetrate that layer of compaction. Which, in most instances, would make soil stay cooler longer.
Soil Color: A darker soil absorbs the radiant energy of the sun and will warm up faster than a lighter colored soil.
Direction of a Slope or Hill: Due to the amount of sunlight received, the south side of a slope or hill will warm up faster than the north side of the same hill or slope.

In my experience, I see differences in soil temperatures in fields/soils that are healthier or have more biological activity. I do not know if I can prove this, however, it seems that fields that have good fertility, neutral pH, as well as a history of some type of manure in my opinion warm up faster than fields that do not.