I always feel that spring is a fun time with new calves and lambs and watching the earth come back to life after a long, cold break. With all the excitement, however, comes plenty of planning and work. March and early April are typically time for small-grain planting, but often times, cool soil temperatures can slow down emergence.

Small grains are some of the most frost-tolerant crops we plant, but we still must be mindful of soil and air temperatures when planting.

The growing point on small grains does not emerge above the soil surface until jointing, after which time the crop is much more susceptible to frost damage than any time previous. Small grains may be smarter than we think, however.

Drought or several days of temperatures below 50°F can cause the plant to go through a hardening process, increasing frost tolerance. However, once the growing point emerges after jointing (when reproductive tissue is forming), the crop becomes more susceptible to frost damage, and this is when detrimental losses could occur should temperatures not cooperate. From boot to flowering, small grains are most sensitive to frost; temperatures under 28°F will cause moderate to severe injury depending upon growth stage and length of time low temperatures are sustained.

There is no hard and fast planting rule involving air temperatures and small grains, but later planting dates (due to moisture or other delays) may help reduce the risk of plants freezing off after coming up.

So how do we determine the best window to plant small grains? Begin by monitoring three-day average soil temperatures in the early spring. A great reference for soil temperature in your area is the South Dakota Mesonet network.

This growing weather station network measures soil temperature at five depths in several locations throughout South Dakota.

Although our small-grain planting depths can be quite shallow, the agricultural engineering standard for environmental observations is at a 4-inch soil depth under bare soils, making this measurement the one to rely on for planting-related soil temperature data (current agronomic recommendations take the difference in depth into account). The Mesonet site provides daily averages based on 10-minute incremental updates.

When taking a quick look at temperatures across the state this week, we see that soils are warming up but still somewhat cool, with the SD Mesonet weather stations showing the 4” bare soil temp ranging from 32-43°F as of April 6. Depending on Mother Nature’s mood, this could change relatively quickly.

To check out statewide soil temperature date, visit https://climate.sdstate.edu/ and click the "Archive" button at the top. From there choose "State Maps" and then select the "Soil Temp, 4” Bare" layer on the map; this will allow you to view the most recent data and look back at previous days as well. To view recent soil temperature data for an individual station, go to "Current" and then select "Local Data." Selecting a station will lead you to the current observations for that location. Once you are viewing a single station, you can choose the tab for "History" to see the last seven days of measurements by choosing the "7-day Table." This is sometimes easier to view for a quick overview of recent soil temperatures. See Table 1 for specific information on the germination temperatures of common spring-seeded South Dakota crops.