An article in the March 27, 2015 Agronomy eUpdate discussed average soil temperatures for the week of March 16-22 and average last spring freeze dates. Over the past week, changes in soil temperatures have been quite noticeable for the southern section of the state, rising by 1 to 3 degrees F overall (Fig. 1). Soil temperatures in the northern section of the state decreased 1 to 2.5 degrees compared to the prior week. The remainder of the state had only a small or no change in soil temperature.
Figure 1. Change in weekly average soil temperatures at 4-inch depth from the week of March 16-22 to the week of. March 23-29, 2015.
Absolute soil temperatures at the 4-inch depth are still below 50 degrees F in the NE corner of the state (Fig. 2). In the opposite corner of Kansas, the SW area has soil temperatures close to 55 F -- near optimal for beginning corn planting. The lack of precipitation in much of Kansas was a big factor in the dramatic increase in soil temperatures in the western, central, and a section of the SC districts during the past week.
Figure 2. Average soil temperatures at 4-inches for Kansas for the week of March 23-29, 2015.
Compared to historical means, soil temperatures during the last week of March were above normal for all of Kansas. The departure from normal ranged from a few degrees in the SE corner to up to 10 degrees or more in the NW region (Fig. 3).
Figure 3. Departure from normal weekly mean soil temperature at 4-inch depth for the week of March 23-29, 2015.
For the coming days, the amount of precipitation expected will play a critical role in speeding up or slowing the progression of soil temperatures around the state, more precisely in the northern section. Wet soils in a no-till situation are slower to warm. Dry soils will change in temperature more rapidly, and match air temperatures more closely.
Figure 4. Weekly precipitation for the week of March 23-29, 2015.
Still, soil moisture is not the only factor affecting soil temperatures. The absolute change in soil temperatures is also governed by the residue cover (quantity and distribution), tillage system, and landscape position. For summer crops, uneven soil temperature around the seed zone can produce non-uniform crop germination and emergence. Non-uniform stands can affect maximum attainable yield, especially for corn.
Please be sure to consider these factors during the next several weeks before planting your crop. More information about effects on plant stands and uniformity will be provided in coming issues of the Agronomy eUpdate newsletter. Make sure to check our electronic resources:
Department of Agronomy: http://www.agronomy.ksu.edu
Extension Agronomy: http://www.agronomy.k-state.edu/extension/
Mesonet and other weather information: http://www.mesonet.ksu.edu
Ignacio Ciampitti, Crop Production and Cropping Systems Specialist
Mary Knapp, Weather Data Library