An article in the March 25, 2016 Agronomy eUpdate discussed average soil temperatures for the week of March 19 – March 24 and average last spring freeze dates. Over the past week, changes in soil temperatures have been noticeable for the southwestern section of the state, rising by 2 to 3 degrees F overall (Fig. 1). Soil temperatures in the northern section of the state decreased slightly compared to the prior week. The remainder of the state saw a change in soil temperatures of about a degree.
Absolute soil temperatures at the 4-inch depth are still below 50 degrees F across much of the state (Fig. 2). A small area of east central Kansas has temperatures in the low 50s, but no area has soil temperatures close to 55 F – the near-optimal temperature for beginning corn planting. The lack of precipitation in southwest Kansas was a big factor in the dramatic increase in soil temperatures in the district during the past week.
Colder-than-average air temperatures for the last week in March (Fig. 3) will slow the warming pattern in soil temperatures.
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.
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 temperatures 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 upcoming 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