Authors: Christopher Redmond, Mary Knapp, Ignacio Ciampitti

The heat continues in Kansas, particularly with the warm minimum temperatures (Figure 1). For the 11-day window of June 10-20, parts of the South Central and Southeast divisions had lows above 70 degrees F almost every night. Most of the eastern half of the state saw those elevated lows for over half of the nights. Only the western third of the state had two or less nights with minimum temperatures above 70 degrees F.

Night time temperatures in excess of 70 degrees F for more than two consecutive days will increase the risk of stress to livestock. As with people, the stress is cumulative.

Figure 1. Total days with minimum temperature greater than 70 degrees F. Source: Weather Data Library

The heat this June can also cause problems for corn in Kansas (Figure 2). The effect of combined heat and drought stresses can reduce plant size, primarily when the plant is entering the stem elongation process. When the crop reaches the V10 (tenth-leaf) stage, nutrient and water demands (0.25 inch/day) are high. At this specific point, a combination of heat plus drought stresses will affect potential number of kernels and ear size. Overall mean temperatures above 90 degrees F, and more importantly, lower fluctuations between day and night temperatures, will produce critical impacts on plant and potential ear sizes and the yield components of corn.

Heat stress will have more of an impact on corn at this stage of growth when combined with drought stress. But even in the absence of drought stress, heat stress alone can still hasten vegetative phases and tasseling, potentially increasing the asynchrony between pollen shed and silk extrusion when corn reaches flowering time. The potential for yield reductions from stress at this stage of growth is small, however, compared with severe stress occurring right around pollination.

Figure 2. Leaf rolling in corn from the combined effect of heat and drought. This can also affect final plant size. Photo by Ignacio Ciampitti, K-State Research and Extension.

The K-State Mesonet web site has a special page that tracks the current heat index at: http://mesonet.k-state.edu/weather/heat/

There is also a page that tracks growing degree accumulation for multiple crops. With this tool, you can pick the planting/emergence date for the start of the interval. Selecting the graph will illustrate the growing degree accumulation for this season versus normal and plant stage. You can access the page at: http://mesonet.k-state.edu/agriculture/degreedays/

The data updates every five minutes when you refresh the page and is available for all 58 stations.

Christopher Redmond, Mesonet Network Manager

Mary Knapp, Weather Data Library

Ignacio Ciampitti, Crop Production and Cropping Systems Specialist