Authors: Mary Knapp, Ignacio Ciampitti

Weather models are indicating a return to the warmer weather that was prevalent in mid-June. By the end of next week, temperatures are expected to be in the low 100’s as shown on the map below:

Overnight low temperatures are not expected to provide much relief. Again, by Friday of next week, low temperatures are expected to stay in the mid to upper 70’s, as illustrated below:

Areas that missed out on this week’s moisture are more likely to show signs of stress.

Below is a map of the 7-day precipitation totals ending on July 15th at 7:00 a.m.

The heat in the coming weeks can cause problems for all summer row crops in Kansas. With corn, the latest Crop Progress and Conditions Report from USDA-NASS shows that most of the crop has already reached 50% silking, except in the western districts of the state. At this point, high heat could have an impact on abortion of early-formed grains -- and could also impact pollination across the western section of the state. Overall, temperatures above 95 degrees F, and more importantly lower fluctuations between day and night temperatures, will have a critical impact on kernel number (abortion process) and also on the duration of grain filling (occurring in southeast Kansas), consequently impacting final kernel size (grain weight).

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 will increase the asynchrony between pollen shed and silk extrusion when corn reaches flowering time. The potential for yield reductions around pollination are quite high, diminishing as the crop progresses into later stages (blister and milk stage).

For soybean and sorghum, heat stress next week could also impact plant growth and maximum yield potential but the risk is less than for corn at this point in the season since soybeans and sorghum are not yet in the high-water-demand period. Based on the last Crop Progress and Conditions Report from USDA-NASS, soybeans are just blooming in some areas of the state and sorghum is only starting to head in the Eastern and South Central Districts of our state. These crops would have a higher level of risk of yield reductions due to high temperatures, combined with drought stress, if the stress were to occur toward the end of July.

For more information on summer row crops growth and development, visit all K-State and KSUCROPS Lab publications.

Corn: http://www.bookstore.ksre.ksu.edu/pubs/MF3305.pdf

Soybean: http://unitedsoybean.org/wp-content/uploads/52618-11_Kansas-Soybean-Growth-Chart.pdf

Sorghum: https://www.bookstore.ksre.ksu.edu/pubs/MF3234.pdf

Mary Knapp, Weather Data Library

Ignacio Ciampitti, Crop Production and Cropping Systems Specialist