The drought monitor, as of Tuesday, April 7th, indicates a continued increase in drought conditions with only 15% of the state now out of dry conditions. Our entire area is now in moderate drought. Only East Central Kansas is in good shape. The six to ten day forecast (April 13 to April 17) indicates a 50 to 60% chance of likely above normal for temperatures and a 40 to 50% chance of leaning above normal for precipitation. The eight to fourteen-day forecast indicates (April 15 to 21) indicates a 50 to 60% chance of likely above normal for temperatures and a 33 to 50% chance of leaning above normal for precipitation.
. It’s certainly been an unusual spring with well above normal temperatures followed by brief cold spells, usually with strong winds. We have had ninety degree highs followed by lows in the lower twenties and upper teens. Many were concerned about native plants and their early blooming flowers and trees. There was concern about the wheat crop. So, today a little refresher on how temperature affects plants, both positively and negatively.
· All things being fairly equal, temperature has the greatest effect on plant growth and development. The is a concept termed “cardinal effects.” There is a cardinal minimum temperature below which growth ceases or can severely damage and kill the plant. There is a cardinal maximum beyond which the plant can suffer severe damage or even die. Between these is a range termed the cardinal optimum where plant growth is ideal.
· There is no one minimum, maximum, or optimum for plants as it varies by species. Cool season and warm season plants; annuals, biennials, and perennials; monocots and dicots. For a crop like winter wheat or canola, you aren’t concerned about it being to cold for germination. You are concerned in the spring about excessive heat causing the plant to complete its life cycle too rapidly and having the crop die prematurely rather than mature. For crops like corn, grain sorghum and soybeans, we are concerned about minimum soil and air temperatures for germination and seedling establishment. We want rapid germination, emergence, and growth. However, with current seed treatments, seeds can normally survive cool soil temperatures with slower emergence. The bigger concern is below freezing air temperatures after emergence. With the growing point staying below ground for grass crops until about V6, it’s typically not a major concern. With dicots, soybeans and sunflowers, the growing point is above ground at emergence so freezing temperatures are more likely to damage or kill it and so also the plant.
· For wheat, it’s that late spring hard freeze that can damage or destroy the emerging head and vascular tissue.
· And we have to remember we are not simply speaking to air temperature but also soil temperature. And for our spring planted crops, where the growing point is located at seedling emergence.
· The takeaway is simple, plant as early as practical, especially for dryland crops in Western Kansas.