First as usual, a drought update is in order. Northwest Kansas and a fair portion of North Central Kansas are completely out of drought as of this past Tuesday. Our area remains essentially as it was last week, primarily moderate drought with a small slice of Barton/Rice border in severe drought. There was a slight easing of conditions in Southwest Kansas. The eastern third of Kanas is pretty much unchanged. We did receive rain in much of the area but with the heat and wind, we didn’t gain any ground on the drought but we didn’t go backwards either. In spite of this, summer crops overall look surprisingly good and the heat has pushed the corn with much of it tasseling and silking. And overall crops aren’t exhibiting a great deal of heat/moisture stress systems. Today’s topic is why crops look so much better this year than last.
Quite simply, the weather has, with a hiccup or two, been good to excellent for crops and not so much for people and animals, especially compared with last year. Why?
• Overall timelier planting of summer row crops, especially compared to many fields last year. Corn was in the ground and able to establish a root system and access soil moisture. Last year’s weather resulted in late planting, very late in many cases. While this year may temperatures were well above normal, there was enough precipitation to help it establish. Similarly weather cooperated and producers didn’t delay in planting soybeans and even grain sorghum.
• June rains, especially the last half of the month, and rains in early July were adequate enough to keep crops going and growing in the area. While not enough to recharge subsoil moisture and significantly ease/eliminate the drought, they were enough to provide topsoil moisture and minimize moisture stress in most fields. Remember, when precipitation occurs is just as important as how much. We have had just in time rain for summer crops.
• Temperatures in May were well-above average and with the exception of a break or two above average in June. However, the area lacked a great number of one-hundred degree plus days. Corn and grain sorghum develop based on the accumulation of heat and there was plenty to go around. Beans also prefer warm temperatures but their reproduction is keyed to increasing night length not temperature. And what also helped is the next item.
• In addition to the rain, one other factor helped plants deal with the heat more effectively – humidity. What makes us uncomfortable is great for crops. Plants move water from roots throughout the plant and out the leaves in response to a humidity gradient. The humidity of the air, except when humidity is 100%, is less than in the leaves and that helps water to move up and out the plant. When the gradient becomes too steep for the plant to keep up, it must shut down, curled leaves and wilting, in response as a defense mechanism. Several factors determine if the plant can keep up: soil moisture and root system development, wind speed, air/soil temperature, and humidity. The higher humidity makes it somewhat easier for the plant to pump enough water and eases the effects of air temperature since more heat is used to evaporate water. And the humidity has been higher as evidence by the dew points and actual dew on the grass in late June/early July. This also can keep air temperatures a bit lower since solar radiation is being used to evaporate water. The humidity also helps with corn pollination, especially during warm nights.
So while we may not be thrilled with the weather, plants are enjoying it.
Dr. Victor L. Martin is the agriculture instructor/coordinator for Barton Community College. He can be reached at 620-792-9207, ext. 207.