By Matt Reese
While some parts of the state got some moisture over the weekend to provide a little relief, many parts of Ohio continue to suffer from the hot, dry conditions that have plagued the state early in the 2012 growing season.
Weather patterns suggest that the overall trend of dry weather will remain in place. Slightly above normal temperatures and below normal rainfall is likely for the next several weeks.
Different crops handle the current stress of Ohio’s dry conditions in different ways. In the last week or two, as the dry conditions were a growing concern in many parts of the state, corn ranged from the V5 to the V10 stages of development, meaning that ear formation was underway in many fields.
“As early as the V4 or V5 stage, ear shoot initiation is completed and the tassel is initiated on the top of the growing point. During the rapid phase of corn vegetative growth (which generally starts by V7), ear yield components are being determined. Kernel row numbers per ear are generally established by about V7,” wrote Peter Thomison, Ohio State University Extension corn specialist, in a recent CORN Newsletter. “Will the recent moisture stress impact ear formation and yield potential? It takes fairly severe stress conditions during the early vegetative growth stages to impact kernel row numbers per ear. Kernel row numbers are usually less affected by environmental conditions than by genetic background. Therefore, in most corn fields, it’s unlikely that kernel row numbers have been impacted significantly by recent dry conditions. However, unlike kernel rows per ear, kernels per row can be strongly influenced by environmental conditions.”
Thomison points out that determination of kernels per row (ear length) is not usually complete until V12 to V15, which can be hindered by drought stress during the two weeks prior to pollination.
“If we begin to get rain, the corn crop won’t recover completely, but it will be better than we thought,” said Bob Nielsen, Purdue Extension agronomist. “We’re tip-toeing on the edge of something serious. Right now, it’s wait-and-see. It could go either way.”
The soybeans are also starting to show signs of drought stress around Ohio. According to Purdue Extension agronomist Shaun Casteel, soybean plants begin flipping leaves over to reflect the sun when stressed. In more severe cases, plants go into survival mode. In addition, some later planted fields have not yet emerged.
“Late-planted beans in dry soil might still emerge with rainfall,” Casteel said. “However, if the seed has cracked open and the root emerged it could become a worst-case scenario.”
Hay producers are also increasingly plagued by the dry weather. Purdue Extension forage specialist Keith Johnson said some forages initially were damaged during hard freezes in April and have struggled in the hot, dry weather of May and June.
The early hay harvest this year could also contribute to the problem. If harvested prematurely, the crop could have been lacking in carbohydrate reserves needed for the next crop to regrow. Harvesting second and subsequent cuttings before the plants have time to rebuild vigor could cause stands to suffer into the future. Johnson advises waiting until just after late bud or on into some flowering before harvesting again.
“If we’ve harvested relatively early a couple of times, we really have put some stress on that plant,” he said. “We probably should give it an opportunity to get beyond late bud and maybe into some flowering to give us more days to put carbohydrates into the reserves in the crown and taproot. Then there should be enough vigor for regrowth.”
The lack of rain also has created conditions that exaggerate potato leafhopper damage in alfalfa. During feeding, it injects the crops with toxins that stunt growth and limit yield.
Johnson encouraged growers to scout for the potato leafhopper with a sweep net intended for this pest. Insecticide treatments could be warranted when the average number of potato leafhopper in a single sweep of the net is 0.1 leafhoppers per inch of alfalfa height. For example, an alfalfa crop 10 inches tall would need more than one leafhopper per sweep to warrant control. Those insecticides, however, also kill beneficial insects.
Moving forward, growers need to avoid harvesting forage crops too late in the season to allow plants to build up sufficient carbohydrate reserves after a stressful growing season.