Across Ohio, the corn crop in general is set up for high yields based largely on ample amounts of precipitation and moderate temperatures during most of the 2013 growing season. Lately, rainfall has been at a premium with some areas receiving adequate moisture and others needing a good shower to finish the crop. The questions that remain are, will my corn crop mature and what should I be looking for prior to harvest? This update attempts to address both of those questions.
Overall GDU (heat) accumulation during 2013 is currently below normal across most of Ohio. As a result, corn grain fill, drydown and harvest maturity are delayed. Prevailing weather conditions between now and harvest will dictate how fast field drying will occur versus harvesting at higher moisture and using artificial drying methods for the corn crop. The rule of thumb, based on research conducted at Ohio State University, is that field drying rates of standing corn range from half to three-quarters of a point of moisture per day up until mid-October, and decline to a quarter to half a point until early November. After that, field drying is negligible, even when left in the field until mid-December or later.
Among most corn fields evaluated this year, pollination and grain fill are very good. However, corn fields that have had excessive amounts of precipitation are also showing nutrient deficiencies, especially nitrogen (N). N deficiency in corn is characterized as “firing” of corn leaves from the bottom of the plant up to and sometimes including the ear leaf.
Since N is a mobile nutrient, it makes sense that the older leaves would show N loss first, since any remaining N would move to the newest growth at the top of plant, and ultimately to the developing ear. The good news is that, according to research from Penn State University, when there were 4 to 5 green leaves below the ear, corn plants were not N deficient 95% of the time. Four or fewer green leaves resulted in N deficiency 50% of the time.
The other weather event not often mentioned, and equally important, is the quality of solar radiation (sunlight) during the growing season. This year, with reduced amounts of sunlight, corn plants will typically result in taller plant and ear height. Later planting dates can also influence this effect.
With the combination of N loss, weather effects and high yield potential, we are set up for potential stalk quality concerns prior to harvest. In the absence of adequate nutrients and moisture to sustain the plant and fill grain on the ear, corn hybrids will cannibalize stalks and other plant parts to fulfill its purpose of finishing grain fill.
As we approach harvest, there are a few things we can do to reduce harvest losses in the field. First, make sure the combine is ready to roll with appropriate clearances, ground and header speed and considerations for harvesting higher yielding, and likely higher moisture, corn grain. Second, prioritize fields for harvest by selecting a few random areas in each field and pinching the lower stalks to determine their integrity. If 15% or greater of pinched stalks are deteriorating, schedule that field for harvest first, regardless of grain moisture content. It is more profitable to dry harvestable grain than to take chances on stalk lodging and potential field losses, especially later in the harvest season when field drying is minimal and weather effects can further deteriorate the crop.
Hybrids differ in stalk strength, so it is a good idea to consult with your local seed representative for more information.