Late-season dry weather raises concerns
Any effect of the lack of sunlight might have had on photosynthesis was moderated by the fact that the 2013 crop was behind in its development and the weather was cool in parts of July and early August. Conditions during and after pollination generally resulted in good kernel numbers, and by the start of rapid grainfilling, when the amount of daily photosynthesis becomes the critical factor for yield, sunlight had returned to more normal levels. This, along with higher temperatures, meant high rates of photosynthesis in fields with enough soil water. As is always the case, more sunlight usually means less rain, and on balance water tends to be more limiting than sunlight, so depending on when it happens and whether it means more rain, low sunlight is not always a negative factor.
Another concern as we head toward harvest is how well stalks will stand in fields where stress at the end of the season means an early end to grainfilling.
Keeping stalks healthy depends on having enough sugars in the stalks up to the end of the grainfilling period. In years like this, when stress lowers the production of sugars, stalks can lose sugars to the ear, and stalk health can suffer. One factor that may counter this to some extent in 2013 is that the favorable conditions in July seem to have allowed the plant to produce more than normal amounts of lignin, which is the woody material that strengthens stalks. If there is enough lignin in stalks, they will often stand well even there is not enough sugars to keep their cells alive. One piece of supporting evidence for this is the fact that wind storms have tended to push stalks over (root lodging) this year, but not broken the stalks. Still, it pays to check stalk strength at or before maturity to identify fields for early harvest.
Corn drydown rates should benefit considerably from earlier maturity brought on by high temperatures. It helps that husks seem to be drying well as maturity comes on; this usually means that they will loosen so air can reach the grain to help drying. We can expect drying rates of ½ point or so per day in September, but this will slow as the weather cools and if rain returns. As we often see when it’s dry in September, grain moistures often drop more quickly than expected.
Finally, I’ve had a few questions about the potential for aflatoxin problems given the recent dry weather and high temperatures. While there are no guarantees, the Aspergillus fungus that produces aflatoxin infects kernels in mid-season, and tends to be favored by hot, dry conditions and plant stress. Conditions in July 2013 were not hot and dry like those in 2012. We hope this means that we won’t see the problem this year.