Sometimes, the most important bushels you manage aren’t the ones that you create but rather the ones you save from loss.
Yield losses due to stalk quality range from 5-25% percent annually across the US. This percentage doesn’t reflect the reduced quality of grain that can also result from stalk lodging. On the whole, stalk issues can be costly to our total yield. The good news is that reductions in stalk quality and stalk lodging itself are mostly manageable situations. Reviewing the conditions you encountered during the growing season can give you a window into any stalk quality issue you might encounter and is key to managing loss through harvest logistics.
There are two types of lodging. The first type is lodging caused by a root issue, which tends to occur before physiological maturity of the plant and is preventable. Compaction, ponded soils, and root pruning by rootworm are the causes of this type of lodging. The second kind of lodging is caused by stalk quality issues, and it occurs after physiological maturity. There’s a variety of causes for this type of lodging, including severe weather, pest pressures, and stalk rot, and while such causes may not be preventable, they are, overall, at least manageable.
Of the three major causes of this second type of lodging, pest pressures are the most preventable and severe weather the least (as we, unfortunately, have no say in the matter). Stalk rot occupies the foggy middle ground of this spectrum. We have hybrids that boast varying genetic resistances to stalk rot organisms, but no hybrid is immune. It’s a sad fact that almost any kind of stress occurring at almost any time during the growing season can make a corn plant susceptible to invasion by any of the stalk rot fungi.
Controlling stalk rot then is tied up in protecting your plants against stress, both before and after pollination. Nutrient deficiencies, weed competition, compaction, high plant populations, insect damage, and extremes in soil moisture can all cause pre-pollination stress to your corn plants. Stress inflicted on a plant before pollination slows the rate of photosynthesis, which slows growth rate and results in smaller than normal plants. A smaller plant not only has a reduced leaf area but also a smaller stalk diameter, which makes for reduced sugar production and storage later in the season.
Disease and reduced sunlight are the two stressors that can occur after pollination. Fighting against either causes a corn plant to reduce sugar production at the same time that it is trying to develop ears. To compensate, a plant will reallocate sugars to take care of its greatest priority, which means that it will pull sugars from the stalk to put into the ear. This weakens the stalk and allows for the proliferation of any fungi that may have set up shop after an early-season stress. The combined effect of the reduction of sugars and the growth of fungi damages the vascular tissue inside the stalk, causing it to rot and leaving it hollow and susceptible to lodging.
Over the course of the winter, we can talk about ways to combat stressors, but there’s not much to be done about them this season. What you can do at this moment is scan your memory and notes for any stressor that you encountered this season and prioritize harvest accordingly. A field by field and hybrid by hybrid evaluation with a trusted advisor can help you determine where to start harvesting first to best manage stalk lodging issues and their attending yield reduction.
We don’t normally think about harvest in terms of ears, but humor me for a minute with some harvest math: if you have a twelve row corn head and due to stalk lodging, you drop five ears over ten feet of travel, you’re losing almost seven bushels per acre. That’s nearly $25 per acre. But the problems don’t stop there—check out the photo. Those dropped ears grow into a volunteer population next year and cost you an additional thirty bushel yield reduction in affected spots. That’s another $20 to $25 per acre cost for a total $50 per acre cost over two years— and that’s a problem.
Addressing stalk rot by working to prevent plant stress is a worthwhile expenditure of your time and energy next season. For this season, though we are well past the point of preventing stalk rot, we can yet manage the issue with a well-thought harvest strategy that will reduce your yield loss this season and tamp down volunteer corn issues next.