What was the moisture situation like on your farm this year? Was it too dry even for a few weeks at any point? If not, it may be in a future year. I want to explain what happens in a corn plant during a dry spell.
There are some harvesting issues best explained by weather conditions from early this season, specifically drought-induced potassium deficiency. In dry areas of the country, like where we farm, this is exactly why we heavily promote building high soil test K levels. Think of it this way. If you just barely get enough potassium into plants when moisture conditions are normal, when you have half of normal rainfall you will likely only get half as much potassium into your crop.
That can be overcome by boosting the level of K in your soil. Here are a few of the things not having enough potassium uptake can lead to.
Potassium is one of the nutrients that helps regulate the opening and closing of the stomatas on leaves. Stomatas allow air and water movement in and out of the plant.
Properly functioning stomatas can reduce moisture loss in dry weather.
If you run short of potassium in your soils or if you haven’t gotten enough moisture in the soil to make potassium available for uptake, you’re going to see much less drought tolerance with any corn hybrid you’ve planted in that part of the field. One of the unseen ways that happens is with poorly-operating stomatas.
Potassium is a mobile nutrient inside the plant. If new growth or if the seed being produced demands more potassium, the plant will rob it from the lower leaves.
Leaves with brown starting on the outside edges are showing a visual deficiency in potassium.
If your soil is short in potassium, this kind of problem wouldn’t surprise you. What if your soil tested high in potassium? We’ve pulled soil tests at each inch going down looking at all the nutrients and studying nutrient stratification.
One thing we’ve noticed in many fields is a high percentage of the potassium is located in the top three inches of the soil profile.
Obviously, this is also where soil first dries out, making it difficult to impossible for plants to extract soil potassium.
Did you notice a shorter-than-normal husk cover on your corn ears this season? Compare the higher-moisture-holding areas of your fields versus the lighter, drier hilltops. If you notice insufficient husk covers, a contributing factor is poor potassium uptake, which could be caused by dry soils or low overall potassium in the soil.
If you run short in potassium, one of the first places it will show up is in the stalk, which will have a thinner diameter and poor standability. We shoot for 4% base saturation potassium on soil tests at a minimum, with 7% to 8% being the ultimate target in heavy soils. In low cation exchange capacity soils (sandy ground), you may need an even higher percentage to begin the season in order to deliver sufficient pounds of potassium to the crop.
Download the free Ag PhD Fertilizer Removal app to see exactly how many pounds of potassium are needed by almost any crop at any yield level.
In 2022 and almost every year, somewhere there will be ear drop issues. While it’s awesome to have great big, heavy ears, personally I’d rather have two smaller ears that add up to the same yield (or even more). The way plant architecture is, though, you’re going to see big ears when you do many things right. To hold those ears on the plant, you need a thick and strong shank.
When shanks are very thin, it’s often due to insufficient potassium, especially earlier in the season.
Enzymes & Horomones
Finally, I just wanted to point out that potassium is involved in dozens of enzymatic and hormonal processes in the plant. While micronutrients often get the attention (and rightly so) for their impact on these types of reactions and systems in plants, potassium also has a key role. Lack of potassium even for a few weeks (and especially early in the season) can impact that plant in many unseen ways.