Go on vacation when corn is 6 inches tall, leave someone else to scout it, and come back when it's waist high and dark green. It will change your whole perspective on how good your corn crop might be for the year. Most fields most years go through an awkward phase, kind of like kids at the middle school age, where they're not quite ready to take on the world but not babies nay longer either. It's a difficult stage for kids, and for corn plants.
One of the things that can happen to corn plants, and has again this year in some locations, despite a good spring for planting and early growth, is that some corn plants turn purple. It's a big enough issue to look at when corn plants turn purple while small. And what, if anything, it means for yield this year or for potential management changes in your corn program in the future.
Dave Nanda, crops consultant and director of genetics and technology for Seed Consultants, Inc., Washington Courthouse, Ohio, says there are several potential causes, beginning with a natural pigment in the leaves called anthocyanin. When sugars produced by chlorophyll can't be put into the stalks, leaves and roots sugars are converted to this trend compound, Nanda says.
Acid soils where the pH is lower than 5.5 can produce purple seedlings. It could be corrected for the future with soil testing and liming as recommended, beginning this fall. Wet soils that inhibit nutrient uptake can also cause purple leaves.
Plant stressed that reduce phosphorus uptake will lead to this condition, he notes. The stress could be early planting, followed by cool nights and warmer days. By now, several warm, sunny days have likely corrected the problem if that was the cause. Another stress that can cause it is soil compaction. Pruning roots if you still cultivate young plants or get too close with an N applicator bar could also be a factor.
Herbicides and insects may be implicated in certain situations. If the whole field is purple, or if every field of a certain hybrid number shows the same purpling, it may simply be a genetic trait. In any case, the purple color itself does not cause slower growth. Instead, what can bring it on are cooler temperatures, which also contribute to slower growth.
The good news is that purple color in seedlings doesn't generally affect corn yields this year, Nanda says. By the V8, or eight leaf stage, corn is usually a green, healthy color and the purple discoloration has disappeared.