MANHATTAN, Kan. – The saying goes something like this: if you don’t like the weather in Kansas, wait a minute and it will change. For young crops across the state, the changing weather can be a good thing – or not.

A quick shift to cool weather in mid-May after a hot spell brought out "purpling" on the leaves of some young sorghum plants, said Kansas State University agronomist Dale Fjell. When the soil turns cooler, he explained, the plant takes up less phosphorus from the soil. Phosphorus plays a key role in the plant’s ability to metabolize nutrients.

"The purple color on the leaves is a symptom that the phosphorus is not there like it should be, but it’s not necessarily a long-term problem," added Fjell, who is a crop production specialist with K-State Research and Extension. "It’s very hybrid-specific – some [hybrids] will show it and others won’t."

If the cool period lasts for an extended time, the plant’s development could be impeded, but typically the weather turns warm soon enough that the plants rebound and develop normally.

The cool weather may have had a similar effect on recently-emerged corn, which also may show a purple color on the leaves. Corn plants that were planted several weeks ago and are further developed, however, are unlikely to be affected by the cooler weather, he said.

Fjell said he’s received calls from some Kansas producers about "rootless corn." In such cases, a grower finds an occasional corn plant in the field that has blown over. Usually, the plant would be 6-8 inches tall, and has crown roots that have not developed well.

"Many things can cause this, but this year it’s probably due to dryness in some areas," Fjell said, noting that most of the calls he’s received about "rootless corn" have come from northeast Kansas. In these cases, the plant had begun growing from the seed but once it was developed enough for the crown roots to come into play, if there was not enough moisture, the crown roots did not develop properly. That kept the whole root system from developing normally. Without a proper root system to anchor it, the plant falls over – particularly in windy conditions.

"You won’t typically see whole fields with this problem, or even big parts of fields," he said. "Soil moisture varies so much, even from one part of a field to another, that the incidence of rootless corn can be very scattered."

If rain falls in a timely manner and the plants haven’t fallen over, corn with poorly developed crown roots can rebound and become healthier, the agronomist said.