Causes for yellow corn leaves

CHATHAM, Ill. — Yellowing corn leaves are often a sign of a problem with nutrient uptake process, either due to water competition from nearby grass or drought conditions.

Corn plants get 13 of the 16 required nutrients for growth through the soil, either through direct contact as roots grow, via mass flow or diffusion.

“Our environment is dynamic,” said Matt Montgomery, Pioneer field agronomist. “Yes, these are potash deficiency symptoms, but the issue isn’t potash.

“The issue in this case is moisture availability, and that’s because we’ve had this combination of drought and grass roots competing for moisture. If we looked at nothing but symptoms, we would have jumped to incorrect conclusions.”

Nutrients are taken up into the corn plant in three main ways: directly by the roots, mass flow and diffusion.

Mass flow is the process by which nutrients are dissolved in water and taken in by the plant roots. Mass flow is responsible most transport of nitrate, sulfate, calcium and magnesium.

Diffusion is most likely responsible for potassium-deficient corn plants displaying yellow leaves, Montgomery said.

Diffusion occurs when nutrients move from a high-concentration area to a low-concentration area to reach equilibrium.

Higher concentrations of nutrients in the soil move via a thin film of water molecules to the lower concentration root surfaces where they can be taken up. This process is particularly important for the transport of phosphorous and potassium.

“It’s another way we can appreciate this complex system we raise crops in,” Montgomery said.