If wheat seems to have poor vigor and is lacking a healthy green color this fall, it may be due to aluminum toxicity and low soil pH levels, said Dorivar Ruiz Diaz, nutrient management specialist with Kansas State University Research and Extension.
Aluminum toxicity begins to occur when soil pH levels are less than 5.0 and free aluminum levels are greater than 25 parts per million, he said. The symptoms of aluminum toxicity include poor tillering and sometimes, but not always, a purplish color, Ruiz Diaz said.
“Older leaves may appear drought stressed and withered. Plants either will be stunted throughout the season -- even with adequate moisture and nitrogen -- or may die,” he said.
High concentrations of aluminum reduce root development, giving them a short, stubby appearance. The roots often have a brownish color, and the root tips may have a burned appearance. This effect on roots limits nutrient uptake, and plants may show some deficiency symptoms, even with good nutrient levels.
Low soil pH (below 5.0) can reduce the availability of such plant nutrients as calcium, magnesium, phosphorus and potassium.
“There’s not much a producer can do to correct aluminum toxicity problems once the wheat has emerged,” Ruiz Diaz said. “However, the producer should make a note of the condition and take action before planting another crop on that field. Lime applications on low-pH soil should be a high priority. Even half-rates of lime will do some good.”
In addition to liming, it also helps to use a phosphorus starter fertilizer when planting wheat in low-pH soils. This helps reduce free aluminum in the soil solution, he said. Some varieties of wheat, such as Everest and Overley, have better tolerance to low-pH soils and high aluminum levels.