Greg Roth
Associate Professor
Penn State
January, 2003

Background

     During late June, severely stunted, yellow areas were noticed in this cornfield in Centre County. Corn growth surrounding the yellow areas was excellent. The soil was a well drained sandy loam soil and the fertility program on the field was adequate to avoid any N, P, or K deficiency problems. The field had been in hay for several years and this was the first year in corn production. (Click on the image to the right for a larger view)

     The problem area was roughly a large circle about 75 feet in diameter with a relatively abrupt change between the yellow and normal corn. Within the problem area, there was some striking variation in plant growth within the row. (Click on the image to the right for a larger view)

     Individual plants exhibited splotches of yellow and white spots on the lower leaves. These symptoms were consistent with those encountered on corn in low soil ph areas. (Click on the image to the right for a larger view)

Diagnosis

     We collected soil samples from the affected area of the field and then in adjacent good areas of the field. This is a basic technique that is often useful for diagnosing these type of problems. Soil nutrient tests are also inexpensive, so they should be the first diagnostic test to consider, especially when soil nutrients are suspected as part of the problem.

     The soil tests showed that the pH in the poor area was 4.5 and the pH in the good area was 5.4. This confirmed that the problem was likely due to low pH. At low pH levels in our soils aluminum and manganese levels in the soil solution become elevated to toxic levels to the corn plant. In some cases swollen root tips can be observed if the plants are dug carefully from the soil.

     The remedy for this field is to have lime applied following harvest. The recommendation for the poor areas of the field was 2.3 tons/A. There is nothing that can be done during the season.

     This is a common problem in Pennsylvania and the case history and symptoms in this field are typical. The problem usually occurs in patches and is often found on newly rented ground with marginal pH. It is also surprising how well the corn grows in the "good" areas of these fields with relatively low pH. The soil pH levels were toxic symptoms occur vary among soils depending on their levels of aluminum and manganese.