Walking across the Corn Illustrated plots at Edinburgh, Ind., sponsored by Farm Progress Companies and Indiana Prairie Farmer, it didn't take long to notice something that didn't add up. Every once in a while, in the replicated nitrogen-rate testing plot, covering less than 10 acres, there would be two shorter rows between taller, greener rows. It wasn't tall-corn, short-corn per se- the height within rows was uniform, it just varied between one pair of rows and those around them.
The other surprise was that although there are two hybrids in the plot, the shorter, less-green rows and the taller, darker rows were of the same hybrid, at the same rate of nitrogen. And while the effect was most pronounced in the 100-pounds of nitrogen sidedress plot, it was visible at other point sin the field. The plot also received 20 pounds of N pre-plant, so the actual rate in the spot where the biggest difference was noticed was 120 pounds per acre.
Tom Bechman, Indiana Prairie Farmer editor, helping with the plot, decided to investigate. Tools he took to the field included a tile probe, sampling bags for leaves and soil, a soil probe and a bucket of water. He identified a spot where plants were growing well, and where they were growing poorly, both within the same hybrid and same rate.
First, he tried the tile probe. Could soil compaction be the answer? A tile probe can give an indication, but it's not as useful as a sturdier penetrometer, which usually has a gauge or dial that reads measurements. The measurements aren't important by themselves. What matters are individual, relative rankings between various parts in the field. The question boils down simply to: "How hard is it to push through the soil?"
Using the flimsy, tile probe with a tip on the end proved to be less than scientific. Roughly, it was about twice as hard to push it into the soil where the plants were not as tall or green. It would go in about five to six inches deep in the area where corn looked better.
Next, Bechman got out the shovel and dug up a shorter plant form the poor-performing row, and a good plant from a taller, greener, good looking row. There was no evidence of layering underneath the normal plant. There was good root distribution. However, a couple layer shelves stood out on the soil removed from around the poor plant. Even then, though, there was decent rooting down through the layer into the lower part of the soil.
Not convinced that soil compaction explained everything he saw, Bechman decided to pull 'good' and 'poor' soil samples and leaf tissue samples from each spot. The current tenant has only farmed this land two years- this being his first crop of corn. It's always possible that some event that occurred several years ago, even decades ago, could still be having an effect. Standard procedure is to do both soil testing and soil tissue testing from a good spot and then a problem area n the field.
Soil and tissue samples were sent to Great Lakes A & L Labs in Ft. Wayne. Leaf samples have also been sent to Purdue University's Plant Diagnostic Lab. When those results return with explanations, perhaps experts can determine what's going on in that spot of the field.