Try to solve this cornfield mystery. In 2013, Jeff Phillips, Tippecanoe County ag educator and Pete Illingsworth, farm technician, planted plots at Purdue University's Throckmorton Research Center near Romney, Ind., to compare downforce and depth of planting.
There was moisture in the soil when the plots were planted, and the row units on the Deere vacuum planter were all set the same in each particular plot.
But when corn emerged two weeks later, some rows had near perfect stands, even at shallow depths, while other rows appeared missing. Upon closer examination Phillips found there was typically some corn spiking through here and there.
The pattern tended to repeat itself across the trial, even though depth and downforce varied pass to pass. The rows tended to be on the outside of each pass. Center rows were typically more uniform.
So what could cause such variation within a pass even though the planter was set the same? Phillips thought the answer was really elementary – seeds responded to differences in moisture. It takes about 30% moisture for corn seed to begin germination. Obviously, some seed in outside rows on certain passes couldn't access enough moisture. Seeding depth must be involved.
But how could that be? Pete rechecked the planter. There were no problems with row units. It was equipped with typical coil springs for downforce.
Finally Pete remembered that the field cultivator used to prepare the plot via conventional tillage did not tend to leave soil even across the width of the pass because of wear. He speculated that since the soil was uneven, somewhat in a pattern, after the field cultivator passed through, it could be the explanation for why some rows didn't go as deep and the seeds wound up in dry dirt.
Phillips concurred that the problem was likely with field preparation and not the planter in this instance. However, he noted it was important to diagnose the cause soon after the corn emerged. In this case nothing could be done to help this year's stand. Besides, it was in a plot. But it would be possible to make corrections before next year. That might mean reworking and repairing the field cultivator, trading it off, or perhaps working the ground in a different pattern.