Bob Recker’s plant-by-plant findings confirm long-term research by Purdue University that plant-to-plant variability matters in corn yields, especially in no-till continuous corn. A 14-year study there from 1981 to 1994 showed greater plant height variability at week 4, especially in no-till continuous corn, was associated with yield drops. In that study, increases of 23% to 30% variations in plant height were associated with 6-bushel to 41-bushel per acre drops in yield. No-till continuous corn had the greatest plant height variability and lowest yield (see table).

 “We now know that the variation in final plant yield has very little to do with small differences in seedling emergence time or even plant spacing,” says Purdue Agronomy Professor Tony Vyn, who led research in this area.  “Plant-yield variability has a lot more to do with variation in flowering times and stalk diameter near flowering stage. Plant heights are one indicator of a plant’s competitiveness, but stalk diameter and the time between pollen shed and silk emergence is another,” Vyn adds.

            “Another really important story is that plant-to-plant variation really increases with plant stress in the season resulting from things like high plant density or low N fertility. ”

 His research recommends paying close attention to management practices that reduce variability that include 1) distribute residue evenly, 2) avoid soil compaction, 3) place seed with consistent spacing and depth, and 4) apply N precisely and consistently at a safe distance from each plant in the row. For more information see

For more reading on the importance of plant uniformity, see