One “rural legend” is that when planting corn-on-corn, the big hit on yield is reduced in the second year and goes away after five years. Not true, says Fred Below, professor of plant physiology at the University of Illinois.
“That’s not what my data shows. You’re giving up 25 bushels per acre with corn on corn, and the penalty gets worse with time,” he says. “The seventh year is even worse.” As a result, it’s important to factor that in when determining nitrogen levels. Below spoke on how to obtain top yields at Top Producer’s Summer Seminar in Bettendorf, Iowa.
- The top seven factors in achieving high yields, Below says, are these in order of importance: weather (accounting for 70 bushels/acre)
- nitrogen (70 bushels)
- hybrid (50 bushels)
- previous crop 25
- plant population (20)
- tillage (15)
- growth regulators (10 bushels)
“These things interact,” he says, adding that “everything about nitrogen is driven by the weather.” Below says that many producers are giving up yield by planting too small of plant populations. With higher plant populations, big yield gains are possible with today’s genetics, he says.
His data on yields show that when planting hybrids that provide rootworm control, yields increase beyond what is gained by controlling rootworms alone, and seem to be important in nitrogen use. Because of that, he even advises producers without rootworm problems to consider planting hybrids with rootworm control. He speculates that the reason for the benefit is because the corn roots get additional protection that increases nitrogen use efficiency.
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