Corn is using less nitrogen than in the past, says George Rehm, University of Minnesota Extension soils specialist.
U of M trials confirm what many farmers have suspected the last several years – it takes less N than before to produce a bushel of grain.
U of M trials confirm that corn following corn is using between .87 and .90 pounds of N to produce a bushel of corn, depending upon soil type.
N efficiency ranged from .47 to .69 pounds per bushel of yield in corn following soybeans, depending upon soil type.
The standard conversion rate used to be 1.25 pounds of N per bushel of yield.
Rehm attributes the increased efficiency to new hybrids. They have more extensive root systems than old hybrids, he says.
That in turn leads to improved nutrient uptake.
There's less weed pressure than in the past. Weeds compete with corn for both nutrients and water. With fewer weeds for competition, more nitrogen in the soil system is available for corn.
There is less corn borer and corn rootworm pressure, thanks to new biotech hybrids with insect control built into the seed.
Reduced damage to stalks and ears from corn borers has a positive impact on uptake of both nutrients and water. With reduced rootworm pressure, there is a larger, more effective root system resulting in improved uptake of fertilizer N.
"Improved efficiency in the use of fertilizer N is a good thing," Rehm says. "With improved efficiencies, lower N rates are needed to achieve optimum yield."
U of M uses the new efficiency rates in making N recommendations for corn.
Make sure you know the efficiency rate is being used in determining how much N you should apply to corn, Rehm advises.