New Method Can Boost Yields, Lower
Fertilizer Use By David Elstein June
29, 2004
Grain crop farmers who need to know how much nitrogen fertilizer
to apply to the soil could save money--and protect the environment--by using a
fertilizer application method recently studied by
Agricultural Research Service scientists
and cooperators.
Farmers who grow grain usually use what's called the
"yield-goal" method to figure out how much nitrogen to use. They determine the
amount of fertilizer based on the estimated yield. But ARS and
University of Missouri-Columbia
scientists have completed a large-scale study on corn showing that farmers who
use this method may be losing per-acre profit--and using too much nitrogen.
Soil scientist Newell R. Kitchen and agricultural engineer
Kenneth A. Sudduth, of ARS' Cropping
Systems and Water Quality Research Unit at Columbia, and university
collaborators found that yield was a poor predictor of how much nitrogen was
needed.
That's because it's hard to determine the season's yield months
before harvest. The yield-goal method does not take into account changes in
weather or the soil variability within fields. Using new methods, the
researchers found that yield only accounts for about 15 percent of what is
known as corn's "economically optimal nitrogen fertilizer rate" (EONR).
They discovered that if farmers were able to grow corn knowing
the EONR and how that varies within fields, they could make on average $15 more
per acre---excluding costs associated with determining EONR and variable-rate
fertilizer application--than if they allocated fertilizer by the yield-goal
formula. The increase in profit would come from higher yields and less
fertilizer.
These researchers, along with other ARS scientists, are trying
to develop better tools to determine the EONR. One method they are developing
is to use a canopy reflectance sensor to monitor crop vigor, thereby estimating
just how much nitrogen fertilizer the corn needs.
ARS is the U.S. Department of
Agriculture's chief scientific research agency. |