2008 Joint Annual Meeting (5-9 Oct. 2008): Using Precision Agriculture Technologies to Grow Winter Wheat in Delaware.

In Delaware approximately 75,000 acres are planted to wheat each year, which is about 12% of Delaware crop land.  The average wheat yield for the state is 57 bu/ac.  The most important fertilizer application is nitrogen (N) topdressing in the spring after growth resumes.  Over-fertilization with N in the fall can produce wheat susceptible to disease and winterkill, and can increase leaching losses during dormancy.

Precision agricultural practices have the potential to increase wheat producer incomes while reducing possible negative environmental impacts of over fertilization.  Precision agriculture effectiveness is highly dependent on how much variability exists within a field and the ability to identify best management practices for each production issue.  The use of remote sensing to characterize early spring wheat canopy has the potential to enable producers to employ precision agriculture technologies when and where appropriate.  A simple color-infrared aerial image acquired of a wheat field during green-up can characterize the biomass variability, growth rate variability, and nitrogen content variability of the canopy.  Armed with such information, a producer can variable-rate-apply nitrogen fertilizers in such a way to maximize monetary net returns.

This study evaluated the use of remote sensing to characterize economic optimal spring nitrogen fertilization rates for a Delaware winter wheat field.  Sixty-three percent of the variation in yield was explained by the following factors: N rate applied, biomass at the time of N application, and an interaction between N rates applied and plant biomass.  Poorer stands of wheat required high rates of spring-applied N to maximize net returns, but for excellent stands of wheat the lowest rate of N was sufficient to maximize returns.  A comparison of net returns indicated that the variable-rate strategy of fertilization resulted in more dollars per acre: more than enough to pay for the variable rate N applications.