Topography maps
In 1996, the use of topography soil sampling greatly increased in the Red River Valley as another Precision Ag option for detecting nutrient variability in soils. Topography maps were generated on approximately 5,000 acres for the use in evaluating drainage and soil sampling by elevation. Topography maps were produced to soil sample by zones on 25 fields totaling over 2500 acres for 1997's sugarbeet crop. Results of elevation sampling in 1996, as in the past, have shown a direct correlation between the available nitrogen and the separate elevations of fields with varying topography. The lower areas of a field have trended lower in available nitrogen and the higher areas have trended higher in available nitrogen.
Satellite imagery recently became available to help visualize the vegetative vigor differences in a crop. These differences can sometimes appear extreme with only minor changes in final yield. It has been suggested that zones could also be derived from these satellite images for soil sampling.
OBJECTIVE
Objectives of the study were to determine how well nitrogen values, obtained from soil sampling using management zones derived from both satellite imagery and topography maps compare to normal grid sampling. Since topography sampling had been ground truthed using soil sampling, and satellite imagery has never been ground truthed in the Red River Valley, it was time to do so.
