|Franzen, David -|
|Sims, A -|
|Lamb, J -|
|Casey, F -|
|Staricka, James -|
|Halvorson, M -|
|Hofman, Vern -|
Submitted to: Precision Agriculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 27, 2010
Publication Date: November 10, 2011
Citation: Franzen, D., Long, D.S., Sims, A., Lamb, J., Casey, F., Staricka, J., Halvorson, M., Hofman, V. 2011. Evaluation of methods to determine residual soil nitrate zones across the northern Great Plains of the USA. Precision Agriculture. 12:594-606. Interpretive Summary: Different mapping methods are available for dividing farm fields into smaller units, or management zones, for spatially varying the application of nitrogen fertilizers. These include the use of aerial photographs, satellite images, topographic maps, soil electrical conductivity (EC) maps, and crop yield maps. The objective of this study was to determine the best mapping method for identifying these management zones in the northern Plains. Numerous wheat fields were mapped in Montana, North Dakota, and western Minnesota. No single method worked consistently well in all fields, but topographic maps produced zones that were most often correlated with variation in soil nitrogen fertility than any other method. Two mapping methods together worked better than any single method for this purpose.
Technical Abstract: A four-year study was conducted from 2000 to 2004 at eight field sites in Montana, North Dakota and western Minnesota. Five of these sites were in North Dakota, two were in Montana and one was in Minnesota. The sites were diverse in their cropping systems. The objectives of the study were to (1) evaluate data from aerial photographs, satellite images, topographic maps, soil electrical conductivity (ECa) sensors and several years of yield to delineate field zones to represent residual soil nitrate and (2) determine whether the use of data from several such sources or from a single source is better to delineate nitrogen management zones by a weighted method of classification. Despite differences in climate and cropping, there were similarities in the effectiveness of delineation tools for developing meaningful residual soil nitrate zones. Topographic information was usually weighted the most because it produced zones that were more correlated to actual soil residual nitrate than any other source of data at all locations. The soil ECa sensor created better correlated zones at Minot, Williston and Oakes than at most eastern sites. Yield data for an individual year were sometimes useful, but a yield frequency map that combined several years of standardized yield data was more useful. Satellite imagery was better than aerial photographs at most locations. Topography, satellite imagery, yield frequency maps and soil ECa are useful data for delineating nutrient management zones across the region. Use of two or more sources of data resulted in zones with a stronger correlation with soil nitrate.