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item Erskine, Robert - Rob
item Green, Timothy
item Dunn, Gale

Submitted to: ESRI Conference Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 9/7/2001
Publication Date: 10/23/2001
Citation: Erskine, R.H., Green, T.R., Dunn, G.H. 2001. Gps/gis methods for collecting and analyzing grain and forage yield data. ESRI Conference Proceedings. October 2001.

Interpretive Summary: The future of "precision farming" and agricultural research will rely heavily on GPS technology and GIS software. This fact is supported by the numerous applications in this paper alone. Cooperation of farmers, scientists, and the developers of GPS/GIS will be crucial for continued advancements and improvements in the technology. As farmers and scientists apply the tools currently available, additional needs will be discovered. More potential applications exist in agriculture that we know of today. Before the 1999 harvest of foxtail millet, there was no expectation of locating some 400 hay bales by GPS. Instead, in a year that no yield data was expected to be collected, a yield map was produced. For the research presented, the assumed relationship between landscape topography and crop yields has not been discarded, despite the low correlation obtained in the regression analysis. A multiple regression including more explanatory varia ables, such as other topographic attributes, can improve the correlation. Also, the point-to-point method of comparison may have been too restrictive in capturing the relationship between the wetness index and crop yield. There was obvious similarity in the spatial pattern, as shown on the maps, but the correlation may be at a larger scale and require some aggregation of data before doing regression analysis. These will all be investigated. obvious similarity in the spatial patterns, as shown on the maps, but the correlation may be at a larger scale and require some aggregation of data before doing regression analysis. These possibilities will all be investigated with the aid of GIS.

Technical Abstract: Global positioning system (GPS) technology and geographic information system (GIS) techniques have made broad applications of "precision farming" possible. In the present application,grain yield monitors and satellite-differentially corrected GPS (DGPS) are used to collect winter wheat yield data in space. A method of spatial yield data collection for foxtail millet, a non-grain forage crop, is introduced. This method incorporates DGPS-located bales, bale mass, and driving directions of the baler to produce yield per area estimates. ArcViewTM version 3.2 (ESRI, Inc.) is used to process field-collected data into yield maps. Spatial patterns of winter wheat and foxtail millet yields harvested in 1997 and 1999, respectively, from a 65 ha field in northeastern Colorado are compared. A grid digital elevation model (DEM) is produced for this site from point elevation data. Dual-frequency, real-time kinematic GPS (RTKGPS) is used to collect elevation data at approximately 5-meter resolution while mounted on an all-terrain vehicle. Yield data are related to various landscape topographic attributes, derived from the DEM. The use of ArcView for the creation of DEMs, computation of topographic attributes, and analysis of yield/topography relationships is demonstrated.