Realistic Yield Expectations (RYE) have been developed in North Carolina to assist in site-specific farming decisions that will improve N-use efficiency and reduce N contamination of ground- and surface water, especially in the Neuse River Basin. This study was conducted to determine whether correlations exist between soil chemical properties, actual yields, soil map units, zones, and RYEs. Soil surveys of the fields were completed at an approximate scale of 1:3500 in 2002 (remapped soil map units) and compared to existing county soil surveys (original soil map units). Samples from equilateral triangle grid soil sampling were analyzed and used to map the spatial distribution of soil pH, soil P, and soil K and lime requirement. Interpolated maps were created to display the spatial distribution of the investigated soil chemical properties. To represent zones (transition zone or map unit interior), 20 m buffers centered on map unit boundaries were created in order to investigate these highly unique and variable areas. Soybean (Glycine max [L.] Merr) and wheat (Triticum aestivum L.) yield data was collected for two site-years in one Piedmont field, while wheat and corn (Zea mays L.) were sampled for one site-year in the two remaining Piedmont fields. Soybean and wheat yield data was collected for three site-years in two Coastal Plain fields. Interpolated nutrient maps showed visual correlations between soil map units and soil K values in the Coastal Plain, but no other relationships between soil chemical properties and soil map units or zones were visually apparent for either location. Yield maps showed visual relationships with soil map units in the Coastal Plain but not in the Piedmont. Various statistical models were utilized to analyze the data and the spatial covariance model was determined to be more efficient than the independent and identically distributed fixed effects model in capturing a significant proportion of the variability for tested soil chemical properties and crop yield in both locations. Remapped and original soil map units were also studied to determine their effectiveness in capturing the variability of soil chemical properties and crop yield. The remapped soil map units were more effective than the original soil map units in capturing this variability in most cases. Soil K was highly significant among the remapped soil map units in the Field 7 in the Piedmont where r2=0.82. In all locations, other investigated parameters also displayed significance, but none as highly significant as soil K in Field 7. RYEs were found to be greater than actual yields for all crops harvested in both locations.
| Identifer | oai:union.ndltd.org:NCSU/oai:NCSU:etd-08152004-201104 |
| Date | 09 November 2004 |
| Creators | Lohman, Mindy |
| Contributors | Deanna Osmond, Jeffrey White, David Crouse, Randy Weisz |
| Publisher | NCSU |
| Source Sets | North Carolina State University |
| Language | English |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://www.lib.ncsu.edu/theses/available/etd-08152004-201104/ |
| Rights | unrestricted, I hereby certify that, if appropriate, I have obtained and attached hereto a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to NC State University or its agents the non-exclusive license to archive and make accessible, under the conditions specified below, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report. |
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