APPLYING GIS FOR INTERPRETATION OF SPATIAL VARIABILITY IN YIELD: A CASE STUDY

Authors: BAKHSH, A - IOWA STATE UNIVERSITY; Colvin, Thomas; Jaynes, Dan; KANWAR, R - IOWA STATE UNIVERSITY; TIM, U - IOWA STATE UNIVERSITY

Submitted to: American Society of Agricultural Engineers Meetings Papers
Publication Type: Abstract Only
Publication Acceptance Date: 5/1/1999
Publication Date: N/A
Citation: N/A

Interpretive Summary:

Technical Abstract: Site specific farming methods have the potential to maximize crop yields with possibly reduced inputs. This study investigated the relationship between soil attributes and corn-soybean yield variability using 1995-98 yield data from a 25-ha field in central Iowa. In order to compare yield variability among crops and years, yield data was normalized, based on fertilizer treatments, for subsequent analysis. The soil attributes of bulk density, cone index, organic matter, aggregate uniformity coefficient and plasticity index were determined from field data collected at 42 sampling sites. The correlation matrix and stepwise regression analysis for the different soil types of the field reveled that the Tilth Index did not show a significant relationship with yield data for any year and may need modification for this field. The regression analysis showed a significant relationship of soil attributes with yield data for Harps and Ottosen soils which was further explored with a map overlay analysis of yield, soil type, and topography done with ARC/INFO, GIS software. The map overlay analysis showed that at lower elevations higher yield polygons may be influenced by management practices and topography. GIS analysis showed that areas of lower yield in the vicinity of Ottosen and Okoboji soils for corn were consistent from year to year. Areas of higher yield were variable. Both analyses concluded that the interaction of soil type and topography have an influence on yield variability patterns for this field.