Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/12/2003
Publication Date: 5/19/2004
Citation: Chang, J., Clay, D.E., Carlson, C.G., Clay, S.A., Reese, C.L., Malo, D.D., Ellsbury, M.M. 2004. Defining yield goals and management zones to minimize yield and nitrogen and phosphorus fertilizer recommendation errors. Agronomy Journal. 96: 825-831.
Interpretive Summary: Fields are a mosaic of habitat types, each having unique characteristics that influence soil properties and crop yields. The effectiveness of the management zone approach rests on the ability to identify the boundaries associated with different habitats. A commonly accepted approach for testing the effectiveness of the zone boundaries is not available.The objectives of this study were to propose an approach for evaluating the effectiveness of different management zone boundaries and to use this approach to determine the impact of different approaches for identifying zone boundaries on N and P fertilizer recommendations. Corn and soybean yields had a significant amount of temporal and spatial variability. Much of this variability was predictable. The yield potential was stable at the summit/shoulder areas (low temporal variability and low yield), moderately stable at backslope areas (moderate temporal variability and high yield), and unstable at footslope areas (high temporal variability and low-high yield). In footslope areas, yields were limited by too much water in wet years, while insummit/shoulder areas yields were limited by too little water. The 4-ha block sampling hadlower N and P fertilizer recommendation MSE values than the other techniques tested. Sampling the old homesteads separately from the rest of the field improved P recommendation MSE values and did not influence N recommendation MSE values. The strategy that had the lowest P and N recommendation error was the 4-ha block sampling combined with using seasonal and/or landscape specific yield goals.
Technical Abstract: Universally accepted techniques to identify and evaluate management zone effectiveness are not available. The objectives of this study were to propose an approach for evaluating zone boundaries and to use this approach to determine the impact of different approaches for identifying zone boundaries of N and P fertilizer recommendations. This study was conducted in two east central South Dakota fields between 1995 and 2000. The crop rotation was corn (Zea mays L.) followed by soybean (Glycine max L.). Approaches evaluated for locating N and P management zone sampling boundaries included: (i) sampling areas impacted by old homesteads or grazing separately from the rest of the field; (ii) sampling different blocks; (iii) using geographic information systems (GIS) or cluster analysis to identify zones based on apparent electrical conductivity (ECa), elevation, aspect, and distance(connectedness) information; and (iv) sampling each soil series separately. Two statistics, pooled variances and mean square error (MSE), were used to assess the effectiveness of the different management zone boundaries and an F-statistic was used to test these values. Corn yields had a significant amount of temporal and spatial variability. The 4-ha block sampling had lower P and N fertilizer recommendation MSE values than the other techniques tested. Sampling the old homesteads separately from the rest of the field reduced the P recommendation MSE and did not influence the N recommendation MSE. The strategy with the lowest P and N MSE was the 4-ha block sampling combined with season/landscape specific yield goals.