EVALUATION OF TREATMENT BY ENVIRONMENT INTERACTIONS ON SANBORN FIELD, 1950–19901*

Abstract

Agronomic interpretation of results from long-term projects is often complicated by treatment by environment interactions. Sanborn Field, the oldest continuously operated crop management research site west of the Mississippi River, was targeted for further study utilizing stability analysis. Specific treatments where long-term management has not changed since 1950 were evaluated by regressing treatment means on the environment mean (average yield of all treatments in a given year). Included in this analysis were continuous corn (Zea mays L.), continuous winter wheat (Triticum aestivum L.), and a corn–soybean (Glycine max L.)–wheat rotation. Stability analysis showed that winter wheat is more sensitive to low P than corn and/or soybean since decreased yields in the absence of P were constant, regardless of the environment. Where no nutrients were applied, corn yields did not increase with increasing environment means, while modest increases in wheat yields were noted as environment means increased. The latter was considered to be a function of how residues are managed following harvest. Stability analysis was useful in evaluating treatment by environment interactions, however, one must still apply agronomic and biological principles to explain differences. *Contribution from the Missouri Agricultural Experiment Station. Journal Series Number 3,028.