APPLICATIONS OF STABILITY ANALYSIS FOR SINGLE-SITE, LONG-TERM EXPERIMENTS

Stability analysis, which is the linear regression of treatment yield on the environmental mean yield, has been proposed for use in single-s ite, long-term experiments (treatments applied to the same plots year after year), without first determining if treatment,yield reveals a si gnificant relationship with year (experiment years plotted sequentiall y in time). This research was initiated to demonstrate potential probl ems associated with stability analysis on long-term, wheat fertility e xperiments where treatment yield may be correlated with year. Three si ngle-site, long-term experiments were evaluated using stability analys is and linear regression of treatment yield on year. Each study was a replicated, longterm, continuous winter wheat (Triticum aestivum L.) f ertility experiment, receiving annual rates of N, P, and K fertilizer. Of the single-site, long-term trials evaluated, one was not suitable for stability analysis, as grain yield decreased significantly with ea ch ensuing year that the experiment was conducted, In this case, a neg ative residual yield response was noted with time (year) in plots rece iving N and no P. Therefore, the environmental mean in stability analy sis no longer reflected the random influence of climate (e.g., low and high rainfall or temperature) which could be used to decipher variabl e treatment response in seasonably wet or drg; years, without prior ev aluation of the relationship between treatment yield and year in singl e-site, long-term experiments, stability analysis can be inappropriate .