A stability analysis of the Iowa Corn Yield Test

The study was undertaken to examine the potential for using stability analysis as a criteria for hybrid selection in the state of Iowa. The purpose of the study was to determine differences in yield stability among corn hybrids, to determine if yield stability can be estimated, and to examine the relationship between yield stability and the plant characters, kernel moisture and stalk lodging. The study was conducted using data from the Iowa Corn Yield Test for the five year period from 1982-1986. There were 17 farm locations within seven districts in the test;A regression analysis of the grain yield of hybrids common in each district on the environmental index demonstrated that hybrids differ in yield stability. Hybrids were found that have high yield and stability, high yield and low stability, low yield and high stability, and both low yield and stability;A greater environmental variation was found to give a more accurate prediction of future yield stability (b values). Using six or less environments was found to give a poor estimate of b values while eight or more environments gave a more accurate estimation of yield stability;Hybrids with greater stalk strength also had greater stability because stalk strength is correlated with the yield response in corn. Examples of a relationship between yield stability and maturity as determined by kernel moisture at harvest were found in two districts, however, most districts did not show this relationship to be significant;A linear regression model using yield stability and the environmental index from the 1984 and 1985 data was used to estimate yields for 1986. Examples of both over and under estimation of yields were found depending upon the grouping of the data by districts. Two years of data did not provide an accurate prediction for yield using the regression model