The researchers studied different pea varieties in northern and southern Turkey to see how they performed in different environments. They found that the type of pea had the biggest impact on seed yield, followed by the location and the interaction between location and year. By using a special analysis called GGE biplot, they were able to show that the first principal component explained most of the variation in seed yield, with the second component explaining the rest. This information can help farmers choose the best pea varieties for their specific location and improve overall crop yield.