Graphic Analysis of Genotype, Environment, Nitrogen Fertilizer, and Their Interactions on Spring Wheat Yield

Interest in growing hard red spring wheat ( Triticum aestivum L.) in eastern Canada is increasing due to its potential returns relative to other small‐grain cereals and oilseed crops. The objectives of this study were to determine the effects of year, site, genotype, N application, and their interactions on the yield of hard red spring wheat (HRSW) and to demonstrate the application of the recently developed biplot methodology in visualizing agronomic research data. Ten HRSW cultivars were grown in five locations across three provinces from 1998 to 2000, constituting a total of 11 year–site combinations. In each environment, four levels of fertilizer N (50, 100, 150, and 200 kg ha −1 ) were applied. The N main effect, N × environment interaction, and N × genotype interaction were not significant. However, biplot analysis did reveal crossover N × environment interactions: Although higher N rates generally led to higher yield, the opposite was true in some environments. This was attributed to heavy Fusarium head blight ( Fusarium graminearum Schwabe) and/or foliar diseases in these environments, which was exacerbated by higher N rates. The strong genotype × environment interactions were mainly associated with two cultivars that yielded well in most environments but very poorly in two environments in which Fusarium head blight was severe. This study thus highlighted the importance of Fusarium head blight resistance in HRSW production in eastern Canada. An environment × factor biplot was described for the first time, which was highly effective in revealing the interrelationship among environmental factors and in revealing the weather and soil patterns of the environments.