Effect of nitrogen fertilization and genotype on the yield and yield components of winter wheat

The effect of N fertilization on the yield, yield components, harvest index (HI), and chlorophyll content (SPAD (soil plant analysis development) index) of winter wheat cultivars was investigated in a long-term experiment in Hungary between 2006/2007 and 2008/2009. Maximal grain yield was reached at 80 and 160 kg · ha^–1 N treatments, the higher N rate did not lead to a further yield increase in any of the years. A substantial year effect was observed for the yield and yield components. A negative correlation was found between grain number and thousand-kernel weight (TKW). Mv Verbunkos gave among the varieties the highest grain yield, grain number per spike, and SPAD value. There was a significant (P<0.001) positive correlation between the yield and the number of grains per square meter (r=0.85) and between the yield and the SPAD index (r=0.59). A significant (P<0.01) negative correlation was detected between the yield and the TKW (r=–0.44) and a positive correlation between the yield and the HI (r=0.51). Regression analysis revealed a significant linear relationship between the yield and the yield components (number of grains per square meter and TKW) at the various N levels.