Response of semi-dwarf and conventional winter wheat varieties to the application of nitrogen fertilizer

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Abstract
Summary: Winter wheat varieties of contrasting height were grown in a series of yield trials to investigate their response to nitrogen fertilizer. The treatments also included application of fungicides and the use of nets to prevent lodging. The varieties were ‘semidwarfs’ based on the Norin 10 genetic factor Rht2 or taller ‘conventional’ varieties, all well adapted to the U.K. environment. The average response of the semi-dwarf varieties was similar to the conventional and there were varietal differences within each group. There was a marked tendency for the newer varieties to be more responsive but the varietal differences were not consistent between trials, the occurrence of powdery mildew (Erysiphe graminis) being a major factor. When this disease was prevalent, response to nitrogen was greatest in resistant varieties and increased by application of fungicides. In farm practice the optimum rate of nitrogen application for a variety will depend on its physiological response, resistance to lodging and resistance to diseases if these are not controlled by fungicides. No evidence was obtained that the gene Rht2 necessarily confers a greater response to nitrogen.