[Attempt to obtain high protein levels in wheat grain in the chalky soils of Champagne area]

abonos nitrogenados azote cereal crops chalk soils champagne ardennes champagne-ardennes contenido proteico crop yield cultivos de cereales fertilisation fertilizer application graine nitrogen nitrogen fertilizers protein content rendement des cultures rendimiento de cultivos seeds semilla site factors sol crayeux suelo fino de yeso triticum aestivum variedades varieties